Effect of Soil Moisture on Alfalfa Yield, P-Uptake from Labelled Fertilizer and Subsequent Release to Alfalfa.

Increasing soil moisture from 40 to 70 of the water holding capacity increased P absorption by plant from both soil and fertilizer but much more from fertilizer than from soil. The percentage increase was 20.4 and 78.8 for P-soil and P-fertilizer, respectively. The average release of P32 from added plant material to a calcareous soil was 21.1 and 27.5 (of that added) for treatment watered daily and every three days respectively. The release of 32 p with progress of time was discussed in relation to the pathway of p from plant letter to plant uptake. It was concluded that the release of P from plant material added to calcareous soils would be enhanced by wetting and drying, and a significant portion of the plant's P requirement could be satisfied from this source