Movement of surface and deep-placed phosphorus in a sandy loam soil in relation to initial soil wetness, amount of water applied, and evaporation potentials
1985
SHARMA, P. K. | Sinha, A. K. | CHAUDHARY, T. N.
In laboratory studies we investigated the effect of initial soil water content and amount of water applied on the movement of surface (0 to 2 cm) and deep-placed (8 to 10 cm) P, under different potential evaporation rates (2.2 and 7.5 mm/d PE), in a sandy loam (Typic Ustochrept) soil. We applied phosphorus as diammonium hydrogen orthophosphate at the rate of 300 ppm P labeled with 10 μCi P/g P. The distribution of P and water in soil columns was examined immediately after infiltration of water and after 15 d of redistribution, with and without evaporation.Initial soil wetness affected P displacement by affecting the time needed to leach the soil. Phosphorus mobility increased with the amount of water applied, but the P front lagged behind the water front. Increasing rates of evaporation did not affect the total depth of P penetration, but did affect the distribution of P in the displaced zone. Phosphorus peaks shifted upward, and their number increased from one under no-evaporation to two under evaporation conditions. The effect of PE was more pronounced-on the displacement of surface-placed P than on the deep-placed P. Even under higher PE, deep-placed P was better distributed in subsoil than surface-placed P, which showed a tendency to accumulate in the surface soil layers.
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