Interest in developing most economical weed control method continues to increase because of the economic implications of repeated weeding. Costs, including those of man power and yield losses due to weed infestation lower the profitability of crop production in the tropics especially those of highly cherished but slow growing crops like water yam. Tithonia diversifolia, an aggressive weed has become a major economic problem to arable crop production in Nigeria in general but water yam in particular. Thus, this study assessed the economics of weed control methods with a view to identifying the most profitable for water yam production. The experiment was conducted at Ogunba village near Baaya-Oje in Surulere Local Government Area, Ogbomoso, Oyo State. The treatments; Weed control with Black plastic mulch, Grass mulch, 2 hoe weeding, 3 hoe weeding, Atrazine, Diuron, IWM (Atrazine + Diuron + Plastic mulch) and unweeded plot, were evaluated in a Randomized Complete Block experiment with three replicates. Yam setts were planted at a spacing of 1m x 1m. Black plastic mulch was applied at the rate of 10,000 m2/ha, Grass mulch was applied at the rate of 5 tons/ha. Two (2) hoe weeding were done at 3 and 6 weeks after planting (WAP), while 3 hoe weeding was done at 3, 6 and 9 WAP. Atrazine and Diuron were applied at the rate of 2.5kg a.i/ha while they were applied each at half recommended rate (1.25kg/ha) before applying plastic mulch. The weedy plot was the control. Partial budgeting was used to evaluate the economics of each method. Results showed that weed control methods significantly (P = 0.05) affected water yam yield and net profit. The mean costs of water yam production under the weed control methods were: N786,000.00 (plastic mulch), N362,000.00 (Grass mulch), N312,800.00 (2 hoe weeding), N324,800.00 (3 hoe weeding), N256,800.00 (Atrazine), N286,800.00 (Diuron), N617,600.00 (IWM) and N283,500.00 (unweeded). The profitability of the weed control methods measured by the change in profit were: 3 hoe weeding (N625200.00) > 2 hoe weeding (N53000.00) > Diuron (– N161, 200.00) > grass mulch (– N187,200.00) > Atrazine (– N211,200.00) > IWM (– N277,700.00) > Plastic mulch (– N361,200.00) > Unweeded (– N761200.00). From the result it is concluded that 3 hoe weeding is the most economical for water yam production in the study area.

Keywords: Economics, Weed Control Methods, Tithonia Diversifolia , Water Yam