53
2
This research was prepared on behalf of the Walton Family Foundation: www.waltonfamilyfoundation.org
Datu Research is a consulting firm that provides decision-makers the economic analysis they need to inform strategies that protect natural resources, improve food security, and develop local economies. www.daturesearch.com
Cover photo courtesy of Practical Farmers of Iowa.
AUTHORS
Sarah Mine, Sarah Zoubek, Damon Cory-Watson, and Marcy Lowe
ACKNOWLEDGEMENTS
The authors are grateful to the many Iowa corn growers and landowners, as well as personnel from
industry associations, government, NGOs, and universities, who generously contributed their time and
expertise to this project. Special thanks to Ryan Stockwell, Lara Bryant, Julie Sibbing, and Trisha White at
the National Wildlife Federation and to Sarah Carlson of Practical Farmers of Iowa for their support and
valuable input.
The opinions or comments expressed in this study are not necessarily endorsed by the facilitating
partner agencies mentioned or individuals interviewed. Errors of fact or interpretation remain
exclusively with the authors. We welcome comments and suggestions. Inquiries can be directed to
©December 2014. Datu Research, LLC.
3
EXPERT REVIEWERS
We thank the following individuals who generously shared their time and expertise to review and
provide feedback on this report.
Mahdi Al-Kaisi, PhD, Professor, Soil Management/Environment, Iowa State University
J. Gordon Arbuckle Jr., PhD, Associate Professor/Extension Sociologist, Iowa State University
Mollie Aronowitz, Land Manager, Peoples Company
Todd Barker, Senior Partner, Meridian Institute
Lara Bryant, Agriculture Program Coordinator, National Wildlife Federation
Sarah Carlson, Midwest Cover Crops Research Coordinator, Practical Farmers of Iowa
Keith Collins, PhD, Economist, National Crop Insurance Services; Former Chief Economist, United States
Department of Agriculture
Ben Gleason, Sustainable Program Manager, Iowa Corn Growers Association
Julie Grossman, PhD, Assistant Professor, Department of Horticultural Science, University of Minnesota
Jerry Hatfield, PhD, Laboratory Director and Supervisory Plant Physiologist, USDA Agricultural Research
Service
Bradley Hayes, Agricultural Real Estate Appraiser and Sales Agent, Peoples Company
Tim Hoffmann, Director, Product Administration and Standards Division, USDA Risk Management
Agency
Eileen Kladivko, PhD, Professor, Agronomy, Purdue University
Matt Liebman, PhD, Professor of Agronomy and Wallace Chair for Sustainable Agriculture, Iowa State
University
Claire O’Connor, Agricultural Water Policy Analyst, Natural Resources Defense Council
Jamie Ridgely, Chief Operating Officer, Agren, Inc.
Joan Stockinger, Co-op Development Specialist, Cooperative Development Services
Ryan Stockwell, PhD, Senior Agriculture Program Manager, National Wildlife Federation
Trisha White, Senior Agriculture Policy Specialist, National Wildlife Federation
Paul Wolfe, Policy Specialist, National Sustainable Agriculture Coalition
4
ABBREVIATIONS
AIP
Approved Insurance Provider
APH Actual Production History
ARMS
Agricultural Resource Management Survey (USDA)
BYE
Biotech Yield Endorsement
CCITF
Conservation and Crop Insurance Task Force
CSHT Cornell Soil Health Test
CSR2
Corn Suitability Rating (2nd version)
CTIC Conservation Technology Information Center
ERS Economic Research Service (USDA)
FCIC
Federal Crop Insurance Corporation (UDSA)
FMC
Farmland Management Company
ISU
Iowa State University
MoE Margin of Error
MPCI
Multiple Peril Crop Insurance
N-BMP
Nutrient Best Management Practices
NGO Non-governmental Organization
NRCS
Natural Resources Conservation Service (USDA)
PPP
Prevented Planting Payments
NASS National Agricultural Statistics Service (USDA)
NRDC Natural Resources Defense Council
NWF National Wildlife Federation
RMA Risk Management Agency (UDSA)
SARE Sustainable Agriculture Research and Education
SOM
Soil Organic Matter
USDA
United States Department of Agriculture
WFRP
Whole-Farm Revenue Protection
5
Contents Tables ............................................................................................................................................................ 6
Figures ........................................................................................................................................................... 6
Executive Summary ....................................................................................................................................... 7
Methods ...................................................................................................................................................... 14
Introduction ................................................................................................................................................ 16
Adoption of Conservation Agriculture in Iowa ........................................................................................... 17
Soil Conservation Benefits ...................................................................................................................... 18
Reductions in Input Costs ....................................................................................................................... 19
Impacts on Yield ...................................................................................................................................... 20
Effects on Net Revenues ......................................................................................................................... 22
Recent Research on Adoption Rates ....................................................................................................... 23
Datu Survey ............................................................................................................................................. 24
Could Landowners Incentivize Farmers to Adopt? ..................................................................................... 27
Future Potential of Crop Share and Custom Leases ............................................................................... 29
Could Crop Insurers Incentivize Farmers to Adopt? ................................................................................... 30
Using 508(h) to Make Incremental Change, and Selecting a Practice .................................................... 35
Smaller Opportunities: Prevented Planting Payments and Whole Farm Revenue Protection ............... 38
Other Possibilities in the Value Chain ......................................................................................................... 40
Seed Corn Providers ................................................................................................................................ 41
Cellulosic Ethanol Producers ................................................................................................................... 42
Recommendations ...................................................................................................................................... 43
Conclusion ................................................................................................................................................... 45
References .................................................................................................................................................. 46
6
Tables Table 1. Summary of interviews ................................................................................................................. 14
Table 2. Summary of Datu survey response statistics ................................................................................ 15
Table 3. Selected evidence that the three target practices maintain or build SOM .................................. 18
Table 4. Selected research on changes in corn yield following adoption of the practices ......................... 20
Table 5. Selected findings on effect of the practices on net revenues ....................................................... 23
Table 6. Types of land rental arrangements ............................................................................................... 29
Table 7. Selected research on effect of the practices on drought and excess soil moisture mitigation .... 33
Table 8. Experience with the practices by percent of respondents ........................................................... 38
Figures Figure 1. NRCS-recognized conservation purposes of the three target practices ...................................... 17
Figure 2. Anticipated effects of the practices on input costs, compared to conventional ......................... 20
Figure 3. Characteristics of Datu survey respondents ................................................................................ 25
Figure 4. Adoption of the practices by percent of respondents ................................................................. 26
Figure 5. Cover crop acreage by percent of respondents ........................................................................... 26
Figure 6. Land rental and crop insurance segments in the Iowa corn value chain ..................................... 27
Figure 7. Variables considered in Iowa agricultural land valuation ............................................................ 28
Figure 8. Distribution of Iowa farmland by tenure ..................................................................................... 30
Figure 9. Changes in gross premiums and indemnities for Iowa corn policies ........................................... 32
Figure 10. Risk mitigation mechanisms between the federal government and AIPs ................................. 34
Figure 11. Other potential opportunities to incentivize the practices in the Iowa corn value chain ......... 41
7
Executive Summary Conservation agriculture is a set of sustainable farming practices that build soil health while reducing
erosion and nutrient loss. This study focuses on three practices: cover crop use; crop rotations; and
reduced tillage. Used alone or in various combinations, these practices can provide many soil
conservation benefits. Their potential to combat erosion and nutrient loss also makes them an
important tool for protecting water quality. Agriculture accounts for over 70% of the nitrogen and
phosphorus that enters the Gulf of Mexico via the Mississippi River, nutrients that have already created
a nearly 5000-km2 low-oxygen, or “hypoxic,” zone that threatens marine life in one of the nation’s
largest and most productive fisheries (Alexander et al. 2014). Widespread adoption of conservation
agriculture could therefore create far-reaching environmental and economic benefits.
Adoption of Conservation Agriculture in Iowa
To what extent are Iowa farmers adopting conservation agriculture? Several observations have emerged
from a series of recent surveys, including a Datu survey of Iowa corn farmers and landowners conducted
in June 2014. For cover crops, adoption levels remain low, although the number of first-time users is
growing across the country, including in Iowa, the focus of this study. The Datu survey found that a
sizeable minority (23%) of Iowa respondents were using cover crops, mostly on fewer than 100 acres,
suggesting that farmers may be trying them out before committing to adoption on a larger scale.
For crop rotations, when a corn soybean-rotation is included, adoption is highest of the three practices.
The Datu survey of Iowa respondents found that 80% rotate their acres yearly between corn and
soybeans. It is important to note that the United States Department of Agriculture (USDA) Natural
Resources Conservation Service (NRCS) does not consider a corn-soybean rotation to be a “conservation
crop rotation”1 (NRCS 2010a). Compared to corn-soybean, evidence suggests that third- and fourth-crop
rotations, which include additional crops such as small grains or alfalfa, have greater conservation
benefits, including decreased nitrogen fertilizer and herbicide use (Liebman et al. 2008). Our survey
found a much smaller group (19%) used a third-crop rotation.
For reduced tillage, the Datu survey found that 70% of respondents were using minimum or
conservation tillage (retaining at least 30% of residue). Almost half (47%) reported using no-till (drilling
seeds into undisturbed soil), but this number shrank to 21% when respondents were asked whether
they had continued the practice over many years. Only 4% used strip till (tilling and planting in only a
narrow band).
The available data suggest that an important obstacle to wider adoption of these three practices is that
farmers may have to wait several years before they experience an economic benefit. For example, it can
take a decade or more for total organic matter to significantly increase after a management change (Lal
et al. 2007). Research from Iowa and surrounding states suggests that yields may also moderately
decrease in the first several years of adoption, particularly for no-till (see Table 4). The potential lag time
1 NRCS’s definition of “conservation crop rotation” states, “[a] two-crop sequence must contain a warm season and
a cool season crop” (NRCS 2010a). Corn and soybeans are both warm season crops (ARS 2012).
8
between adoption and economic benefit means that, for adoption to increase, farmers need additional
short-term incentives. This report examines opportunities to provide such incentives via other actors
within the Iowa corn value chain.
Value Chain Incentives
The purpose of this research is to examine Iowa corn farmers’ existing business relationships to find
actors who may themselves benefit from increased adoption of conservation agriculture, and so may be
willing to offer incentives to farmers. Such incentives can come from large, powerful entities in the value
chain. For instance, the Soil Health Partnership2 is currently leveraging support of seed company
Monsanto to identify, test, and measure management practices that improve soil health, with a goal of
demonstrating benefits to farmers’ bottom lines (Soil Health Partnership 2014). A 2014 report by Ceres,
Water & Climate Risks Facing U.S. Corn Production, identifies ways that top firms in the fertilizer, seed,
pesticide, equipment, and other key segments of the agricultural industry can encourage farmers to
contribute to a more sustainable value chain (Barton and Clark 2014).
This report seeks to complement these critical efforts. Since no single source will likely be adequate to
induce farmers to change their soil management practices, it is worth seeking additional value chain
actors to provide further incentives. This analysis focuses on two target value chain actors: owners of
farmland, and providers of crop insurance. Each actor is analyzed for its potential to find a “win” for
itself in increased farmer adoption of conservation agriculture.
Could Landowners Incentivize Farmers to Adopt Conservation Agriculture Practices?
More than half (55%) of farmland in Iowa is rented (Duffy and Johanns 2012). This means that in most
cases, land management decisions do not just affect operators, but also non-operating landowners.
Since conservation agriculture practices have been demonstrated to maintain or improve the quality
and health of soil, we examine whether this can translate into economic benefit3 for a landowner—thus
potentially motivating landowners to reward operators for adoption.
Soil quality measures the ability of soil to function as a life-supporting ecosystem, while soil health refers
to the vitality of soil organisms. High-quality, healthy soil supports crop production by promoting root
development, increasing the nutrient pool, increasing beneficial biota, and decreasing pest and weed
pressure (Lal 2012; Lal, Kimble, and Follet 1998). These benefits may be highly valued by some
landowners—especially those for whom long-term, sustainable crop productivity is a priority, along with
co-benefits such as reduced nutrient loss into waterways. However, Iowa landowners currently have no
formal mechanism for translating this into a direct economic benefit, at least not via higher land values.
In the current system of land valuation, soil quality and soil health are not among the factors used to
2 According to interviews, the National Corn Growers Association’s Soil Health Partnership seeks to answer many
economic questions about reduced tillage and cover crops by conducting 5-year strip trials on 100 or more farms. 3 Although the purpose of this analysis is to identify economic incentives, we recognize that conservation
agriculture also provides landowners, tenants, and society with many non-economic benefits that may play a role in adoption.
9
determine land value. Most variables that determine the value of Iowa farmland are structural, and thus
cannot be improved through conservation agriculture.
The only accepted land valuation factor that can be affected by conservation agriculture practices is
yields. To date, the link between improved yields and two of the three practices—cover crop use and
reduced tillage—is unclear. The available data for Iowa suggest that these practices in some instances
decrease yields in the short-term, requiring several years to return to previous levels. The time horizon
for increasing yields appears even longer—possibly decades—in the case of no-till. Without firm
evidence on how and when cover crops and reduced tillage increase yields, it is difficult to link them
with land value. Adequate data on the effects of conservation agriculture practices on yields are thus a
requirement before landowners would find it in their economic best interest to incentivize operators to
adopt conservation agriculture.
In the meantime, until such data are available, could the practices offer landowners some other short-
term economic benefit? Under certain lease arrangements, conservation agriculture practices can
potentially benefit landowners via savings on inputs. Currently, 14% of leases in Iowa are crop share or
custom arrangements, in which the landowner supplies some or all inputs (Duffy and Johanns 2012).
These two types of landowners could indeed benefit economically from farmer adoption of conservation
agriculture, which reduces, to varying degrees, use of fertilizer, pesticides, fuel, equipment, or labor.
Could Providers of Crop Insurance Incentivize Farmers to Adopt Conservation Agriculture Practices?
Federal crop insurance is a critical component of the U.S. farming system, allowing producers to manage
risk and withstand declines in yield and changes in price. It is also a multi-billion dollar industry, with
approved insurance providers (AIPs) taking in $11.8 billion in premiums and paying out $12 billion in
indemnities nationally in 2013 (FCIC 2014d). Severe weather creates costs for insurers via indemnity
payments to farmers (RMA 2013). In principle, companies that sell crop insurance would try to reduce
indemnities, perhaps by rewarding farmers for adopting risk-reducing practices. In light of evidence that
conservation agriculture can increase crop resilience in conditions of drought, flood, and excessive soil
moisture, insurers could in theory reduce their risk by encouraging conservation agriculture.
This analysis concludes that ultimately, the data currently available are likely insufficient to build an
actuarially-sound case for offering farmers a discount for using conservation agriculture practices. Much
more research is needed to link the three practices with reduction in insurers’ risk.
Two added obstacles further limit this opportunity. First, risk sharing with the federal government limits
AIPs’ sensitivity to risk, weakening the case for actively rewarding farmers for risk reduction. Second,
AIPs are not permitted to incentivize risk-reducing farming practices without approval by the Risk
Management Agency (RMA). They are also prohibited from offering discounted rates for existing plans
(FCIC 2014a).
Removing these obstacles would require an overhaul of federal policy—which is unlikely to occur, and
may not be desirable because of the unique nature of agricultural insurance. Yet in the absence of a
10
federal overhaul, incremental change to reward conservation agriculture adoption is still possible.
Section 508(h) of the Federal Crop Insurance Act provides a mechanism for introducing new crop
insurance policies, provisions of policies, and rates of premium (75th U.S. Congress 1938).
Two key precedents used the 508(h) mechanism to provide a premium rate reduction based on
adoption of a technology or practice. In 2008, Monsanto acted as a co-submitter for the Biotech Yield
Endorsement (BYE) pilot program. The Federal Crop Insurance Corporation (FCIC) Board approved a
premium rate reduction for farmers using Monsanto’s biotech seeds,4 concluding that the seeds
lowered “yield risk” (RMA 2010). In 2003, the Nutrient Best Management Practices (N-BMP)
Endorsement pilot reduced rates for farmers who applied only a recommended level of nitrogen and
phosphorus (RMA 2003). The BYE pilot was approved only after Monsanto provided years of data,
including some 15,000 side-by-side field trials, thousands of pages of documentation, and expert
testimony from university professors (RMA 2010). Datu interviews indicate that demonstrating effects
of a production practice on either total yield or yield stability is essential.
