Grain Sorghum Yield with Hybrid Advancement and Changes in Agronomic Practices from 1957 through 2008

Sorghum [Sorghum bicolor (L.) Moench] grain yield has improved since the deployment of hybrid sorghum in the mid-1950s. However, information on the contribution of different factors to this yield increase for irrigated and dryland sorghum production is scarce. The objective of the present study was to determine the magnitude of change in irrigated and dryland sorghum yields with hybrid improvement and changes in agronomic practices. Data from selected irrigated and dryland grain sorghum performance trials conducted in Kansas from 1957 to 2008 were analyzed. The mean yield of the highest-yielding hybrid over years was 9.3 Mg ha(-1) at irrigated sites and 5.8 Mg ha(-1) at the dryland sites. There was an increase in hybrid yield of nearly 50 kg ha(-1) yr(-1) in dryland sites over the 52 yr analyzed. Irrigated grain sorghum yields, however, remained unchanged over the same period. Agronomic practices such as planting date, P fertilizer use, and planting density changed over these years but were not found to contribute to increased dryland sorghum yields. Hybrid advancement and increased N fertilizer application were responsible for changes in dryland yields. The yield focus of sorghum hybrid development was effective in dryland sorghum production, likely because of intentional or inadvertent selection of hybrids with better drought tolerance.