Abstract: Changes of rice biomass(including grain and straw yields),yield-increasing effect of nutrient and paddy soil fertility were investigated in a long-term NPK fertilization experiment under a double-cropping system.The effects of N,P and K fertilization at different ratios on total rice biomass were ranked as follows:NPK>NP>PK>NK>CK.The yield-increasing effects of N,P and K on rice biomass were 41.2%-54.8%、66.3%-88.2% and 10.3%-10.9%,respectively.The coefficients of variance of yield-increasing effect on rice biomass for N,P and K were reversely varied with their yield-increasing effect.It illuminated that the higher the yield-increasing effect on rice biomass was,the better its stability was.Early rice was obviously better than later rice with respect to the yield-increasing effect and its stability.The application of N,P and K fertilizer could markedly enhance the concentration of soil organic matter and total N in soil.The phosphorus fertilization significantly increased the content of total P and available P in soil.The potassium fertilizer application enhanced the concentration of total K and exchangeable K content in soil,however,the output of rice biomass significantly reduced.In fact,the balance between input and output of K limited the changes of total K and exchangeable K content in soil.The application of N,P and K fertilizer discordantly affected soil pH value,the N fertilization(urea)decreased soil pH value,whereas the P fertilization(calcium magnesium phosphate)slowed the soil pH value decline.

Key words: red soil, rice, nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, yield-increasing effect, soil fertility, long-term experiment, fertilization

摘要： 通过红壤区水稻试验，分析了长期使用氮磷钾肥条件下双季水稻的生物量（包括稻谷产量和秸秆量）、养分增产效应和土壤肥力的变化。氮磷钾肥的配合施用对双季水稻生物量的影响顺序为NPK>NP>PK>NK>CK。N、P、K对水稻的增产效应系数分别为41.2%~54.8%、66.3%~88.2%和10.3%~10.9%。N、P和K增产效应的变异系数规律与其增产效应相反，说明养分对双季水稻增产效应越高，其稳定性越好。双季水稻的增产效应及其稳定性均表现为早稻优于晚稻。氮磷钾肥的配施可显著提高土壤有机质和全氮含量。磷肥的使用明显增加了土壤全磷和有效磷含量。钾肥使用提高了土壤全钾和交换性钾含量，然而水稻生物量的输出却与之相反，两者的平衡决定着土壤全钾和交换性钾含量的变化。氮磷钾肥对土壤pH值影响则不一致，氮肥（尿素）的长期使用降低土壤pH值，而磷肥（钙镁磷肥）的使用减缓了土壤pH值的降低。

关键词: 红壤, 水稻, 氮肥, 磷肥, 钾肥, 增产效应, 土壤肥力, 长期定位试验, 施肥