Seasonal Emergence and Growth of Sorghum almum

Abstract

Field studies on time of emergence, influence of planting date on growth and reproduction, and winter survival of rhizomes were conducted on sorghum-almum grown in corn and crop-free environments. In 1985, peak emergence of sorghum-almum occurred during early May in crop-free plots and mid-May in corn. In 1986, two peaks of emergence, one in early June and one in late June, were noted in both crop-free and corn plots. Emergence after mid-July was 4% or less of the total emerged in 1985, and no sorghum-almum emerged after mid-July in 1986. In planting date studies, sorghum-almum was seeded alone or in corn at 2-week intervals. Corn competition reduced sorghum-almum shoot, rhizome, and root growth at all planting dates. Maximum sorghum-almum seed production was 43 110 seed/plant when grown without competition but only 1050 seed/plant when grown with corn competition. When grown with corn competition, no seed developed on sorghum-almum seeded 6 or more weeks (mid-June or later) after corn planting. Shoot dry weight of sorghum-almum grown with corn competition was 3 g/plant or less for plants seeded 4 or more weeks (early June or later) after corn planting. Therefore, controlling sorghum-almum in corn through mid-June should prevent seed production and corn yield losses due to sorghum-almum competition. Rhizomes produced by sorghum-almum grown alone or with corn competition did not survive the winter; therefore, in Minnesota, sorghum-almum survival from one growing season to the next depends on seed production.