Influence of no‐till and a winter rye cover crop on nitrate losses from tile‐drained row‐crop agriculture in Iowa

Abstract

Artificial subsurface drainage is necessary to maintain agricultural production in the soils and climate of north‐central Iowa. However, it can result in adverse environmental impacts, because it intercepts and diverts some water and soluble NO3–N directly to streams. We investigated the impact of no‐till and a winter rye cover crop (Secale cereale L.) on seasonal and annual NO3–N concentration and loading in leachate from a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation. The eight treatments are chisel plow (CT), chisel plow with winter cereal rye (CTr), no‐till (NT), and no‐till with winter cereal rye (NTr), with “‐C” indicating corn and “‐S” indicating soybeans. Plots with artificial subsurface drainage were monitored for water quality from 2011 to 2015. The NT and CTr treatments consistently decreased NO3–N loss on the seasonal and annual scales compared with CT. Compared with NT, NTr did not reduce NO3–N loading nor concentration in leachate, probably because of low NO3 leaching potential from NT combined with low rye cover crop biomass throughout the study with NT. The 5‐yr average annual NO3–N concentrations were: 16.9 mg L−1 with CT‐S, 16.7 mg L−1 with CT‐C, 12.6 mg L−1 with NT‐S, 12.0 mg L−1 with CTr‐S, 11.8 mg L−1 with CTr‐C, 11.4 mg L−1 with NTr‐S and NTr‐C, and 11.1 mg L−1 with NT‐C. Overall, both no‐till and a cover crop showed potential for improving N management for water quality.

Water quality of an integrated crop–livestock system in the northern Great Plains

“…Similar to trends observed for surface runoff concentrations and loads, infiltration water N and P concentrations were generally lower in grass pasture compared to cover crop and wheat and postgraze concentrations were lower than pre-graze. Infiltration water NO 3 − -N and PO 4 3− -P concentrations were greater in cover crop and wheat phases, yet these concentrations were up to an order of magnitude lower than observed in leachate of previous studies (Delgado, Shaffer, & Brodahl, 1998;Waring, Lagzdins, Pederson, & Helmers, 2020;Wilson, Tyler, Logan, & Turnage, 1991), indicating a low leaching potential for ICL system vegetation types in the northern Great Plains ecoregion examined herein.…”

Split‐nitrogen application with cover cropping reduces subsurface nitrate losses while maintaining corn yields

“…Cereal rye (Secale cereale L.) has been widely used in the upper Midwest because of its winter-hardiness and its ability to scavenge postharvest soil N compared with other species (Kaspar & Bakker, 2015). While previous studies have shown reductions in NO 3 -N concentrations in subsurface drainage provided by cereal rye (Kaspar et al, 2007(Kaspar et al, , 2012Ruffatti et al, 2019;Waring et al, 2020), many producers remain apprehensive about cover crop adoption. One of the obstacles of planting cereal rye ahead of corn is the potential reduction of early-season soil N availability due to net N immobilization, resulting in 0.1-12% yield reductions…”

Evaluating drainage water recycling in Central Iowa: Long-term yield and financial implications

“…Subsurface drainage from agricultural fields in Iowa has been identified as a major source of nitrogen and phosphorus delivered to downstream water bodies (Baker et al, 1975;Helmers et al, 2005;Waring et al, 2020). These nutrients are known to cause hypoxia in the Gulf of Mexico (Hypoxia Action Plan, 2008).…”

“…Existing subsurface drainage infrastructure is rerouted from usual outlets or nearby streams to a storage reservoir near the field. Because a large portion of Iowa's subsurface drainage usually occurs in the spring (Waring et al, 2020), it is kept in the reservoir until rainfall and stored soil water cannot meet crop water 2 demands. At this point the captured subsurface drainage water is applied to the field to alleviate drought stress in the crop (Frankenberger et al, 2017).…”

“…This enables producers to access fields with heavy machinery during critical periods of time for crop management events such as fertilization and planting and for crop root systems to develop further throughout the soil profile (Singh et al, 2007). These subsurface drainage systems, however, have long been documented to increase nutrient loads to the downstream waterways (Baker et al, 1975;Helmers et al, 2005;Waring et al, 2020).…”