Vol. 11, Special Issue 3 (2022)

Author(s):
Kajodmal Ghasal, Dr. Kalyan Pathak and Gauri Mohan

Abstract:
A field study was conducted during autumn season, 2016at the Instructional-Cum-Research Farm of Assam Agricultural University to evaluate the potential of P use efficiency in aerobic rice. The treatment consisted of three phosphorus sources viz., S_1: Single super phosphate (SSP), S₂: Diammonium phosphate (DP) and S₃: Rock phosphate (RP), three doses of phosphorus viz., D_1:10 kg P₂O₅ ha^-1, D₂:20kg P₂O₅ ha^-1 and D₃:30 kg P₂O₅ ha^-1 and two biofertilizer treatments i.e. B_1: without biofertilizer and B₂: Azospirillum + phosphorus solubilizing bacteria (PSB). One absolute control was included for comparison. The experiment was laid out in factorial randomized block design (RBD). Recommended doses of N (40 kg ha^-1) and K (20 kg ha^-1) were applied in all the treatments. Out of the three phosphorus sources, rock phosphate recorded the highest grain (2.61t ha^-1) and straw (4.70 t ha^-1) yield followed by single super phosphate. Among the doses, highest grain (2.7t ha^-1) or straw (4.93 t ha^-1) yield were recorded in 30kg P₂O₅ ha^-1. In case of bio-fertilizer, Azospirillum + phosphorus solubilizing bacteria (PSB) recorded highest grain yield (2.61t ha^-1) and straw yield (4.82 t ha^-1). Significantly higher N, P and K uptake were recorded with phosphorus application through rock phosphate which was statically at par with single super phosphate. Rock phosphate recorded higher values of agronomic (39.76kg kg^-1) and physiological use efficiency (207.02kg kg ^-1) of phosphorus which was followed by the source single super phosphate. Application of 30kg P₂O₅ ha^-1 recorded higher values N, P and K uptake by grain, straw and total and significantly higher available P₂O₅ (31.2 kg ha^-1) in soil after harvest. Out of the three doses of phosphorus, application of 10kg P₂O₅ ha^-1 registered highest agronomic use efficiency (36.16kg kg^-1) and the highest physiological use efficiency of phosphorus (234.18kg kg ^-1) was recorded with 30kg P₂O₅ ha^-1. Azospirillum ₊ PSB exhibited significantly higher N, P, K uptake, agronomic use efficiency (39.43kg kg-¹) and physiological use efficiency of phosphorus (223.48kg kg ^-1) than without biofertilizer treatment.