Efficacy of Three Botanicals in Cowpea Field, Oyo State, Nigeria

Aims: To evaluate the effects of different concentrations of the plant extracts of Eucalyptus camaldulensis (EU), Eucalyptus torreliana (ET) and Leucaena leucocephala (LL) on seed-germination, seedling-growth, weed flora and yield performance of cowpea.

Study Design: The study was laid out in a completely randomized design (CRD) with eighteen ttreatments replicated three (3) times, totaling fifty-four (54) experimental samples. The whole experiments were repeated in two trials.

Place and Duration of the Study: This study was carried out on the roof top garden of department of Crop Protection and Environmental Biology, University of Ibadan, Nigeria from 2015 to 2017.

Methodology: Leaves of EU, ET and LL were harvested, air-dried, milled and assayed for phytochemicals (mg/g) following standard-procedures. Milled samples (144, 108, 72, 36 and 0 g) of each botanical were dissolved in 1 L distilled-water to obtain Aqueous-Leaf-Extracts (ALE) of 100, 75, 50, 25 and 0% (control) concentrations. Ten seeds of cowpea-Ife brown in petri dishes were treated with the different concentrations. Data were collected on Seed Germination-SG (%). In pots containing 10 kg soil, cowpea-seeds (2 plants/pot) were sown. Each botanical-extract at different concentrations and paraquat (5 mL/L/ha) were applied, before and five Weeks-After-Sowing (WAS). Data were collected on Plant height-PH (cm) at 3,5,7,9 and 11 WAS, while Grain Yield-GY (g/pot) was determined at maturity. Relative Importance Values (RIVs) were determined following standard-procedures. Data were analysed with descriptive-statistics and ANOVA at α0.05.

Results: Total phenols (32.04±0.10), tannins (27.40±0.04) and saponins (20.15±0.03) were significantly higher in EU than in ET and LL. Cowpea SG ranged from 80.0±0.5 (50% LL) to 100.0±1.2 (100% LL). Cowpea PH ranged from 18.2±2.0 (100% ET) to 48.5±3.2 (100% EU) both at 9-WAS. Cowpea GY ranged from 0.1±0.1 (25% LL) to 4.2±0.5 (50% LL). Mitracarpus villosus had highest RIV of 52.3 (100% EU at 3-WAS) but reduced to 28.5 (100% EU at 9-WAS). Aqueous-leaf-extract of Eucalyptus camaldulensis at 100% reduced Mitracarpus villosus populations, while Leucaena leucocephala at 50% improved grain yields.