Effect Of Tillage, Weed Control Method And Mulching On Spearcrass (Imperata Cyliizdrica (L.) Raeuschel] Suppression And Soybean (Glycine Max (L.) Merr.J Yield In An Ultisol.

ABSTRACT

Field studies were conducted at the Research Farm of the National Horticultural Research Institute (NHRI), Okigwe, imo State in the 2005 and 2006 cropping seasons to investigate the effect of tillage, weed control method and mulching on speargrass I/1i/)L'FUI(l c)'/i/k/rica (L.) Raeuschel] in soybean [Glycine max. (L.) Merr.] The experiment was set up as a split plot in a Randomised Complete Block Design (RCBD). The main plots consisted of deep tillage (DT), Conventional tillage (CT), and Zero tillage (ZT). 'Ihe subplot treatments comprised of three weeding strategies and two mulch types (live mulch and dry niulcli). The results obtained indicated significant differences in spearr,i ass shout and iliizume density between tillage systems and weed control methods (P<0.0() I). l)cep lillage and sweet-potato plots had the lowest speargrass shoot and rhizoiiie density and dry matter in both years. Mulching with diy speargrass shoots at 150 kg/ha was as effective as keeping the plots free of sperrgiass for up to six weeks afler l)l1I1t ilig (WAI>) soybean. Also, tillage systems and weed control method significantly influenced soybean grain yield in both years. The result therefore suggest that deep tillagc, in combination with mulching with dry speargrass shoots at 150 kg ha 1is effective n suppressing speargrass for six WAP. 1-lowever, a combination of deep tillage and/or sweet potato cover at 10,000 plants/ha arc effective in suppressing speargrass for optimum soybean yield.