Food and agricultural policy group AGree is currently leading a first-step effort to more clearly document
conservation agriculture’s effects on yields and yield variability. The AGree-led Conservation and Crop
Insurance Task Force (CCITF) is engaging with USDA in an effort to integrate and analyze existing data
within USDA on conservation practices, yield, variability, soil health, and other key environmental
indicators. This effort may help reduce the costs of gathering the data needed for a new product to win
approval via 508(h), though it is likely that funding for new research, and in particular side-by-side field
trials, will still be necessary.
Before selecting a conservation agriculture practice or practices to include in a 508(h) proposal,
advocates need to better understand the potential market for each practice. Based on preliminary
investigation into market potential, cover crops seem to be worthy targets of further research. Adoption
of cover crops remains low, but interest is growing and barriers to adoption are not insurmountable.
Datu survey respondents expressed some experience using them, and proficiency could be improved
with more training.
This initial data may be useful to advocates currently testing the waters of a conservation-focused pilot
program via 508(h). AGree and the CCITF are presently exploring crop insurance-based opportunities
and may eventually identify one or more conservation practices to drive through the 508(h) process. To
this effect, the group continues to convene meetings between AIPs, academia, and industry to assess
the potential of a possible 508(h) effort and, more broadly, how a data integration and analysis effort
could lead to changes in the crop insurance program.5 The group identified at least one AIP that has
expressed interest in the idea, recommending a wait-and-see stance at least until new programs in the
2014 farm bill have been implemented, freeing up some USDA bandwidth.
4 An interview with an RMA official indicated the discount also applied to DuPont Pioneer, Syngenta, and Dow
stacked traited hybrids. 5 This same data may also help inform industry agricultural sustainability standards (i.e., supply chain sustainability
standards) and support emerging markets for ecosystem services.
11
NRDC is also actively looking for partnerships to start a 508(h) process. The environmental advocacy
group is growing their food and agriculture work, including encouraging improved soil health via section
508(h). They have discussed their proposal with actuaries who have prepared submissions for past
508(h) products and are interested in moving forward on the development of a new product.
Two smaller opportunities within crop insurance are also worth monitoring: Prevented Planting
Payments (PPP) and Whole-Farm Revenue Protection (WFRP). Prevented planting is a failure to plant an
insured crop by the final planting date due to an insured cause of loss that is general to the surrounding
area, for instance, sustained rainfall (RMA 2014). Farmers claiming prevented planting will typically
receive a payment of 60% of the production guarantee under their revenue protection or yield
protection policies, which represented 98% of policies sold to Iowa corn farmers in 2013 (FCIC 2014c;
RMA 2014). In PPP situations, cover crops become an attractive alternative to fallow land. A majority of
Datu survey respondents felt that cover crops make economic sense in a prevented planting situation,
with 67% agreeing with this statement. In addition, 66% of those who received a prevented planting
payment had planted cover crops on their prevented planting acres.6
Whole-Farm Revenue Protection is a new insurance pilot program required by the 2014 farm bill, which
will be available for the 2015 crop year in most states (FCIC 2014c). WFRP will allow producers to insure
the entire value of their operation under a single policy instead of insuring each commodity separately
(USDA 2014). Of possible significance for advocates is the premium subsidy WFRP will provide for
farmers producing at least two different commodities on one farm (NSAC 2014; Shea 2014). WFRP has
some potential to incentivize crop rotation by rewarding producers who grow more than one type of
crop. Because a corn-soybean rotation is already very common in Iowa, WRFP may have the greatest
potential to increase adoption of third-crop rotations. Full policy details were expected by late 2014.
Additional Possibilities in the Value Chain
Our interviews with farmers, landowners, academics, and industry representatives suggested two other
actors in the Iowa corn value chain that could potentially incentivize farmers to adopt conservation
agriculture practices: seed corn providers and cellulosic ethanol producers. Seed corn providers refer to
major seed companies such as Monsanto, DuPont Pioneer, and Syngenta who contract with farmers in
Iowa to grow hybrid corn seeds. Our interviews suggest that seed corn operations may be particularly
vulnerable to compaction. To combat this challenge and help farmers take advantage of nutrient- and
soil organic matter (SOM)-building benefits, seed companies may want to encourage the farmers who
grow their products to use cover crops. Our interviews suggest that seed corn companies are beginning
to explore the benefits of cover crops. For instance, DuPont Pioneer has started two projects with
Practical Farmers of Iowa to investigate use of cover crops on the company’s seed corn plots. The
company provided most of the seed needed for farmers to test out cover crops.
6 Because only a subset of our sample had received PPP (N=32), the margin of error for this finding (+/-17.32%) is
higher than that for most of our survey findings (+/- 6.72%).
12
Cellulosic ethanol producers make fuel from corn stover, as opposed to the starch from corn kernels
used to make standard ethanol. Corn stover consists of the aboveground corn plant material, excluding
grain: the stalks, leaves, shuck, silk, tassel and cobs that remain after harvest (Arora, Licht, and Leibold
2014). Residue removal for cellulosic ethanol production carries the risk of heightened erosion, nutrient
removal, and decreased soil quality if carried out at unsustainable rates. Since practices such as cover
crop use can help farmers remove more residue sustainably, cellulosic ethanol producers may be willing
to incentivize the practice to increase the amount of residue they can sustainably harvest.
Recommendations
This report examines several challenges to providing incentives to increase farmer adoption of
conservation agriculture. In the process, we also identify some opportunities. Below are our
recommendations for next steps:
1) Fully demonstrate the potential of conservation agriculture practices to improve yields. Yield effects
are likely the most critical piece of information a farmer, landowner, or crop insurer can have about a
management practice. Documenting a clear link between conservation agriculture practices and
improvements in yield or yield stability is the most concrete way to increase adoption and reward
farmers. To date, the available data on conservation agriculture’s impacts on corn yields in Iowa are
mixed. Although initial data for the three practices’ effects on yield stability are promising, more data
are needed to fully document the impact on yields, encompassing a wide variety of crops, geographies,
and climates.
In the short term, a high priority is to fully harness existing data. This report has referred to a body of
research on yield effects. Much more data exists within government agencies that could be integrated,
analyzed, and made available to farmers and advocates. The AGree-led CCITF provides an example via its
support for a USDA-led effort to integrate and analyze existing data at different government agencies on
conservation practices, yield, variability, soil health, and other key topics. A number of active, long-term
cropping system studies exist at land-grant universities including University of Wisconsin-Madison,
North Carolina State University, and others whose findings could be compiled and systematically
analyzed (Posner 1993; NCSU 2014).
Much could be accomplished by conducting new research to document the effects of soil quality and soil
health on yields. Conservation agriculture practices have been solidly demonstrated to improve soil
quality and soil health, control erosion, and improve availability of water and nutrients in the soil.
Additional research is needed to document the effects of healthy, high-quality soils on yields. Tools such
as the Haney Test and the Cornell Soil Health Test—which measure more aspects of soil health,
including microbial activity—can help researchers better understand the relationship between soil
health and yield outcomes.
To fully determine the practices’ effects on yields, it is important to conduct side-by-side field trials.
Side-by-side field trials across a wide variety of soil types, geographies, and climates over 10 years are
the gold standard for demonstrating yield-boosting or -stabilizing effects. This is the most definitive, but
13
also most expensive, way to determine the extent to which conservation agriculture practices have a
positive impact on yields.
2) Inform landowners currently using crop share and custom leases about the cost-saving benefits of
conservation agriculture. Since landowners are unlikely to incentivize farmers to adopt conservation
agriculture until better documentation is available on the yield benefits, a good interim step is to tap the
two land rental arrangements we identified: crop share and custom leases. Although results will vary
from farm to farm, conservation agriculture practices are likely to result in reductions in input costs.
These reductions can benefit landowners under the lease types mentioned. Currently, these
arrangements make up about 14% of leases in Iowa (Duffy and Johanns 2012).
3) Continue to evaluate the potential of a submission under section 508(h) of the Federal Crop Insurance
Act, focused on cover crops. In general, crop insurers lack both the motive and the means to incentivize
conservation agriculture adoption. Although an overhaul of the current system is unlikely, incremental
change is possible. The most promising opportunity is to propose a pilot program through the 508(h)
process to offer a “good producer discount.” Among conservation agriculture practices, the likeliest to
win approval may be cover crops, although more market research is needed. Two smaller opportunities
also exist within the current crop insurance framework: prevented planting payments can encourage
first-time use of cover crops, helping spread permanent adoption if farmers have a positive first
experience, and Whole-Farm Revenue Protection may encourage crop rotation by providing a premium
subsidy for growing more than one crop (the strength of this incentive will be determined after full
policy details are released).
4) Conduct research to evaluate the potential of other identified possibilities in the value chain.
Preliminary research points to the potential to find market-based incentives within the seed corn and
cellulosic ethanol segments, although more research is needed. Seed corn operations may be
particularly vulnerable to compaction. To combat this challenge, seed companies may want to
encourage the farmers who grow their products to use cover crops. Residue removal for cellulosic
ethanol production carries the risk of heightened erosion, nutrient removal, and decreased soil quality if
carried out at unsustainable rates. Cellulosic ethanol producers may be willing to incentivize cover crops
to increase the amount of residue they can sustainably harvest.
In conclusion, conservation agriculture offers considerable societal benefits that extend well beyond the
farm, translating into important economic value and environmental sustainability for future generations.
Yet, in general, farmers do not receive a clear, immediate economic benefit from adopting. For adoption
to increase, short-term economic incentives are needed. Achieving widespread adoption requires
ensuring that a fair share of the economic benefit accrues directly to farmers.
14
Methods This study examines selected entities in the Iowa corn value chain for their potential to incentivize
growers to adopt the conservation agriculture practices of cover crop use, crop rotations, and reduced
tillage. To begin the research, we reviewed the existing literature related to the impact of conservation
agriculture on soil, yields, and net revenues, as well as current levels of adoption. We confined our
search to studies conducted in Iowa and the surrounding Upper Mississippi River Basin states (MN, WI,
IL, MO), where climatic conditions are similar to Iowa, also including select multi-state meta-analyses
where data were limited. We only included studies that examined grain corn.
Next, in March 2014, we visited four distinct regions of Iowa,7 conducting in-depth, qualitative
interviews with 34 farmers, landowners, and other stakeholders. We followed up with dozens of phone
interviews with additional industry contacts, government representatives, non-governmental
organization (NGO) staff, and academics, conducting over 100 interviews in total. We used NVivo
software to code interview data. For a summary of interviews, please see Table 1.
Table 1. Summary of interviews
Stakeholder Type Number
Approved Insurance Provider8 6
Corn Grower/Landowner 26
Farm Advisor 2
Farm Credit Provider 3
Farm Management Company 8
Government 13
Industry Association 4
NGO 12
Reinsurer, Private 4
Retailer 3
Risk Modeling Provider 1
Soil Lab, Private 4
University 15
TOTAL 101
In June 2014, we conducted a survey of Iowa corn growers and landowners to better understand
present conservation agriculture adoption patterns and investigate concepts raised in interviews—
especially regarding the potential of landowners and crop insurers to incentivize farmers to adopt the
practices. Using the data service Farm Market ID, we selected a random sample of 1,500 from a total
population of 75,337 corn farms of over one acre in the state of Iowa, across all 99 counties. Farm
7 We interviewed farmers and landowners located in the following Iowa Department of Natural Resources
Landform Regions: Southern Iowa Drift Plain, Iowan Surface, Des Moines Lobe, and Northwest Iowa Plains. 8 In our conversations with approved insurance providers, we spoke with managers working in sales, research and
development, insurance services, claims, and underwriting.
15
Market ID’s population list was dated from harvest year 2012, using the United States Department of
Agriculture (USDA)’s Farm Service Agency9 program participant information, along with other
proprietary sources, including satellite imagery to verify what is grown. Farm Market ID estimates that
this method accurately identifies 95% of growers and the crops they grow nationwide.
Using a modified Dillman method,10 we mailed a survey and introductory letter to each sampled farmer
or landowner, following up with a call when a phone number was available. We received 212 eligible
responses, meaning the respondent was a corn grower or landowner and had completed the majority of
the survey. Thirty surveys were marked as undeliverable by the post office. Farmers who received a two-
dollar bill (with 759 of the surveys) responded at a rate of 21%, with an overall response rate for the
survey at 14%. Using the total population provided by Farm Market ID (75,337) and a sample size of 212,
the maximum margin of error (MoE) for our survey findings is +/- 6.72% at the 95% confidence level.11
For a summary of response statistics, see Table 2.
Table 2. Summary of Datu survey response statistics
Statistic Value
Farmers Randomly Sampled 1500
Eligible Responses (Sample) 212
Ineligible Responses 15
Undeliverable 30
Response Rate – $2 Bill 20.95%
Response Rate – No $2 Bill 7.15%
Response Rate – Total 14.13%
Margin of Error +/- 6.72%
We must note that the random sample drawn did not capture any producers with over 4,500 acres, and
the small sample size of 212 responses returned may mean that some counties are over and under-
represented. The small sample size also means we must be cautious about drawing conclusions about
the larger population of Iowa corn farmers. Therefore, our discussion of findings is related to Datu
survey respondents. Because of the subject matter, it is possible that respondents who were more
conservation-minded could have responded in higher numbers, potentially skewing results. We compare
our results to other surveys with larger sample sizes as a reference point. Before publication, our report
was reviewed by a panel of 20 experts in fields ranging from agronomy to economics to policy.
9 The Farm Service Agency oversees federal farm programs, including conservation programs, disaster assistance
programs, farm loan programs, and the new Agricultural Risk Coverage (ARC) and Price Loss Coverage (PLC). 10
The Dillman Total Design Survey Method instructs surveyors to mail a booklet-type questionnaire, return postcard, and return stamped letter to each desired participant. One week after the initial mail-out, reminder postcards are mailed. Two to six weeks later, replacement questionnaires are mailed (Hoddinott and Bass 1986). 11
In cases where only a portion of participants were instructed to respond to a question, the MoE may be higher than 6.72%. For example, one question began, “If you answered YES to the previous question...” This type of question reduced the sample size, thereby increasing the MoE. In such cases, the actual MoE is reported.
16
Introduction Conservation agriculture is defined as a set of sustainable farming practices that build soil health while
reducing erosion and nutrient loss. Used alone or in various combinations, these practices can provide
many soil conservation benefits. Their potential to combat erosion and nutrient pollution also makes
them an important tool for protecting water quality. Agriculture accounts for over 70% of the nitrogen
and phosphorus that enters the Gulf of Mexico via the Mississippi River, nutrients that have already
created a nearly 5000-km2 low-oxygen, or “hypoxic,” zone that threatens marine life in one of the
nation’s largest and most productive fisheries (Alexander et al. 2014). Widespread adoption of
conservation agriculture has the potential to create far-reaching environmental and economic benefits.
This study focuses on farmer adoption of three conservation agriculture practices: cover crop use; crop
rotations; and reduced tillage. These management practices, combined or on their own, can increase
soil quality (physical and chemical components) and health (biological functions) while reducing erosion,
potentially decreasing the need for fertilizer and pesticide inputs and reducing nutrient loss. Figure 1
illustrates the conservation purposes that, in general, each practice serves, as recognized by the USDA
Natural Resources Conservation Service (NRCS).12 Newer soil testing methods like the Soil Health and
Nutrient Tool, widely referred to as the “Haney Test,” and the Cornell Soil Health Test (CSHT) measure
nutrients made available to crops via microbial activity and may help further document the soil health
benefits of conservation agriculture (Haney 2013; Cornell University 2014).13
The soil quality and conservation benefits of the three practices take time to accrue. For example, it can
take a decade or more for total organic matter, an important element of soil health, to significantly
increase after a management change (Lal et al. 2007). Yet the costs of adoption are immediate: farmers
may need to purchase new equipment, seeds, and other inputs and invest the time to learn a new
practice. In some cases, they may also experience moderate reductions in yields at the beginning,
depending on the practice and how and where it is implemented. This mismatch between short-term
costs and longer-term benefits creates a significant barrier to adoption. To overcome it, farmers need
economic incentives upfront.
