Planting Date Affects Rainfed Sorghum Forage Yields in Semiarid, Subtropical Environments

Abstract

Increasingly, sorghum [Sorghum bicolor L. (Moench)] forage producers in semiarid regions must maximize yield under rainfed conditions. Dry matter hay yields of a brown midrib (BMR) photoperiod-sensitive sorghum-sudangrass (Sorghum bicolor var. Sudanese) hybrid (PS) and a BMR forage sorghum (FS) were compared in four randomized complete blocks over four planting dates each in 2004 and 2005 in a one-cut system without irrigation at New Mexico State University's Agricultural Science Center at Tucumcari. On average, PS outyielded FS (1.38 vs. 0.99 tons/acre, respectively, P < 0.01) and sorghum forages planted in May or early June outyielded sorghum forages planted in late June or July (1.66, 1.45, 0.93, and 0.70 tons/acre for sorghum forages planted approximately 19 May, 9 June, 30 June, and 21 July, respectively, P < 0.05). The year × planting date × sorghum forage type (FS or PS) interaction also was significant, likely because the positive effect of differences in precipitation distribution on yield of PS. While yields of FS and PS were similar when planting took place in a dry seedbed in 2004, PS had greater yields than FS when planted before the end of June in moist soil in 2005. Late-season precipitation may impact yield of sorghum forages planted after mid June.