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Subject: Agronomy × End date: 2017 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    PHOSPHORUS MANAGEMENT IN AEROBIC RICE
    (AAU, Jorhat, 2017-07) Ghasal, Kajod Mal; Pathak, Kalyan
    A field experiment entitled „Phosphorus management in aerobic rice‟ was carried out in the Instructional-cum-Research (ICR) Farm, Assam Agricultural University, and Jorhat during autumn season of 2016. The treatment of the experiment consisted of three phosphorus sources viz., S1: single super phosphate, S2: diammonium phosphate and S3: rock phosphate, three doses of phosphorus viz., D1:10kg P2O5 ha-1, D2:20kg P2O5 ha-1 and D3:30kg P2O5 ha-1 and two biofertilizer treatments i.e. B1: without biofertilizer and B2: Azospirillum + PSB. One absolute control was included for comparison. The experiment was laid out in factorial randomized block design (RBD) replicated thrice with the objectives to study the performance of aerobic rice under different sources and levels of phosphorus and to evaluate the phosphorus use efficiency of aerobic rice. The soil of the experimental site was sandy loam in texture, medium in available N (285.36kg ha-1), P2O5 (22.85kg ha-1) and K2O (138.04kg ha-1) and organic carbon (0.62%) with pH value of 5.2. The rice variety “Inglongkiri” was sown on 11th March, 2016 and harvested on 08th July. 2016. The rainfall received during the crop season was only 1350 mm. The weekly average maximum temperature ranged from 24.9 to 33.5°C and minimum temperature 15.9 to 26.1°C, respectively. Out of the three phosphorus sources, rock phosphate recorded the highest grain (26.19q ha-1) and straw (47.05q ha-1) yield followed by single super phosphate. Among the doses, highest grain (27.43q ha-1) and straw (49.39q ha-1) yield were recorded in 30kg P2O5ha-1 and the lowest grain (22.37q ha-1) and straw (37.70q ha-1) yield were found in 10 kg P2O5ha-1. In case of bio-fertilizer, Azospirillum + PSB recorded higher grain yield (26.17q ha-1) than that of without bio-fertilizer (22.87q 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. So far the economics is concerned, the treatment combination that included application of rock phosphate at the rate of 30kg P2O5 ha-1 inoculated with Azospirillum + PSB recorded the highest net return of .56,717.00 ha-1 and with highest benefit-cost ratio (B:C) of 2.63.