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Lu Ru-Kun; Shi Zheng-yuan; Qian Cheng-liang (Institute of Soil &Science, Chinese Academy of Scieuces, Nanjing 210008)  
Decline of available P (Olsen-P) in red earth with time may be devided into two stages: fast and slow stages. The former stage can be described with a straight line equation, y=a+bx, the second stage with a curve equation, y=a+blogx, where y= available P still remained, and x= incubation periods (month).Available P decline has a significant correlation with the amount of active Al content in soils but not with the amounts of active Fe and exchangeable Al. Pot experiment with three different types of soils: acidic red earth, neutral paddy soil, and calcareous fluvo-aquic soil, using wheat and rye grass as test plant, showed that the yield decline with soil and P reaction periods and ceased at different time with different soils. For the neutral paddy soil ,the decline in yield ceased after 8 months' incubation, for fluvo-aquic soil, after 16 months, but for red earth the decline ceased after more than 28 months. This may be due to different in extent of the formation reactions of P chelate ring structure and diffusing into the deeper layer under the surface of R2O3, and calcite in the soils. In neutral paddy soil this two reactions were weaker and led to higher available P remained after incubation period, while in acidic red soil and calcareous fulvo-acquic soil they were much more stronger especially in red soil, and lasting longer time.
【Fund】: 国家重点基金!49631010
【CateGory Index】: S158
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