Increasing the A vailability of Rock Phosphate by Mixing with Slops

Abstract

Two sets fo rock phosphate and slops from Phetchabun and Ratchaburi provinces were mixed at differnet ratios of 30:0, 27:3, 24:6, 21:9, 18:12, and 30:0, 24:6, 18:12 and 12:18 respectively. The first set of mixtures was incubated for 1,10 and 20 day periods, and the seconds set was incubated at 1,7,14,21, and 28 day periods. Available phosphate and pH were determined after incubation. Application of slops increased available phosphate after incubation. Higher amount of applied slops caused further increase in phosphate availability. The highest increase of available phosphate was found at the highest rate of applied slops at pH 8.6 for the first set and at pH 5.9 for the second set. A greenhouse experiment was conducted using the mintures made from different ratios of rock phosphate and slop from Ratchaburi Corn (Zea mays L.), as an indicator crop, was planted in Pakchong soil series in comparing with the effect of superphosphate on plant height and dry weight, the mixtures of rock phosphate and slops did not show significant difference. However increasing amount of slops tended to increase plant height, dry weight, and total uptake of nitrogen, phosphate, and potassium by corn plant. It was concluded that the rock phosphate and slops mixture shoul dbe applied at planting time.