Influence of continuous cropping on a phosphorus deficient soil
1988
Orticio, M.R. | Neue, H.U. (International Rice Research Inst., Los Banos, Laguna (Philippines). Dept. of Soils)
The use of physiological efficient varieties on soils deficient in some nutrients has raised the possibility that those varieties would exhaust the soil nutrient supply and cause yield decline. To evaluate the long term effects of continuous use of these varieties on 4P-deficient soils the experiment was set up in the greenhouse in pots. Continuous cropping on 4 phosphorus deficient soils and 2 rices caused a gradual depletion of total P contents and a depletion of available P. The soils with the highest amount of available P decreased the fastest. All soils tended to attain a stable value of 1 mg/kg after the 10th year. Soils cropped to a P efficient variety IR26 had slightly lower P content indicating this variety extracted higher amount of P from the soil. Yield declined continuously with the decrease in soil P. Double cropping per year in 4 soils did not reduce total P content below the critical level of 0.02% P (Kawaguchi and Kyuma, 1977) but available P concentration fell below the critical level of 5 mg/kg Olsen P (IRRI 1978).
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