Effect of Organic, Inorganic fertilizers and liming on persistence and degradation of phorate in acid laterite soil of Orissa

An acid laterite soil of Bhubaneswar was treated with the inorganic fertilizers viz. urea (46% N), single superphosphate (16% P₂O₅) and muriate of potash (60% K₂O) at the recommended dose of 100–50–50 of N, P₂O₅-K₂O kg ha⁻¹. Farmyard manure was used as an organic manure and applied @ 10 t ha⁻¹. Liming material (CaCO₃) was applied @ 2.7 t ha⁻¹. The technical grade phorate was applied at the recommended dose of 1 kg ha⁻¹ and double the recommended dose of 2 kg ha⁻¹ along with a control to assess the degradation behaviour. The soil was submerged with water and samples were drawn at 0, 5, 15, 25 and 35 days after treatment of the pesticide. The estimation of phorate residues was done by colorimetric method. With chemical fertilizers, the rate of degradation of phorate was more than the control-soil and was in the order: phosphatic > potassic > nitrogenous fertilizers. When soil was treated with FYM the rate of degradation of phorate was more than that of all the fertilizer treatments. With the application of lime, the rate of degradation was the fastest amongst all the treatments.