PHOSPHATE AND PHOSPHATASE DISTRIBUTION IN SEDIMENT DEPTHS OF ROCKPHOSPHATE TREATED CARP CULTURE SYSTEM

Distribution pattern of phosphates (Al-P, Ca-P, Fe-P), available-P, ci trate soluble-P and phosphatases (acid and alkaline) was examined in t hree sediment layers (0-2.5 cm, 2.6-5.0 cm, 5.1-7.5 cm) of carp (Cirrh inus mrigala) culture system fertilized with varying levels (43.66 kg and 87.32 kg P) and frequencies (7, 15 and 30 days) of rock phosphate. Whereas layer differences of phosphate and phosphatases were signific ant in any of the treatments employed, significant treatment differenc es were restricted to first and second layer, but not in third layer i mplying that uppermost layer was the most active site of treatment act ion. Large variations in fish yield among six treatments were directly related with P-content of surface sediments, and hence P-level of ove rlying water. The variations of alkaline phosphatases in the first lay er of sediment in each treatment was strongly influenced by Al-P (99.7 8%), available-P (0.16%) and Fe-P (0.05%), whereas the variations in s econd layer was mainly affected by Al-P (99.02%). None of these factor s were related to the small variations of alkaline phosphatase in thir d layer of sediment.