Strategies for Reducing Nitrate Leaching from Irrigated Potato ProductionProduction
Carl RosenDepartment of Soil, Water, & ClimateUniversity of Minnesota
Minnesota Ground Water Association ConferenceU of M, St. Paul
November 9, 2010
TopicsPotato production in Minnesota
Specific potato production factors contributing to nitrate leaching
Best management practices identified that reduce nitrate leaching
Challenges involved - Case study in Perham, MN
General conclusions and long-term solutions
Background Irrigated potato production in Background gMinnesota
~50,000 acres mostly on loamy sand soils with low organicsand soils with low organic matter70% for processing
Russet BurbankRusset Burbank450 – 600 cwt/A
30% fresh marketEarly harvest redsEarly harvest redsSome russets/whites300 – 500 cwt/A
$100 million in ra prod ct$100 million in raw product valueIrrigation is essential for optimizing yield and quality
BackgroundPotatoes have a relatively shallow root system – most roots in the top 12”
Sensitive to N and water stressRates of 160 to 300 lb N/A appliedRates of 160 to 300 lb N/A applied
Rainfall averages about 12” during the growing seasongrowing season
Rainfall after an irrigation is a problemWater holding capacity ~ 1” in the top ft
All these factors contribute to a high potential for nitrate leaching
Nitrate Concerns - Statewide Results1993 20051993-2005
10 to 20 % of the wells% of wells testing > 10 ppm 10 to 20 % of the wells tested in the potato growing regions were above 10 ppm NO3-N
Many individuals and municipalities have had
k ito take action to remediate the problem
Nitrate Testing Clinic Program(Over 50,000 observations – Data courtesy of Minnesota Department of Agriculture)
BMPs to Address Nitrate Concerns
Response to GroundwaterResponse to Groundwater Protection Act – 1989
N fertilizer management planCentral tool is adoption of BMPs
Vol ntarVoluntaryResearch-basedFocus is on N fertilizersManure management also considered
Published in 2008 for potatoPublished in 2008 for potato
http://www.extension.umn.edu/distribution/cropsystems/DC8559.pdf
Specific N BMPs for PotatoesSelect a realistic N rate
VarietyVarietyHarvest date (based on market)Yield goalP i /Previous crop/manureIrrigation water nitrate-N
Time N application to meet N demands of the crop
Split applications of soluble NSplit applications of soluble N No preplant N and limit the amount of N in the starter
Consider use of controlled release N sources
Potato Growth Characteristics
Five general growth stagesFive general growth stages
Each with a different nutrientEach with a different nutrient requirement
Length of each stage depends i t / li ton variety/climate
Growth Stage Ig
Sprout developmentp p
Seed is the primary source ofSeed is the primary source of nutrients
Occurs within 30 days of planting
Water and nutrient demand is low
Growth Stage IIgVegetative growth
30-55 days after planting
Relative water and nutrient demand is low to moderate
Growth Stage IIIgTuber initiation and set
Tuber formation is sensitive to nutrient supply at this stage
50 to 70 days after planting
Vegetative growth increasesVegetative growth increases rapidly
Water and nutrient demand isWater and nutrient demand is moderate to high
Growth Stage IVgTuber bulking
Vegetative growth slows down
60 to 90 days after planting - early
70 to 110 days after planting – late
Water and nutrient demand is moderate to highmoderate to high
Growth Stage Vg
T b t tiTuber maturation
Vines begin to die
Transport of nutrients to tubers
Water and nutrient demand is low
Potato Seasonal N Accumulation & Dail Acc m lation RateDaily Accumulation Rate
Sprout Veg T.I. Bulking Maturation
N A l tiN Accumulation Rate
Russet Burbank – Becker, Minnesota
Suggested Nitrogen Timing
Timing of Application% of Total Nitrogen to Apply___ ___ _
Early Maturing Variety Late Maturing VarietyTiming of Application Early Maturing Variety Late Maturing Variety
Preplant/planting 10-40% 10-20%Preplant/planting 10 40% 10 20%
Emergence 40-60% 20-40%
Final hilling (or tuber initiation)
0-40% 30-60%
Post-hilling 0 0-40%
Total N applied to potatoes typically ranges from 160 to 250 lb N/A
Diagnostic Tools to Help Determine In season N ApplicationsIn-season N ApplicationsPetiole nitrate analysis
4th-5th leaf from growing point4 5 leaf from growing pointWorks well with indeterminate varieties and when bulking conditions are optimumApply N when petiole nitrate-N is at or below the optimum rangethe optimum range
In-season soil nitrate testingSample to 1 ft in hillInterpretations not well calibratedWide fluctuations due to rainfall
Chlorophyll meter & other reflectance techniques
Area of active research
Interpretation of Petiole Nitrate-N Concentrations Through the Growing Season (d w basis)Through the Growing Season (d.w. basis)
%)
2 02.53.0
ncn.
