Nitrate leaching is a major concern in coarse-textured agricultural soils because it can cause economic losses for farmers and contaminate groundwater. While some nitrate leaching may be inevitable when growing corn on sandy soils, there are several management strategies that can be implemented to limit nitrate loss. Here are some key takeaways from a recent five-year study looking at three major factors impacting nitrate leaching: drainage, nitrogen availability, and cropping system.

Legumes still can provide valuable N to today’s cropping systems. Legumes also contribute a non-nitrogen rotation effect due to addition of soil organic matter and improvement in soil health. Corn grown following alfalfa stands that are 2+ years old (and contained at least 50% alfalfa) require no nitrogen fertilizer on many soils. Red clover N credits are less than for alfalfa.

Cover crops were almost as effective as restored prairie at reducing nitrate concentrations in tile-drained water, according to recent research at Iowa State University.This was one of the key findings from a study led by Marshall McDaniel, associate professor of agronomy at Iowa State. The project was designed to better understand how the quantity and quality of tile drainage water impacts in-stream potential for nutrient enrichment, leading to growth of algae and depletion of vital oxygen in aquatic ecosystems.

Cover crops are used to address multiple resource concerns and can provide a wide range of conservation benefits including reduced soil erosion, scavenged residual soil nitrogen, weed suppression, and supplemental livestock forage. The carbon to nitrogen (C:N) ratio of the cover crop determines the durability of the cover crop residue.