Effects of Different Tillage Methods on Soil Nutrients and Biological Properties of Dry Land in Northeast China

In order to improve soil quality and crop yield in the black soil region and promote the sustainable development of regional agriculture. A field experiment for four consecutive years under three tillage treatments, including subsoiling tillage（ST）, no tillage（NT） and conventional tillage（CT） were set up to investigate the effects of tillage methods on soil available nutrients, soil microbial quantity and enzyme activities. Results showed that, compared with CT, ST could significantly increase the contents of alkaline nitrogen, available phosphorus and available potassium in the upper soil layer（0-20 cm）（by 23.6%, 49.6%, and 63.3%, respectively）, also for content of available phosphorus in the lower soil layer（20-40 cm）（86.2%）.The pH of ST in the upper soil layer significantly increased, while the pH changed less among different treatments of in the lower soil layer; ST and NT treatments could significantly increase the number of bacteria and fungi in the upper soil layer, while ST significantly increased the number of actinomycetes; the differences of microbial quantities among in the lower soil layer were relatively small, decreased in the order: ST＞NT＞CT.There were highest activities of sucrase and catalase in the upper soil layer under ST, while NT increased soil urease and phosphatase activities. Except for catalase, the activities of other enzymes were higher in the upper soil than in the lower soil. ST and NT could increase the content of soil available nutrients, the number of microorganisms and enzyme activities, which helps to improve soil chemical and biological properties, thereby improving soil quality. Among them, subsoiling tillage played an important role in fertilizing soil and maintaining the living environment of soil organisms.