ABSTRACT

 Field experiments were conducted at the eastern farm of the Michael Okpara University of Agriculture, Umudike and lila farm at Uyo central in 2007 rainy season to evaluate the effect of sweet potato varieties and different weed control methods on weed density, weed dry weight, crop leaf area index, photosynthetically active radiation and tuber yield. The study was established as a split-plot treatment with sweetpotato varieties (T1S86/0356, T1S87/0087, Ex-Igbariani and OP/T1S2532.1.SP.13), as main plot treatments. The subplot treatments comprised six weed control methods: three rates of' Primextra(at 1.3 kg a.i had , 1.98 kg and 2.64 kg a.i had ), manual weeding carried out once and twice, and an untreated control. Results obtained indicate that swectpotato varieties and weed control methods had significant influence on weed density and dry matter. In Umudike, OP/T1S2532.l.SP.13 followed by T1S8710087 significantly reduced total weed density better than other varieties. In Uyo, lowest total weed density was obtained from plots planted to Ex-Ighariam, though not significant when compared with other varieties. In Umudikc, Priniextra at 2.64 kg a. I had , and 1.98kg a i ha,lijllowed by plots weeded twice controlled weeds better than the other treatments. In Umudike, there was no significant difference between swcctpotato varieties in the control of' wed biomass. In Uyo, T1S87/0087 reduced weed biomass by 25% compared with OP/T1S2532. I.SP.13. In Umudike, Primextra sprayed at the rate of 2.64 kg a.i ha' and 1 98 kg a.i ha1 reduced weed hiomass by 2 1% and 44% respectively over the unwccdcd check. In Uyo, the plot weeded twice followed by Plots treated with Primextra 2.64 kg a.i ha' and 1.98kg ai ha 1 , reduced weed biomass better than all other treatments. In conclusion, T1S87/0087 and Ex-Igbariam with Primextra at the rate of 2.64 kg a.i ha1 and 1.98 kg a.i ha were more effective in suppressing weed density, dry matter, leading to higher tuber yield compared with manual weeding. Averaged over locations, Primextra at the rate of 2.64 kg a.i ha1 and 1.98 kg a.i ha1 gave 80-91% higher tuber yield than unweeded check and are therefore recommended for weed control to achieve optimum sweet potato yield.