Abstract:

To solve the prominent problems such as the quality decline in black soil cultivated land and the environmental pollution caused by burning excess straw resources in the east foot of the Great Khingan Mountains, the conditions of straw returning to field were established combined with 7 tillage methods: deep ploughing + heavy harrow (SDH), subsoiling + heavy harrow (SSH), subsoiling and shallow ploughing + heavy harrow (SSS), heavy harrow (SH), rotary tillage (SRT), no tillage (SZT) and traditional tillage (CK). By studying the effects of different tillage methods on soil chemical properties under the condition of straw returning to field for two years, we obtained the following results: the soil organic matter increased rapidly in a short time after straw returning to field, and the organic matter level decreased again after a growth cycle. Compared with those under CK, the contents of available phosphorus and total potassium increased in 0-40 cm soil layer under SDH, SSH, SSS and SH in the first year; and the contents of alkali-hydrolyzable nitrogen, available potassium, total nitrogen and total phosphorus increased significantly under SDH, SSH and SSS. After harvest in the second year, SDH, SSH and SSS increased the contents of alkali-hydrolyzable nitrogen and total phosphorus in soil; SSH and SSS increased the contents of available phosphorus, available potassium and total nitrogen in 0-60 cm soil. Under the condition of straw returning, SSH and SSS could increase soil nutrient content significantly.

Key words: straw returning, tillage methods, black soil, chemical properties, nutrient