Onion yield and quality response to two irrigation scheduling strategies

Irrigation technologies that conserve water are necessary to assure the economic and environmental sustainability of commercial agriculture. This study was conducted in the Rio Grande Valley in Texas to evaluate yield and quality of subsurface drip irrigated onions (Allium cepa L) using different scheduling strategies and water stress levels. One strategy consisted of initiating irrigation when the reading of a granular matrix sensors (Watermark(k) (1) soil moisture sensor, Irrometer, Co., Riverside, CA) installed at 0.2 m depth reached 20 kPa (optimum), 30 kPa and 50 kPa. The second strategy was to replace 100%, 75%, and 50% of crop evapotranspiration (ETc) weekly. Higher total yields, and jumbo onion size yields were obtained when the soil moisture was kept above 30 kPa. Yields were not affected when water applications were reduced from 100% to 75% ETc and from -20 to 30 kPa. The ETc strategies of 100%, and 75% ETc: resulted in similar water usage to the Soil Moisture monitoring strategies of initiating irrigation at 20 and 30 kPa. Total yields dropped significantly when soil water stress increased below 50 kPa. For the ET based strategy yields also dropped with the 50% ETc treatment. Onion bulb pungency and brix were unaffected by water level. (C) 2008 Elsevier B.V. All rights reserved.