Soybean Weed Control Systems in Two Southern Coastal Plain Soils

We compared eight weed control systems in soybeans [Glycine max (L.) Merr.] using several combinations of the herbicides trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), alachlor [2-chloro-2′,6′-diethyl-N-methoxymethyl)acetanilide], dinoseb (2-sec-butyl-,4, 6-dinitrophenol), chloroxuron [3-[p-(p-chlorophenoxy)phenyl]-1,1- dimethylurea], and linuron [3-(3,4-dichlorophenyl)-1- methoxy-1-methylurea] with or without cultivation to cultivation only and cultivation plus handhoeing. Cultivation plus handhoeing controlled the most weeds. Eight weed control systems using herbicides or herbicides plus cultivation controlled more weeds in soybeans than the system using only three cultivations. There was no significant difference in soybean yield between the system using three cultivations and six other systems using herbicides or herbicides plus cultivation. Trifluralin or alachlor applied as a preemergence treatment followed by postemergence treatments of chloroxuron, dinoseb, and linuron controlled weeds nearly as well as cultivation plus handhoeing. When dinoseb was applied repeatedly to leaves early after emergence, it severely injured soybeans, reduced soybean yield, and did not control sicklepod (Cassia obtusifolia L.). Sicklepod was the dominant weed species remaining at harvest.