Light after treatment was found to be required for the herbicidal activity of nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] following postemergence applications of both herbicides to greenbean (Phaseolus vulgarisL. ‘Spartan Arrow’). The effect of photosynthate and/or light before treatment was investigated. A 24-hr dark period prior to postemergence treatment of the bean seedlings had no effect on herbicidal activity when light followed treatment. The effect of plant pigments on the activity of both herbicides was studied using mutants of corn (Zea maysL.) and soybean [Glycine max(L.) Merr.]. A white mutant of corn was much more resistant to the herbicides than a greenish-yellow mutant or the normal plant. A yellow mutant of soybean was equally as susceptible as the normal type. Studies with radiolabeled foliar applications of both herbicides showed no significant difference in translocation in the light or dark.

The adsorption of nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) and oxyfluorfen [2-cholor-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] from aqueous solution by muck soil, and by kaolinite and bentonite saturated with hydrogen or calcium ions, was studied using14C-labeled herbicides. Both compounds were readily adsorbed from solution by muck soil and Ca- and H-Al-bentonite but only slightly by Ca- and H-Al-kaolinite. Very little of the adsorbed compounds was desorbed after four extractions with distilled water. A bioactivity study using sorghum seedlings (Sorghum bicolorL. ‘RS610′) was conducted with the herbicides in a silica sand medium amended with 1% (w/w) of the various adsorbents. The herbicides were strongly inactivated by muck soil but there was very little inactivation by the clays. There was essentially no movement of either herbicide through 5-cm columns of a silt loam soil and a fine sand soil.

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The site of uptake of nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether) and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene] was studied using a double pot technique. Sorghum [Sorghum bicolor(L.) Moench ‘RS610′] and pea (Pisum sativumL. ‘Alaska’) were the test plants. Herbicidal activity measured by the reduction in fresh weight of the roots and shoots of treated plants showed that exposure of the shoot zone to the herbicides caused much more injury to the plants than root exposure. Translocation of both compounds from root applications to tops of pea and sorghum was studied using14C-labeled herbicides. There was very little movement of the compounds from the roots of both species. Translocation of the compounds from foliage application was studied using greenbean (Phaseolus vulgarisL. ‘Spartan Arrow’) and soybean [Glycine max(L.) Merr ‘Wayne’]. Almost all of the applied14C-herbicides remained at the point of application.

Experiments were conducted to evaluate the performance of some sugarcane varieties against natural weed infestation. The trials were laid out in a randomized complete block design with split-plot arrangement and three replications. The sugarcane varieties were the main plots while the sub-plots consisted of weeding regimes. Recommended cultural and agronomic practices were followed to raise the crops. Data were collected on weed density, weed biomass, sugarcane tiller count and cane yield. Our results revealed that Rottboellia cochinchinensis (Lour.) W.D.Clayton, Panicum maximum Jacq, Imperata cylindrica L., Panicum repens L., Cynodon dactylon L. and Cyperus rotundus L. were the major weed problems of sugarcane in Ilorin. The monthly hoe weeded treatment had significantly higher tiller count which translated to higher cane yield (22.61 to 72.54 t/ha) than other weed control treatments. The reduction in cane yield was between 80.51 and 97.55% depending on duration of weed infestation. Association of weed parameters with cane yield was negative and significant showed that a decrease in weed infestations will result in simultaneous increase in sugarcane yield. Therefore, in selecting sugarcane variety(s) for breeding programmes, emphasis should be placed on sugarcane growth parameters that negatively and significantly correlated with weed infestation.