Effect of Alectra vogelii (Benth) Aqueous Extract on the Growth Parameters of Cowpea (Vigna unguiculata (L.) Walp) Varieties in Zaria, Kaduna State

Abstract

A study was conducted to evaluate the effect of Alectra vogelii (Benth) aqueous extracts on the growth parameters of cowpea (Vigna ungiucuata (L.) Walp). The experiment was carried out in the Orchard of the Department of Agronomy, Institute of Agricultural Research, Ahmadu Bello University, Samaru, Zaria, Nigeria in 2018. Qualitative and quantitative phytochemical screening of Alectra vogelii whole plant was carried out at National Research Institute and Chemical Technology (NARICT), Zaria. Alectra vogelii aqueous extract was applied on four varieties of cowpea: Sampea 7, Sampea 9, Sampea 10 and IAR-00-1074 at 0, 50, 100, 150 and 200 g/l, and the treatment were laid in complete randomized design with three replications. The growth parameters evaluated included plant height, number of leaves and root noodles at 5, 7 and 9 weeks after planting (WAP). Data obtained for growth parameters were analyzed using Analysis of Variance with Duncan’s New Multiple Range Test used to separate means that were significant. The result for phytochemical composition of A. vogelii whole plant showed the presence of five active phytochemical constituents: Saponins (46.50%), flavonoids (16.04%), tannins (0.247%), cyanogenic glycoside (0.212%) and alkaloids (0.08%). Significant difference (P≤0.05) was found in the effect of the extracts on growth parameters of cowpea. There is marked reduction in the growth parameters with increase in A. vogelii aqueous extract concentration. This implies that, A. vogelii extracts inhibits growth of cowpea with 200mg/l having the highest effect. Thus, the inhibitory action of A. vogelii can probably be attributed to the active phytochemicals present in the extracts Therefore, it is recommended that, A. vogelii residues should be well removed from farms as may inhibit the growth of cowpea due to their allelochemicals content.