Peanuts [Arachis hypogaea (L.) ‘Florunner’], infested with sicklepod (Cassia obtusifolia L.) and Florida beggarweed [Desmodium tortuosum (Sw.) DC.] were grown in 20.3-, 40.6-, and 81.2-cm rows on Dothan sandy loam at Headland, Alabama, and on Greenville sandy clay loam at Plains, Georgia. In-row seeding rates were equal, regardless of row width. Peanuts were maintained free of sicklepod and Florida beggarweed for 0, 2, and 5 weeks after emergence or throughout the season. In either the absence or presence of weeds, peanut yields generally increased with decreasing row width. Quality of peanuts was not adversely affected; in fact, desirable attributes such as percent sound mature kernels (SMK's) were sometimes increased as the row width decreased. Weed growth with close rows was much less than with standard 81.2-cm rows. Although yields of peanuts were lower with increasing time of weed competition, the influence of row spacing on competitiveness of the peanut canopy remained relatively constant on both soil types. Generally, weeds from either seeded or natural stands produced equivalent competitive results.

The competitive effects of hemp sesbania [Sesbania exaltata (Raf.) Cory] on soybeans [Glycine max (L.) Merr. ‘Forrest’] were studied on Sharkey clay for 2 yr. In full-season competition, hemp sesbania populations of 1,600, 3,200, 3,900, and 5,500 plants/ha did not reduce adjusted soybean yields, but populations of 8,100 to 129,200 plants/ha reduced yields 10 to 80%. Competition by hemp sesbania at 68,000 plants/ha for 1 to 4 weeks after soybean emergence reduced soybean yields 8% or less, whereas competition by the same population for 6, 8, and 10 weeks after soybean emergence reduced adjusted yields 18, 27, and 43%, respectively. Hemp sesbania populations of 3,200 plants/ha or more reduced the grade of harvested soybeans and populations of 5,500 plants/ha increased the level of foreign material found in seed samples taken at harvest. Hemp sesbania populations above 10,700 plants/ha increased the levels of damaged kernels and moisture in harvested soybean seed. Early-season control was required for highest soybean yields and total returns. The most critical period for control was 4 to 10 weeks after emergence of soybeans.

Florida beggarweed [Desmodium tortuosum (Sw.) DC] reduced peanut (Arachis hypogaea L. ‘Florunner′) yields more than sicklepod (Cassia obtusifolia L.) when the crop and weeds were allowed to compete for the full season. Regression analyses within years indicated peanut yield reductions of 15.8 to 30.2 kg/ha for each Florida beggarweed per 10 m2 vs. 6.1 to 22.3 kg/ha for each sicklepod per 10 m2. Each kilogram fresh weight per hectare of Florida beggarweed reduced peanut yields 0.15 to 0.74 kg/ha. Reductions in peanut yields ranged from 0.08 to 0.23 kg/ha for each kilogram fresh weight per hectare of sicklepod. Peanut yield reductions correlated more closely with the weights of the weeds than with their populations.