Effects of continuous straw mulching on soil physical and chemical properties and crop yields in paddy-upland rotation system

A long-term (20082010) experiment was conducted to study the effects of straw mulching on soil physical and chemical properties and crop yields in paddy-upland rotation system. The results show that compared with no straw mulching treatment, the soil bulk density is reduced in 05cm soil layer, and soil water contents are increased in 05cm and 515cm soil layers with the straw mulching treatment. The contents of soil organic matter, alkali N, available P and available K in 025cm soil layer are increased under the straw mulching. Influences of the straw mulching on soil nutrient conditions in 05cm soil layer are higher than those of 515cm and 1525cm soil layer. The nutrient contents increase sequence in 05cm soil layer after 5 seasons of the straw mulching are: available K (7.64%15.33%) available P (7.52%10.03%) alkali. N (7.30% 8.74%) organic matter (6.08%7.53%). The results also indicate the straw mulching increases the crop yields, and the effects of the straw mulching on wheat and rapeseed are higher than that of rice, and the increases of mulching times and the amount of straw have significantly positive effects on the crop yields. The key components of the yields are effective panicles of wheat and rice, and pod number and seed per pod of rapeseed.