Irrigated Sunflower Response to Planting Date in the Central High Plains

Abstract

Regional production of sunflower (Helianthus annuus L.) has increased rapidly with the building of processing plants in northwestern Kansas. Few data were available for recommending sunflower planting date and population for the central High Plains. We planted two oilseed and two nonoilseed hybrids on four dates during the 1992, 1993, and 1994 seasons to determine the effect of planting date on yield and quality. Nonoilseed hybrids were thinned to 14 000, 17 000, 21 000, and 23 000 plants/acre. Oilseed hybrids were thinned to 17 000 and 23 000 plants/acre. Although the response varied among years, the optimum planting date for both types was from late May to early June. For nonoilseed hybrids in 1992 and 1993, the yield of large (>22/64 in.) and medium (20-22/64 in.) seed was no less than 3.7 and 2.7 times greater, respectively, with early-June planting than with early-May planting or, in 1994, 3.6 and 1.7 times greater than late-June planting. As population increased from 14 000 to 23 000 plants/acre, yield of large nonoilseed sunflower seed decreased as much as 57%. Population seldom affected yield of oilseed hybrids because seed weight and the number of seeds per head decreased as the number of heads per acre increased. Measured responses indicated that sunflower hybrid performance in the central High Plains can be influenced by planting date and plant population as well as hybrid selection. Therefore, sunflower for performance tests as well as production fields should be planted in late May or early June at populations within a range of 14 000 to 17 000 plants/acre. For nonoilseed hybrids, performance test results should also include seed size distribution to assist growers in making decisions on hybrid selection.