Short‐term Versus Continuous Chisel and No‐till Effects on Soil Carbon and Nitrogen

For various reasons, North American crop farmers are more likely to practice limited‐duration no‐till than continuous no‐till (NT). Little is known about effects of short‐term no‐till (ST‐NT) on organic C and total N relative to NT and conventional‐till systems. A field experiment was initiated in 1980 to study the effects of NT, chisel plow (CP), and moldboard plow in continuous corn (CC; Zeamays L.) and soybean ( Glycinemax L.)–corn (SC) rotations on dark prairie soil. In 1996, the moldboard treatments were split into a ST‐NT subplot and an intermittently chisel‐plowed (STI‐CP) subplot that was chiseled only before corn. In 2003, soil samples were taken incrementally to the 1.0‐m depth from NT, CP, ST‐NT, and STI‐CP plots. Soil C and N accumulation was unaffected by rotation system at any depth interval. Tillage treatments significantly affected soil C and N concentrations only in the upper 50 cm. On an equivalent soil mass basis, C storage to 1.0 m after 24 yr totaled 151 Mg ha −1 in continuous NT, but just 108 Mg ha −1 in continuous CP. Short‐term no‐till and STI‐CP systems resulted in 26 and 21 Mg ha −1 , respectively, more soil C than CP. Total N storage was similar for NT and ST‐NT systems, but was significantly lower (4 Mg ha −1 less) with CP. Our results suggest that the combination of moldboard plowing (17 yr) followed by short‐term (6–7 yr) no‐till or intermittent chisel was generally superior to continuous chisel plowing (24 yr) in soil C and N contents.