Phosphorus releasing power of soils as influenced by organic and inorganic amendments

A laboratory experiment was conducted at Bangladesh Rice Research Institute in 2001 toknow the phosphorus-releasing pattern of soils in repeated extraction and to find out theeffects of organic and inorganic solution P releasing power of soils under submergedcondition. Three composite soil samples collected from the cultivated rice field of Sreepur,Gazipur (Aeric haplaquept) (pH 4.8), BRRI Farm, haplaquept), (pH 6.2) and Benerpota, Satkhira(haplaquept) (pH 7.5). The soils were different in matter and available P content. The soilsamples were incubated under submerged condition tending with cowdung (CD) and PoultryManure (PM) each at the rate of 5 g kg-1, Triple Super 12.5 mg kg-1 and a control with outany amendment. Taking 3 replications the pots were laboratory under room temperature (28plus minus 2 degree C) in Completely Randomized Design (CRD) the 3rd week after incubation,the release of solution P (extracted with 0.01 M CaCl2) was repeated extraction for 8 times. Inall the soils, the concentration of solution P in poultry manure amended sample was greaterthan the others. The release of solution P was not much influenced by the soil amendment.The solution P in the first extraction was found highest in all treatments, which graduallydecreased in subsequent extraction but from 4th to 8th extractions, the P was found identical.The total amount of solution for Satkhira, BRRI and Sreepur soil, respectively. Thecontribution of cowdung and TSP was almost identical in the tested soils and was lower thanpoultry manure extractions was found highest with poultry manure amendment yielding 0.24,0.13 and 0.10 ppm RRI and Srfor Satkhira, BRRI and Sreepur soil, respectively. Thecontribution of cowdung and TSP was almost identical is and was lower than poultry manuretreated samples. The exponential relationship between number of extraction hold good for allthree soils. The co-efficient of determination (r2) of the tion for BRRI soil was 0.8571 to 0.9404(p less than 0.005) followed by Satkhira soil 0.8487 to 0.899 and the lowest in Sreepur soil0.767 to 0.8781.