Strip-tillage decreases soil nitrogen availability and increases the potential for N losses in a cover cropped organic system

Abstract

Reduced-tillage systems that augment soil inorganic N availability while reducing N losses can improve the nitrogen-use efficiency of cover crop-based organic cropping systems. We conducted a three year full factorial field experiment in the upper Midwest, USA to examine the effects of strip-tillage and a cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth) cover crop mixture on (1) soil inorganic nitrogen (N) concentrations throughout the growing season, (2) sweet corn (Zea mays L.) crop productivity and N uptake, and (3) potential N loss via denitrification and leaching. We compared full-width tillage (FWT) vs. strip-tillage (ST) with and without a rye-vetch cover crop. ST decreased soil inorganic N concentrations 16–40% compared to FWT, with soil inorganic N higher in the tilled in-row zone compared to the undisturbed between-row zone in 1 of 3 years. The rye-vetch cover crop did not provide a consistent increase in soil inorganic N. ST increased soil leachate N concentrations by ~50% and increased the potential for denitrification by 18% but depressed sweet corn biomass and N contents in only one of three years, when hairy vetch biomass and soil moisture was lowest. We conclude that utilizing ST in combination with a cover crop is not likely to improve N use efficiency or crop yields, and may increase N losses within an organic cover crop-based cropping system.