Water Stress On Alternate Side of Root System to Improve Water Use Efficiency of Sunflower.

Water resource for irrigation in the Southern High Plains is declining and innovative ways to improve water efficiency in agriculture are needed. Role of root systems of crops in sensing stress and triggering physiological responses to regulate water use is an evolving theory. A field experiment was conducted to study the physiology and yield responses of two sunflower cultivars to 150mm and 300mm irrigation at New Mexico State University, Agricultural Science Center at Clovis. Using surface drip tapes laid out on both sides of 75cm wide sunflower rows, irrigation was applied both side in conventional irrigation and alternate sides of row for each irrigation in alternate irrigation treatments. Crop growth, biomass production, yield and plant water relations were examined in relation to partial root system water stress in sunflower. In general, alternate stressing of part of the root systems while providing the same amount of water did not affect sunflower growth and productivity. Oil content, harvest index and seed yield remained the same regardless of conventional irrigation or alternate row irrigation. In both dwarf and tall cultivars highest seed yield was recorded with 300 mm alternate row irrigation, but they were not significantly different from that of 300 mm conventional irrigation treatment.  Photosynthesis response to light intensity indicated that alternative row irrigation maintained higher photosynthesis rate at higher light intensities on some days. Dwarf and tall cultivars differed in some of the physiological observations. Leaf area development of dwarf sunflower under alternative row irrigation was slower, resulting in lower intercepted radiation compared to the conventionally irrigated sunflower. The study is being repeated in 2009 to validate the results. Lack of significant yield response to partial root systems stressing indicates that the technology needs further research that include gradual levels of decreasing irrigation to assess the potential benefit of the technique.