Semidwarf and Conventional Height Sunflower Performance at Five Plant Populations
Semidwarf sunflower (Helianthus annuus L.) hybrids have been developed by several commercial companies and could be grown on large hectarage in the future. Information on the total water use and other agronomic traits of the semidwarf (SD) types as they compare to conventional or standard height (SH) sunflower is not available. This field study was conducted to: (i) determine total water use (TWU) and water use efficiency (WUE) of SD and SH sunflower, and (ii) determine the effect of plant population on harvest index (HI), stalk diameter, plant height, and leaf number of both plant types. Two experimental SD and two SH hybrids of similar maturity from the Cargill and Sigco Research breeding programs were grown at dryland populations of 32 123, 49 420, 66 717, 84 014, and 101 311 plants/ha over a 3-yr period (1982-1984) at Fargo, Carrington, and Prosper, ND. Data were collected and calculated for nine characteristics in this study. Total water use and WUE data were determined only at a plant population of 49 420 plants/ha. All hybrids evaluated had similar TWU, WUE, HI, and stalk diameter. The Cargill SH had the fewest number of leaves. It was concluded that reductions of plant height do not affect internode number, TWU, and HI. Other agronomic traits as a response to plant population were similar for both plant types, and observed differences were often due more to genotype origin than to plant type. Increasing plant population reduced HI, grain yield per plant, biomass per plant, and stalk diameter. Increasing plant population increased plant height of all hybrids except the Sigco SD.
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