水稻-油菜轮作模式下秸秆还田替代钾肥的效应

【目的】研究稻-油轮作条件下秸秆还田配施钾肥对水稻和冬油菜产量、 地上部钾素累积量、 钾肥利用率以及土壤钾素含量的影响,明确长期秸秆还田替代钾肥的效果,为秸秆还田下稻-油轮作中钾肥的合理施用提供科学依据。【方法】2011~2014年在湖北省粮油主产区-江汉平原选择土壤供钾能力较高的农田,布置水稻-冬油菜轮作定位试验。试验共设7个处理,分别为: 1)CK(-K); 2)+K; 3)+S; 4)S+1/4K; 5)S+1/2K; 6)S+3/4K和7)S+K。其中K和S分别表示钾肥和还田秸秆,K2O用量为90 kg/hm2。【结果】 1)与不施钾(-K)相比,施用钾肥和秸秆还田均不同程度地增加了水稻和冬油菜年均产量和钾素吸收量,尤以秸秆还田配施钾肥处理(S+K)的水稻和冬油菜产量和地上部钾素吸收量最高,与对照(-K)相比增产率分别为12.8%和19.1%; 地上部钾素(K2O)累积吸收量增幅分别达到35.7%和79.3%。2)在当前推荐钾肥用量条件下,秸秆还田对水稻和冬油菜的钾肥吸收利用率没有显著影响,但均使两种作物的钾素吸收利用率显著降低。与秸秆不还田相比,秸秆还田后水稻季的钾肥与钾素农学利用率明显降低,而冬油菜季则分别显著提高与持平; 秸秆还田后,水稻季的钾素农学利用率显著降低,而冬油菜季则持平。3)通过对秸秆还田条件下钾肥用量与增产率、 地上部吸钾量增幅的相关分析得出秸秆还田后当前的推荐钾肥用量偏高。根据肥效模型并结合实际产量和农田钾素养分平衡拟合得出,水稻和冬油菜的年均适宜钾肥用量分别为52.0和61.9 kg/hm2,比推荐用量可分别减少42.2%和31.2%。【结论】在土壤钾素含量较高的情况下,稻-油轮作区开展连续秸秆还田不仅能够降低钾肥投入量,获得较高的粮油经济产量,还可以提高土壤有效钾含量并维持农田系统养分平衡以及秸秆钾素资源的良性循环。

Substituting effect of crop residues for potassium fertilizer in rice-rapeseed rotation system

Objectives]In order to provide a scientific basis for crop residue management and potassium ( K ) fertilization, effects of straw returning to field and recommended K fertilizer rate on yields of rice and winter oilseed rape, potassium accumulation amounts of shoots, K use efficiencies, and soil K contents in rice-rapeseed system were studied.Methods]A long-term(2011-2014)field experiment was carried out in a selected high K level soil in Jianghan plain.There were seven treatments with three replications,1)CK(-K);2)+K;3)+S;4)S+1/4K;5)S+1/2K;6)S+3/4K, and 7)S+K, where K and S denoted K fertilizer and crop residues, respectively.The K2 O application amount was 90 kg/hm2 .Results] 1 ) The application of K fertilizer and straw returning to field could increase the crop yields and K uptakes of shoots at varying degrees for the six growth seasons.Compared with the CK treatment(-K) , the straw incorporation with the K fertilizer treatment( S+K) has the best effect, and the yield increased rates are 12.8%and 19.1%for rice and rapeseed and the K uptake increase rates are 35.7%and 79.3%, respectively.2)The straw returning to field has no significant impacts on the KfREs(K fertilizer recovery efficiency) of rice and winter oilseed rape, but observably decreases the KREs ( K recovery efficiency ) under the recommended K fertilizer rate.Meanwhile, the straw returning to field also decreases the Kf AE ( K fertilizer agronomic efficiency)of rice, but enhances the KfAE of winter oilseed rape.The KAE(K agronomic efficiency of straw K with chemical K) of rice is reduced, but that of winter oilseed rape is equivalent compared with the Kf AE without the straw incorporation.3) The correlation analysis among the yield increase rates, K accumulation amounts and K-fertilizer amounts indicates that the recommended rates of K fertilizer are higher than the actual demand for rice and rape growth in consideration of the continuous straw returning to field.Using the fertilizer efficiency model and considering the straw returning to field and nutrient balance, the optimum annual average amounts of K fertilizer(K2O)are 52.0 and 61.9 kg/hm2 for rice and winter oilseed rape, which are 42.2%and 31.2%less than the recommended amounts in this region.Conclusions] Under the high soil K level condition, we conclude that the straw returning to field can not only replace partial chemical potassium and get higher yield, but also improve soil available K, maintain the nutrient balance of soil system and assure the virtuous circle of straw potassium resources in rice-rapeseed rotation system.