Such incentives can come from large entities in the value chain. The Soil Health Partnership14 initiative is
currently leveraging the support of seed company Monsanto to identify, test, and measure management
practices that improve soil health, with a goal of demonstrating benefits to farmers’ bottom lines (Soil
Health Partnership 2014). A 2014 report by business and sustainability advocacy group Ceres, Water &
Climate Risks Facing U.S. Corn Production, identifies ways that top firms in the fertilizer, seed, pesticide,
equipment, and other key segments can incentivize farmers to contribute to a more sustainable value
chain (Barton and Clark 2014).
12
In the figure, in accordance with the NRCS definition of “conservation crop rotation,” “crop rotation” does not include corn-soybean (NRCS 2010a). See also note 1. 13
Dr. Rick Haney of USDA-ARS developed the Haney Test to measure the effect of soil biology on nutrient availability (Haney 2013). The CSHT assesses a number of soil attributes in addition to those measured via standard fertility tests, including respiration and protein (Cornell University 2014). 14
According to interviews, the National Corn Growers Association’s Soil Health Partnership seeks to answer many economic questions about reduced tillage and cover crops via five-year strip trials on 100 or more farms.
17
Figure 1. NRCS-recognized conservation purposes of the three target practices
Sources: NRCS 2010a; NRCS 2010b; NRCS 2012; NRCS 2011; NRCS 2013
Photo credits: eOrganic 2013; Pedersen 2004; NRCS 2014
In addition to these critical efforts, it is also worth seeking additional value chain segments that stand to
gain by incentivizing farmers to adopt conservation agriculture. Additional actors within farmers’
existing business relationships may be needed, in combination with larger entities, to provide farmers
sufficient economic incentive. We highlight two such actors: landowners and crop insurance providers.
This report will first summarize the research on the benefits of conservation agriculture, then assess
what is known about rates of farmer adoption in Iowa, and then examine the potential to tap two value
chain segments to incentivize farmers: landowners and crop insurers. We will also identify other value
chain segments worthy of further study and conclude with recommendations.
Adoption of Conservation Agriculture in Iowa Our farmer interviews indicated that a desire to preserve and improve the land was a primary factor
spurring adoption of conservation agriculture practices, whether farmers hoped to benefit in their own
18
lifetime or to pass the gains to their children. Many interviewees had also seen soil loss on neighbors’
farms and, equating soil removed from one’s field to dollars lost from one’s pocket, felt that
conservation agriculture just makes sense. Below we examine the reasons farmers adopt the practices,
acknowledge the obstacles, and assess the state of current adoption.
Soil Conservation Benefits Chief among reasons farmers adopt conservation agriculture is that it is beneficial to the soil. Cover
crops—legumes, grasses, and brassicas planted in the period between cash crops for seasonal cover and
other conservation purposes—have a number of specific benefits in addition to the soil-quality, erosion-
control, and water-use benefits that all three practices share (see Figure 1 on the previous page).
Depending on the plant species, cover crops may also fix atmospheric nitrogen, capture and recycle
nutrients, and reduce soil compaction via root growth.
Crop rotation is the practice of growing crops in a planned sequence on the same field. Where possible,
this report distinguishes between corn-soybean rotation and rotations of three crops or more, typically
including a small grain (such as oats) or alfalfa (used for hay). NRCS does not include corn-soybean in its
definition of a “conservation crop rotation”15 (NRCS 2010a). Evidence suggests that third- and fourth-
crop rotations have greater conservation benefits, including decreased nitrogen fertilizer and herbicide
use, compared to corn-soybean (Liebman et al. 2008). As Figure 1 illustrates, by introducing diverse crop
and root phenologies, rotations can help reduce nutrient imbalances. Rotating crops can also reduce
weed and pest pressure (see Figure 1).
Reduced tillage can be three types: minimum or conservation tillage, which is the limiting of soil-
disturbing activities and retaining at least 30% of residue as surface cover;16 no-till, meaning drilling
(planting) seeds directly into undisturbed soil; and strip till, tilling and planting in only a narrow band of
earth. Reduced tillage practices can reduce carbon dioxide and particulate emissions (see Figure 1).
Our review of studies on corn in Iowa and surrounding states yielded evidence that each practice may
also maintain or build soil organic matter (SOM), defined as the living, decaying, and stable biological
material in soil that holds nutrients. The many conservation benefits of SOM include further decreasing
erosion, as well as enhancing the microbial community, stabilizing soil structure, increasing water and
nutrient holding capacity, filtering pesticides and herbicides, and improving water filtration (Lal 2012;
NRC 2010; Blanco-Canqui and Lal 2010; Iqbal et al. 2005; Lal 1995; NRCS 2014). See Table 3 for a list of
selected studies providing evidence that each practice improves SOM.
Soil conservation benefits take time to accrue. A measurable increase in organic matter alone may take
decades, with the exact rate depending on climate, soil type, and site-specific management (Lal et al.
2007). Providing upfront benefits would help more farmers adopt these practices.
15
NRCS’s definition of “conservation crop rotation” states, “a two-crop sequence must contain a warm season and a cool season crop” (NRCS 2010a). Corn and soybeans are both warm season crops (ARS 2012). 16
Interviews with soil scientists suggest that 30% residue retention is no longer considered sufficient to protect soil quality and health; retention of 60 – 70% may be needed.
19
Table 3. Selected evidence that the three target practices maintain or build SOM
Practice Study
Cover Crops Wander et al. 1994
Wander and Traina 1996
Third-Crop Rotations
Odell et al. 1984
Al-Kaisi 2001
Karlen, Hurley, and Andrews 2006
Reduced Tillage
Wander et al. 1998
Needelman et al. 1999
Duiker and Lal 1999
Wander and Yang 2000
Al-Kaisi 2001
Al-Kaisi and Licht 2005
Blanco-Canqui and Lal 2008
Syswerda et al. 2011
Reductions in Input Costs Savings on inputs may help bring benefits forward. For example, it is possible that using a leguminous
cover crop one year could decrease the need for nitrogen fertilizer for the subsequent crop, cutting
fertilizer costs over the span of just one year. Several of the adopters we spoke with described
themselves as “low-cost producers.”17 Compared to non-adopter farmers, they used fewer inputs such
as fertilizer, pesticides, fuel, equipment, and labor.
Each practice can reduce input use, thereby decreasing the cost of growing corn (see Figure 2). Because
they can provide fixed atmospheric nitrogen to crops and help retain soil, cover crops may reduce
fertilizer costs for subsequent crops. Research from southwestern Ontario found nitrate levels in corn
soil following red clover were 2.8 times greater than without clover (Vyn et al. 1999). As the figure on
the following page illustrates, cover crops do entail additional seed costs; planting them, either via aerial
seeding or drilling, may also increase fuel, equipment maintenance, and labor costs. Whether growers
experience a net reduction in input costs with this practice is likely to vary by operation.
For crop rotation, Liebman et al. (2008) found in their Boone, IA study that three- and four-year crop
rotations that included corn, soybeans, a small grain, and either red clover or alfalfa reduced nitrogen
fertilizer and pesticide use. A 16-year study at the Rodale Institute in southeastern Pennsylvania also
found that a three-year rotation with corn, soybean, and a mix of legumes and small grains reduced
pesticide costs (Hanson, Lichtenberg, and Peters 1997). Generally speaking, with less need to apply
fertilizer and pesticides, over time equipment maintenance and fuel costs may also decrease (Duffy
2012). Depending on the rotation selected, this practice may reduce input costs the most.
17
Economists use this term to describe producers in any industry who achieve cost savings through economies of scale. Our use here differs.
20
Figure 2. Anticipated effects of the practices on input costs, compared to conventional
Note: Size of arrows not indicative of size of anticipated effect
Sources: Duffy 2012; IDALS, IADNR, and ISU 2013; Vyn et al. 1999; Hanson et al. 1993; Exner et al. 1999; Gibson et al. 2006;
Snapp et al. 2005; Stivers-Young and Tucker 1999; Liebman et al. 2008; Smith, Gross, and Robertson 2008; Hanson, Lichtenberg,
and Peters 1997; Harper 1996; O’Connor2013;Uri 2000; Boyle 2006; Davis et al. 2012
A 2006 reduced tillage literature review found that by decreasing the number of passes needed across a
field, the practice can lower labor, fuel, and equipment wear-and-tear costs (Boyle 2006). At the same
time, reducing or eliminating tillage removes a weed control tool; thus pesticide, including herbicide,
costs may increase (Harper 1996).
Impacts on Yield For reductions in input costs to ultimately benefit a farmer’s bottom line, savings must not be offset by
the cost of a possible decrease in yield. In general, research on corn yield impacts of conservation
agriculture in Iowa and nearby states suggests that no-till has the greatest negative, short-term impact
on yields, followed by cover crop use. Both may be able to produce similar, or even greater, yields to
conventional methods after a number of years. A properly managed third-crop rotation is not associated
with any yield decrease, but rather has the greatest potential to increase yields. A summary of findings
on the corn yield effects of the three practices in Iowa and surrounding states can be found in Table 4.
Some research suggests that, in Iowa, corn growers may experience some moderately reduced yields in
the first few years of cover crop adoption (Singer and Kohler 2005; Kaspar 2010). In properly managed
systems, yields can regain by about the third year: through a meta-analysis of 31 U.S. studies comparing
either corn or sorghum under leguminous cover crops to conventional systems, Tonitto, David, and
Drinkwater (2006) found, after two to three years, no significant difference in yield. An ongoing Iowa
study also found no significant change in corn yield following winter rye adoption by the third year, with
the lack of yield difference continuing into the fifth year (ILF and PFI 2014). Evidence from a nationwide
survey suggests that cover crops can even have a positive effect on yield—likely over a longer time
horizon—finding an average corn yield increase of 11 bushels per acre (CTIC and SARE 2013). This
supports the findings of a 2005 meta-analysis of 36 studies conducted throughout the U.S., which found
biculture (grass and legume) cover crops increased corn yields by an average of 21% (Miguez and Bollero
2005). Yield effects are very dependent on the type of cover crop as well as factors such as weather, soil
type, and management.
21
Table 4. Selected research on changes in corn yield following adoption of the practices
Study State Crop Species or Rotation
Length (years)
% Yield Decrease*
+
% Yield Increase*
+
Co
ver
Cro
ps
ILF and PFI 2014 IA Cereal rye 5 No significant difference
IDALS, IADNR, and ISU 20131,M
UMBR Rye NS 7
IDALS, IADNR, and ISU 20131,M
UMBR Oat 3 5
Sawyer, Pantoja, and Barker 2009
IA Winter rye 1 6
Singer and Kohler 2005 IA Cereal rye 3 No significant difference
Kaspar 2010 IA Winter rye, wheat, and triticale
3 6
Tonitto, David, and Drinkwater 2006
M
Varied Over-wintering non-legumes
2-3 No significant difference
Tonitto, David, and Drinkwater 2006
M
Varied Over-wintering legumes
2-3 10
Miguez and Bollero 2005M
Varied Grass + legume Varied 21
CTIC and SARE 2013 UMBR NS 1 10
Thir
d-C
rop
Ro
tati
on
s
IDALS, IADNR, and ISU 20131,M
UMBR At least 2 years of alfalfa in a 4 or 5 year
rotation
NS 7
Nafziger et al. 2013
IL S-W-C or W-S-C 15 30
Davis et al. 20122
IA C-S-SG + red clover or C-S-SG + A-A
8 4
Riedell et al. 2009 SD C-S-W + A-A 8 26
Smith, Gross, and Robertson 2008
MI C-S-WW + cover crops 3 100
Mallarino and Ortiz-Torres 2006
3 IA C-C-O-A 26 14
Mallarino and Ortiz-Torres 2006
3 IA C-C-O-A or C-0-A-A 10 14
Huggins, Randall, and Russelle 2001
MN CRP-C-C-S 8 14
Roth 1996 PA C-A-A 20 11
C-S
Ro
tati
on
Erickson 2008 IA C-S 25 14
Erickson 20084, M
Varied C-S Varied 9
Lauer, Porter, and Oplinger 1997
WI & MN
C-S 5
3
Re
du
ced
Till
age
IDALS, IADNR, and ISU 20131,M
UMBR NS Varied 6
Nafziger et al. 2013 IL C-C 15 10
Al-Kaisi and Oneal 2010 IA C-C 5 16
Hoorman et al. 2009 OH NS 5-7 10
Roth 1996 WI NS NS 8
Robertson et al. 2014 MI NS 23 4
Robertson et al. 2014 MI NS 1 21
Al-Kaisi and Oneal 2010 IA C-C 5 5
UNL CropWatch 20145 NE C-S 24 4 2
Harper 1996 PA NS 4 3
22
* Percentage indicates the largest difference expressed during the last year of the study. In some cases, studies reported data on different cultivars, rotations, regions, tillage and, nitrogen application rates. Refer to specific studies for details +As compared to conventional methods unless otherwise indicated
MMeta-analysis
1Averages based on a review of multiple studies
2Three-and four-year rotations with three or more crops as compared to a two-year corn-soybean rotation.
3Data in study collected from two separate sites, with separate data points
4Average calculated by Datu Research (SD = 8%)
5Fields were in no-till soybean-sorghum for 22 years and converted to corn-soybean in the last two years of the study.
Increases and decreases are a result of the multiple tillage methods studied
UMBR = One or more Upper Mississippi River Basin state (WI, MN, IL, IA, MO)
NS = Not specified C = Corn; W = Wheat; WW = Winter Wheat; S = Soybean; SG = Small Grain; A = Alfalfa; O = Oats; CRP = Conservation Reserve Program; C-C = Continuous Corn
Minimum or conservation tillage adoption in Iowa generally produces corn yields equivalent to
conventional tillage (Al-Kaisi and Oneal 2010). For no-till, yield may initially decrease in some cases, and
the time horizon for recovery appears somewhat longer than that of cover crops: a 2010 study across 32
sites in Iowa found clear reductions in corn yields on no-till plots, compared to both reduced and
conventional till, for the five-year duration of the study (Al-Kaisi and Oneal 2010). Data from Ohio
suggest that it can take five to seven years for yields to recover after converting to no-till from
conventional (Hoorman et al. 2009). In general, the best evidence that no-till can eventually increase
yields likely comes from the W.K. Kellogg Biological Research Station at Michigan State University, which
found that no-till corn yields were about 9% to 21% larger than conventional after 26 years (Robertson
et al. 2014), suggesting that the yield benefits of no-till may take a particularly long time to accrue.
Crop rotations, especially those involving three or more crops, were generally found to have a positive
effect on corn yields in the region around Iowa. A nationwide review of studies examining yield effects
of corn-soybean rotation, compared to corn-on-corn, found an average increase of 8%, with one Iowa
study showing an increase of 11% (Erickson 2008). However, new research on corn in Iowa suggests that
the conventional corn-soybean method may result in yield reductions over time due to depleted SOM
(Castellano, Hofmockel, and Rouse 2014). A number of studies documented the yield-increasing effects
of rotations with three or four crops; one Iowa study found that three- and four-year rotations involving
three crops were more productive and cost-effective than traditional corn-soybean rotations (Davis et
al. 2012).
Effects on Net Revenues Given that adoption can affect both input costs and yields, effect on net revenue is particularly difficult
to predict. Available data from Iowa and the surrounding region suggest that the effect on corn growers’
net revenues is extremely variable. Some key takeaways can be found in Table 5.