(%
Excess
1 01.52.0
N C
on
Optimum
0 00.51.0
itrat
e- Deficient
0.030 50 70 90 110
N
Days after Emergencey g
The Nitrogen Cycle
X
X
Enhanced Efficiency N Sources yControlled release nitrogen
Ph i l h i l b i t l d l bilitPhysical or chemical barrier to slow down solubilitySulfur coating around prillPolymer coating around fertilizer prill (usually urea)
Example: ESN (manufactured by Agrium, Inc.)“Environmentally Smart Nitrogen”Only economically viable slow release currently available for potatoOnly economically viable slow release currently available for potatoCoated urea - mode of action - lowers solubilityRelease rate depends on soil moisture and temperature
Polymer Coated TechnologyPolymer Coated Technology
Agrium U.S. Inc., 2005
Release rate depends on: coating thickness, temperature, and moisture
N Release from ESN - “Mesh Bag” Method -
Visual assessment of ESNgranules through the
igrowing season
Nitrogen Uptake and Growth
100wth
40
60
80
100
Upt
ake
or G
row
VineTuberT t l N
0
20
40
0 20 40 60 80 100 120 140
% T
otal
N U Total N
0 20 40 60 80 100 120 140
Days After Planting
Vine kill
8-10” depth
2 3” d th2-3” depth
Comments on Polymer-coated UreaWhen used properly leaching is lower during the growing seasongrowing season
Susceptible to damage during handling and application
F l f it t hi h t ill lt iFalse sense of security – too high rate will result in leaching
Growers tend to apply soluble N later in the seasonGrowers tend to apply soluble N later in the season when ESN is used
M h ti t h l i t dMore research on coating technology is warranted
Other Recommended PracticesSound irrigation management
“Checkbook” methodW t it i d i
700
/AWater monitoring devices
Use of cover cropsE i ll ft l h t
400
500
600
A Yield, cwt/
Especially after early harvest potatoesNot effective for long season potatoes
200
300
0 100 200 300
Grade
A
Russet BurbankAlturas
potatoes
Use of N efficient varieties/cropsActive area of research
0 100 200 300
Nitrogen Rate, lb N/A
Active area of research
Amendments to increase soil t h ldi itwater holding capacity
Case Study in Perham, Minnesotay
High density of center pivots with potato in the rotation
One pivot near the center of town
Giloman siteBelieved to contribute to elevated nitrate in drinking water
In cooperation with MDA
The Giloman Site…
Field Surface>24”
• Suction lysimeters installed to a 4 ft depth >24
deepto a 4 ft depth
• The approximate area where the lysimeters are located
Reducing Nitrate Leaching is a Challenge!!
Giloman
100
120
m)
Nitrogen Suction Lysimeter Data near Perham - 4ft Depth
BurbankPotato2000
Umatilla Potato 2008 (ESN) + fertigation N
250 lb N/A250 lb N/A
120 lb N/A
60
80
Nitr
ogen
(ppm
Soybeans 2001
AlturasPotato 2002 Alfalfa
Alfalfa 2007('06 winter kill)
Edible Beans2009170 lb N/A
0
20
40
Nitr
ate- 2001 2002 Alfalfa
2003
Alfalfa 2004 Alfalfa
2005
Alfalfa 2006
0
Data – Courtesy of the Minnesota Department of Agriculture
Overall ConclusionsGrowing potatoes on irrigated sandy soils in Minnesota is a leaky systemMinnesota is a leaky system
BMPs can help in reducing nitrate losses butBMPs can help in reducing nitrate losses, but in many years leaching will still occur
Integrated approach is neededIntegrated approach is needed
Long term solution gGrow N efficient varieties with lower N ratesAvoid growing potatoes in areas were there are sensitive aquiferssensitive aquifers