Effects of chemical desiccation and early harvesting on Sorghum [Sorghum bicolor (L.) Moench] seed germination

Abstract

Field and laboratory experiments were conducted at two locations over two years in Texas. Objectives of these experiments were to study effects of chemical desiccation and seed maturity at harvest on sorghum seed germination. Sorghum plants were desiccated in the field at 35, 30, 25, and 23% grain moisture contents for the desiccation study and harvested at 12 to 15% grain moisture. For the grain maturity study seed were harvested at 30, 35, 40, 45, and 50 days after anthesis. The different cultivars could be grouped by their differences in response to desiccation. The first group included cultivars with germination that increased gradually with decreasing field grain moisture content, implying a gradual release of dormancy. The second group included cultivars with germination that decreased gradually; indicating accumulation of dormancy. In the third group of cultivars, seed germination remained relatively constant throughout the moisture range of this study. At Lubbock, cultivar effects also were significant. Over all cultivars, germination percentage tended to increase with a decrease in moisture content in the grain at time of desiccation. Germination also increased with increased days after harvesting. Three groups could be established by considering the cultivars response to harvesting at different maturity stages. The first group includes those that germination increased gradually with increase in number of days of harvest after anthesis. The second group reacted the same way of the first group, but seed harvested 45 days started to decline in germination percentage. In the third group of cultivars, germination remained relatively constant. The fourth group shows a development of dormancy, which can he seen by the sharp decline of germination with increase in number of days of harvest. Results indicated that at College Station the optimum time for harvesting could be between 35 and 45 days after anthesis. At Lubbock germination percent increased to a peak at 50 days after anthesis. Implying that at Lubbock the best harvest date may not have been reached in the range covered by this study, or that seeds could be harvested as early as 50 days post-anthesis. Advantages of this scenario is the avoidance of environmental catastrophes like frost, rainfall, and late season insect pests and diseases, that can cause,deterioration of sorghum seed.