Combined effects of tillage systems and crop rotations on soil enzyme activities in Inner Mongolia, China

Soil enzyme activity, an important determinant of soil biological quality, was studied under rain-fed condition of Inner Mongolia, China. In 20062009, effects of tillage (conventional tillage [T], no-tillage with low stubble [NL], no-tillage with high stubble [NH], no-tillage with low stubble mulching [NLS] and no-tillage with high stubble mulching [NHS]) and crop rotation (soybean-corn-oat, corn-oat-soybean and oat-soybean-corn) on soil enzyme activity were estimated. Observations made on four soil enzyme activities showed that in all five tillage treatments the activities increased after the rotations were applied. Under no-tillage, enzyme activities increased more than under the conventional tillage in all soil depths. The change in soil enzyme activity was more pronounced in 0-10 cm soil layer after one cycle of rotation than in the 10-20 or 20-30 cm layers. The catalase, invertase, urease and alkaline phosphatase activities of no tillage with high stubble mulching increased 9.4, 68.2, 37.7 and 37.8%, respectively, compared to conventional tillage in oat-soybean-corn rotation pattern. Among crops, soybean was the best for increasing soil enzyme activity in one year, whereas, among the rotations tested, oat-soybean-corn was best. These results, for the first time indicated that crop rotation combined with notillage was important for Inner Mongolia dryland agriculture and thus, should be implemented for the maintenance and improvement of soil quality in this area.