Soil Health
MSU Soil Fertility Extension
Clain Jones [email protected] 994-6076
Fairfield MT dust storm, Feb 2020, by Darryl Flowers, Fairfield Sun Times
Montana Farmers UnionVirtual meeting, September 3, 2020
Objectives
• Show agronomic practices that benefit soil health
• Focus on ways to increase soil organic matter• Describe impact of soil pH on plant
productivity and soil health• Present pros and cons of soil health tests• Leave lots of time for questions
Tools• Rotations• Residue
management• Amendments
Measurable impacts• SOM• Soil N/PMN• Microbes/enzymes• Aggregation• Soil pH
Image from Freecreatives
Increasing SOM increases many other soil health parameters
Agronomic practices that benefit soil
Less productivity → less SOM. This is a big deal to soil health (and income)! For example:
Fisher et al., 2007Australia, irrigated, variety of soil types
Small SOM increases → large improvement in soil structure Water infiltrationRoot growthReduced water and wind
erosion
The basis for soil health is biological activity, OM is the fuel for that activity. In Montana, 10 yrs of recrop or CRP increased SOM (‘02- ’12)
Engel et al. 2017, Gallatin Valley, MT
For higher OM soil in say 20 years, you need to start now.
Best way: recrop and apply recommended fertilizer rates, or grow perennials
SOM change depends on residue returned & inputs
Engel et al. 2017, Gallatin Valley MT, 16” precip zone
Need ~1.8 ton shoot residue/ac/yr (Shrestha et al. 2013 SK; Engel et al. 2017 MT) to maintain SOM in more productive NGP regions.
CRP
forage
Why? Slope = 0.4
What % of residue C still in soil after 10 yrs?
Why?
Annual wheat and pulse systems
Diversify – how could you & how would it help SOM?• Rotate species across time• Polycultures = mix species w/in field• Genetic diversity = mix varieties w/in
field• Mixed cover crops:More stable yearly production, reduced
risk. Unlikely all species in the mix will produce poorly or completely fail (Miller et al. unpub. data, Khan & McVay 2019)
More biomass when include legumes in low N soil (Miller et al. unpub. data)
Legumes increase available N if >40% of biomass (Sullivan & Andrews 2016)
Image by P. Miller
Norton et al. 2012, Albin WY; Ingram et al. 2008, Cheyenne WY. P 0.05 for 0-12” total SOM
Cultivated systems have lower SOM than perennial
Soil acidification is threatening productivity and SOM input. It is a major problem in parts of Montana.
Caused by N fertilization Leads to: Reduced nodulation in legumes Aluminum toxicity Changed herbicide effectiveness and
residual Increased disease - Fusarium crown
rot and Ceph strip Prevent by:
• Increase N use efficiency• Include legumes to supply N• Plant crops that require less N
Barley crop loss due to acidic soilPhoto courtesy Rick Engel
pH 3.8
pH 5.1
Legume cover crops increase microbial populations
Biederbeck et al. 2005, 6 yrs of rotations, SK. Organisms in top 4”, sampled after wheat phase in Oct, 15 months after cover crop termination.
Agrees with MT study at 4 & 2 locations after 2 & 4 rotations: pea or mixed cover crop generally greater microbial biomass than fallow (Tallman 2014, Housman 2016, D’Agati unpub data).
Soil Health Tests, e.g. Haney or Cornell
• Measure and monitor over time or between fields
• Useful to assess effect of management or evaluate problem areas
• Standardized methods may not yet be in place
• Currently no calibration between test values and fertilizer recommendations for N. Great Plains
Jones and Boss, 2014 unpub data, Havre, MT
How much does Haney test and standard fertility testing explain winter wheat yield variability?• Haney (15%) - Dissolved organic C most important variable• “Standard” (25%) 6 – 24” Nitrate most important• Haney + “Standard” (39%) 6 – 24” Nitrate most important
How can I manage for healthy soils?
Know your soil properties and only add amendments as needed
Avoid compaction:• Reduce tillage and traffic when wet
Feed the microbial community, increase organic matter content:
• Minimize fallow, possibly add cover crops• Moderate grazing
Maintain cover with vegetation or residue Be patient, but start now
Thank you!Questions?
Image by Meg Housman
This presentation and additional information on soil fertility topics are available at
http://landresources.montana.edu/soilfertility
