Ontogeny and Water Use of No‐Tillage Sorghum Cultivars on Dryland

Abstract

AbstractGrain sorghum [Sorghum bicolor (L.) Moench] yields are strongly influenced by soil water content at planting and use of that water during the growing season. Sorghum on Pullman soils (fine, mixed, thermic Torrertic Paleustolls), however, usually does not use water from as deep in the soil as other crops, thus possibly not attaining its full yield potential. This study was conducted from 1986 to 1989 to determine whether eight sorghum hybrid cultivars grown under no‐tillage conditions on a dryland Pullman clay loam at Bushland, TX, differed with respect to water use depth, growth, yield, yield components, total water use, and water use efficiency. The hybrids were Pioneer 8493; Funk 1498 and 499; DeKalb DK‐46, DK‐42, and DK‐41Y; and Richardson 9112 and Sprint. Determinations included precipitation and soil water use, water use efficiency, grain and stover yield, harvest index, panicles harvested, panicle/seedling ratio, seed per panicle, seed per unit area, and weight per seed. Based on water content measurements, there was no conclusive evidence that any cultivar depleted soil water deeper or to a greater extent than the others, but the highest yielding cultivar (DK‐41Y, mean yield of 5.22 Mg ha−1) was among the highest water users each year, suggesting that this cultivar uses water effectively for grain production. Multiple regression analyses involving all cultivars showed that grain yield was most strongly affected by weight per seed, but this was closely followed by seed per unit area. Other variables significantly related to grain yield were planting seed (number per gram), panicle/seedling ratio, panicles harvested, and stover yield. Overall, this study showed that high grain yields are achieved by cultivars that use available water supplies or that respond to improved water conditions during the growing season to produce vigorous plants capable of converting photosynthate into high quality grain. Although deeper and more intensive soil water use is desirable, sorghum improvement programs should not neglect other traits that can also result in more efficient grain production.