Potential of Aqueous Extracts from Parts of the Pepper Tree (Schinus molle L.) to Affect Emergence and Seedling Development of Wheat (Triticum sativa L.) and Weeds in a Manure Amended Soil

Abstract

The allelopathic potential of aqueous extracts from fruits, leaves, roots and bark of the pepper tree (Schinus molle L.) were investigated on emergence and seedling development of wheat (Triticum sativa L.) and agricultural weeds. Different concentrations of the original extract (undiluted, 1:1, 1:3 and water, v/v) were applied to a soil amended with cattle manure in 2-litre pots. Extracts from all the tree parts significantly (p < 0.05) reduced seedling emergence, height and dry matter yields of wheat and weed seedlings compared to the control (water). The inhibitory effects on both wheat and weed seedlings were consistently in the order fruit=leaves >roots>bark. The inhibitory effects were however progressively reduced by diluting the original extracts suggesting that there was reduction in the concentration of the compounds inhibiting the emergence and development of seedlings.

The weed population and species composition were negatively affected by tree extracts but improved with dilution of the extracts. It was observed that grass weed species were relatively more adversely affected by the inhibitory compounds in the extracts than broad leaf species at each level of extract dilution. The results confirm the presence of water-soluble compounds in the tissues of the pepper tree which can inhibit seedling emergence and growth of wheat and weed seedlings. It is concluded that the pepper tree posses allelopathic characteristics that may be explored for weed management in agriculture. Further investigations are recommended to elucidate the nature of the phytotoxin, formulation, mode of application and the appropriate economic way of exploiting this potential.