23
Table 5. Selected findings on effect of the practices on net revenues
Practice Effect on Net
Revenues
Detail Supporting Evidence
Cover Crops
Positive
Increases soil N and yields Stute and Posner 1995
Returns greater profit and profit stability compared to mono-cropping
Exner et al. 1999
Maintains a profit Hanson et al. 1993
Negative
Returns may be very dependent on species, rotations, and regions
Gibson et al. 2006
Lowers net profits when compared to conventional systems
IDALS, IADNR, and ISU 2013
Limits profits in cases where operation difficulties are present
Snapp et al. 2005
Third-Crop
Rotations
Positive
Returns higher yields with lower inputs, suggesting higher or comparable profits for rotations with three or more crops
Davis et al. 2012; Liebman et al. 2008; Karlen, Hurley, and Andrews 2006; Hanson, Lichtenberg, and Peters 1997
Negative Produces variable, and sometimes negative, profits and returns
IDALS, IADNR, and ISU 2013; ISU 2008
Reduced Tillage
Positive Saves resources Duffy 2012
Reduces costs Harper 1996; O’Connor 2013
Negative Returns may be limited by environmental and other constraints
Harper 1996
Mixed findings suggest that more tracking is needed on how the three practices affect farmers’ bottom
lines. Farmers should already be in the habit of tracking costs and revenues—a necessary part of any
business. Newer testing tools that capture more soil features, including microbial activity, can be added,
allowing farmers to fully assess the effect of different management practices. The Soil Renaissance, a
project of the not-for-profit Farm Foundation and the Samuel Roberts Noble Foundation, is actively
evaluating ways to incorporate soil health measures into standardized soil testing (Farm Foundation
2014).
Recent Research on Adoption Rates A number of recent surveys have examined adoption at the national or regional level. In particular, two
groups reported important new data on cover crops. The conservation group National Wildlife
Federation (NWF) estimated that in 2011, total cover crop acreage in the Mississippi River Basin was
between 1.8 and 4.3 million acres, less than 2% of total cropland area (Bryant, Stockwell, and White
2013). In their 2012 – 2013 Cover Crops Survey, promoters of sustainable agriculture research the
Conservation Technology Information Center (CTIC) and Sustainable Agriculture Research and Education
(SARE) found that first-time cover crop users had increased more than 120-fold since 2001 (CTIC and
24
SARE 2013).18 Together, these studies suggest that while cover crop adoption levels remain low, the
number of first-time users is growing across the country.
A similar trend is occurring in Iowa. Combined, acreage and farmer adoption estimates suggest that a
sizeable—and growing—minority of Iowa farmers is using cover crops, on a relatively small number of
acres. In 2010, Iowa State University (ISU)’s Iowa Farm and Rural Life Poll found just 12% of respondents
had planted cover crops within the previous five years (Arbuckle and Ferrell 2012). In contrast, the 2012
poll found a total of 28% of respondents who indicated either limited (18%), moderate (8%), or heavy
(2%) use of cover crops (Arbuckle and Rosman 2014). In terms of acreage, the 2012 Census of
Agriculture estimated that only 1% of total Iowa cropland was planted to a cover crop; those who used
cover crops did so on an average of 53 acres (USDA NASS 2012).
When a corn-soybean rotation is included, crop rotation is the most adopted practice in Iowa, with corn-
soybean the most common by far. To underscore just how common rotation is, the Iowa Farm and Rural
Life Poll found that 95% of respondents were using various crop rotations to some degree (Arbuckle and
Rosman 2014). In 2010, USDA’s Agricultural Resource Management Survey (ARMS) found that corn was
the previous crop on only about 30% of Iowa corn acres; in contrast, approximately 67% had been
planted to soybeans the previous year, indicating the prevalence of corn-soybean rotation (ERS 2013).
The same ARMS survey estimated that small grains, which can be used as third crops in a rotation, were
the previous crop on only about 0.1% of 2010 corn acres in Iowa, suggesting that rotations with greater
conservation benefit are much less common (ERS 2013).
Because of varying estimates and definitions, reduced tillage adoption is harder to assess. ARMS
estimated about 18% of Iowa corn acres are under no-till, while the census estimated this figure at 23%
for all commodity acres (ERS 2013; USDA NASS 2012). Although a portion of the difference may be
explained by the observation that ARMS data are just for corn acres while the census figures include all
acres, differing practice definitions used by the agencies that oversee the surveys, USDA’s Economic
Research Service (ERS) and National Agricultural Statistics Service (NASS), likely played a role. We were
unable to compare other types of reduced tillage because the sub-categories differed between surveys.
Datu Survey In June 2014, Datu surveyed corn growers and landowners in Iowa about their use of conservation
agriculture practices. Datu survey findings reaffirm several key trends in adoption and help fill in gaps
created by a lack of definitional clarity. Figure 3 illustrates key characteristics of survey respondents.
18
Statistical sampling methods were not used for this opt-in survey. Results should be interpreted with caution.
25
Figure 3. Characteristics of Datu survey respondents
Note: N=212, MoE = +/- 6.72%
Source: Datu survey
Figure 4 shows the resulting adoption rates for each practice. Our cover crop findings are in line with
national trends, and may suggest that more Iowa farmers are trying them out before committing to
adoption on a larger scale. A sizeable minority (23%) of respondents were using cover crops.
Respondents tended to grow cover crops on a relatively small number of acres, with the majority of
users growing them on less than 100 acres (see Figure 5).
The Datu survey further indicated that most respondents were testing their soil frequently for a limited
number of components. More than half (59%) reported testing one or more field every one, two, or
three years. Another 29% tested every four or more years. Only 3% indicated they never performed soil
testing. Testing for phosphorus, potassium, minor nutrients like zinc, pH, and percent organic matter
was most common, reported by 69% of respondents.19 More specialized soil tests were less common,
with only 19% using testing that assesses one or more of the following: microbial respiration, nitrate,
cation exchange capacity, soil organic carbon and nitrogen, or water-extractable organic carbon and
nitrogen.20 At least 49% of respondents were “very interested” in getting additional information,
including a soil health score, from their soil tests. More respondents consulted their fertilizer retailer
(52%) for interpretation of soil test results than an independent, paid consultant (32%).21
19
This finding (69%) is based on a slightly reduced sample size (N= 204) with MoE = +/- 6.85%. 20
This finding (19%) is based on a slightly reduced sample size (N= 204) with MoE = +/- 6.85%. The Solvita CO2-Burst ppm, PLFA, or FAME tests can be used to assess microbial respiration levels. “Soil organic carbon and nitrogen” refers to the reserve of nitrogen and carbon present in soil organic matter, whereas traditional testing measures consider the inorganic components. “Water-extractable” refers to the testing methodology used to analyze the levels of soil organic carbon and nitrogen. 21
These findings (52%, 32%) are based on a slightly reduced sample size (N= 205) with MoE = +/- 6.85%.
26
Figure 4. Adoption of the practices by percent of respondents
Note:“Don’tknow”andunansweredresponsesincludedincalculations,butnotdisplayed;N=212,MoE=+/- 6.72%
Source: Datu survey
Figure 5. Cover crop acreage by percent of respondents
Note:“Don’tknow”andunansweredresponsesincludedincalculations,butnotdisplayed;N=212,MoE=+/- 6.72%
Source: Datu survey
42%
9% 8% 6%
1%
0 acres 0.5-50 acres 51-99 acres 100-249 acres 250-499 acres
27
To increase conservation agriculture adoption, farmers need a market mechanism that brings the long-
term economic gains forward to cover the short-term costs. Building on the work of Ceres and others,
the following sections examine the potential to tap two entities within farmers’ existing business
relationships to incentivize adoption of conservation agriculture practices: landowners and crop
insurers. Figure 6 situates these two entities within the Iowa corn value chain.
Figure 6. Land rental and crop insurance segments in the Iowa corn value chain
Sources: Barton and Clark 2014; Lowe and Gereffi 2008
Could Landowners Incentivize Farmers to Adopt? More than half (55%) of farmland in Iowa is rented (Duffy and Johanns 2012). This means that in most
cases, land management decisions do not just affect operators, but also non-operating landowners.
Conservation agriculture has been demonstrated to have a positive effect on farmland, but is the effect
of these practices sufficiently great to entice landlords to pay tenants to adopt them? In other words, do
landowners stand to gain from adoption enough that they are willing to help farmers cover the short-
term costs?
Conservation agriculture does have a positive effect on farmland: it maintains or improves the quality
and health of soil compared to conventional practices, protecting a landowner’s asset from
28
deterioration.22 Soil quality is a measure of soil’s ability to function as a life-supporting ecosystem. Soil
health refers to the vitality and diversity of organisms in the soil. High-quality, healthy soil can support
crop production in several important ways, including by promoting root development, increasing the
nutrient pool, increasing beneficial biota, and decreasing pest and weed pressure (Al-Kaisi 2014; Lal
2012; Bot and Benites 2005; Lal, Kimble, and Follet 1998).
Yet soil quality in itself does not bring economic reward to a landowner; 23 it is not one of the factors
that fetch a higher price for land.24 As Figure 7 illustrates, most variables that determine farmland value
in Iowa are either structural, and thus cannot be improved through conservation agriculture, or cannot
be upgraded for other reasons (e.g. CSR2 components).
Figure 7. Variables considered in Iowa agricultural land valuation
Source: Iowa Department of Revenue 2008b
22
Another way to approach the question of landowner self-interest would be to ask whether and how much an owner stands to lose by failing to incentivize adoption. Dr. Richard Cruse of ISU and others have conducted preliminary work quantifying the productivity loss associated with erosion, which could translate into lost value for a landowner in the future (Cruse 2005). 23
The purpose of this analysis was to identify economic incentives, yet we recognize that there are non-economic benefits associated with conservation agriculture that accrue to landowners, tenants, and society that may play a role in adoption. 24
Trends in Iowa farmland value and cash rental rates appear to be closely linked, rising and falling nearly in tandem. See Edwards and Johanns 2014a and Duffy 2014.
29
The Corn Suitability Rating (CSR2) is a tool created by ISU for use in land appraisal. It rates potential row
crop productivity on a scale of 5 to 100 points (100 being the most ideal) based on soil type, slope, and
erosion class. Soil type and slope are static variables and cannot be upgraded. Although conservation
agriculture practices do reduce erosion, there is no mechanism through which these improvements can
be reflected in erosion class—a factor in land valuation. This is because erosion classes are based on
USGS soil survey maps, which are typically updated only every 30 to 40 years; interviews suggest USGS
has no current plans to remap them. Changes in erosion levels are thus unlikely to improve land value.
Yields are the only factor used in land valuation that conservation agriculture can have an effect on. To
date, the link between improved Iowa corn yields and two of the three practices—cover crops and
reduced tillage—is unclear.25 As our literature review demonstrated, these practices may actually
decrease yields in the short-term. It can take years for yields to return to previous levels, and the
potential to increase yields over a longer time span is uncertain. Without firm evidence that cover crops
and reduced tillage increase yields, it is difficult to prove that they improve land value. Thus, monetary
land value is not a reward for increased adoption and cannot be used as a selling point for landowners.
Future Potential of Crop Share and Custom Leases Are there other ways to reward landowners in the short term? Savings on inputs can benefit
landowners, but only under certain types of lease arrangements. Table 6 illustrates the most common
types of rental arrangements in Iowa. In fixed and flexible cash arrangements, the tenant is responsible
for supplying all inputs. By contrast, under crop share and custom farming, the landowner must supply a
portion or all of the inputs, potentially increasing landowner interest in conservation agriculture
adoption.
Table 6. Types of land rental arrangements
Rental Arrangement
Description
Fixed Cash Rent
Land is leased to a tenant for a fixed cash payment. Tenant purchases all inputs, has all management responsibilities, and is full owner of the crop
Flexible Cash Rent – Cash Plus
Rental rate finalized after crop harvest, based on actual prices and/or yield for that year. Owner share typically based on gross revenue, unless the base rent includes a consideration of the tenant’s cost of production
Crop Share Landowner contributes half of the costs of inputs and then receives half of the crop. This 50-50 division is a common permutation in Iowa
Custom Operator supplies all labor and equipment, receiving a fixed payment per acre or for each operation. Landowner pays all other expenses and receives all of crop revenue
Sources: Edwards 2014; Edwards and Johanns 2014; Leibold 2013
Over the past 20 years, the percent of land under crop share and custom leases in Iowa has been
decreasing; currently, these arrangements make up less than 14% of leases (see Figure 8). This shift has
25
As our literature review indicated, crop rotations are demonstrated to improve yields. Since a corn-soybean rotation has already been adopted by the vast majority (67% – 95%) of Iowa farmers, other practices may be a more effective focus of further attention. Challenges of third-crop rotations will be addressed in the next section.
30
corresponded to demographic changes among Iowa landowners, who are generally older and more
distanced from the land than they used to be (Duffy and Johanns 2012). In general, these changes mean
that landowners are less able to be involved in day-to-day farm operations, contributing to the trend
toward cash rent instead of crop share and custom leases, which require more involvement on the part
of the landowner.
Figure 8. Distribution of Iowa farmland by tenure
Source: Duffy and Johanns 2012
In order for use of these lease types to grow, both tenants and landowners need to know more about
them. Farmland management companies (FMCs)—who act as brokers between landowners and tenants,
representing owners’ interests—currently provide some lease negotiation services and education. One
FMC told us these services make up approximately 10% of their land management business, and several
mentioned landlords had asked them to serve as arbiters for lease negotiations. Between 2007 and
2012, use of FMCs in Iowa more than doubled from 5% to 11%; if use of FMCs continues to increase,
they could play an increasingly important role in educating landowners about crop share and custom
leases (Duffy, Edwards, and Johanns 2013).
Could Crop Insurers Incentivize Farmers to Adopt? Federal crop insurance is a critical component of the U.S. farming system, allowing producers to
affordably manage risk and withstand declines in yield and changes in price. It is also a multi-billion
dollar industry, with approved insurance providers (AIPs) taking in over $11.8 billion in total premiums26
and paying out over $12 billion in indemnities nationally for the 2013 crop year (FCIC 2014a).
26
“Total premiums” include both the portion paid by the producer and the federal subsidy (Carter 2014).
55%
50%
41%
40%
40%
21%
27%
40%
46%
46%
21%
22%
18%
13%
13%
1%
1%
1%
1%
1%
0% 20% 40% 60% 80% 100%
1982
1992
2002
2007
2012
Owner-operated
Cash rent lease
Crop share lease
Other type of lease
31
Most (85%) Iowa corn producers carry some type of federal crop insurance (ERS 2013). The program’s
popularity is explained, in part, by the government’s role in keeping premiums affordable: in 2013,
federal subsidies averaged 62% of premiums, nationally (Shields 2013). The most common type of
federally-subsidized farm insurance, Multiple Peril Crop Insurance (MPCI), provides coverage for most
natural threats, including drought and excessive moisture.
The private crop insurance market provides coverage for exposure to additional, localized weather
events like wind and hail. Because conservation agriculture has no bearing on how well crops withstand
these specific weather events, this inquiry focuses on the federal insurance market.
In theory, companies that sell crop insurance should be interested in reducing their risk of making a
payment on a claim, referred to as an “indemnity.” Crop insurers can reduce their exposure by
rewarding customers who use risk-reducing practices.27 In the automobile insurance industry,
companies often reward customers who file fewer claims with a “safe driver discount” on their premium
rate. In principle, crop insurance companies might want to provide a similar reduction for farmers whose
management practices result in fewer indemnities—a “good producer discount.”28 In its 2013 issue
paper Soil Matters, the Natural Resources Defense Council (NRDC) called for such a discount as a way for
federal crop insurance to manage weather-related risks (O’Connor 2013a).
Indemnities are important to insurance companies because of their role in determining loss ratios. To
determine the loss ratio for an insurance product over a certain period, simply divide indemnities by
premiums. In order to break even, insurers need loss ratios to equal 1.0 over the long run, indicating
that costs of indemnities are fully covered by premiums.29 To build a surplus for insurance companies
that can be used to pay claims in large loss years, the Risk Management Agency (RMA), which oversees
federal crop insurance, aims for a loss ratio of 0.88 when it sets rates (according to interviews with
former and current RMA officials).
