Soil Carbon and Nitrogen Changes on Initiation of No‐Till Cropping Systems

Abstract

Abstract Previous research indicates that increased cropping intensity (crops/time) under no‐till may increase soil organic C and N contents and reduce risk for NO 3 ‐N leaching, compared with tilled and frequent‐fallow systems. This study was conducted to determine the effect of cropping intensity on changes in soil organic C and N and NO 3 ‐N after 4 yr (1985–1989) of no‐till and perennial grassland management. The effects were examined over three toposequences in the west‐central Great Plains that had been previously under tilled and frequent‐fallow systems for >50 yr. Production systems included wheat ( Triticum aestivum L.)‐fallow (WF), wheat‐corn ( Zea mays L.) or sorghum ( Sorghum bicolor [L.] Moench)‐millet ( Panicum miliaceum L.)‐fallow (WCMF), and perennial grass (CG). Organic C and N accumulated, was maintained, and declined in 0‐ to 2.5‐, 2.5‐ to 5‐, and 5‐ to 10‐cm soilayers, respectively, for all systems in the relatively short study period (4 yr). More intense systems (WCMF and CG) had greater contents of soil organic C and N in the aggregate 0‐ to 10‐cm layer than WF after 4 yr. Smaller profile (0–180 cm) NO 3 ‐N contents occurred under WCMF (60 kg ha −1 ) and CG (10 kg ha −1 ) than WF (120 kg ha −1 ) systems, and showed promise for reducing NO 3 ‐N leaching risk with increased cropping intensity. This study indicates that rapid changes in C and N occur with initiation of no‐till in soils previously managed under tilled and frequent‐fallow systems and that increased cropping intensity will promote higher equilibrium levels of organic C and N, but lower levels of NO 3 ‐N.