The effect of successive croppings on soil organic phosphorus
1974
Appiah, M.R., Cocoa Research Institute, P. O. Box 8, Tafo, Ghana | Thomson, E.J., Department of Crop science, University of Ghana Legon
To investigate the effect of successive croppings on soil organic P, soil samples were cropped to maize, cowpea and tomato. Results showed a decrease in organic P during the first two cropping periods but a rapid build up in organic P during the third period. Uncropped soils showed minor change in organic P content over the three cropping periods. Phosphatase activity observed from the test plants indicated that the most likely cause of the decrease in organic P content seemed to be an increase in rate of mineralization of soil organic P associated with enhanced phosphatase activity in the soil around the roots. However, the inability of the extracts to mineralize soil organic P in the absence of plants suggests that the phosphatase activity becomes important after the initial breakdown of organic matter. The increase in organic P content of cropped soils during the third cropping period might have resulted from microbial immobilization of P as a result of increased microbial activity caused by plant secretions into the soil, by direct addition to the native organic P by plants and probably by re-wetting and airdrying of soils.
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