To maintain a favorable average loss ratio, in general insurers can seek to either increase premiums or
reduce indemnities. Between 1989 and 2013, average loss ratios for Iowa corn policies spiked above 1.0
four times; three of the four spikes occurred in the last six years (see Figure 9). Premiums have been
increasing at an unprecedented rate: as Figure 9 illustrates, although they decreased in 2014, gross
premiums on Iowa corn policies nearly tripled between 2006 and 2013. If spikes in indemnities like
those witnessed in 2008, 2012, and 2013 continue to occur with the frequency witnessed since 2007, it
27
One way crop insurers are already protected from risk is via the requirement that producers use “good farming practices.” Producers are required to follow practices that would achieve the insurance guarantee but for the effects of an insured peril. If a producer does not use good farming practices, an insurer may deny the claim (RMA 2011). 28
According to interviews, the Federal Crop Insurance Corporation (FCIC) considered the “good producer discount” idea in the mid-2000s and again around 2011—rejecting it both times. FCIC also considers the term “good producer discount” as inappropriate, using instead “good experience discount.” For clarity of concept, we use the term good producer discount, recognizing that this is not the term FCIC uses. 29
According to interviews, insurers cede about 20% of premium every year to FCIC. They need a loss ratio of 1.0 on the 80% of premium that they retain. Retained loss ratio data for Iowa corn policies are not publicly available.
32
is possible that premium increases may eventually be insufficient to maintain loss ratios at or below 1.0.
Under these conditions, it makes sense to examine ways to reduce indemnities.
Figure 9. Changes in gross premiums and indemnities for Iowa corn policies
Note: 2014 indemnity data not shown because complete data were not yet available
Source: FCIC 2014d
Severe weather is a significant source of indemnities. In 2013, AIPs paid out $1.8 billion in indemnities
on Iowa corn policies caused by drought, flood, or excessive moisture (RMA 2013). This is about 70% of
the total indemnities paid on Iowa corn polices that year (RMA 2013; FCIC 2014a). In theory, farmers
using practices that reduce the risk of crop loss in drought or excessive moisture conditions would be
good candidates for a good producer discount.
There is some evidence that conservation agriculture may benefit yield stability by increasing crop
resilience in drought, flood, and excessive soil moisture conditions. A small number of studies have
shown cover crops improve corn and soybean yields in drought years (Gallaher 1977; CTIC and SARE
2013). One study found that water use efficiency was 21% greater for soybeans in a corn-soybean-alfalfa
rotation as compared to a corn-corn (Huggins, Randall, and Russelle 2001). Reduced till practices have
been shown to decrease soil compaction, which promotes favorable water retention and mitigates
pooling, and increase stability of SOM, which helps wet soils drain (Al-Kaisi and Oneal 2010). Table 7
summarizes some of the key research on crop resilience effects of conservation agriculture.
Ultimately, the data currently available are likely insufficient to build an actuarially-sound case for a
good producer discount. Based on our experience reviewing studies on corn in Iowa, the amount of
research on conservation agriculture’s effect on yield and yield stability appears quite small. Without
more research—encompassing a wide variety of crops, geographies, and climates—the link between the
three practices and reduction in insurers’ risk is difficult to prove.
$
$200M
$400M
$600M
$800M
$1000M
$1200M
$1400M
$1600M
$1800M
$2000M
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
Gross Premiums Indemnities
Loss Ratio > 1
33
Table 7. Selected research on effect of the practices on drought and excess soil moisture mitigation
Practice Study Results
Cover Crops Gallaher 1977 Leaving rye mulch resulted in 46% higher yields after 3
periods of moisture stress
CTIC and SARE 2013 Yields were 10% higher during a drought year
Third-Crop Rotations
Huggins, Randall, and Russelle 2001
Water use efficiency was 21% greater for soybeans in a corn-soybean-alfalfa rotation as compared to a corn-corn
Reduced Tillage
Robertson et al. 2014 Soybean yields were almost 50% higher during the 2012 drought
Sauer, Hatfield, and Prueger 1996
Soil water evaporation reduced by 34% to 50%
Steiner 1994 Detailed review concluded that crop residues increase water infiltration and decrease evaporation
Yet even if there were stronger evidence that conservation agriculture reduces insurers’ risk, AIPs’
relationship with the federal government would still limit their sensitivity to risk (see Figure 10). AIPs are
private companies that signed an agreement to sell federally-backed crop insurance. One process that
limits AIPs’ risk is “fund designation,” in which AIPs can place policies into one of two buckets, or
“funds.” The government then takes responsibility for up to 100% of losses (or gains) from policies
designated to a fund (Shields 2013). The exact percent is determined by the loss ratio for each company,
and for each state, for the fund selected; the government retains a smaller share of losses (or gains) for
policies in the “Commercial Fund” and a larger share of those in the “Assigned Risk Fund.” Seeking to
minimize losses and maximize gains, AIPs told us they generally try to place policies on which they
expect to take a loss in the Assigned Risk Fund and those that are “safer bets” in the Commercial Fund.
Companies place 100% of their policies in either the Commercial Fund or the Assigned Risk Fund; if they
fail to designate a policy, the Federal Crop Insurance Board (FCIC) automatically places it in the
Commercial Fund (FCIC 2014b).
AIPs and the government also share risk via a redistributive mechanism involving “net book quota
share,” or the portion of a company’s net book of business, equal to 6.5% of overall gains or losses, that
must be ceded to the government annually (Shields 2013). In effect, when an AIP experiences a net loss,
the government absorbs 6.5% of it. When an AIP experiences net gains, the government keeps 5% and
the other 1.5% is redistributed to AIPs operating in 17 “underserved” states,30 providing companies a
greater incentive to sell in states that are characterized by low premium and profitability (Shields 2013).
Net book quota share provides an additional mechanism through which the federal government buffers
some AIP risk.
30
There are 17 “underserved” states: Alaska, Connecticut, Delaware, Hawaii, Maine, Maryland, Massachusetts, Nevada, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Utah, Vermont, West Virginia, and Wyoming (FCIC 2014b).
34
In addition to formal risk-sharing arrangements, AIPs also receive a payment to cover a portion of the
costs associated with selling and servicing policies, called the Administrative and Operating (A&O)
subsidy (FCIC 2014b). Payments may total up to $1.37 billion for the 2015 insurance year (Shields 2013).
The point of the payment, which FCIC makes “on behalf of policyholders,” is to pass on reduced costs to
producers in the form of lower premiums (FCIC 2014b). In practice, the combination of A&O subsidy and
underwriting gains also produces sizeable returns for AIPs (Goodwin and Smith 2013). By increasing AIP
profits, the subsidy provides insurers with an additional buffer against risk. Figure 10 illustrates the
nuanced relationship between AIPs and the federal government.
Figure 10. Risk mitigation mechanisms between the federal government and AIPs
Sources: FCIC 2014b; Shields 2013
AIPs also lack the means to incentivize risk-reducing practices. Not only are AIPs unable to market plans
of insurance that have not been approved by RMA, they are generally prohibited from offering
discounted rates for existing plans (FCIC 2014b). It is the federal government, not AIPs, that determines
which policies the company is able to sell, to which producers, and at what rate. Even if they would
prefer to, AIPs are not allowed to compete via federally reinsured MPCI.
Changing the incentives AIPs face and their abilities to offer innovative policies would require an
overhaul of federal policy. Such an overhaul is unlikely to occur, and may not even be desirable, because
of the unique nature of agricultural insurance. Risks that are relevant to agriculture tend to be
35
systemic—they affect the entire market or market segment. For example, drought and excessive
moisture often create yield losses across wide areas (Barnett and Coble 1999). The private insurance
market generally views systemic risks as uninsurable, or insurable only at an exorbitant rate (Barnett
and Coble 1999). This helps explain why there is a strong private market to cover localized weather
events like hail and wind, and not for multiple peril insurance, which covers large-scale weather events.
Some have argued that government involvement is needed to keep insurance rates affordable when
systemic risks are present (Miranda and Glauber 1997).
Using 508(h) to Make Incremental Change, and Selecting a Practice Though a complete federal overhaul is unlikely, incremental change to reward conservation agriculture
adoption is possible. Section 508(h) of the Federal Crop Insurance Act provides a mechanism for
introducing new crop insurance policies, provisions of policies, and rates of premium (75th U.S. Congress
1938).31 It allows an entity, “including an approved insurance provider, a college or university, a
cooperative or trade association, or any other person,” to propose other crop insurance policies and
rates to the FCIC Board (75th U.S. Congress 1938). Advocates can propose a pilot program under 508(h)
to provide a premium discount on MPCI policies for farmers using one or more conservation agriculture
practice.32, 33
There are two key precedents for using the 508(h) mechanism to provide a premium rate reduction
based on adoption of a technology or practice. In 2008, Monsanto acted as a co-submitter for the
Biotech Yield Endorsement (BYE) pilot program. The FCIC Board approved a premium rate reduction for
farmers using Monsanto’s biotech seeds,34 concluding the seeds lowered “yield risk” (RMA 2010). In
2003, the Nutrient Best Management Practices (N-BMP) Endorsement pilot reduced rates for farmers
who applied only a recommended level of nitrogen and phosphorus (RMA 2003). In contrast to the BYE
pilot, which was expected to stabilize or even increase yields, the purpose of the N-BMP pilot was to
protect farmers from a possible yield decrease.
These two pilots show that the process is expensive. According to one former FCIC board member who
was involved in the BYE approval process, “the bar for getting a premium rate reduction for a production
practice is extraordinarily high.” Interview and RMA data indicate that the BYE pilot was approved only
after Monsanto provided years of data, including some 15,000 side-by-side field trials encompassing a
31
Sections 522(b) and 523(d) also provide avenues to propose changes within in the existing crop insurance structure. Section 522(b) allows for “reimbursement of reasonable research and development costs” of policy concepts developed under 508(h); section 523(d) is specifically intended for pilots that reduce rates of premium on existing policies (75th U.S. Congress 1938). Pilots may be initially submitted under 508(h) and approved under one of the other sections, as was the case with the Biotech Yield Endorsement, approved under 523(d) (RMA 2010). 32
For more details on how the 508(h) process can be used to support conservation, see the NRDC’s issue paper Soil Matters (O’Connor 2013a). 33
There is another existing mechanism within crop insurance to reward farmers for adopting risk-reducing practices. A farmer’s Actual Production History (APH) is his or her average historical yield, based on a 10-year history, that determines the insured value of a crop. If a farmer takes action that increases the crop APH, i.e. by reducing losses, the crop’s insured value increases and the farmer’s premium rate for the crop decreases (Coble et al. 2010). 34
An interview with an RMA official indicated the discount also applied to DuPont Pioneer, Syngenta, and Dow stacked, traited hybrids.
36
wide variety of geographies and climates, thousands of pages of documentation, and expert testimony
from university professors showing lower yield risk for farmers using their biotech seeds (RMA 2010).35
Our interviews suggest that solidly demonstrating effects of a production practice on total yield or yield
stability is essential. Such research is costly in time and money.
In the case of N-BMP, interviews indicate that determining whether a producer had applied the practice
correctly proved complex, leading to a costly process of developing and implementing guidelines for
producers and claims adjusters, who determine whether to make payment on a claim. The greater the
potential variability in how a practice is implemented, the more difficult (and costly) it becomes to
identify the practice, monitor, and loss adjust it.36 These costs can be minimized to the extent that
developers of a conservation agriculture-based 508(h) product have options for reducing their costs.
Section 522(b) of the Federal Crop Insurance Act allows for partial reimbursement, in advance, of the
costs of developing a new insurance product (75th U.S. Congress 1938). To receive this funding, 508(h)
developers need enough initial data to convince the FCIC board that the case for a conservation
agriculture-based product is compelling, but do not need to have calculated details of the proposed
policy, such as the actuarially fair rate, at the outset (according to interviews).
Another way to reduce costs is to make more efficient use of existing data. Food and agricultural policy
group AGree is currently leading a first-step effort to more clearly document conservation agriculture’s
effects on yields and yield variability. The AGree-led Conservation and Crop Insurance Task Force (CCITF)
is working to encourage and support a USDA-led effort to integrate and analyze existing data at different
government agencies on conservation practices, yield, variability, soil health, and other key topics. This
effort may help reduce the costs of gathering the data needed for a new product to win approval via
508(h), though it is likely that funding for new research, and in particular side-by-side field trials, will still
be necessary.
Before selecting a conservation agriculture practice or practices to include in a 508(h) proposal,
advocates need to better understand the potential market for each practice. The N-BMP pilot illustrated
the importance of knowing the market: despite the product’s availability across four states, only three
policies were sold in the first year (RMA 2003). An RMA employee indicated that one policy was sold in
the second year, and that the pilot was not continued for a third year. The “market” for conservation
agriculture practices is the body of farmers who might adopt.
Examining current adoption is key to assessing the market size for each conservation agriculture
practice. Our survey found the least used practices are strip till (4%), a corn-soybean-third crop rotation
35
According to interviews, the BYE was eventually discontinued because adoption was sufficiently widespread that there was no longer any basis for offering a special discount to adopters. This is because the current premium rating method is based on a county’s weighted average historical losses over a 20-year period. As more producers adopt a risk-reducing practice, the practice will eventually be reflected in county losses, and the general premium rate will reflect the change in risks. This means that a premium rate reduction achieved via 508(h) may be temporary. 36
According to interviews, the practice must also be able to be rated for the various plans of insurance, which adds expense. The expense can be lessened to the extent the agronomic research on the practice is thorough.
37
(19%), long-term no-till (21%), and cover crops (23%).37 Because adoption rates are currently low, the
size of the market for these four practices should be relatively large, compared to the other practices.
Understanding the reasons for low adoption rates can shed light on the market potential for each
practice. More research is needed to fully assess market potential, but we can offer a few insights here.
For cover crops, the challenges interviewees mentioned were primarily related to a lack of inputs and
confusing regulation. These problems are solvable. If there is sufficient demand for cover crop seeds,
companies may be willing to step in to provide them. The adoption data included in this analysis suggest
that cover crop use may be on the rise, which would suggest that demand for seeds is growing. NRCS,
the Farm Service Agency, and RMA recently streamlined regulations around cover crop use and crop
insurance, and these changes may eventually lessen producers’ concerns (NRCS 2013a). Although a
short planting window was also cited as a primary challenge, there is a market-based solution here:
producers can pay a bit more for aerial seeding by a custom operator, extending the cover crop planting
window. Seed companies may also be able to play a role in developing faster-growing cover crop
varieties.
A primary concern about rotations with three or more crops that farmers cited was the lack of a market
(i.e., lack of demand). A farmer cannot add a third crop like alfalfa (for hay) for the soil quality benefits
alone—he or she needs a buyer who will pay a remunerative price for the crop. Corn and soybeans are
the dominant crops grown in Iowa, accounting for 78% of total crop acres (USDA NASS 2014). Hay was
once a major crop in Iowa, but now that livestock are primarily corn fed, interviewees told us the hay
market has largely disappeared. Without a market for third crops, adoption is unlikely to increase. 38, 39
The practice selected should also have a relatively small margin for operator error. One way to reduce
operator error is to select a practice with which farmers are already somewhat familiar. Looking just at
the practices from our survey with the lowest adoption rates, respondents indicated having the most
experience with corn-soybean-third-crop rotations (26%), long-term no-till (25%), and cover crops (18%)
(highlighted in orange in Table 8).
Based on this preliminary investigation into market potential, cover crops seem to be worthy targets of
further research. Adoption of cover crops remains low, but there is growing interest in the practice and
barriers to adoption are not insurmountable. Survey respondents expressed some familiarity with using
them, and proficiency could be improved with more training.
37
Extended corn-soybean rotation, which involves several years of corn-on-corn, was not considered a conservation practice. See note 1. 38
A representative from an Iowa farmer industry association also noted that because a corn-soybean is so common, there is social pressure against growing third crops, and farmers often lack the equipment required for hay production, including mowers, rakes, and balers. 39
Interviewees were not asked about challenges specific to long-term no-till adoption.
38
Table 8. Experience with the practices by percent of respondents
Note: N=212, MoE = +/- 6.72 %
Source: Datu survey
This initial data may be useful to advocates currently testing the waters of a conservation-focused pilot
program via 508(h). AGree and the CCITF are presently exploring crop insurance-based opportunities
and may eventually identify one or more conservation practices to drive through the 508(h) process. To
this effect, the group continues to convene meetings between AIPs, academia, and industry to assess
the potential of a possible 508(h) effort and, more broadly, how a data integration and analysis effort
could lead to changes in the crop insurance program.40 The group identified at least one AIP that has
expressed interest in keeping the idea on the minds of other insurance companies, recommending a
wait-and-see stance at least until new programs in the 2014 farm bill have been implemented, freeing
up some USDA bandwidth.
