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Sunflower’s Viability Under Deficit Irrigation

Monday, January 30, 2017
filed under: Irrigation/Water Use

Right: KSU irrigation engineer Freddie Lamm (left) and crops research scien- tist Rob Aiken (right) were principal in- vestigators on the three-year Colby sunflower irrigation research project.

For years, numerous High Plains irrigators have produced sunflower successfully under overhead sprinkler systems with lower-capacity wells stemming from aquifer depletion. Since sunflower can attain a greater percentage of its maximum yield — compared to corn or soybeans—with limited irrigation, the crop has proven itself a valuable agronomic and economic partner in many fields across the region. When insufficient water is available for a full circle of corn, splitting it with sunflower —which requires less and has a shorter period of irrigation needs—can make a lot of sense (and dollars). Sunflower’s low yield threshold for water use, competitive yield response to water use, tolerance of heat and soil alkalinity stress—and its deep rooting system—all factor in to its competitive performance.
       A three-year research project in northwestern Kansas now underscores that reality. The 2014-16 project, titled “Timing of Irrigation for Tall and Short Stature Sunflower Hybrids to Help Improve Land Allocation Decisions,” was partially funded by the National Sunflower Association. Freddie Lamm, irrigation engineer at the Kansas State University Research-Extension Center in Colby, and Rob Aiken, crops research scientist at KSU-Colby, were the principal investigators.
       The study, conducted on a deep silt loam soil and under a lateral move irrigation system, looked at yield, yield components, canopy formation, water use and water productivity. It compared performance in those categories of a tall and a short sunflower hybrid under three irrigation durations (four, six or eight weeks). Water applications centered around the R-5 (flowering) stage under three irrigation capacities (maximum of one inch every four, eight or 12 days).
       Study results, averaged across the three years, can be summarized as follows:

Per-acre yields averaged 3,237 lbs, 3,383 lbs and 3,678 lbs, respectively, for the 2014, 2015 and 2016 seasons. Sunflower yield was not significantly affected by irrigation window duration, irrigation capacity or hybrid. “Production was tolerant of low capacities and short irrigation windows,” Lamm and Aiken report. This suggests what many producers already have experienced: that it can make a lot of agronomic—and economic—sense to split their limited-capacity pivots between (1) a crop with less water stress tolerance, such as corn, and (2) sunflower.
Oil content was not greatly affected by irrigation treatment or hybrid. Oils averaged 43.6, 43.2 and 44.5%, respectively, for 2014, 2015 and 2016.
Although final yields were not significantly different, the shorter hybrid did have, on average, 6% greater plant population at harvest and 21% greater leaf area index (maximum) than the taller hybrid.
Water use and water productivity (yield/ET) both followed anticipated trends, with water use trending greater with longer irrigation windows and greater capacity, while water productivity trended to be greater for more-deficit irrigation regimes. The water productivity was significantly different in only one of the three years, however.

“Summarizing the results, successful sprinkler-irrigated sunflower production can be achieved on this soil type under deficit-irrigation regimes and with a short irrigation window duration,” Lamm and Aiken note. “This assumes relatively full soil water profiles at planting (approximately 75% of field capacity),” they add.

— Don Lilleboe