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These three tests provide the best information for N management decisions.
- Preplant nitrate test. A soil nitrate test measures the amount of residual or carryover N in the active root zone.
- Pre-sidedress soil nitrate test allows you to apply more N for peak growth.Sample when corn plants are 6-12 in. tall, just before rapid growth and high N uptake.
- Fall stalk nitrate test can help farmers adjust N programs for the following spring.
You have to go back into the fields and test in the exact same spots where the nitrate tests were taken. Interpretation of the results is key.
Nitrogen testing for soybeans
Farmers may not traditionally test for N deficiency in soybeans, but some experts predict such a test could have merit and is one or two years away. Minnesota agronomy consultant Tom McGraw says N fertilization for soybeans may not work in every instance, but notes Kansas State University university research shows N applications to soybeans through fertigation may enhance yield potential. The study demonstrated that N applied to N-deficient soybeans at pod development or early pod fill can increase yields.