Autoallelopathy of selected multipurpose tree species and the effect of their leachates on Agricultural test crop

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Date
2017
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Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara
Abstract
A study carried out in the tree nursery of College of Forestry, Vellanikkara, Thrissur to assess the autoallelopathic effect of selected multipurpose trees and the effect of their leachate on agricultural test crop. The study on allelopathy is very essential in agroforestry as it effect the yield and performance of the trees and crops grown together and is essential to make judgment on the compatibility of trees and crops. The allelopathic effect of different tree part leachates such as leaf leachate, bark leachate and root leachate of selected trees viz., Acacia auriculiformis, Acacia mangium, Ailanthus. triphysa, Grevillea robusta and Swietenia macrophylla on the germination and growth of their own seedling and an agricultural test crop cowpea (Var. Anaswara) were studied. The soil for the pot culture experiment was collected from well established plantations of the MPTs and is used as potting mixture with sand in equal proportion. The pots were irrigated with leachates of different tree parts of these trees by soaking the tree part in water for 24 hours in 1:10 w/v concentration. The monthly variation in nutrient status of the soil used for pot culture experiment and the variation in the physicochemical properties of leachates at six intervals is also estimated. The effect of tree part leachates considerably varied among the germination and biomass production in both allelopathic and autoallelopathic studies. The observations on the germination per cent in allelopathic and autoallelopathic study revealed greater inhibition in the pots treated with leaf leachate in all tree species, except for S. macrophylla. With regard to biometric observations and biomass production also, S. macrophylla performed as the best compared to other selected species investigated for autoallelopathy. In case of the test crop also, it showed a better growth in pots treated with the leachates from S. macrophylla. The physicochemical analysis of the leachate of tree parts used to irrigate the pots showed increasing trend in total solid, electrical conductivity, total phenol, total carbohydrate and a decreasing trend in pH upto 36 hours. The physicochemical analysis of leachates for total phenol showed a greater concentration in the leaves than the bark and root. Results converge to the generalisation that among the five selected tree species the effect of auto allelopathy is negligible in case of S. macrophylla. The better growth performance of the test crop in S. macrophylla tree part leachates shows the compatibility of the test crop with the tree than the other selected tree species.
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