Effects of panicle removal and nitrogen on yield of grain sorghum

Abstract

Grain sorghum is the principal food crop in Botswana. It is often grown in low fertility, coarse-textured soils. It is a common practice within some ethnic groups in Botswana to remove the primary panicle with the expectation that this will increase the grain yield by promoting tillers.

A factorial experiment was conducted in the greenhouse to investigate the effect of panicle removal at anthesis and N on growth and yield of grain sorghum. Two N rates (25 or 100 kg/ha), three cultivars (Segaolane, Northrup King 2660, and Korwane), two main panicle treatments (present or removed), and five replications were used. Panicle removal increased the number of tillers and kernel weight but decreased yield (by reducing kernel number) in Segaolane and NK 2660. The kernel weight in Korwane did not respond to panicle treatments, but grain yield was reduced by panicle removal. In all cultivars, photosynthesis was reduced when the main panicle was removed. Korwane invested more assimilates in vegetative material (harvest index = 0.15), while Segaolane and NK 2660 partitioned more photosynthates into grain yield (harvest index = 0.5). Nitrogen application increased total dry matter, tillers, grain yield, and number of kernels in each variety except that Korwane was not responsive in kernel number. Nitrogen fertilization decreased kernel weight in two of the varieties but not Korwane. Kernel weight of Korwane was not affected by any of the treatments in this test.

In summary, panicle removal appeared not to be a positive management practice for increasing grain yield of any of the varieties studied. On the other hand, N fertilization was beneficial to yield.