NRDC is also actively looking for partnerships for starting a 508(h) process. The environmental advocacy
group is growing their food and agriculture work, including encouraging improved soil health via section
508(h). They have discussed their proposal with actuaries who have prepared submissions for past
508(h) products and are moving forward on the development of a new product.
Smaller Opportunities: Prevented Planting Payments and Whole Farm
Revenue Protection Two smaller opportunities within crop insurance are worth watching to determine their potential to
incentivize adoption: prevented planting payments and Whole-Farm Revenue Protection.
40
This same data may also help inform industry agricultural sustainability standards (i.e., supply chain sustainability standards) and support emerging markets for ecosystem services.
39
Prevented planting payments (PPP) may encourage producers to use cover crops for the first time.
Prevented planting is a failure to plant an insured crop by the final planting date, or during the late
planting period, due to an insured cause of loss that is general to the surrounding area (RMA 2014). A
good example of an insured cause of loss is sustained rainfall that affects a large area. Farmers claiming
prevented planting will typically receive a payment of 60% of the production guarantee under their
revenue protection or yield protection policies, which represented 98% of policies sold to Iowa corn
farmers in 2013 (FCIC 2014c; RMA 2014).
Cover crops become more attractive as an alternative when farmers are prevented from planting their
primary crop. For most farmers faced with a prevented planting decision, the essential choice is
between leaving the soil fallow or planting a cover crop. Leaving the soil fallow, or black, can be more
expensive. Black soil is exposed to what some growers refer to as “fallow syndrome,” a loss of micro-
organisms due to a deficiency of the plant-exuded sugars that feed them. Our interviews with
agronomists indicated that micro-organisms like mycorrhizae, symbiotic fungi that colonize the roots of
plants, support crop growth in a number of important ways, including by helping plants use phosphorus.
If these fungi populations die under black soil because they are unable to get enough plant sugars to
“eat,” they may be slow to repopulate the following year, and crops may not get the phosphorus they
need. Other costly problems of black soil include erosion and weeds, which, depending on whether
herbicide had been applied prior to the prevented planting conditions, may create management
problems that are costly in time and labor to deal with.
While there is a cost to planting cover crops—roughly $40 acre, depending on the type of cover crop
and planting or seeding method—the cost of cover crops can be balanced by soil benefits, again
depending on the type of cover selected and the farm (IDALS, IADNR, and ISU 2013). In this way, not
using cover crops on prevented planting acres can be seen as a missed opportunity. A majority of Datu
survey respondents felt that cover crops make economic sense in a prevented planting situation, with
67% agreeing with this statement. In addition, 66% of those that received a prevented planting payment
had planted cover crops on their prevented planting acres.41
PPP can serve as a jumping off point that spurs producers to use cover crops consistently. Acreage
affected by prevented planting is relatively small—just 726,951 acres were affected in Iowa in 2013, of
which 619,806 were corn acres (FSA 2014). It is important that farmers using cover crops under
prevented planting have a positive first experience so the practice can spread. Tools like the Midwest
Cover Crops Council’s Cover Crop Decision Tool can help producers select a cover crop that is right for
their farm (MCCC 2014). Dr. Rick Haney, creator of the Haney Test, noted that his test can also provide a
cover crop recommendation.
Another opportunity advocates should monitor is Whole-Farm Revenue Protection (WFRP). WFRP is a
new insurance pilot program required by the 2014 farm bill, which will launch by 2015 in most states,
including Iowa (FCIC 2014c). WFRP will allow producers to insure the entire value of their operation
under a single policy instead of insuring each commodity separately (USDA 2014).
41
Because only a subset of our sample had received PPP (N=32), the margin of error for this finding (66%) is +/-17.32%, higher than that for most of our survey findings (+/- 6.72%).
40
Of possible significance for advocates is the premium subsidy WFRP will provide for farmers producing
at least two different commodities on one farm (NSAC 2014; Shea 2014). WFRP has some potential to
incentivize crop rotation by rewarding producers who grow more than one type of crop. For farmers
presently growing just corn, for example, the subsidy could entice them to add soybeans, provided it is
significant enough. Once farmers are growing multiple crops on a single farm in the same year, it is a
simple and natural next step to begin rotating those acres to capture associated yield benefits (see Table
4 above).
WRFP may have the greatest potential to increase adoption of third-crop rotations. As adoption surveys
including our own have noted, a corn-soybean rotation is already very common in Iowa (Arbuckle and
Rosman 2014). Rotations involving at least three crops are less common. Whether WFRP is able to help
farmers overcome the previously-mentioned challenges with third-crop adoption will be determined by
the amount of subsidy and whether it increases as additional crops are added. Although the full details
of the subsidy had not been released as of this writing, our interviews with agricultural insurance
experts suggest it would be logical from an insurance standpoint to increase the subsidy as the number
of crops grown increases (up to a point). Full policy details were expected by late 2014.
Other Possibilities in the Value Chain Interviews with farmers, landowners, academics, and industry representatives revealed two additional
possibilities within the Iowa corn value chain that could potentially be used to incentivize conservation
agriculture adoption (see Figure 11). The following possible opportunities could be examined further for
their potential to encourage adoption.
41
Figure 11. Other potential opportunities to incentivize the practices in the Iowa corn value chain
Sources: Barton and Clark 2014; Lowe and Gereffi 2008; Datu industry interviews
Seed Corn Providers Major seed companies such as Monsanto, DuPont Pioneer, and Syngenta contract with farmers in Iowa
to grow hybrid corn seeds on their land. Our interviews suggest seed corn operations may be
particularly vulnerable to compaction. To combat this compaction and help farmers take advantage of
nutrient- and soil organic matter (SOM)-building benefits, seed companies may want to encourage the
farmers who grow their products to use cover crops.
Seed corn acres may be more prone to compaction than other corn acres because of the increased
number of passes large equipment must make. Industry interviews indicate that after male inbred rows
have pollinated the female inbreds, the male rows are destroyed to prevent seed contamination. The
females are harvested after the ears have matured. The need to manage and harvest male and female
rows separately increases the number of equipment passes required compared to other corn acres.
Cover crops, particularly those with very deep roots like oilseed radish, may be able to mitigate
compaction while providing ground cover for erosion protection (NRCS 2010b). Interviews with farmers
and seed companies suggest that producers often view these companies as trusted advisors. Companies
42
may therefore be motivated to recommend practices like using cover crops, which may help mitigate
the possible side effects of growing seed, in order to maintain their good reputation with farmers.
Seed corn growers may even find it easier to plant cover crops than other Iowa corn growers. A
commonly voiced challenge associated with growing cover crops in Iowa is the narrow planting window.
Interviews suggest that Iowa’s harsh winters and cool, wet soils can make it difficult to get a cover crop
planted and established after harvest and before frost. Seed corn may alleviate this problem because,
depending on the specific hybrid, it may be harvested earlier, extending the cover crop planting window.
Seed corn is grown on a relatively small number of Iowa acres, but endorsement of a practice by a seed
company may influence farmers far beyond the actual seed corn acres. Out of 13,348,307 total Iowa
acres planted to corn in 2013, Iowa farmers reported planting just 237,503 acres of yellow seed corn
(FSA 2014). While not everyone can grow seed corn and companies are often very selective about
growers, if seed companies embrace cover crops, this would be a notable signal to farmers that the
practice is sound and would likely influence more farmers to try it.
Our interviews suggest that seed corn companies are beginning to explore the benefits that cover crops
can provide. DuPont Pioneer has started two projects with Practical Farmers of Iowa to investigate use
of cover crops on the company’s seed corn plots,42 and even paid for most of the seed needed for
farmers to test out cover crops. To investigate this potential opportunity, further research will need to
glean more about the unique challenges of seed corn operations, the nature and content of seed corn
contracts, and how to incentivize conservation agriculture practices in a contract.
Cellulosic Ethanol Producers Residue removal for cellulosic ethanol production can heighten risks of erosion, nutrient loss, and soil
degradation if carried out at unsustainable rates. Practices such as cover crop use can help farmers
remove more residue sustainably. The cellulosic ethanol industry may be willing to incentivize the
practice to increase the amount of residue they can sustainably harvest.
Cellulosic corn ethanol is fuel made from corn stover as opposed to the starch from corn kernels, which
is used to make standard corn ethanol. Corn stover consists of the aboveground corn plant material,
excluding grain: the stalks, leaves, shuck, silk, tassel, and cobs that remain after harvest (Arora, Licht,
and Leibold 2014).
Although stover removal offers some benefits—including promoting warming of the soil for planting,43
reducing the need for intense tillage, and eliminating issues with planting interference—removing too
much stover can take away nutrients and expose the soil to erosion (ISU 2014). The optimal sustainable
level of residue removal is likely to vary by operation (Arora, Licht, and Leibold 2014).
42
A representative from a farmer industry association confirmed that one of these projects is the Benton-Tama Nutrient Reduction Demonstration Project. 43
Some producers are beginning to challenge the long-accepted truism that residue inhibits soil warming, taking the temperature of their no-till and cover crop soils and finding them comparable to or higher than tilled fields (Stockwell 2014).
43
New research suggests cover crops marry particularly well with corn stover removal. A recent Purdue
study found that nearly two tons more stover can be sustainably removed per acre by using cover crops;
in general, the cover crop mitigates the effect of increased erosion and SOM loss from removal of
residue (Pratt et al. 2014). A study examining five Corn Belt states including Iowa also found that use of
cover crops increases the amount of residue that can be sustainably removed (Bonner et al. 2014).
To promote production of renewable fuels, including cellulosic ethanol, the Energy Independence and
Security Act of 2007 mandated that 36 billion gallons of biofuels be produced annually by 2022, of which
16 billion gallons were expected to come from cellulosic feedstocks like corn stover (DOE 2013).44 This
mandate, the renewable fuel standard (RFS), is helping to spark an emerging cellulosic ethanol industry:
in 2012, just 20,069 renewable identification numbers, which track batches of biofuels, had been
generated nationally for cellulosic ethanol; by 2013, this number had expanded to 422,740—a more
than 20-fold increase (EPA 2014). In Iowa, three new cellulosic plants are set to come online in 2014,
with a present total capacity of approximately 52 million gallons per year (Doom 2014; Nunez 2014;
DuPont Biofuel Solutions 2014). If cellulosic ethanol producers were to incentivize cover crop use among
their stover growers, the visibility and number of cover crop success stories could increase, helping
spread adoption.
Recommendations This report has examined several challenges to providing incentives to increase farmer adoption of
conservation agriculture. In the process, we have also identified some opportunities. Below are our
recommendations for next steps:
1) Fully demonstrate the potential of conservation agriculture practices to improve yields. Yield effects
are likely the most critical piece of information a farmer, landowner, or crop insurer can have about a
management practice. Documenting a clear link between conservation agriculture practices and
improvements in yield or yield stability is the most concrete way to increase adoption and reward
farmers. To date, the available data on conservation agriculture’s impacts on corn yields in Iowa are
mixed. Although initial data for the three practices’ effects on yield stability are promising, more data
are needed to fully document the impact on yields, encompassing a wide variety of crops, geographies,
and climates.
In the short term, a high priority is to fully harness existing data. This report has referred to a body of
research on yield effects. Much more data exists within government agencies that could be integrated,
analyzed, and made available to farmers and advocates. The AGree-led CCITF provides an example via its
support for a USDA-led effort to integrate and analyze existing data at different government agencies on
conservation practices, yield, variability, soil health, and other key topics. A number of active, long-term
cropping system studies exist at land-grant universities including University of Wisconsin-Madison,
North Carolina State University, and others whose findings could be compiled and systematically
analyzed (Posner 1993; NCSU 2014).
44
As of this writing, the U.S. Office of Management and Budget was reviewing a proposed rule that could potentially lower the mandated level of production.
44
Much could be accomplished by conducting new research to document the effects of soil quality and soil
health on yields. Conservation agriculture practices have been solidly demonstrated to improve soil
quality and soil health, control erosion, and improve availability of water and nutrients in the soil.
Additional research is needed to document the effects of healthy, high-quality soils on yields. Tools such
as the Haney Test and the CSHT—which measure more aspects of soil health, including microbial
activity—can help researchers better understand the relationship between soil health and yield
outcomes.
To fully determine the practices’ effects on yields, it is important to conduct side-by-side field trials.
Side-by-side field trials across a wide variety of soil types, geographies, and climates over 10 years are
the gold standard for demonstrating yield-boosting or -stabilizing effects. This is the most definitive, but
also most expensive, way to determine the extent to which conservation agriculture practices have a
positive impact on yields.
2) Inform landowners currently using crop share and custom leases about the cost-saving benefits of
conservation agriculture. Since landowners are unlikely to incentivize farmers to adopt conservation
agriculture until better documentation is available on the yield benefits, a good interim step is to tap the
two land rental arrangements we identified: crop share and custom leases. Although results will vary
from farm to farm, conservation agriculture practices are likely to result in reductions in input costs.
These reductions can benefit landowners under the lease types mentioned. Currently, these
arrangements make up about 14% of leases in Iowa.
3) Continue to evaluate the potential of a 508(h) filing, focused on cover crops. In general, crop insurers
lack both the motive and the means to incentivize conservation agriculture adoption. Although an
overhaul of the current system is unlikely, incremental change is possible. The most promising
opportunity is to propose a pilot program through the 508(h) process to offer a “good producer
discount.” Among conservation agriculture practices, the likeliest to win approval may be cover crops,
although more market research is needed. Two smaller opportunities also exist within the current crop
insurance framework: prevented planting payments can encourage first-time use of cover crops, helping
spread permanent adoption if farmers have a positive first experience, and Whole-Farm Revenue
Protection may encourage crop rotation by providing a premium subsidy for growing more than one
crop (the strength of this incentive will be determined after full policy details are released).
4) Conduct research to evaluate the potential of other identified possibilities in the value chain.
Preliminary research points to the potential to find market-based incentives within the seed corn and
cellulosic ethanol segments, although more research is needed. Seed corn operations may be
particularly vulnerable to compaction. To combat this challenge and take advantage of nutrient- and
SOM-building benefits, seed companies may want to encourage the farmers who grow their products to
use cover crops. Residue removal for cellulosic ethanol production carries the risk of heightened
erosion, nutrient removal, and decreased soil quality if carried out at unsustainable rates. Cellulosic
ethanol producers may be willing to incentivize cover crops to increase the amount of residue they can
sustainably harvest.
45
Conclusion The benefits of conservation agriculture practices extend well beyond the farmers who use them.
Conservation agriculture in Iowa promotes clean water in the Gulf of Mexico by cutting down on
fertilizer and pesticide inputs and reducing nutrient loss. The soil-quality, soil-health, and SOM-
increasing benefits of the practices can help build or maintain productive soil for future generations. Yet,
in general, farmers do not receive a clear, immediate economic benefit from adopting. For adoption to
increase, short-term incentives are needed.
The Iowa corn value chain can be tapped for direct incentives. Conservation agriculture practices benefit
a variety of stakeholders in the chain, creating opportunities to engage a combination of value chain
segments to incentivize adoption. Since no single leverage point is likely enough by itself, it is important
to tap several different segments.
This report has examined the potential within two segments: landowners and crop insurers. At present,
there is no strong, economic mechanism to reward Iowa landowners for encouraging conservation
agriculture adoption. The soil-quality and erosion-reducing benefits of conservation agriculture do not
increase the economic value of land. However, reductions in input costs can benefit landlords under
crop share and custom leases, which make up 14% of Iowa leases, making this the likelier landlord
incentive in the absence of a well-established link between the practices and increased yields.
Within the current crop insurance structure, incremental changes to encourage adoption are possible.
