EFFECTS OF JOHNSONGRASS (SORGHUM-HALEPENSE), HEMP SESBANIA (SESBANIA-EXALTATA), AND DELAYED HARVEST ON SOYBEANS

The effect of delayed harvest was investigated with two soybean cultiv ars that were grown weed free or in competition with johnsongrass or h emp sesbania over a 3-yr period. Johnsongrass reduced the yield of ear ly-maturing 'Hill' soybean 32, 35, and 36% when harvested at an averag e of 1, 2, or 3 wk after maturity, when compared to weed-free yields o f 2490, 2430, and 2270 kg ha-1, respectively. Late-maturing 'Lee 68' y ields were reduced 27, 29, and 39% on three harvest dates compared to weed-free yields of 2570, 2310, and 2200 kg ha-1, respectively. Seed g rades of both cultivars improved with delayed harvest, but this was of fset when johnsongrass was present. Hemp sesbania reduced yields of Hi ll 23% on the first harvest date and 26% on the second and third dates . Yields of Lee 68 were reduced 16, 22, and 28% by hemp sesbania on th ree successive harvest dates. The value of soybean yields adjusted for excessive foreign material, moisture, and damaged kernels was decreas ed by delayed harvest when hemp sesbania was present in Lee 68 and whe n johnsongrass was present in both cultivars.