The feasibility of herbicide and crop rotation for the control of johnsongrass [Sorghum halepense(L.) Pers.] in corn (Zea maysL.) was studied in field experiments. Light infestations of johnsongrass were initially present, but it became the predominant weed after 4 yr of continuous corn treated with atrazine [2-chloro-4-(ethylamino)-6-(isopropylamine)-s-triazine], cyanazine {2-[[4-chloro-6-(ethylamino)-s-triazin-2-yl]amino]-2-methylpropionitrile}, and linuron [3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea], alone and in combinations at rates of 2.24, 2.24, and 0.84 kg/ha, respectively. The infestation of johnsongrass was effectively controlled by growing corn in rotation with cotton (Gossypium hirsutumL.) in a cropping sequence of corn-cotton-cotton-corn, in which trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), fluometuron [1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea] and MSMA (monosodium methanearsonate) at 0.56, 2.24, and 2.24 kg/ha respectively, were used for weed control in cotton. In the corn-cotton-cotton-corn cropping sequence, the herbicide treatments also prevented increases in the populations of other indigeneous weeds including prickly sida (Sida spinosaL.), prostrate spurge (Euphorbia supinaRaf.), spotted spurge (Euphorbia maculataL.), common purslane (Portulaca oleraceaL.), tall morningglory [Ipomoea purpurea(L.) Roth], common cocklebur (Xanthium pensylvanicumWallr.), spurred anoda[Anoda cristata(L.) Schlecht.], hemp sesbania [Sesbania exaltata(Raf.) Cory], redroot pigweed (Amaranthus retroflexusL.), goosegrass [Eleusine indica(L.) Gaertn.], junglerice [Echinochloa colonum(L.) Link], large crabgrass [Digitaria sanguinalis(L.) Scop.], and purple nutsedge (Cyperus rotundusL.).
Assessment of The Efficacy of Chelate-Assisted Phytoextraction of Lead By Coffeeweed (Sesbania exaltata Raf.)