"The purpose of this two-year study was to investigate how deficit irrigation and plant density affect yield, quality and quercetin levels in the short-day onion, which is an important crop for Texas, especially in South Texas and the Winter Garden area," Leskovar said.
Quercetin, a plant-based flavonoid found in onions and other vegetables, may have anti-inflammatory and antioxidant properties, and is being investigated for other possible health benefits, Leskovar explained.
"Our research on vegetable crops, including short-day onions, takes into account various genetic, environmental and agronomic pre-harvest harvest factors which are already known to have an impact on the yield, quality and phytochemical content of fruits and vegetables," he said.
During the 2007-2008 and 2008-2009 growing seasons, researchers used irrigation rates of 100 percent, 75 percent and 50 percent of crop evapotranspiration, or ETc. Crop evapotranspiration is the sum of evaporation from the soil surface and plant transpiration from the leaves into the atmosphere. The irrigation rate at each stage of development also took into account the plant size, leaf number and height, as well as the reflectance of the crop-soil surface, canopy resistance and soil evaporation.
During both seasons, onion seeds were planted at densities of 397,000 seeds per hectare (approximately 2.47 acres) and 484,000 seeds per hectare. The onions were drip-irrigated at the three different rates to determine effect on onion shoot growth and bulb-size distribution among small, medium, large, jumbo and colossal onions, plus effect on yield and quality components.