Influence Of No-Till And A Winter Rye Cover Crop On Nitrate Losses From Tile-Drained Row-Crop Agriculture In Iowa

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 (Seca le 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.