Herbicide Combinations in Irrigated Cotton

Abstract

Combinations of herbicides as single or separate applications to the soil were compared in furrow-irrigated cotton (Gossypium hirsutumL.). In seven tests, preplanting applications of four herbicides, primarily effective for grass control, were combined with postemergence applications of 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron). Preplanting applications of 4-(methylsulfonyl)-2,6-dinitro-N,N-dipropylaniline (nitralin) andα,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) before furrowing retarded growth of cotton and sometimes reduced stands. Herbicides applied after furrowing did not appear to affect cotton development. Combinations of the four herbicides with diuron gave satisfactory control of annual weeds until harvest. In 15 tests, preplanting applications ofO,O-diisopropyl phosphorodithioateS-ester withN-(2-mercaptoethyl) benzenesulfonamide (bensulide) were combined with preplanting or postemergence applications of four herbicides primarily effective for control of broadleaf weeds. Preplanting applications of 3-(p-chlorophenyl)-l,l-dimethylurea (monuron) usually caused temporary chlorosis and stunting of cotton seedlings. Postemergence applications of monuron and 2,4-bis(isopropylamino)-6-(methylthio)-s-triazine (prometryne) sometimes caused temporary chlorosis of cotton foliage. Combinations of herbicides controlled weeds until harvest in 14 of the 15 tests. There was no difference among the herbicide combinations in yield of cotton in 21 of the 22 tests. In the 15 tests sampled there were no differences in fiber properties and boll components among herbicide combinations.