Comparative quality of phosphocomposts and single superphosphate and response of green gram (Vigna radiata L. Wilczek)

Abstract

Phosphocomposts containing approximately 5.7% P2O5 were prepared from paddy straw by incubating the straw for 4 months with the addition of 5% P2O5 in the form of low-grade Mussoorie rock phosphate containing 17.2% P2O5. The rock phosphate was applied to the straw in an aqueous slurry of 1:1:0.5 (dry weight) cow dung: alluvial soil: well-rotted compost to assist the composting process. Phosphonitrosulphocomposts were similarly prepared containing approximately 7.0% P2O5 and 1.4-1.6% N by adding through the slurry 5% P2O5 as rock phosphate, 10% pyrite (S 22.2%), and 1 % urea-N. Composts of moist paddy straw alone without slurry or other ingredients were also incubated. The quality and crop response to phosphocomposts were substantially improved compared with pure paddy straw composts; they contained higher total P, water-soluble and citrate-soluble P, total N, and NO3-N. Phosphocomposts at 10 t ha-1 performed similarly to single superphosphate at 30, 40, or 50 kg P2O5 ha-1 in terms of growth, nodulation, dry matter accumulation, seed yield, and P uptake by Vigna radiata.