The benefit of the interface effect on the perennial pigeonpea growthappeared to be confined to the first row only, probably because the plantswere already fairly widely spaced at 1 m apart, and partly because of theintense shading by the outermost perennial pigeonpea row. Although it wasnot possible to separate the benefit at the interface due to below groundinteractions, the extensive lateral root distribution suggests that access towater and nutrients was significantly greater at the TCI. The neutronmoisture techniques used in this study was unsatisfactory for quantifying thewater uptake at the TCI because access tubes could not be installed toadequate depth and there was insufficient number of tubes across the TCI.Thus it is not possible to make firm conclusions about the water uptake bythe pigeonpea plants. A more appropriate approach is the sap-flow techniquedescribed by Ong et al. [7] which is relatively simple to use and furthermoreis non-destructive.