Effect of a Sulfonylurea herbicide in weed management and field performance of maize
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Maize is a crop of global importance, unfortunately its productivity and production is greatly hampered to about 40% by weeds. Chemical weed control by use of herbicides is recommended by several researchers in managing weed problems of maize over the manual control methods as it is cheaper and faster although the commonly used herbicides of Glyphosate is believed to be carcinogenic, and have associated weed resistance whereas Ametryn is persistent and bio accumulating in the environment. Therefore Nicosulfuron herbicide due to its low mammalian toxicity and wide spectrum effects on weeds is a possible alternative, but prior efficacy trials are needed before any recommendation. A field experiment was conducted at Makerere University Agricultural Research Institute Kabanyolo (MUARIK) between September 2021, and January 2022 to evaluate the efficacy of Nicosulfuron herbicide in comparison with other commonly used herbicides in weed management of maize. The experiment was set up in a completely randomized block design with treatments including Glyphosate IPA salt 41% applied pre-emergence at 200ml/20L of water, post-emergence treatments of Nicosulfuron 40g/L OD at 60ml/20L of water and Ametryn 500SC at 200ml/20L of water all applied once to weeds not more than 5cm. The controls were Hand hoe weeding more than two times and the unweeded. Experimental results showed that the maize fields at MUARIK were infested by 66.7% of broad leaved weeds such as Ipomea purpurea and oxalis latifolia and 33.3% of blade leaved weeds taking into account of Cyperus rotundus, Cynodon dactylon among others. The treatments significantly (P<001) reduced weed density for both blade and broad leaved weeds. The least number being observed in the Hand hoe weeded plots (0.0, 0.0gm-2 ), followed by Ametryn 500SC (105.6, 10.50 gm-2 ), Nicosulfuron OD (142.6, 14.00 gm-2), Glyphosate IPA salt (266.8, 30.25 gm-2 ) and the highest recorded in the unweeded plots (506.8, 80.33 gm-2 ) for both blade and broad leaved weeds respectively. Hand hoe weeded plots registered a significantly (P<001) lower weed biomass, followed by Nicosulfuron OD, Ametryn 500SC, Glyphosate IPA salt and the highest observed in the unweeded plots. The treatments significantly (P<001) increased maize growth characteristics with the lowest plant height, number of leaves, length, width and Area of the 3rd leaf being observed in the unweeded plots, followed by Glyphosate IPA salt, Ametryn 500SC, Nicosulfuron OD and the highest registered in the hand hoe weeded plots. The highest significant maize grain yield (3933kg/ha)was registered in Hand hoe weeded plots, followed by Nicosulfuron OD (2037kg/ha), Ametryn 500SC (1615kg/ha), Glyphosate IPA salt (1370kg/ha) and the least in the unweeded plots (848kg/ha). Nicosulfuron OD herbicide can be a good alternative as it significantly controlled weeds and contributed to maize growth and grain yield as other commonly used herbicides of Glyphosate IPA salt and Ametryn 500SC which are believed to be carcinogenic and bio accumulating in the along the food chain respectively. However hand hoe weeding performed way above the herbicide treatments hence it should be maintained over herbicides for better weed management and maize grain yield despite its major drawback of labor shortage during the peak periods of the season. Therefore more research should be done to evaluate combined efficacy of one time Hand hoe weeding and Nicosulfuron OD herbicide applied post-emergence.