Crop performance and water use efficiency in aerobic rice (Oryza sativa L.) relative to irrigation schedule, planting geometry, and method of planting in northern transition zone of Karnataka, India.

Field experiment was conducted at Main Agricultural Research Station, Dharwad, Karnataka, India during SouthWest monsoon, 2013 and 2014 to work out the optimum irrigation schedule and standardize the method of planting and planting geometry for higher productivity in rice under aerobic condition. The experiment consisted of twenty-four treatment combinations comprising four main plots (irrigation schedule) as I-1: irrigation at Irrigation Water/Cumulative Pan Evaporation ratio of 0.8, I-2: irrigation at Irrigation Water/Cumulative Pan Evaporation ratio of 1.0, I-3: irrigation at Irrigation Water/Cumulative Pan Evaporation ratio of 1.2, and I-4: irrigation at critical stages of crop growth, i.e., tillering, panicle initiation, flowering, and grain filling with 60 mm depth of each irrigation, three subplots (planting geometry) as G(1): 30 cm x 10 cm, G(2): 30 cm x 15 cm, and G(3): 30 cm x 20 cm, and two sub-subplots (method of planting) as P-1: sowing of dry seeds and P-2: sowing of sprouted seeds which were replicated thrice. Two years data on agro techniques revealed that treatment combination of sowing sprouted seeds at 30 cm x 10 cm planting geometry with irrigation at critical stages produced significantly higher grain yield (4383 kg ha(-1)), straw yield (6788 kg ha(-1)), productive tillers m(-2) (631.05), dry matter production (1390.42 g m(-2)), and higher net returns (Rs 40,482 ha(-1)) with benefit-cost ratio of 2.42. Scheduling irrigation at critical stages of the crop growth registered the higher water use efficiency (70.93 kg ha-cm(-1)).