Abs tract. Speargrass, Imperata cylindrica (L.) Raeuschel, is a serious weed, threatening crop productivity in smallholder farms in West Africa. Since the use of more effective practices such as deep tillage and chemical control is beyond the means of resource-poor farmers who carry out most agricultural activities in this region, low-input alternative technology needs to be developed. F ield studies were conducted during the 1993/1994 and 1995/1996 growing seasons to investigate the influence of three velvetbean accessions and two levels of fertilizer on the control of speargrass during the year of cover crop planting and one year later. The velvetbean accessions in 1993 were: Mucuna cochinchinensis and M. pruriens var. utilis. In 1995, M. pruriens var. IRZ was included in the study. M. cochinchinensis in 1993 and M. pruriens var. IRZ in 1995 had the highest ground cover rating early in the growing seasons whereas M. pruriens var. utilis had the lowest ground cover rating in both years. Inorganic fertilizer at 30 kg ha Ð 1 each of N, P and K increased velvetbean ground cover by 2 ± 22%, with M. cochinchinensis (14 ± 22%) and M. pruriens var. IRZ (5 ± 15%) showing the highest response in 1993 and 1995, respectively. M. pruriens var. utilis showed the least response in both years. After one growing season M. pruriens var. utilis, M. cochinchinensis, and M. pruriens var.IRZ reduced speargrass shoot density by 50, 76, and 68%, and shoot dry matter by 72, 92, and 79%, respectively. Fertilizer reduced speargrass growth in velvetbean plots, while the opposite occurred in plots without velvetbean. Velvetbean residue effectively suppressed speargrass until the beginning of the subsequent cropping season. Maize grown 1 year after velvetbean required 50% less weeding than plots without velvetbean. Maize shade reduced speargrass shoot growth by 30 ± 80% but regrowth of the weed occurred 4 weeks before maize harvest. Maize grain yield was higher in plots previously seeded to velvetbean than in plots without velvetbean. Speargrass shoot density and dry matter were negatively correlated with maize grain yield (r = Ð 0.42 and r = Ð 0.32, respectively, P < 0.01). Although velvetbean may effectively reduce speargrass during the year of establishment and the subsequent cropping phase it has a limited effect on rhizomes and, as such, does not provide a long term control.

Imperata cylindrica is a noxious weed that infests annual and perennial crops in most tropical regions. High crop densities may offer opportunities to reduce I. cylindrica competition in small-scale farming systems. The competitive ability of maize relative to I. cylindrica was evaluated in an addition series experiment in the forest savannah transition zone in 2006 and 2007 at Ibadan, Nigeria. Maize and I. cylindrica were planted in eight monoculture densities (4, 8, 12, 16, 20, 32, 48 and 64 plants m À2 ) and in a 1:1 mixture at eight total densities (2:2, 4:4, 6:6, 8:8, 10:10, 16:16, 24:24 and 32:32 maize: I. cylindrica plants m À2 ) as in monoculture. Non-linear regression models were used to relate crop and weed shoot biomass to their densities and total grain yield to maize density. In maize, intraspecific competition was more than interspecific competition; in I. cylindrica, interspecific competition was higher than intraspecific. As expected, total grain yield was lower in the mixture than in maize monoculture at all total densities. Average maize grain yield in maize monoculture differed from that in mixtures by 0.77 t ha À1 in 2006 and 0.57 t ha À1 in 2007. Niche differentiation indices were <1 in 2006 and >1 in 2007, indicating that both species competed for similar resources in 2006, but not in 2007. The greater competitive ability of maize over I. cylindrica may be associated with rapid growth and canopy development observed in the field.

Field experiments to determine the influence of supplementary hoe weeding on the efficacy of ButaForce (N-(butoxymethyl)-2-chloro-N-2,6-dimethyl acetanilide) for low land rice (Oryza sativa L.) weed management was conducted at the Faculty of Agriculture Teaching and Research Farm of the University of Port Harcourt during the early cropping seasons of 2018 and 2019. Seven treatments were used for the experiment namely: ButaForce at 1.5 L/ha + SHW (21 DAS), ButaForce at 2.0 L/ha + SHW (21 DAS), ButaForce at 2.5 L/ha + SHW (21DAS), ButaForce at 3.0 L/ha (recommended rate), weed-free (weekly weeding), hoe weeded twice at 21 and 42 DAS and weedy check. The treatments were laid out in a Randomized Complete Block Design (RCBD) with three replicates. Results from the study showed that weed-free check (weekly weeding) was more effective in weed control in lowland rice. It also gave the highest growth and yield attributes over all other treatments. Weed suppression and rice performance was better in plots treated with ButaForce at 2.5 L/ha + SHW (21 DAS) than in other supplementary hoe weeding. The economic analysis showed that although hoe weeded plots had higher yields, the profit obtained from them were lower when compared with the supplementary hoe weeding and ButaForce at 3.0 L/ha. Among all the weed control treatment, plots treated with ButaForce at 2.5 L/ha with supplementary hoe weeding gave the highest profit. Since the highest profit was recorded in plots treated with ButaForce at 2.5 L/ha with supplementary hoe weeding, it is therefore recommended to rice farmers in the study area.

Field experiment was conducted in Faculty of Agriculture Teaching and Research Farm University of Port Harcourt, Port Harcourt, Rivers State, South Eastern Region of Nigeria between March and September 2017; to evaluate the effect of planted short fallow legume cover crop on maize performance and weed growth. The experimental design was a 5 x 2 factorial in randomized complete block design (RCBD) in a plot size of 4 m x 4 m with four replicates. The treatments consisted of four different legumes cover species fallow and a natural fallow as follows: Mucuna [Velvet bean (Mucuna pruriens (L.) DC var. utilis), Lablab (Lablab purpureus (L.) Sweet), Pigeon pea (Cajanus cajan (L.) Mill spp)], Centrosema (Centrosema pascuorum (L.) and a natural fallow (No Legume Cover) and two levels of inorganic fertilizer as NPK 15: 15: 15 (0 and 15 Kg ha-1 NPK). All legume cover growth characteristics were negatively correlated with weed cover and weed dry weight (r = -0.58 and r = -0.59 at P=0.0001). Legume dry weight had a positive correlation with all maize parameter (r =0.64 at P=0.0001) except for stem diameter (r = -0.43 at P=0.0051). Similarly, all weed attributes were negatively correlated to maize parameters. Maize height was better in plots that received short fallow legumes than natural fallow. There was increase in soil Nitrogen level after 10 weeks of fallow. Legume cover crop short fallow has the potentials for weed suppression, soil fertility and productivity improvement in maize culture.

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