Effects of water stress on the rooting, nodulation potentials and growth of cowpea (<i>Vigna unguiculata</i> (l) walp)

Abstract

Rooting, nodulation and growth ability of cowpea growing under limited water supply was investigated at the Teaching and Research Farm of the Imo State University, Owerri, Nigeria. The experiment was conducted in plastic buckets arranged in a completely Randomized Design with three replications, and treatments represented as 500ml, 1000ml, and 1500ml of water, respectively. Control treatment was represented by cowpea plants that grown with rain-fed water. The 500ml and 1000ml of water were applied two times a week to the receiving cowpea plants while the 1500ml was applied daily to the receiving cowpea. Data were collected on the number of nodules/plant, root length/plant (cm) measured at 2 and 4 wks after planting (WAP) respectively, number of leaves/plant, number of branches/plant and seed yield (kg/ha) ollected data were subjected to analysis of variance at the 5% level of significance. Results showed that cowpea plants that received 500ml of water produced mean nodule of 6.0 which was significantly (p<0.05) from the mean nodule of 13.2 produced by cowpea plant that grew under rain-fed condition. Cowpea plants that received 500 and 1000ml of water produced mean roots length of 9.8cm and 19.5cm at both 2 weeks and 4 weeks after planting, respectively, which were significantly (p<0.05) longer than 5.2cm and 13.4cm meanroots length in the control, at 2 and 4 WAP. Cowpeas that received 500ml of water produced mean plant height of 117cm and number of branches of 1.0 which were significantly different (p<0.05) from the mean plants height of 47cm and number of branches of 4.1 in the control plants. Seed yield was significantly (p<0.05) higher in the control plants than in the plants that received 500 and 1000ml of water, respectively. It was concluded that root characteristics nodulation potential and seed yield of cowpea were affected by the limiting water supply. Optimal water supply for cowpeas growing in pots should therefore be studied for better irrigation management and optimal performance of cowpea.

Keywords: Nodulation, water stress, cowpea, growth, rooting
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