Soil available phosphorus and its uptake by soybean (Glycine max. (L.) Merrill) as influenced by organic manures, inorganic fertilizers and weed management practices

Field experiments were conducted from June 1994 to April 1996, covering two kharif and two summer seasons to evaluate the combined effect of organic manures and inorganic fertilizers with different weed management practices on the soil available phosphorus status and P uptake of soybean. Application of blo-dlgested slurry @ 5.0 t ha⁻¹ + 30:120:40 kg NPK ha⁻¹ recorded the highest P uptake by soybean in all the seasons. During the early stage (20 DAS), the P uptake by soybean was higher with the application of alachlor 1.0 kg ha⁻¹ followed by pendimethalin 0.75 kg ha⁻¹. At later stage (40, 60 DAS and at harvest), hand weeding twice considerably increased the P uptake of soybean. Soil available P was higher in plots where bio-dlgested slurry @ 5.0 t ha⁻¹ + 30:120:40 kg NPK ha⁻¹ was applied. Hand weeding twice favourably Increased the availability of P in soil, followed by alachlor + hand weeding.