摘要
Changes of soil organic nitrogen forms and soil nitrogen supply under continuous rice cropping system were investigated in a long-term fertilization experiment in Jinhua, Zhejiang Province, China. The fertilizer treatments included combination of P-K, N-K, N-P, and N-P-K as well as the control. After six years of continuous double-rice cropping, total soil N and hydrolysable N contents remained stable in plots with N treatments, while the hydrolysable N contents were substantially reduced in those plots without N application. Compared to the unbalanced fertilization treatments, P and K increased the percentage of hydrolysable ammonium N in the total soil N with the balanced application of N, and also maintained higher rice grain yields and nitrogen uptake. Grain yield was positively correlated with total N uptake (r = 0.875**), hydrolysable N (r = 0.608**), hydrolysable ammonium N (r = 0.560**) and the hydrolysable unknown N (r = 0.417**). Total N uptake was positively correlated with hydrolysable N (r = 0.608**), hydrolysable ammonium N (r = 0.440**) and hydrolysable unknown N (r = 0.431**). Soil nutrient depletion and/or unbalanced fertilization to rice crop reduced N content in soil microbial biomass, and therefore increased C/N ratio, suggesting a negative effect on the total microbial biomass in the soil.
Changes of soil organic nitrogen forms and soil nitrogen supply under continuous rice cropping system were investigated in a long-term fertilization experiment in Jinhua, Zhejiang Province, China. The fertilizer treatments included combination of P-K, N-K, N-P, and N-P-K as well as the control. After six years of continuous double-rice cropping, total soil N and hydrolysable N contents remained stable in plots with N treatments, while the hydrolysable N contents were substantially reduced in those plots without N application. Compared to the unbalanced fertilization treatments, P and K increased the percentage of hydrolysable ammonium N in the total soil N with the balanced application of N, and also maintained higher rice grain yields and nitrogen uptake. Grain yield was positively correlated with total N uptake (r = 0.875^**), hydrolysable N (r = 0.608^**), hydrolysable ammonium N (r = 0.560^**) and the hydrolysable unknown N (r = 0.417^**). Total N uptake was positively correlated with hydrolysable N (r = 0.608^**), hydrolysable ammonium N (r = 0.440^**) and hydro, lysable unknown N (r = 0.431^**). Soil nutrient depletion and/or unbalanced fertilization to rice crop reduced N content in soil microbial biomass, and therefore increased C/N ratio, suggesting a negative effect on the total microbial biomass in the soil.
基金
Project supported by the International Fertilizer Industry Association (IFI), Francethe Potast & Phosphate Institute (PPI), USA and Canadathe International Potassium Institute (IPI), Switzerland
关键词
微生物
土壤生物学
有机氮
水稻
continuous cropping, microbial biomass, organic N forms, rice