稻麦轮作下秸秆还田对稻麦产量和稻田可溶性有机碳含量的影响

为阐明稻麦轮作体系下秸秆还田对作物产量与稻田可溶性有机碳（DOC）的影响，通过连续2年盆栽试验研究了两种典型土壤（壤土和黏土）在无秸秆还田、半量秸秆还田、全量秸秆还田3种处理下稻麦产量和稻季土壤溶液DOC浓度的动态变化。结果表明，秸秆还田显著增加了两种土壤大多数处理的水稻产量，增幅1.6%~11.9%，其中全量秸秆还田的增产效果大于半量秸秆还田（第1年不显著，第2年显著）。秸秆还田对小麦产量的影响因土壤类型而异，壤土中小麦产量显著增加7.2%~10.6%（第1年）或增产不显著（第2年），但全量秸秆还田和半量秸秆还田处理之间没有显著差异；黏土中小麦显著减产（5.0%~9.3%），其中第2年的全量秸秆还田减产效应显著大于半量秸秆还田。秸秆还田及土壤类型显著影响水稻前期（烤田之前）的土壤溶液DOC浓度，全量秸秆还田、半量秸秆还田分别比无秸秆还田处理平均增加141.7%、61.9%，壤土比黏土平均增加89.6%；间歇淹水之后，所有秸秆还田处理及土壤类型的DOC浓度均迅速降低。总体上，秸秆还田对两种土壤的水稻增产都有利，但对黏土小麦增产不利，秸秆还田显著增加了稻田前期的DOC浓度，间歇淹水可以迅速降低稻田DOC浓度。

Effects of straw incorporation on crop yield and dissolved organic carbon concentration at rice growing season in rice-wheat rotation cropping system

In recent years, straw incorporation as an important way of straw utilization and culture fertility has been applied widely to achieve sustainable development of agriculture. However, straw incorporation also creates some novel problems. One of the most important of these is a large amount of crop straw returned to the field affecting the growth of rice and wheat at seeding stage. Even though lots studies reported that straw incorporation increased crop yield, there were also many reports that had a negative effect on crop yield. Another problem is that straw decomposition in rice field can produce lots of dissolved organic carbon (DOC), which has a close relationship with water eutrophication. Many studies reported the effect of straw incorporation on DOC concentration of paddy field at harvest time or on the dynamic of DOC concentration in soil incubation experiment. But little is known about effect of straw incorporation on the dynamic of DOC in rice growing season with different rate of straw returned and soil types. A two-year pot experiment was conducted to investigate the effects of straw incorporation on the yield of wheat & rice and DOC concentration in soil solution in rice growing season in two types of soil, loamy soil (L) and clay soil (C). According to the level of straw incorporated into soil, each soil type consisted of three treatments:1) 0% straw returned from previous crop to soil (S0); 2) 50% straw returned from previous crop to soil (S1); 3) 100% straw returned from previous crop to soil (S2). Compared with no straw treatment, straw incorporation significant increased rice yield in most of treatments in both soil types (1.6%-11.9%), and the yield increases of S2 treatment were higher than those of S1 treatment (no significant in first year but yes in second year). However, straw incorporation had different effects on wheat yield for two soils:in loamy soil, wheat yield increased in straw incorporation treatments in both years but only significantly in first year (7.2%-10.6%), and there was no significant difference between S1 and S2 treatments; in clay soil, wheat yield decreased significantly in straw incorporation treatments in both years (5.0%-9.3%), and the yield decrease of S2 treatment were higher than that of S1 treatment (no significant in first year but yes in second year). As to the DOC concentration in soil solution in rice growing season, compared with treatment of no straw returned, DOC concentration of S2 and S1 treatments significantly increased by 141.7% and 61.9%, respectively, and DOC of loamy soil was 89.6% higher than that of clay soil on average in the early rice growing stage, but all straw treatments and soils would decrease quickly once intermittent flooding. In conclusion, straw incorporation had a positive effect on rice yield for both loamy and clay soil, but a negative effect on wheat yield for clay soil, and also increased DOC concentration significantly. The intermittent flooding could rapidly reduce the concentration of DOC in paddy soil.