Changes in availability of heavy-metal micronutrients in soils treated with P-fertilizers
1997
Salam, A.K. (Universitas Lampung, Bandar Lampung (Indonesia). Fakultas Pertanian)
Availabilities of heavy-metal micronutrients in soil are suggested to be reduced by phosphate fertilization. This research was to evaluate the effect of some agricultural P-fertilizers and a pure phosphate chemical on availabilities of heavy-metal micronutrients in an Ultisol from Central Lampung, Indonesia. Evaluation was conducted with two different experiments. In the first experiment, soil was field-treated with different sources of P-fertilizers (TSP, SP-36 and rock phosphate) at rates ranging from 0 to 250 kg/ha for TSP and SP-36 and from 0 to 500 kg/ha for rock phosphate and was sampled after a 4 weeks planting with soybean. Soil pH, available P, and available metal micronutrients were then determined. In the second experiment, soil sample from an untreated field adjacent to the treatment plots of the first experiment was treated with KH2PO4 at rates ranging from 0 t0 800 kg P/ha and/or lime at rates equivalent to 0-6 CaCO3/ha in a laboratory experiment. The available of Cu and Mn were negatively correlated with P-fertilizer additions, that tended also to increase the soil pH. The lime additions consistently decreased the soil available metal micronutrients. However, the laboratory experiment showed that the available metal micronutrients were not reduced by KH2PO4 treatments. These observations suggest that P fertilizers reduce the availabilities of metal micronutrients due to their effect on soil by increasing soil pH, not to their liming phosphate component's reaction with soil solid surfaces
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