Row Width and Plant Density Effects on Texas High Plains Sorghum

Dryland grain sorghum [ Sorghum bicolor (L.) Moench] production is normally limited by water deficits in the semiarid Texas High Plains. All producers use reduced plant densities to limit water use and some producers use wide row spacings or “skip‐row” planting patterns in an attempt to reduce early season water use. Our objectives were to determine sorghum response to a wider‐than‐normal row spacing and to evaluate the validity of using wide rows as a grain production practice to minimize water stress effects. Dryland sorghum (Hybrid DK‐46) was grown for 3 yr (1986–1988) at Bushland, TX, using 30‐ (standard) and 60‐in. row widths and within‐row seed spacings of 3.4‐ (high density) and 6.7‐in. (normal density). Due primarily to tillering effects, doubling the seeding density within each row width did not affect total biomass production or leaf area index (LAI). It did, however, reduce grain yield in 1 of 3 yr (1988) on standard rows while increasing grain yields in 1 of 3 yr (1986) on wide rows. Increasing row width from 30‐to 60‐in. decreased biomass production and LAI every year, and decreased grain yield during favorable growing seasons (1986 and 1987). Water‐use efficiency was generally unaffected by within‐row seeding density, but was decreased in 1 of 3 yr (1986) by using wide rows. Regression analyses projected that a plant population of 24 000/acre would produce highest yields; however, a wide range in plant population (from about 16 000–34 000 plants/acre) existed within which grain yields were not reduced more than 5% by population effects. Low rates of seedling emergence (68% average) in this single hybrid study indicate that planting rates may need to be increased considerably to attain a specified plant population. With the above normal rainfall received during this experiment, the best sorghum production strategy with DK‐46 was to use 30‐in. rows planted at 31 000 to 35 000 seed/acre. Use of wide rows to minimize water stress resulted in considerable sacrifice of grain yield during these favorable growing seasons.