Effect of irrigation scheduling and fertigation on nutrient and water-use efficiency in drip-irrigated direct-seeded rice (Oryza sativa)

Abstract

A field experiment was conducted during the rainy (kharif) seasons of 2016 and 2017 at Gangavathi, Raichur, Karnataka, to study the effect of irrigation scheduling and fertigation on nitrogen and water-use efficiency of drip-ir- rigated direct-seeded rice (Oryza sativa L.) in clay soil. The experiment laid out in split-plot design with 4 irrigation scheduling based on irrigation water : cumulative pan evaporation (IW : CPE) ratios assigned to main plots and 4 drip fertigation levels were allocated in subplots and replicated thrice. Irrigation scheduling at an IW : CPE ratio of 1.50 recorded significantly higher nutrient-use efficiency, viz. nitrogen (35.2 kg/kg), phosphorus (85.4 kg/kg) and potassium (102.5 kg/kg) and but lower water-use efficiency (7.69 kg/ha-mm) and water productivity (0.61 kg/m3). Among the drip fertigation levels, drip fertigation at 75% recommended dose of nitrogen (RDN) recorded higher ni- trogen-use efficiency (41.5 kg/kg). Treatment of 125% RDN resulted in higher phosphorus-use efficiency and po- tassium-use efficiency (84.1 and 101.0%, respectively) and water-use efficiency and water productivity (7.22 kg/ ha-mm and 0.59 kg/m3 respectively).