Conducting nutrient research on-farm allows researchers to evaluate performance of various practices designed to reduce nutrient loss (i.e. winter cover cropping) under real farming conditions. That’s why Lowell Gentry and his team from the University of Illinois are conducting research using whole fields to investigate fertilizer practices as well as in-field and edge-of field techniques that show promise for reducing nutrient runoff, especially nutrients in tile drainage water.
This university research team has 3 complementary NREC grants that are producing relevant results. A collection of what they have learned over the past three years follows:

1.) Cover crops can work.
Cereal rye after corn and ahead of no-till soybeans can reduce tile nitrate loads by 40% without decreasing soybean yield. Lowell recommends that farmers try cover crops first on a small field to see how the system performs on their land. Further evaluation of other cover crops is ongoing, including oat and radish after soybean and ahead of corn; and cereal rye in
continuous corn.

2.) Wait to apply nitrogen in the spring.
A 50/50 split between spring and sidedress application of nitrogen reduced N loss by 30% compared to fall N with an inhibitor (10 lbs/A less tile N load) following the warm winter of 2016; corn yields were unaffected. The wet spring of 2017 created enough N leaching from the fall N treatment to significant decrease corn yield by 7% compared to the 50/50 split application (195 bu/A vs. 210 bu/A).

3.) Avoid phosphorous application in low spots.
Low spots (closed depression that do not drain to a waterway) can contribute disproportionately more P to tile lines than the rest of the field as these areas tend to have high organic matter that contains large amounts of P. Another contributing factor is that low spots occasionally pond and drown out the crop, thus eliminating P removal for that year. Soil sampling needs to take into account closed depression and variable rate application can then help avoid adding more P to areas already rich in P.

This is the field configuration where some of Lowell’s on-farm research is taking place in east central Illinois. At this site, a corn-soy-wheat rotation with cover crops is being compared to a corn-soy rotation under conventional production agriculture. Additionally, cereal rye in continuous corn is also being evaluated at this site. This research has demonstrated that a longer rotation with cover crops and a bioreactor can nearly eliminate nitrate leaching; however, an abundance of radish and turnip after wheat in 2015 increased the required amount of fertilizer N for corn by 60 lbs/A during the following year. These data suggest that there is a balance between cover crop biomass production and the potential for the cover crop residue to immobilize soil N, which can lead to delays in early crop growth and yield.

NREC has produced a video on terminating cover crops. You can view the video on NREC’s YouTube channel.

Read more stories and information like this in the January issue of the NREC newsletter here.

ILLINOIS NUTRIENT RESEARCH AND EDUCATION COUNCIL / www.illinoisnrec.org