Effects Of Cultivation Practices On Rice Seedling Growth Under Wheat Straw Returning

China produces the largest amount of crop residue in the world.Straw returning by burning has the risk of polluting the air and has a threat to transportation.Incorporation of straw into the soil has the positive effect on soil organic matter contents,thus improving soil physical-chemical properties and subsequently increasing crop yield.However,growth of rice seedlings is vulnerable to be stunted by short-term straw returning.This study investigated the effect of transplanting pattern,water and nitrogen on growth and nutrients uptake of rice seedlings under wheat straw returning,with the objective of elucidating the underlying mechanisms of stunted seedlings and thereby formulating counteracting agronomical measures.The main results were as follows:(1)Effect of transplanting pattern on growth and nutrients uptake of rice seedlings under wheat straw returning was determined.Compared with the control(non-straw returning),incorporation of wheat straw decreased shoot dry weight,tiller number and plant height of rice seedlings under both machine and hand transplanting by 12.8%,18.1%and 9.4%,respectively.Machine transplanting negatively affected shoot dry weight,tiller number and plant height,respectively.Compared with hand transplanting,machine transplanting decreased root dry weight and root by 64.6%and 27.5%,respectively.Seedling growth of machine transplanting rice is more vulnerable to be stunted by short-term straw returning,which is caused by inhibited root growth and impaired root activity.(2)Effect of water management on growth and nutrients uptake of rice seedlings under wheat straw returning was determined.Compared with the control(non-straw returning),incorporation of wheat straw decreased tiller number,N concentration of shoot and root activity of rice seedlings under both continuous flooding and soil aeration by 9.0%,14.2%and 19.4%,respectively.Soil aeration positively affected tiller number and N concentration of shoot of rice seedlings,respectively.Compared with continuous flooding,soil aeration increased root activity significantly by 20.3%.Soil aeration at tillering stage can increased root activity and thus alleviated worse performance of rice seedlings under wheat straw returning.(3)Effect of nitrogen management on growth and nutrients uptake of rice seedlings under wheat straw returning was determined.Compared with the control(non-straw returning),incorporation of wheat straw decreased dry weight,tiller number,plant height and N concentration of shoot;dry weight,root activity and N concentration of root of rice seedlings under both 0 and N fertilizer by 21.1%,17.4%,15.9%and 9.7%;8.1%,26.6%and 13.2%,respectively.N fertilizer positively affected dry weight,tiller number,plant height and N concentration of shoot of rice seedlings,respectively.Compared with no N fertilizer,N fertilizer increased dry weight,root activity and N concentration of root of rice seedlings significantly by 86.1%,45.0%and 29.7%,respectively.Increasing the ratio of tiller fertilizer improved root activity,tiller number and dry matter accumulation at high N level treatment.Weak function of root was the cause of worse performance of rice seedlings under wheat straw returning,which can be alleviated by increasing basal N fertilizer at transplanting.