Performance of crops under Eucalyptus tree-crop mixtures and its potential for adoption in agroforestry systems

Abstract

Competition for scarce land resources between food crops and trees has intensified and there is need for a balance to accommodate both, either in rotation programs or in agroforestry systems. Successful intercropping of Eucalyptus trees with crops is hindered by competition for light between trees and crops, soil nutrient dynamics and the allelopathy from Eucalyptus trees. The aim of this study was to establish and assess the performance of farm crops under Eucalyptus grandis tree plantations so as to evaluate the potential of the trees for agroforestry. The crops i.e. common beans, Irish potatoes and black Nightshade (Solanum villosum) were planted along rows of Eucalyptus trees (3 and 6 years) in plot sizes of 4 m by 2 m adopting a factorial arrangement in RCBD with open field as control. The assessment of the performance of the crops was mainly on; germination, Leaf Area Index (LAI) and possible yields. In addition, the amount of photosynthetically active radiation (PAR) reaching the understory crops was measured. From the results, Germination of crops under trees was higher than in the open field. Germination was delayed under trees when compared to those grown in the open field. The age differences in the Eucalyptus tree plantations had no significant effect on the amount of PAR reaching the understory crops. The leaf area index (LAI) of the understory crops was significantly affected by Eucalyptus trees of different ages (p < .001). The crops grown under Eucalyptus trees gave higher yields compared to crops grown in open fields but not fertilized. The effect of Eucalyptus plantation age significantly affected the yields of beans and potatoes (p < .001) but not nightshade; therefore, the vegetable can be grown under Eucalyptus tree shade without reduction in yield. Irish potato and common beans are potential crops for agroforestry with Eucalyptus trees but need further research as their yields were low and had selected disease incidences.