Cocklebur Control in Soybeans as Affected by Cultivars, Seeding Rates, and Methods of Weed Control

Four field experiments were conducted to study the effects of row width, cultivation, soybean population, soybean cultivar, and herbicides on soybean [Glycine max (L.) Merr.] yields and control of common cocklebur (Xanthium pensylvanicum Wallr.). When the same herbicide practices were applied to all treatments, common cocklebur was controlled better in soybeans planted in 100-cm rows and grown with cultivation than in those planted in 18 or 33-cm rows and grown without cultivation. Increased soybean yields and better common cocklebur control were obtained when soybean populations were increased from 80,000 to 350,000 plants/ha. Common cocklebur reduced the yield of ‘Bragg’, one of the most competitive cultivars, 7% when grown in 100-cm rows with cultivation and 39% when grown in 33-cm rows without cultivation. The yields of six other cultivars were reduced about 20% in 100-cm rows and 32% to 52% in 33-cm rows. Cross cultivation controlled common cocklebur more effectively than did conventional cultivation in 100-cm rows, but cross cultivation was not advantageous when metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one] and bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were applied.