Picture: Cover crop after seed corn in Dodge County.
This is Dr. Nathan Mueller, your local agronomist with Nebraska Extension. Have you ever thought of cover crops as a groundwater management tool? Educational efforts and proactive protection of groundwater from nitrate contamination can help reduce the need for regulation. So, let’s answer 3 questions today.
First, what factors influence groundwater nitrate contamination? The volume of water moving through the soil, nitrate concentration in soil water, soil texture, and the depth to groundwater are all factors. As producers, we can affect the volume of water moving through the soil profile and the nitrate concentration in soil. We can control these two factors with our irrigation management, nitrogen fertilization program, and our cropping system.
Second, how can my cropping system affect soil nitrate concentration and water moving through the soil profile? Using winter cover crops as a part of our cropping systems, such as cereal rye, can help reduce soil nitrate-nitrogen concentration and reduce the volume of water moving through the soil profile. Research in the Midwest over the last decade as shown that adding winter cover crops, such as cereal rye into the corn and soybean rotation, can reduce nitrogen losses from the root zone by 13 to 61%. Adding alfalfa into our crop rotation can also help reduce nitrate losses. Research has shown that over a 4 year period, alfalfa can reduce leaching losses by as much as 175 lbs of nitrogen per acre compared to the corn/soybean rotation.
Third, will cover crops steal soil moisture and reduce my corn and soybean yields? Sandy soils are the most prone to nitrate leaching and can only store 1 to 1.5” of water per foot of soil. On average, northeast Nebraska receives more precipitation from October through April than sandy soils can hold in the root zone. In this situation, water used by the cover crop is water that we couldn’t store anyway for our corn or soybean crop. Cover crop research has shown very little if any reduction in soybean yield following a cover crop. Corn yield reductions following a cover crop occurs more frequently. Effectively managing a cover crop before corn is much more critical from the soil moisture, soil temperature, and in-season nitrogen management standpoint.
For more information using alternative cropping systems to help protect groundwater, visit our local website at croptechcafe.org. Know your crop, know your tech, know your bottom line. This is Dr. Nathan Mueller, your local agronomist for Nebraska Extension on KTIC radio.
