Allelopathic effects of mango (Mangifera indica L.) leaf extract on growth and biochemical parameters of cowpea (Vigna unguiculata (L.) Walp)

Fallen mango leaves were collected from the orchard, and an aqueous extract of powdered dried leaves was prepared. Different concentrations of extract (20%, 40%, 60%, 80%, and 100%) were applied to cowpea seeds sown in the pots. The effect of the extract was recorded on germination, growth, and biochemical parameters. With an increasing leaf extract concentration, seed germination progressively decreased. A gradual decrease in root length, shoot height, fresh and dry weight was found. In contrast, the moisture content of plants increased slightly from 35.65% in control to 36.43% in 100% fallen leaf extract (FLE) treated plants. Chlorophyll content decreased from 6.68mg.g⁻¹ FW in control to 3.37mg.g⁻¹ FW in 100% FLE treated plants. Similarly, carotenoid content decreased from 2.27mg.g⁻¹ FW in control to 1.62mg.g⁻¹ FW in 100% FLE treated plants. In addition, leaf protein content decreased from 19.12% in control to 9.81% in 100% FLE treated plants, and carbohydrates content decreased from 34.33% in control to 20.96% in 100% FLE treated plants. Contrary to this, total phenol content in leaves increased from 0.18 mg.g⁻¹ FW in control to 0.32 mg.g⁻¹ FW in 100% FLE treated plants. Study reveals that fallen leaves of mango cause allelopathic effect on cowpea, a leguminous crop often grown as intercrop in mango orchards. Fallen leaves of mango adversely affect the growth and yield of cowpea. Although, total profitability of the mango orchards with cowpea as intercrop may increase, cowpea yield and quality will be adversely affected by fallen mango leaves.