Study On Soil Fertility Under Straw Mulching Of Rice-wheat/rape Cropping System On The Paddy Field In Central Hilly Area Of Sichuan

The straw mulching experiment was carried out in Jian yang city, Central Hilly Area of Sichuan. The paper studied the change of straw decomposition, soil physical and chemical property, soil nutrient and crop yields under straw mulching. It shows that:(1) Straw is very rich in nutrient, the speed of decomposition was from fast to slow, the change of straw nutrient was ebb and flow. Soil got the abundant N, P, K when straw returned to soil, according to crop yields and straw drying weight, the result shows using rice straw per hectare was equal to carbamide 120.60kg, superphosphate 25.05kg, potassium chloride 477.45kg; using wheat straw per hectare was equal to carbamide 48.45kg, superphosphate 14.40kg, potassium chloride 181.20kg; using rape straw per hectare was equal to carbamide 33.60kg, superphosphate 19.50kg, potassium chloride 23.85kg. Three monthes after returning straw, the weightlessness of wheat straw, rape straw and rice straw averaged out about 60%. During the decomposition, the change of straw nutrient was characterized as the following:K>P>N, and nutrient release velocity of straw burying was over of straw mulching. After 180 days, the coarse fibre of wheat and rice were remained by 15.3%, 21.5%, the lignin and coarse ash were showing a tendency to increase.(2) Effects of water storage and water conservation which caused by straw mulching were very apparent in the soil layer which the depth of 0-20cm, and the effects were increased with the increase of straw mulch. Soil moisture content of straw mulching treatments in 0-10cm was more than CK. As compared to CK, but the effect on soil moisture content of straw mulching treatments in 10-20cm weren't apparently better than CK. As compared to CK, the improvement of water use efficiency was by 5.90%-26.89% in March. In winter, the improvement of water use efficiency wasn't apparent.(3) Straw mulching could improve soil physical properties to some extent. As compared to CK₁, CK₂, straw mulching reduced soil bulk density by 0.03-0.05 g/cm² and by 0.06-0.07 g/cm², individually. Straw mulching could increase soil porosity and induce disperse coefficient. In water stable aggregate of soil of point, straw mulching could improve...