Cover crops in the upper midwestern United States: Potential adoption and reduction of nitrate leaching in the Mississippi River Basin

Abstract

Nitrate (NO 3 ) losses from agricultural lands in the Midwest flow into the Mississippi River Basin (MRB) and contribute significantly to hypoxia in the Gulf of Mexico. Previous work has shown that cover crops can reduce loadings, but adoption rates are low, and the potential impact if cover crops were widely adopted is currently unknown. This paper provides an analysis of potential cover crop adoption and relative benefits to water quality across the five-state region of Ohio, Indiana, Illinois, Iowa, and Minnesota in the upper midwestern MRB. Two agricultural counties were selected in each of the five states, and the potential for fall-planted cover crop adoption was estimated based on cash crop rotation and tillage systems. In these 10 counties, an estimated 34% to 81% of the agricultural land could have cover crops integrated into their corn (Zea mays L.) and soybean (Glycine max L.) cropping systems. These adoption rates would in some cases require shifts of current tillage practices from fall to spring, but could be even higher with increased adoption of no-till and mulch-till. Nitrate reduction simulated with the Root Zone Water Quality Model for the tile drained portion of the corn-soybean and continuous corn cropping systems in the five-state area, under the assumed management systems and uniform soil properties, showed that cover crops have the potential to reduce NO 3 loadings to the Mississippi River by approximately 20%. These predictions suggest that cover crop adoption would have a beneficial impact on water quality in the MRB and would contribute greatly towards meeting the national goal of significant reduction in NO 3 -nitrogen (N) load entering the Gulf.Key words: adoption-cover crops-hypoxia-Mississippi River-nitrate leaching-water quality Nitrate (NO 3 ) in surface waters of the Mississippi River Basin (MRB) degrades freshwater quality in the region and much of it is eventually transported to the Gulf of Mexico where it contributes to hypoxia (Rabalais et al. 1996). Agricultural land devoted to corn (Zea mays L.) and soybean (Glycine max L.) production in the Upper Midwest makes a major contribution to NO 3 found in surface waters (Burkart and James 1999; Goolsby et al. 2001;David et al. 2010). Alexander et al. (2008) estimated that over 50% of the nitrogen (N) fluxes from the Mississippi River originated from agricultural land producing corn and soybean. In addition, artificial drainage systems used primarily for corn and soybean production increase losses of NO 3 from agricultural land (Goolsby et al. 2001;Royer et al. 2006) by accelerating transport to surface water (Zucker and Brown 1998) and bypassing subsurface flow paths that would reduce NO 3 concentrations through denitrification or other processes (Schilling et al. 2007). As a result, five upper midwestern states (Iowa, Illinois, Indiana, Ohio, and Minnesota), which have large areas of artificially drained land used for corn and soybean production, contribute about 46% of the NO 3 -N load to the Mississippi River that re...

Cover crop adoption in Iowa: The role of perceived practice characteristics

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The trouble with cover crops: Farmers’ experiences with overcoming barriers to adoption

“…The use of an overwinter plant in a corn-soybean cropping system provides in-field benefits such as erosion prevention, improvements in soil quality and nutrient retention (Schnepf and Cox, 2006;Kaspar and Singer, 2011) while contributing to landscape scale environmental benefits such as decreasing sediment and nutrient transport and reducing water pollution (Kladivko et al, 2014). In Iowa, it is estimated that cover crops were only used on 1.6% of cropland hectares during 2012 (NASS, 2014), which is a notably low level of use across the landscape given evident agronomic and environmental benefits.…”

Corn Nitrogen Fertilization Requirement and Corn-Soybean Productivity with a Rye Cover Crop

“…Winter adapted cereal cover crops tend to be more effective than legumes in NO 3 loss reduction in cold northern climates due to better fall and early spring growth (Shipley et al, 1992;Parkin et al, 2006), with RCC as a common cover crop choice (Ranells and Wagger, 1997;Ruffo et al, 2004;Kladivko et al, 2014). In addition, RCC has flexibility in establishment, relatively low seed cost, and winter hardiness (Feyereisen et al, 2006).…”

“…nvironmental concerns related to crop N fertilization is an ongoing issue (USEPA, 2007), including reducing N in surface waters related to hypoxia in coastal surface waters Kladivko et al, 2014). Nitrogen application rate to corn is an important factor in regard to cropping system profitability and NO 3 loss.…”