Advocates can submit a proposed pilot program to provide a “good producer discount” for conservation
agriculture through the 508(h) process. For this effort to be successful, more documentation showing
improved or more stable yields is needed. Market research on the practices is also needed; our
preliminary investigation suggests there may be a growing market for cover crops. Prevented planting
payments and Whole-Farm Revenue Protection are two areas to watch for their potential to increase
adoption of cover crops and third-crop rotations, respectively.
We also identified two additional value chain segments that merit further research. Seed corn providers
and cellulosic ethanol producers both stand to benefit from increased cover crop adoption. Future
research should fully examine the potential of the seed corn and cellulosic ethanol segments to provide
incentives for adoption. By continuing to demonstrate and document the economic impact of
conservation agriculture, we can ensure that a fair share of the benefits end up where they belong—in
farmers’ hands.
46
References 75th U.S. Congress. 1938. Agricultural Adjustment Act Of 1938 & Federal Crop Insurance Act.
http://www.rma.usda.gov/regs/authorizing.html. Al-Kaisi, M. 2001. Impact of Tillage and Crop Rotation Systems on Soil Carbon Sequestration. PM 1871.
Ames: Iowa State University, University Extension. http://agron-www.agron.iastate.edu/Courses/agron392/Pm1871.pdf.
———. 2014. “Professor, Iowa State University. Phone Interview with Datu Staff,” February. Al-Kaisi, M., and J. Grote. 2006. “Cropping Systems Effects on Improving Soil Carbon Stocks of Exposed
Subsoil.” Soil Science Society of America Journal 71 (4). doi:10.2136/sssaj2006.0200. Al-Kaisi, M., and M. Licht. 2005. Resources Conservation Practices: Tillage Management and Soil Organic
Matter. 154. Ames: Iowa State University, Extension and Outreach; Agriculture and Environment Extension Publications. http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1158&context=extension_ag_pubs.
Al-Kaisi, M., and B. Oneal. 2010. Agronomic and Soil Quality Trends Over Five Years of Different Tillage and Cropping Systems Across Iowa. Ames: Iowa State University, Extension and Outreach. http://www.agronext.iastate.edu/smse/tillage/pdfs/research-report.pdf.
Arbuckle, J. Gordon, and Hanna Rosman. 2014. Iowa Farmers’NitrogenManagementPracticesandPerspectives. Iowa Farm and Rural Life Poll, PM 2066. Ames: Iowa State University, Extension and Outreach. http://www.soc.iastate.edu/extension/ifrlp/PDF/PM3066.pdf.
Arora, K., M. Licht, and K. Leibold. 2014. Industrial Corn Stover Harvest. PM 3050. Ames: Iowa State University, Extension and Outreach. https://store.extension.iastate.edu/Product/Industrial-Corn-Stover-Harvest.
ARS, Agricultural Research Service. 2012. Cover Crop Chart. USDA. http://www.ars.usda.gov/SP2UserFiles/Place/30640500/CCC/CCC_v13_5_2012.pdf.
Barnett, Barry, and Keith Coble. 1999. Understanding Crop Insurance Principles: A Primer for Farm Leaders. Research Report No. 209. Mississippi State University, Department of Agricultural Economics. http://ageconsearch.umn.edu/bitstream/15784/1/rr209.pdf.
Barton, Brooke, and Sarah Elizabeth Clark. 2014. Water & Climate Risks Facing U.S. Corn Production. Boston: Ceres. https://www.ceres.org/resources/reports/water-and-climate-risks-facing-u.s.-corn-production-how-companies-and-investors-can-cultivate-sustainability/at_download/file.
Blanco-Canqui, H., and R. Lal. 2008. “No-Tillage and Soil-Profile Carbon Sequestration: An on-Farm Assessment.” Soil Science Society of America Journal 72: 693–701.
———. 2010. “Soil Conservation and Carbon Dynamics.” In Principles of Soil Conservation and Management, 449–76. Springer. http://link.springer.com/chapter/10.1007/978-1-4020-8709-7_17.
Bonner, I., D. Muth, J. Koch, and D. Karlen. 2014. “Modeled Impacts of Cover Crops and Vegetative Barriers on Corn Stover Availability and Soil Quality.” BioEnergy Research 7 (2). doi:10.1007/s12155-014-9423-y.
Bot, Alexandra, and Jose Benites. 2005. The Importance of Soil Organic Matter: Key to Drought-Resistant Soil and Sustained Food Production. Rome: Food and Agriculture Organization of the United Nations.
Boyle, Kevin. 2006. The Economics of On-Site Conservation Tillage. Portland: Natural Resources Conservation Service, West National Technology Support Center. http://tinyurl.com/n3n8a3k.
Bryant, Lara, Ryan Stockwell, and Trisha White. 2013. Counting Cover Crops. Washington, DC: National Wildlife Federation. http://www.nwf.org/~/media/PDFs/Media%20Center%20-%20Press%20Releases/10-1-13_CountingCoverCrops-FINALlowres.ashx.
47
Carlson, Sarah, and Amber Anderson. 2012. Winter Rye Cover Crop Effect on Cash Crop Yields: Year 3. Ames: Practical Farmers of Iowa. http://mysare.sare.org/MySare/assocfiles/947932Cover%20Crop%20Effect%20on%20Following%20Cash%20Crop%20Yield.pdf.
Carter, Barbara. 2014. “Question about Total Premium Data,” October 28. https://mail.google.com/mail/u/0/#inbox/14957053598c3402.
Castellano, Michael, Kristen Hofmockel, and Jim Rouse. 2014. “What Drives Corn Yield Stability?” Leopold Center 2014 Center Progress Report - Quarter 3. http://www.leopold.iastate.edu/grants/e2011-07.
Ceres. 2014. “Water & Climate Risks Facing U.S. Corn Production.” http://www.ceres.org/issues/water/agriculture/the-cost-of-corn.
Coble, Keith, Thomas Knight, Barry Goodwin, Mary Frances Miller, and Roderick Rejesus. 2010. A Comprehensive Review of the RMA APH and COMBO Rating Methodology Final Report. http://www.rma.usda.gov/pubs/2009/comprehensivereview.pdf.
Cornell University, Department of Horticulture, College of Agriculture and Life Sciences. 2014. “2014 Soil Health Testing Services.” June 23. http://soilhealth.cals.cornell.edu/extension/test.htm#results.
Cruse, R. 2005. “Soil Erosion - What Will the Future Bring?” Iowa State University. http://extension.agron.iastate.edu/soybean/documents/SoilErosion.pdf.
CTIC, Conservation Technology Information Center, and Sustainable Agriculture Research and Education SARE. 2013. 2012 – 2013 Cover Crop Survey: June 2013 Survey Analysis. CTIC & SARE. http://www.northcentralsare.org/content/download/70390/998785/SARE-CTIC_CC_Survey_Report_V2.8.pdf?inlinedownload=1.
Davis, Adam S., Jason D. Hill, C. Chase, Ann Johanns, and M. Liebman. 2012. “Increasing Cropping System Diversity Balances Productivity, Profitability and Environmental Health.” Edited by John P. Hart. PLoS ONE 7 (10). doi:10.1371/journal.pone.0047149.
DOE, Department of Energy. 2013. “Bioenergy.” Genomic Science Program, Systems Biology for Energy and Environment. April 4. http://genomicscience.energy.gov/biofuels/.
Doom, Justin. 2014. “Poet and DSM Open Commercial-Scale Cellulosic Fuel Plant.” Bloomberg. September 3. http://www.bloomberg.com/news/2014-09-03/poet-and-dsm-open-commercial-scale-cellulosic-fuel-plant.html.
Duffy, Michael. 2012. Conservation Practices for Landlords. Ag Decision Maker A1-41. Ames: Iowa State University, Extension and Outreach. http://www.extension.iastate.edu/agdm/crops/html/a1-41.html.
———. 2014. 2013 Farmland Value Survey. C2-70. Ag Decision Maker. Ames, Iowa: Iowa State University: Extension and Outreach. http://www.extension.iastate.edu/agdm/wholefarm/pdf/c2-70.pdf.
Duffy, Michael, William Edwards, and Ann Johanns. 2013. Survey of Iowa Leasing Practices, 2012. Ag Decision Maker C2-15. Ames: Iowa State University, Extension and Outreach. http://www.extension.iastate.edu/agdm/wholefarm/pdf/c2-15.pdf.
Duffy, Michael, and Ann Johanns. 2012. Farmland Ownership and Tenure in Iowa 2012. Revised 2014. Vol. PM 1983. Ames: Iowa State University, Extension and Outreach. https://store.extension.iastate.edu/FileDownload.ashx?FileID=1255.
Duiker, S., and R. Lal. 1999. “Crop Residue and Tillage Effects on C Sequestration in a Luvisol in Central Ohio.” Soil Tillage 52: 73–81.
DuPont Biofuel Solutions. 2014. “DuPont Nevada Site Cellulosic Ethanol Facility.” DuPont Cellulosic Ethanol. http://biofuels.dupont.com/cellulosic-ethanol/nevada-site-ce-facility/.
48
Edwards, William. 2014. Computing a Cropland Cash Rental Rate. Ag Decision Maker, C2-20, FM 1801. Ames, Iowa: Iowa State University, Extension and Outreach. http://www.extension.iastate.edu/agdm/wholefarm/pdf/c2-20.pdf.
Edwards, William, and Ann Johanns. 2014a. Cash Rental Rates for Iowa: 2014 Survey. C2-10. Ag Decision Maker. file:///C:/Users/Sarah/Downloads/FM1851.pdf.
———. 2014b. Flexible Farm Lease Arrangements. Ag Decision Maker, C2-21, FM 1724. Ames: Iowa State University, Extension and Outreach. https://www.extension.iastate.edu/agdm/wholefarm/pdf/c2-21.pdf.
eOrganic. 2013. “Hairy Vetch for Cover Cropping in Organic Farming.” eXtension,America’sResearch-Based Learning Network. August 19. http://www.extension.org/pages/18570/hairy-vetch-for-cover-cropping-in-organic-farming#.U9ER3bGqT8t.
EPA, Environmental Protection Agency. 2014. “2013 RFS2 Data.” EPA. March 7. http://www.epa.gov/otaq/fuels/rfsdata/2013emts.htm.
Erickson, B. 2008. Corn/Soybean Rotation Literature Summary. Purdue University. http://www.agecon.purdue.edu/pdf/Crop_Rotation_Lit_Review.pdf.
ERS, USDA Economic Research Service. 2013. “ARMS Farm Financial and Crop Production Practices: Tailored Reports: Crop Production Practices.” USDA ERS. November 26. http://www.ers.usda.gov/data-products/arms-farm-financial-and-crop-production-practices/tailored-reports-crop-production-practices.aspx#Pf646c55f8bc140788d7d563629adbcac_4_66iT0R0T0R0x1.
Exner, D.N., D.G. Davidson, M. Ghaffarzadeh, and R. Cruse. 1999. “Yields and Returns from Strip Intercropping on Six Iowa Farms.” American Journal of Alternative Agriculture 14 (2).
Farm Foundation. 2014. “The Soil Renaissance: Knowledge to Sustain Earth’s Most Valuable Asset.” https://www.farmfoundation.org/webcontent/The-Soil-Renaissance-Knowledge-to-Sustain-Earths-Most-Valuable-Asset-1873.aspx.
FCIC, Federal Crop Insurance Corporation. 2014a. Crop Year Statistics for 2013 As of: August 25, 2014, Nationwide Summary - By Crop/State. USDA RMA. http://www3.rma.usda.gov/apps/sob/current_week/cropst2013.pdf.
———. 2014b. Standard Reinsurance Agreement. 2015 SRA. http://www.rma.usda.gov/pubs/ra/sraarchives/15sra.pdf.
———. 2014c. “Summary of Business - State/Crop.” USDA RMA. August 4. http://www3.rma.usda.gov/apps/sob/stateCrop.cfm.
FSA, Farm Service Agency. 2014. “FSA Crop Acreage Data Reported to FSA.” USDA Farm Service Agency. August 15. http://www.fsa.usda.gov/FSA/webapp?area=newsroom&subject=landing&topic=foi-er-fri-cad.
Gallaher, Raymond N. 1977. “Soil Moisture Conservation and Yield of Crops No-till Planted in Rye.” Soil Science Society of America Journal 41 (1). https://dl.sciencesocieties.org/publications/sssaj/abstracts/41/1/SS0410010145.
Gibson, Lance, Jeremy Singer, Stephen Barnhart, and Brock Blaser. 2006. Intercropping Winter Cereal Grains with Red Clover. Vol. PM 2025. Ames: Iowa State University Extension. http://www.cals.uidaho.edu/edcomm/pdf/BUL/BUL0851.pdf.
Goodwin, Barry K., and Vincent H. Smith. 2013. “What Harm Is Done By Subsidizing Crop Insurance?” American Journal of Agricultural Economics 95 (2): 489–97.
Haney, Rick. 2013. “Soil Testing for Soil Health.” http://www.usda.gov/oce/forum/past_speeches/2013_Speeches/Haney.pdf.
Hanson, J.C., E. Lichtenberg, A.M. Decker, and A.J. Clark. 1993. “Profitability of No-Tillage Corn Following a Hairy Vetch Cover Crop.” Journal of Production Agriculture 6 (3).
49
Hanson, J.C., E. Lichtenberg, and S. Peters. 1997. “Organic versus Conventional Grain Production in the Mid-Atlantic: An Economic and Farming System Overview.” Journal of Alternative Agriculture 12 (1). doi:http://dx.doi.org/10.1017/S0889189300007104.
Harper, Jayson K. 1996. Economics of Conservation Tillage. Conservation Tillage Series 6. University Park: Penn State College of Agricultural Sciences.
Hoddinott, Susan N., and Martin J. Bass. 1986. “The Dillman Total Design Survey Method.” Canadian Family Physician 32 (November). http://www.ncbi.nlm.nih.gov/pmc/articles/pmc2328022/.
Hoorman, James J., Rafiq Islam, Alan Sundermeier, and Randall Reeder. 2009. Using Cover Crops to Convert to No-Till. SAG-11-09; AEX-540-09. Ohio State University Extension. http://www.covercropsolutions.com/documents/scientificResearch/Using%20Cover%20Crops%20to%20Convert%20to%20No-Till.pdf.
Huggins, David R., Gyles W. Randall, and Michael P. Russelle. 2001. “Subsurface Drain Losses of Water and Nitrate Following Conversion of Perennials to Row Crops.” Agronomy Journal 93 (3). https://dl.sciencesocieties.org/publications/aj/abstracts/93/3/477.
IDALS, Iowa Department of Agriculture and Land Stewardship, Iowa Department of Natural Resources IADNR, and Iowa State University College of Agriculture and Life Sciences ISU. 2013. Iowa Nutrient Reduction Strategy: A Science and Technology-Based Framework to Assess and Reduce Nutrients to Iowa Waters and the Gulf. http://www.nutrientstrategy.iastate.edu/sites/default/files/documents/NRSfull-130529.pdf.
ILF, Iowa Learning Farms, and Practical Farmers of Iowa PFI. 2014. “Winter Cereal Rye Cover Crop Effect on Cash Crop Yield.” Iowa Learning Farms and Practical Farmers of Iowa. http://practicalfarmers.org/wp-content/uploads/2014/04/REVISED_Winter_Rye_Effect_on_Yield_Yr5.pdf.
Iowa Department of Revenue. 2008. “Section 2: Land Valuation.” In Iowa Real Property Appraisal Manual. http://www.iowa.gov/tax/locgov/2LANDVALUATIONSECTION.PDF.
Iqbal, M., A.U. Hassan, A. Ali, and M. Rizwanullah. 2005. “Residual Effect of Tillage and Farm Manure on Some Soil Physical Properties and Growth of Wheat (Triticum Aestivum L.).” Nternational Journal of Agriculture and Biology 7: 54–57.
ISU. 2008. “Economic Analysis of Three Iowa Rotations - PM 1001.” Iowa State University, University Extension.
ISU, Iowa State University Extension & Outreach. 2014. “Soil Quality: Corn Stover Availability.” Stover Harvest. http://www.extension.iastate.edu/stover/content/soil-quality.
