By John Nelson, Extension Educator in Lancaster County
Groundwater nitrate has been a problem in Nebraska and throughout the Midwest for many decades and is growing in its scope and severity across our state. As crop producers, we have proven production practices to help reduce the movement of nitrate into the groundwater. One of the simplest solutions is to reduce our nitrogen (N) rates on corn. Nebraska On-Farm Research has produced many studies demonstrating that lower nitrogen rates on corn can have minimal impact on yield while also resulting in greater profitability — see https://go.unl.edu/ofr_results. On-Farm Research was conducted in the Waverly area during the 2024 season to examine the possibility of using less nitrogen in corn production. Two treatments were evaluated: the farmer’s rate of 150 lb N/ac and the reduced rate of 115 lb N/ac. The UNL nitrogen recommendation for this field, with a 185 bu/ac yield goal, was 77 lb N/ac. The table shows that the reduced N rate had no statistically significant effect on corn yield or subsequent net return.
Another method to reduce nitrate leaching through the soil profile is to implement cover crops. An ongoing On-Farm Research study in Lancaster County is examining interseeding cover crops in standing corn as a part of the Highboy Cover Crop Interseeding Project — see https://go.unl.edu/highboycovercrop. The study examines the effect of cover crops on nitrate movement through the soil profile in the fall and following spring.
Figure 1 shows, by spring 2024, the cover crops had taken up a significant amount of nitrate compared to the areas with no cover crops. This nitrate is preserved in the cover crop biomass, rather than being leached out of the root zone toward the groundwater.
These are only two of the many strategies farmers can implement to reduce nitrate losses to the groundwater. These practices offer the additional benefits of improving productivity, soil health and profitability.