Abstract:

120 field trails of phosphate fertilizer (P) application on early rice were conducted in main double-rice cropping regions of Hunan Province during 2005 to 2008. The objective of this research was to investigate the effect of P on early rice yield and profit, and to determine abundance and deficiency indices of soil available P. The results showed that P fertilizer application significantly increased early rice yield and profit compared with no P application. The ranking order of yield increase and profit rate among three study areas were the east-central region > the north region > the south region. Soil available P content significantly affected response in yield and profit with P application, and there were significantly negative correlations between yield increment, VCR and soil available P. The low, medium, high indices for soil available P in the north region were < 8.8 mg/kg, 8.8-26.1 mg/kg and > 26.1 mg/kg, and in the east-central region were < 9.3 mg/kg, 9.3-26.1 mg/kg and > 26.1mg/kg, and in the south region were < 4.0 mg/kg, 4.0-19.4 mg/kg and > 19.4 mg/kg, respectively. The content of available P in the main area of whole province were at medium level, and in 15% of the whole area were at high level, only in small area were at low level.