Croton macrostachyus (Hochst. ex Delile) and Triticum aestivum yield interface in a parkland agroforestry system

An understanding of the nature of tree and crop interactions should provide an important step for improving and designing new agroforestry systems. This study was intended to investigate the effect of Croton macrostachyus (Hochst. ex Delile), which is a common deciduous tree grown scattered on the fields of midland northwestern Ethiopia on wheat (Triticum aestivum) yield and yield components. The experiment was laid out in factorial arrangements with a randomized complete block design. Four blocks having four trees each were selected with the set of predetermined criteria. Data were collected from the four positions centering at the tree trunk. At each tree, plots of 1m x 1m centered at each radial distance (at 1.5m, 3m, 6m and 15m) from the tree trunk were laid and measurements on crop yield and yield attributing components were taken. Consequently, grain yield (p<0.005) and yield attributing characteristics such as effective tiller number (p<0.005), filled grain per spike, thousand seed weight (p<0.01), and harvest index p < 0.01 were significantly affected by the radial distances from the tree trunk. Effective tiller number , thousand seed weight , seed number per spike , and grain yield at 1.5m were found to be significantly lower compared to what is found at 6.0 and 15.0m distance from the tree trunk. However, yield components such as plant height, seed number per spike, and total biomass yield were not significantly affected due to the distance of wheat planting from the Croton macrostachyus (Hochst. ex Delile). Triticum aestivum does perform well near the edge and outside the canopy up to a six-meter distance. It was also observed that the grain yield had a significant and positive association with effective tiller number (R2=0.8**), plant height (R2=0.51*), seed number per spike (R2=0.54**), and total biomass yield (R2=0.52*). These implied that a deliberate integration and intensive management of Croton macrostachyus (Hochst. ex Delile) tree and wheat (Triticum aestivum) in the agricultural system is vital for obtaining the desired optimum benefit from the practice. Therefore, the integration of croton macrostachyus with wheat in parkland agroforestry should be promoted with effective tree crown management to reduce crop shading, particularly near the tree where the shading effect is high.