小麦秸秆还田条件下钾肥减量对水稻产量及养分利用的影响

利用长江中下游稻麦轮作定位试验，研究小麦秸秆还田条件下，钾肥减量施用对土壤钾素含量、水稻产量和钾素累积量以及钾肥利用率的影响，为小麦秸秆还田后水稻钾肥合理施用提供科学依据。试验共设5个处理，分别为：秸秆还田+配方施肥（K_100%），秸秆还田+配方施肥钾肥减量10%（K_90%），秸秆还田+配方施肥钾肥减量20%（K_80%），秸秆还田+配方施肥钾肥减量30%（K_70%），秸秆还田+配方施肥不施钾肥（K₀）。采集3年水稻不同生育期植株和土壤样品，分析土壤钾素动态变化和水稻钾素吸收富集规律，并统计水稻产量和经济效益。3年试验结果表明，与K_100%相比，K_90%处理的土壤全钾和速效钾含量分别提高了3.13%和6.38%，水稻钾素总累积量和净累积量平均提高1.55%和5.13%，水稻平均增产2.19%；K_80%和K_70%处理的土壤全钾和速效钾含量分别平均减少12.58%~15.31%和4.26%~10.64%，水稻钾素总累积量平均减少了7.49%~13.62%，水稻净累积量平均增加了0.48%~1.78%，K_80%处理的水稻产量平均增加2.32%，而K_70%处理的水稻产量则平均降低了6.43%。与K_100%相比，钾肥减量（K_90%、K_80%、K_70%）能够显著增加水稻钾肥农学效率（15.51%~24.53%）、偏生产力（17.96%~25.40%）和钾素吸收利用率（17.53%~55.36%）（P<0.05）。当钾肥减量大于20%时，经济效益呈下降趋势。小麦秸秆还田条件下，与配方施肥相比（K_100%），钾肥减量10%对土壤速效钾含量影响不显著，但能够提高水稻钾素累积量；钾肥减量20%~30%会降低土壤速效钾含量以及水稻钾素累积量，提高水稻钾素净累积量；钾肥减量10%~20%对水稻产量影响不显著，但可以增加钾肥农学效率、偏生产力和钾肥吸收利用率及经济效益。

Influence of potassium fertilizer reduction on rice yield and potassium utilization efficiency under wheat straw incorporation condition

Long-term crop straw incorporation experiments were conducted to understand the effects of wheat straw return and potassium fertilizer reduction on soil potassium content, potassium accumulation in rice, and potassium utilization efficiency, as well as rice yield, under the rice-wheat rotation system along the Yangtze River region. Five treatments, including wheat straw return plus formula fertilization (K_100%), wheat straw return plus formula fertilization and potassium reduction by 10% (K_90%), heat straw return plus formula fertilization and potassium reduction by 20% (K_80%), wheat straw return plus formula fertilization and potassium reduction by 30% (K_70%), wheat straw return plus formula fertilization without potash (K₀)were conducted in the field for 3 years. Compared with K_100%, K_90% increased soil total and available potassium by 3.31% and 6.38%, and the total and net potassium accumulation in rice increased by 1.55% and 5.13%. K_80% and K_70% decreased soil total and available potassium by 12.58%~15.31% and 4.26%~10.64%, respectively, and the total potassium accumulation in rice declined by 7.49%~13.62% (P<0.05). Both K_80% and K_70% increased the net potassium accumulation by 0.48%~1.78%, and K_80% increased rice yield by 2.32%, whereas K_70% decreased rice yield by 6.43%. Compared with K_100%, K_90%, K_80%, and K_70% significantly improved agronomic efficiency (15.51%~24.53%), partial productivity (17.96%~25.40%), potassium absorption, and potassium utilization efficiency (17.53%~55.36%) (P<0.05)of rice. However, reduction of potassium fertilizer over 20% decreased the economic profit.Under the condition of wheat-straw incorporation, reduction of potassium by 10% had no influence on soil available potassium but improved absorption and accumulation of potassium in rice. Nonetheless, reduction of potassium by 20%~30% decreased soil available potassium and absorption accumulation of potassium in rice. The reduction of potassium fertilizer less than 20% did not have significant influences on rice yield, but it increased the agronomic efficiency, partial productivity, absorption, and utilization of potassium fertilizer, as well as economic profit after wheat straw incorporation into the soil.