Growth and Yield Performance of Cowpea (Vigna Unguiculata (L.) Walp) as influenced by Row-Spacing and Period of Weed interference in South-West Nigeria

Abstract

Weed problem appears to be the most deleterious factor causing between 25 and 60% reduction in potential yield of cowpea. Field trials were therefore conducted to study the effect of inter-row spacing and period of weed interference on growth and yield of cowpea (Vigna unguiculata (L) Walp) at the Teaching and Research Farm of the Federal University of Agriculture, Abeokuta (07° 15′; 03° 25′ E) in South Western Nigeria during the early and late wet seasons of 2009. The experiment consisted of eight main plots of weed interference which included initial weed removal for 3, 6, 9, and 12 weeks after sowing (WAS) and subsequently weed -infested until harvest as well as initial weed infestation for corresponding periods and thereafter kept weed free until harvest. There were also sub-plot treatments of three inter-row spacing of 60, 75, and 90 cm. All treatments in different combinations were laid out in a split-plot design with three replications. In both trials, the use of inter-row spacing of 60 cm resulted in significant reduction in weed growth as evident in lower weed dry matter production and subsequent higher cowpea pod and grain yields than those of 75 and 90 cm inter-row spacing. Initial weed infestation of up to 3 WAS did not have any adverse effect on crop growth and cowpea grain yields provided the weeds were subsequently removed. On the other hand, cowpea grain yield loss was not significantly averted by keeping the crop weed free for only 3 WAS without subsequent weed removal. In this study, initial weed-infestation for 6 WAS and beyond significantly depressed various crop growth parameter and cowpea grain yield compared with the crop kept weed free throughout its life cycle. In order to obtain optimum yields similar to that of the weed free cowpea field, it was required to keep the crop weed free for 6 WAS and beyond. However, frequent weeding beyond 9 weeks after sowing did not improve cowpea yield significantly and as a matter of fact it may even result in reduction of cowpea grain yield due to mechanical damage of hoe weeding. The practical implication of this finding is that early weeding starting from 3 WAS is very crucial for cowpea production while the critical period of weed removal for optimum yield in cowpea is between 3 and 9 WAS in the forest-savannah transitional zone of south Western Nigeria.

Weed Interference and Control in Cowpea Production: A Review

“…Allowing weed to interfere with cowpea growth for up to 50 days after crop emergence (DAE) reduced cowpea yield by 26 to 75% (Olorunmaiye & Ogunfolaji, 2002;Adigun et al, 2014). Delaying weed removal for up to 14 DAE was not encouraging as it could reduce cowpea yield by 4 to 15% (Adigun et al, 2014).…”

“…Yield losses cause by weeds alone in cowpea production can range from 25% to 76% depending on the cultivar and environment (Adigun et al, 2014;Gupta et al, 2016;Osipitan et al, 2016;Ugbe et al, 2016). Problems caused by weed in cowpea production include reduction in crop yield, less efficient land use, higher cost of production due to insects and plant disease control, reduction in crop quality, water management problems, and less efficient utilization of labour (Patil et al, 2014;Gatachew et al, 2015;Prabhu et al, 2015;Singh et al, 2016).…”

“…A season long weed interference could potentially reduce cowpea yield by 53 to 76% (Olorunmaiye & Ogunfolaji, 2002;Adigun et al, 2014;Gupta et al, 2016). Allowing weed to interfere with cowpea growth for up to 50 days after crop emergence (DAE) reduced cowpea yield by 26 to 75% (Olorunmaiye & Ogunfolaji, 2002;Adigun et al, 2014).…”

“…Ngouajio et al (1997) in a 3 year study found that the period to prevent more than 10% yield loss was 3-4 weeks after sowing (approximately 14 to 21 DAE), and this level could be obtained by one weeding in beans. However, the critical period of weed control might vary with the environmental conditions, level of weed infestations, composition of weed population, pre-crop emergence management practices, soil moisture and fertility level, cowpea cultivar and plant density (Norsworthy & Oliveira, 2004;Mohammadi et al, 2005;Adigun et al, 2014;Osipitan et al, 2016).…”

“…These constraints include insect pests and diseases (Thio et al, 2016;Abudulai et al, 2017), inadequate knowledge of good cultural practices and high yielding varieties resulting in poor yield (Ajeigbe et al, 2005). Other constraints include planting at sub-optimal plant density, low soil fertility and drought and weeds (Adigun et al, 2014;Kanteh et al, 2014;Adusei et al, 2016;Osipitan et al, 2016).…”