Corn’s nitrogen (N) losses get a lot of attention. This is because corn has a high demand for N and receives at least 40% of the N fertilizer consumed in the U.S., writes Tai McClellan Maaz, Director, Nitrogen Program, International Plant Nutrition Institute. Any fertilizer N that the corn crop does not recover is at risk of gaseous or leaching losses. Fertilizer losses are a concern because they contribute to economic losses and environmental issues such as hypoxia in the Gulf of Mexico.
However, Midwestern fields are not always continuously cropped to corn. Soybean is commonly rotated with corn, and cover crops are also becoming more common between annual cash crops.
What are the loss dynamics while the cropping system is not in corn?
While corn relies mainly on fertilizer inputs, soybean gets its N from biological N fixation, mineralization from soil organic matter, and residual soil N. A cover crop, such as rye, can also be planted to capture or “catch” these two pools of soil mineral N.