Effect of conservation farming practices on soil organic matter and stratification in a mono-cropping system of Northern China

An arid environment under long-term traditional agriculture has resulted in serious environmental and agricultural problems on a number of fragile soils with distinguishing physical and chemical properties in Northern China. Conservation agriculture is an alternative sustainable agriculture management system, which contributes to conserving soil, water and fertility, while changing vertical distribution of soil organic matter (SUM). No-tillage with straw cover (NTSC) and traditional tillage with straw removal (TTSR) in four regions of northern China (Tailai, Wuchuan, Nailin, Yaodu) were investigated to determine how tillage and soil type affected SUM stratification. SUM content, total N (TN), soil water content (SWC) and soil bulk density (rho(d)) in the 0-5,5-15,15-30 and 30-40 cm layers and the time since implementation of tillage treatments were evaluated. The top layer (0-5 cm) and total SUM content were markedly improved by NTSC. The influence dramatically decreased with depth in all sites. SUM content increased during the first 10 years following NTSC implementation, but the rate of increase was reduced in subsequent years. There was high positive correlation between SUM and SWC, high positive correlation between SUM and TN, and high negative correlation between SUM and bulk density. Effects of conservation measures on SUM content were expressed by a stratification ratio. The stratification ratio of SUM, in most sites, under long-term NTSC were >2. These results from northern China, suggest that long-term no-tillage with straw cover significantly improved topsoil conditions and whole of soil profile SUM and this improvement was obvious in different layers. (C) 2015 Elsevier B.V. All rights reserved.