Nitrogen Management Strategies to Reduce Nitrate Leaching in Tile‐Drained Midwestern Soils

TLDR

Nitrate leaching from Midwestern tile‑drained soils is a complex problem driven by factors such as drainage, tillage, crop choice, soil organic matter, hydrology, and climate, and poses a major challenge to balancing crop nitrogen needs with water quality protection. This review aims to assess how century‑long changes in agricultural management have influenced nitrogen dynamics in Midwestern soils and to identify research and management strategies that can reduce nonpoint nitrate leakage into water resources. The authors discuss soil characteristics, management practices, and their effects on nitrate loss, and propose strategies such as optimized timing and rates of nitrogen application, soil testing, crop rotation, cover crops, reduced tillage, nitrification inhibitors, and wetland or biofilter installations to mitigate nitrate leaching.

Abstract

Balancing the amount of N needed for optimum plant growth while minimizing the NO 3 that is transported to ground and surface waters remains a major challenge for everyone attempting to understand and improve agricultural nutrient use efficiency. Our objectives for this review are to examine how changes in agricultural management practices during the past century have affected N in midwestern soils and to identify the types of research and management practices needed to reduce the potential for nonpoint NO 3 leakage into water resources. Inherent soil characteristics and management practices contributing to nonpoint NO 3 loss from midwestern soils, the impact of NO 3 loading on surface water quality, improved N management strategies, and research needs are discussed. Artificial drainage systems can have a significant impact on water quality because they behave like shallow, direct conduits to surface waters. Nonpoint loss of NO 3 from fields to water resources, however, is not caused by any single factor. Rather, it is caused by a combination of factors, including tillage, drainage, crop selection, soil organic matter levels, hydrology, and temperature and precipitation patterns. Strategies for reducing NO 3 loss through drainage include improved timing of N application at appropriate rates, using soil tests and plant monitoring, diversifying crop rotations, using cover crops, reducing tillage, optimizing N application techniques, and using nitrification inhibitors. Nitrate can also be removed from water by establishing wetlands or biofilters. Research that is focused on understanding methods to minimize NO 3 contamination of water resources should also be used to educate the public about the complexity of the problem and the need for multiple management strategies to solve the problem across agricultural landscapes.