Effect of oil palm sludge on cowpea nodulation and weed control in the humid forest zone of Nigeria

Abstract

A field trial was conducted at the Rivers State University of Science and Technology Research and Training farm Port Harcourt to test the effect of oil palm sludge on cowpea nodulation and weed control. The cultivars of cowpea used were Dan Kano, Bornu local and Sokoto local while the oil palm sludge levels applied were 0, 4000, 6000 and 8000 l/ha. The trials were conducted during the rainy and dry season of 2004. It was observed that as the level of oil palm sludge increased, the length of root showed remarkable decrease in length irrespective of cultivars or season. Dan Kano cultivar had the longest root length (26.60 cm) in control plot and least (23.17 cm) was obtained from the highest level
(8000 l/ha) of oil palm sludge application during wet season. This development could be attributed to low wet ability and anaerobic condition created before decomposition by Oil palm sludge which had
higher concentration on the top soil with the majority of the cowpea roots in this highly concentrated zone. On nodulation, results indicated that increase in oil palm sludge favored more number of functional root nodules during both seasons and in all the cultivars and reverse being the case with the non-functional nodules. Weed count was higher (35) in the control plots and lowest in the 8000 l/ha plots (2.0). Similarly, the highest weed weight (670 g/ha) was obtained in control plots while the lowest (170 g/ha) was recorded in 8000 L/ha. On the cultivars tested oil palm sludge at 8000 l/ha favoured more root nodules development and hence more yield with excellent weed control ability.