Phosphate sorption in three soil series in relation to phosphate levels, incubation period and temperature

An investigation was carried out to assess the effect of incubation period, different added phosphorus levels and temperature in different soil series from the vicinity of Tandojam. Surface soil samples were collected, air dried, crushed, passed through 2 mm sieve, and preserved in plastic bags. For phosphate sorption studies 10 grams of soil was taken into plastic bottles (300 ml capacity), and 250 ml of 0.01 M CaCl2 solution was added to each bottle. The samples were treated with the initial phosphorus (PI) levels of 0.0, 2.5, 5.0, 10.0, 25.0, 50.0, 100.0, 250.0, 500.0 and 1000.0 mug g-1 soil. In Lalian-1 soil series soil was clayey (46% clay) in texture, with pH (7.7), EC (0.45 dS m-1), Calcium carbonate (10.9 CaCO3), Organic matter content (0.74 %), and the available phosphorus (0.71 mug g-1 soil). The results of phosphate sorption at 25 plus minus 1 degree C shows that the phosphate sorption was increased with the increasing of initial added phosphorus levels (PA = 2.5, 5.0, 10.0, 25.0, 50.0, 100.0, 250.0, 500.0 and 1000.0 mug g-1 soil), increasing incubation (in days i.e. 1, 2, 3, 7, 15, 30 and 60) and with the increase in incubation temperature (25 plus minus 1 degree C). For the added phosphorus levels of 2.5, 5.0, 10.0, and 25.0 mug g-1 soil, the phosphate sorption equilibrium was obtained after 7 days of incubation. Where as for the added phosphorus levels of 50, 100, 250, 500 and 1000 mug g-1 soil the major portion of the added phosphorus was sorbed within 15 days of incubation, but slow reaction was continued up to 60 days of incubation. For results of Phosphate sorption at 35 plus minus 1 degree C, it was concluded that the phosphate sorption was increased with the increasing of initial added phosphorus levels (PA = 2.5, 5.0, 10.0, 25.0, 50.0, 100.0, 250.0, 500.0 and 1000.0 mug g-1 soil), increasing incubation (in days i.e. 1, 2, 3, 7, 15, 30 and 60) and with the increase in incubation temperature (35 plus minus 1 degree C). For the PA levels of 2.5, 5.0, 10.0, and 25.0 mug g-1 soil, the phosphate sorption equilibrium was maintained after 7 days of incubation. Where as for the added phosphorus levels of 50, 100, 250, 500 and 1000 mug g-1 soil the major portion of the added phosphorus was sorbed within 15 days of incubation, but slow reaction was continued up to 60 days of incubation. It was further observed from the data that higher sorption trend was shown by the soil at incubation temperature of 35 plus minus 1 degree C when compared with the sorption data of same soil series at incubation temperature of 25 plus minus 1 degree C. In Lalian-2 soil series the soil was clay-loam (34.0% clay, 44 % sand and 22 % silt) in texture, with pH (7.9), EC (1.48 dS m-1), Calcium carbonate (8.9 %), Organic matter (0.92%), and the available phosphorus (2.12 mug g-1 soil). Results of Phosphate sorption at 25 plus minus 1 degree C shows that the phosphate sorption was increased with the increasing of initial added phosphorus levels (PA = 2.5, 5.0, 10.0, 25.0, 50.0, 100.0, 250.0, 500.0 and 1000.0 mug g-1 soil), increasing incubation (in days i.e. 1, 2, 3, 7, 15, 30 and 60) and with the increase in incubation temperature (25 plus minus 1 degree C). For the added phosphorus levels of 2.5, 5.0, 10.0, and 25.0. mug g-1 soil, the phosphate sorption equilibrium was maintained after 7 days of incubation. Where as for the added phosphorus levels of 50, 100, 250, 500 and 1000 mug g-1 soil the major portion of the added phosphorus was sorbed within 15 days of incubation, but slow reaction was continued up to 60 days of incubation.