Effect of Nitrogen on Sunflower Hybrid Productivity at Two Locations in Northern Wyoming.

Effect of Nitrogen on Sunflower Hybrid Productivity at Two Locations in Northern Wyoming Austen A. Samet, Axel Garcia y Garcia, Valtcho D. Zheljazkov, Gustavo M. Sbatella Within recent years there has been significant interest in the production of confection and oilseed sunflowers (Helianthus annuus L.) in northern Wyoming. However, there is limited information on the performance and nutritional requirements of these sunflowers being grown in the semi-arid conditions of northern Wyoming. Field studies are being conducted to determine the effects of nitrogen (N) fertilizer applications on yield and quality of five sunflower hybrids, three oilseed (Sierra, Defender, X9452) and two confection (Dahlgreen 9579, Dahlgreen 9512). The study was initiated in 2014 and is being conducted in two separate locations, Powell and Sheridan Wyoming. Sunflowers being grown in Powell are under furrow irrigation and sunflowers grown in Sheridan are rainfed only. The study was set as a Randomized Complete Block Design (RCBD) in a split-plot with four replications, where variety was the main plot and levels of nitrogen fertilizer the subplot. The five sunflower varieties were fertilized with four different N rates which differed between locations and ranged from 0 to 300 lb/acre. The N fertilizer was sidressed applied in stages with all the fertilizer being applied be for floret initiation with the last application occurring 40 Days After Emergence (DAE). The measured responses included seed yield, head size, seed count and seed weight. Soil, plant, and environmental conditions were monitored in each location. Yield measurements were obtained at physiological maturity. The current results suggest that N application rates largely affect the overall yield component in sunflower crops. Increased N rates increased seed yield, head size, seed count and seed weight in both irrigated and rainfed studies but increases were higher in the irrigated field. The study is being repeated in 2015.