Karlen, D., E. Hurley, and S. Andrews. 2006. “Crop Rotation Effects on Soil Quality at Three Northern Corn/soybean Belt Locations.” Agronomy Journal 98: 484–95.
Kaspar, Tom. 2010. “Cover Crop Biomass and Subsequent Corn Yield for 13 Winter Rye, Wheat, and Triticale Cover Crop Cultivars.” presented at the Midwest Cover Crops Council, Ames. http://www.mccc.msu.edu/meetings/2010/2010%20MCCC%20Posters/2010MeetingPoster_Kaspar.pdf.
Lal, R. 1995. “The Role of Residues Management in Sustainable Agricultural Systems.” Journal of Sustainable Agriculture 5: 51–78.
———. 2012. Soil Organic Matter Management for Sustainable Production and Climate Change. Presented at the International Symposium on Mountain Resource Management in a Changing Environment, Aquatic Ecology Center Kathmandu, Nepal. http://presenter.cfaes.ohio-state.edu/link/Dr._Lal_5-21-12_-_Flash_%28Large%29_-_20120521_03.05.22PM.html.
Lal, R., R. Follett, B. Stewart, and J. Kimble. 2007. “Soil Carbon Sequestration to Mitigate Climate Change and Advance Food Security.” Soil Science 172 (12). http://journals.lww.com/soilsci/Abstract/2007/12000/Soil_Carbon_Sequestration_To_Mitigate_Climate.1.aspx.
50
Lal, R., J. Kimble, and R. Follet. 1998. “Pedospheric Processes and The Carbon Cycle.” In Advances in Soil Science: Soil Processes and the Carbon Cycle, edited by R. Lal, J. Kimble, R. Follet, and B. Stewart. Boca Raton: CRC Press, LLC. http://books.google.com/books?id=1hrGaZvSHDIC&printsec=frontcover&source=gbs_ViewAPI#v=onepage&q&f=false.
Lauer, Joe, Paul Porter, and Ed Oplinger. 1997. “The Corn and Soybean Rotation Effect.” University of Wisconsin Extension, Agronomy Advice, April. http://corn.agronomy.wisc.edu/AA/A014.aspx.
Leibold, Kevin. 2013. “How Is Farmland Leasing for 2014 Shaping Up?” ISU Ag Decision Maker Newsletter, August. http://www.extension.iastate.edu/agdm/articles/leibold/LeiAug13.html.
Liebman, Matt, Lance R. Gibson, David N. Sundberg, Andrew H. Heggenstaller, Paula R. Westerman, C. Chase, Robert G. Hartzler, Fabián D. Menalled, Adam S. Davis, and Philip M. Dixon. 2008. “Agronomic and Economic Performance Characteristics of Conventional and Low-External-Input Cropping Systems in the Central Corn Belt.” Agronomy Journal 100 (3). doi:10.2134/agronj2007.0222.
Lowe, Marcy, and Gary Gereffi. 2008. A Value Chain Analysis of Selected California Crops. Durham: Center on Globalization, Governance & Competitiveness. http://cggc.duke.edu/environment/valuechainanalysis/CGGC_CACropsReport_7-4-08.pdf.
Mallarino, A.P., and E. Ortiz-Torres. 2006. A Long-Term Look at Crop Rotation Effects on Corn Yield and Response to Nitrogen Fertilization. Ames: Iowa State University - Integrated Crop Management Conference. http://www.agronext.iastate.edu/soilfertility/info/mallarino_Long-Term_N-Rotation.pdf.
MCCC, Midwest Cover Crops Council. 2014. “Midwest Cover Crops Council Cover Crop Decision Tools.” Midwest Cover Crops Council. http://www.mccc.msu.edu/selectorINTRO.html.
Miguez, Fernando E., and Germán A. Bollero. 2005. “Review of Corn Yield Response under Winter Cover Cropping Systems Using Meta-Analytic Methods.” Crop Science 45 (6): 2318. doi:10.2135/cropsci2005.0014.
Miranda, Mario J., and Joseph W. Glauber. 1997. “Systemic Risk, Reinsurance, and the Failure of Crop Insurance Markets.” American Journal of Agricultural Economics 79 (1). http://www2.econ.iastate.edu/classes/econ642/Babcock/Miranda-Glauber_SystemicRisk.pdf.
Nafziger, E., E. Adee, M. Johnson, B. Mansfield, and A. Peltier. 2013. The Effects of Long-Term Rotation and Tillage on Corn, Soybean and Wheat Yields. University of Illinois Extension. http://web.extension.illinois.edu/nwiardc/downloads/48185.pdf.
NCSU, North Carolina State University. 2014. “Farming Systems Research Unit.” Center for Environmental Farmin Systems. http://www.cefs.ncsu.edu/whatwedo/researchunits/farmingsystems.html.
Needelman, B. A., M. M. Wander, G. A. Bollero, C. W. Boast, G. K. Sims, and D. G. Bullock. 1999. “Interaction of Tillage and Soil Texture Biologically Active Soil Organic Matter in Illinois.” Soil Science Society of America Journal 63 (5). https://dl.sciencesocieties.org/publications/sssaj/abstracts/63/5/1326.
NRC, National Research Council. 2010. Towards Sustainable Agriculture in the 21st Century. Washington DC: National Academies Press. http://tinyurl.com/q5z5ufn.
NRCS, Natural Resources Conservation Service. 2010a. NRCS Conservation Practice Standard - Crop Rotation.pdf. Code 328. NRCS, NHCP. http://efotg.sc.egov.usda.gov/references/public/MN/328mn.pdf.
———. 2010b. NRCS Conservation Practice Standard - Cover Crop. Code 340. NRCS, NHCP. http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1046845.pdf.
———. 2011. NRCS Conservation Practice Standard - Mulch Till. Code 345. NRCS, NHCP. http://efotg.sc.egov.usda.gov/references/public/WI/345.pdf.
51
———. 2012. NRCS Conservation Practice Standard - No Till/Strip Till/Direct Seed. Code 329. NRCS, WI. http://efotg.sc.egov.usda.gov/references/public/VA/VA329.pdf.
———. 2013a. NRCS Cover Crop Termination Guidelines: Non-Irrigated Cropland. USDA NRCS. http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1142986.pdf.
———. 2013b. NRCS Conservation Practice Standard - Reduced Till. Code 345. NRCS, NHCP. http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb1251402.pdf.
———. 2014. “Role of Soil Organic Matter.” http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/soils/health/mgnt/?cid=nrcs142p2_053859.
———. 2014. “No-till Farming Critical for Preventing Loss of Soil Moisture During Drought Conditions.” USDA NRCS Iowa. Accessed July 24. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/ia/newsroom/releases/?cid=nrcs142p2_011847.
NSAC, National Sustainable Agriculture Coalition. 2014. “RMA Levels the Playing Field on Premium Subsidies for New Whole Farm Revenue Protection Insurance.” NSAC’sBlog. October 3. http://sustainableagriculture.net/blog/wfrp-increased-subsidy-level/.
Nunez, Christina. 2014. “‘Fantasy’ of Fuel From Corn Waste Gets Big U.S. Test.” National Geographic, September 11. http://news.nationalgeographic.com/news/energy/2014/09/140911-project-liberty-cellulosic-ethanol-us-test/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%253A+ng%252FNews%252FNews_Environment+(National+Geographic+News+-+Environment).
O’Connor, Claire. 2013a. “Soil Matters: How the Federal Crop Insurance Program Should Be Reformed to Encourage Low-Risk Farming Methods with High-Reward Environmental Outcomes.” New York, NY: Natural Resources Defense Council, no. IP:13-04-A. http://www.tetratech-ffx.com/tfmeeting/sept2013/downloads/soil-matters.pdf.
O’Connor, Claire. 2013b. “Farmers Reap Benefits as No-Till Adoption Rises.” NRDC Switchboard, November 14. http://switchboard.nrdc.org/blogs/coconnor/farmers_reap_benefits_as_no-ti.html.
Odell, R.T, S. Melsted, and W. Walker. 1984. “Changes in Organic Carbon and Nitrogen of Morrow Plot Soils Under Different Treatments 1904-1973.” Soil Science 137: 160–71.
Pedersen, Palle. 2004. “Should We Rotate or Not?” Integrated Crop Management, March 22. http://www.ipm.iastate.edu/ipm/icm/2004/3-22-2004/rotate.html.
Posner, Josh. 1993. Long-Term Study Evaluates Impacts of Six Wisonsin Cropping Systems. Research Brief #11. University of Wisconsin-Madison. http://www.cias.wisc.edu/long-term-study-evaluates-impacts-of-six-wisonsin-cropping-systems/.
Pratt, M., W. Tyner, D. Muth, and E. Kladivko. 2014. “Synergies between Cover Crops and Corn Stover Removal.” Agricultural Systems 130 (September). doi:10.1016/j.agsy.2014.06.008.
Riedell, Walter E., Joseph L. Pikul, Abdullah A. Jaradat, and Thomas E. Schumacher. 2009. “Crop Rotation and Nitrogen Input Effects on Soil Fertility, Maize Mineral Nutrition, Yield, and Seed Composition.” Agronomy Journal 101 (4). doi:10.2134/agronj2008.0186x.
RMA, Risk Management Agency. 2003. Nutrient BMP Endorsement: Common Questions and Answers. USDA RMA. http://www.rma.usda.gov/ftp/Policies/2003/n-bmp/pdf/N-BMP_qa.pdf.
———. 2010. “Biotech Yield Endorsement.” USDA RMA. January 5. http://www.rma.usda.gov/help/faq/bye.html.
———. 2011. Good Farming Practices Protect Your Investment in Crop Insurance. http://www.rma.usda.gov/pubs/2011/good_farming_practices.pdf.
———. 2013. “Cause of Loss Historical Data Files.” USDA RMA. http://www.rma.usda.gov/data/cause.html.
52
———. 2014. Prevented Planting: Iowa, Minnesota, and Wisconsin. St. Paul Regional Office: USDA RMA. http://www.rma.usda.gov/fields/mn_rso/2014/2014preventedplanting.pdf.
Robertson, Phillip G., K. L. Gross, S. K. Hamilton, D. A. Landis, T. M. Schmidt, S. S. Snapp, and S. M. Swinton. 2014. “Farming for Ecosystem Services: An Ecological Approach to Production Agriculture.” BioScience 64 (5). doi:10.1093/biosci/biu037.
Roth, G. 1996. Crop Rotations and Conservation Tillage. Conservation Tillage Series, No. 1. University Park: Penn State College of Agricultural Sciences Cooperative Extension. http://extension.psu.edu/plants/crops/soil-management/conservation-tillage/crop-rotations- and-conservation-tillage.
Sauer, T. J., J. L. Hatfield, and J. H. Prueger. 1996. “Corn Residue and Placement Effects on Evaporation and Soil Thermal Regime.” Soil Science Society of America Journal 60 (5). doi:10.2136/sssaj1996.03615995006000050039x.
Sawyer, John E., Jose L. Pantoja, and Daniel W. Barker. 2009. “Nitrogen Fertilization of Corn Grown with Cover Crop.” Iowa State University Farm Progress Reports Paper 323. http://lib.dr.iastate.edu/farms_reports/323.
Shea, John. 2014. New Whole-Farmer Revenue Protection Insurance Premium Subsidy Established: 2014 Farm Bill Required Policy Offers Diversified Marms More Affordable Protection. RMA-14-159. Washington, DC: RMA. http://www.rma.usda.gov/news/currentissues/farmbill/rma14-159.pdf.
Shields, Dennis A. 2013. Federal Crop Insurance: Background. 7-5700, R40532. Congressional Research Service. http://nationalaglawcenter.org/wp-content/uploads/assets/crs/R40532.pdf.
Singer, Jeremy W., and Keith A. Kohler. 2005. “Rye Cover Crop Management Affects Grain Yield in a Soybean-Corn Rotation.” Crop Management, February. doi:10.1094/CM-2005-0224-02-RS.
Smith, R. G., K. L. Gross, and P. G. Robertson. 2008. “Effects of Crop Diversity on Agroecosystem Function: Crop Yield Response.” Ecoystems 11 (3). http://www.jstor.org/stable/40296291.
Snapp, S. S., S. M. Swinton, R. Labarta, D. Mutch, J.R. Black, R. Leep, J. Nyiraneza, and K. O’Neal. 2005. “Evaluating Cover Crops for Benefits, Costs and Performance within Cropping System Niches.” Agronomy Journal 97.
Soil Health Partnership. 2014. “A Project to Make Agriculture More Productive and Sustainable through Improved Soil Health.” Soil Health Partnership. http://soilhealthpartnership.org/.
Steiner, J.L. 1994. “Crop Residue Effects on Water Conservation.” In Managing Agricultural Residues, edited by P.W. Unger. Boca Raton: Lewis Publishers.
Stivers-Young, Lydia J., and Frances A. Tucker. 1999. “Cover-Cropping Practices of Vegetable Producers in Western New York.” HortTechnology 9 (3). http://horttech.ashspublications.org/content/9/3/459.short.
Stockwell, Ryan. 2014. “Myth Busted: Cover Crops and Soil Temperatures.” Wildlife Promise: Blogs from around the Federation. September 4. http://blog.nwf.org/2014/09/myth-busted-cover-crops-and-soil-temperatures/.
Stute, J.K., and J.L. Posner. 1995. “Legume Cover Crops as a Nitrogen Source for Corn in an Oat-Corn Rotation.” Journal of Production Agriculture 8.
Syswerda, S.P., A.T. Corbin, D.L. Mokma, A.N. Kravchenkoc, and G.P. Robertson. 2011. “Agricultural Management and Soil Carbon Storage in Surface vs. Deep Layers.” Soil Science Society of America Journal 75 (1). doi:10.2136/sssaj2009.0414.
Tonitto, C., M.B. David, and L.E. Drinkwater. 2006. “Replacing Bare Fallows with Cover Crops in Fertilizer-Intensive Cropping Systems: A Meta-Analysis of Crop Yield and N Dynamics.” Agriculture, Ecosystems & Environment 112. http://biogeochemistry.nres.illinois.edu/Biogeochem_lab/pdfs/Tonitto%20et%20al%202006%20Ag%20Ecosys%20Env.pdf.
53
UNL CropWatch, University of Nebraska Lincoln: 2014. “Rogers Memorial Farm: Yields from a Long-Term TIllage Comparison Study.” Crop Watch. Accessed February 3. http://cropwatch.unl.edu/tillage/rmfyields.
Uri, N.D. 2000. “An Evaluation of the Economic Benefits and Costs of Conservation Agriculture.” Environmental Geology 39 (3-4).
USDA NASS. 2012. 2012 Census of Agriculture. Vol. Volume 1, Chapter 1: State Level Data. http://www.agcensus.usda.gov/Publications/2012/Full_Report/Volume_1,_Chapter_1_State_Level/Iowa/.
USDA NASS, USDA National Agricultural Statistics Service. 2014. “USDA/NASS QuickStats Ad-Hoc Query Tool.” Accessed August 25. http://quickstats.nass.usda.gov/results/68E882F5-47F7-3B10-A041-5916A10426D8.
Vyn, Tony J., Ken J. Janovicek, Murray H. Miller, and Eric G. Beauchamp. 1999. “Soil Nitrate Accumulation and Corn Response to Preceding Small-Grain Fertilization and Cover Crops.” Agronomy Journal 91 (1). doi:10.2134/agronj1999.00021962009100010004x.
Wander, M.M., M.G. Bidart, and S. Aref. 1998. “Tillage Impacts on Depth Distribution of Total and Particulate Organic Matter in Three Illinois Soils.” American Society of Agronomy 62 (6). doi:doi:10.2136/sssaj1998.03615995006200060031x.
Wander, M.M., and S.J. Traina. 1996. “Organic Matter Fractions from Organically and Conventionally Managed Soils: I. Carbon and Nitrogen Distribution.” Soil Science Society of America Journal 60 (4). doi:10.2136/sssaj1996.03615995006000040017x.
Wander, M.M., S.J. Traina, B.R. Stinner, and S.E. Peters. 1994. “Organic and Conventional Management Effects on Biologically Active Soil Organic Matter Pools.” Soil Science Society of America Journal 58 (4).
