Nitrogen Management on Sandy Soils: Review of BMPs

Carl Rosen Department of Soil Water and Climate University of Minnesota

Central MN Irrigation Workshop Thumper Pond, Ottertail, MN February 25, 2014

Topics Covered

Background for development of BMPs Understanding the N cycle Risk for N losses and optimizing

yield

Examples of specific BMPs for sandy soils

Definition of Best Management Practices for Nitrogen

Economically sound, voluntary practices that are capable of minimizing contamination of surface and groundwater with nitrate-N

Based upon the concept of total N management Account for all sources of on-farm N Appropriate timing of application

Development is based on research conducted

primarily by the University of Minnesota - Replicated studies at experiment stations and on-farm

Review of the Nitrogen Cycle = N pools = N sources = N losses & Removal

Major factors involved with N leaching

Soil characteristics

Climate Temperature Rainfall

Parent Material and Temperature

Precipitation and Leaching Index

BMP Regions in Minnesota

The BMP Bulletins for Sandy Soils

General BMPs

Account for all sources of N N used in starter fertilizer or other fertilizer sources Legume credit Manure credit

Test manure for nutrient content Calibrate spreader Do not spread on sloping frozen soil Inject or incorporate

Irrigation water

Legume Credits (soybeans covered in actual corn N recs.)

1st Year 2nd Year

General BMPs Select an appropriate N rate Probably the most important BMP Probably the most difficult to determine How much N is supplied from soil? How much

additional N is needed? Uncontrollable factors

Temperature Rainfall

N rate is determined based on the crop grown and

other numerous factors

Relationship between N rate, yield, and N losses

Appropriate N Rates for Corn Productivity characteristics of production

environment (soil and climate) Irrigated sandy soils – high productivity Non-irrigated sandy soils – medium productivity

Cost of N fertilizer/value of a bushel of corn

Producers attitude toward risk

Regional approach to N rates in the Corn Belt

Corn N Rate Recommendations

Background for N Rate Recommendations Minnesota adopted N guidelines based on

the MRTN in 2006

Database for sandy soils was old and lacked sites that had enough N rates to establish a good response curve

We decided to use the high productivity N database for rain-fed heavy textured soils for N guideline

Background (continued)

Minnesota irrigated sandy soils are highly productive, but also at high risk of leaching

Reliable reports that new N guidelines were not

working on irrigated sandy soils

N rate recommendations for sandy soils are being revised and will be discussed in the next talk

Other N Management Considerations

N timing N source Method of application Use of inhibitors Urease and nitrification inhibitors Numerous products on the market N-Serve traditional nitrification inhibitor

Coated products (example – ESN)

Nitrogen Timing

Generalized N uptake for corn through the season

https://www.pioneer.com/home/site/us/agronomy/library/template.CONTENT/guid.1BF7B8F5-99E6-DC1E-0D45-9F5D240A8761

Nitrogen Timing – Sandy Soils

Recommended: Use split applications of N Incorporate/inject all N applications at least 3” or if

irrigated apply irrigation after application Use N inhibitor (N-Serve) for labeled crops when

early sidedress is used Follow proven water management practices to

prevent over-irrigation

Nitrogen Timing – Coarse-textured Acceptable – greater risk

Spring preplant application with N-Serve Single sidedress application early in the growing season

without an inhibitor Spring preplant with coated urea (ESN)

Not recommended

Fall application of any N source with or without N-Serve Spring preplant without N-Serve N fertilizer applied after tasseling Coated fertilizer to edible beans after planting

Nitrogen Timing – Coarse-textured

1981 – leaching year 1982 – dry year

Nitrogen Timing – Coarse-textured

Study shows benefit of using N-Serve with preplant N But split application with N-Serve allowed a lower N rate With higher yields

Nitrogen Timing – Irrigated Potatoes on Coarse-textured soils

Increasing N in starter increased leaching potential and negatively affected yield

On-going BMP research

New technologies Stalk nitrate test

Post-mortum Report card

Sensors Chlorophyll meter Greenseeker Crop circle Remote sensing by plane

Inhibitors and coated urea products

Summary and Conclusions BMP development is based on

credible scientific studies – more studies on sand needed

Recommendations take into account the risk for N losses and optimization of yields

Nitrogen is leaky and getting it right every time is a challenge

Research is on-going and new technologies will help in improving N use efficiency and reducing N losses