Effects of conservation tillage on soil nutrients and enzyme activities in rainfed area

Based on the field experiments conducted in Dingxi of the western Loess Plateau, effects of the conventional tillage and five conservation agricultural patterns, namely conventional tillage, conventional tillage with stubble incorporating, no tillage with no stubble, no tillage with stubble retention, conventional tillage with plastic mulching and no tillage with plastic mulching on soil nutrients and enzyme activities in a rainfed farming system were studied. The results show that contents of soil organic matter, total N, total P, total K, NH4+-N, available P and K, soil urease, alkaline phosphates and invertase activities at the 0–5 and 5–10 cm layers are increased in the two stubble retention systems. Moreover, in the two stubble retention systems, soil organic matter, total K and available K are improved greatly at the 10–30 cm depth of soil. Soil catalase activity is improved at the 0–30cm depth of soil in the three no-tillage systems, while NO3--N content is decreased. There are significant correlations between soil organic matter, contents of the nutrients, alkaline phosphatase and inverstase activities. Principal component analysis indicates that soil organic matter, nutrients and hydrolases could be used to evaluate soil fertility in rainfed areas of Loess Plateau.