Pedosphere 16(3): 345--353, 2006
ISSN 1002-0160/CN 32-1315/P
©2006 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Soil organic n forms and n supply as affected by fertilization under intensive rice cropping system
ZHANG Qi-Chun, WANG Guang-Huo and XIE Weng-Xia
College of Environmental and Natural Resources Science, Zhejiang University, Hangzhou 310029 (China). E-mail: qczhang@zju.edu.cn
ABSTRACT
      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.
Key Words:  continuous cropping, microbial biomass, organic N forms, rice
Citation: Zhang, Q. C., Wang, G. H. and Xie, W. X. 2006. Soil organic n forms and n supply as affected by fertilization under intensive rice cropping system. Pedosphere. 16(3): 345-353.
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