EFFECT OF GRAIN SORGHUM ON GERMINATION OF WEED AND CROP SEEDS

Abstract

Sorghum species are frequently used by horticultural producers as cover crops or green manures. Grain sorghum cover crops are often used in the southern United States. These summer annual grasses grow rapidly producing large quantities of biomass that has been shown to suppress weeds. Although allelochemicals in the roots and shoots have been identified, the precise mode of weed suppression has not been clearly elucidated. We performed a series of studies to evaluate the effect of sorghum on the germination of various weed and crop seeds. Petri dish assays were used to test the effect of germinating sorghum seed on the indicator species. Treatments were arranged in a completely randomized design with 4 replications and 2 experimental runs. Data collected included % germination as well as radicle and hypocotyl length. A modified Parker bioassay using 4 and 8 week old sorghum root and shoot tissue was used to study the effects of sorghum tissue on seed germination of the indicator species. Sorghum residue was observed to inhibit weed and crop seedling growth resulting in chlorosis of susceptible species.