Studies to assess the extent of phosphorus solubility with different lime rates and the efficiency of platform and broadcast methods of fertilizer application were conducted indoor and in ponds
1994
Pahila, I.G. | Pudadera, E.J. (Philippines Univ. in the Visayas, Leganes, Iloilo (Philippines). Coll. of Fisheries)
Soluble phosphorus in water was higher in the platform method of fertilization than in the broadcast. However, extractable phosphorus in soil was observed higher in ponds receiving broadcast fertilization than in the platform method. It is estimated that 1.25 percent to 3.0 percent of the added phosphorus fertilizer was recovered as readily available phosphorus in water in the indoor experiment. In the pond experiment, portions of the added phosphorus fertilizer ranged from .88 percent to 1.0 percent as readily available phosphorus in the pond water. About 56.90 percent-70.45 percent and 63.25-70.22 percent of the added phosphorus fertilizer was extracted from the soil in the indoor and pond experiments, respectively. The estimated amount of unavailable phosphorus which was believed precipitated or fixed was 28.19-40.39 percent in the indoor experiment and 28.67-35.86 percent in the pond experiment. Solubility of phosphorus increased with increasing lime input to 1000 kg/ha CaCO3 (indoor experiment). Limiting beyond 1000 kg/ha CaCO3 enhanced precipitation of phosphorus. The observations during the indoor experiments were not consistent with those in the pond experiment. It appears that solubility of phosphorus in the pond water during the pond experiment was lower, and that pond calcium content of less than 10 to the minus 8 ppm results in precipitation of phosphorus
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