Tree growth and crop yield under agrisilvicultural practices in north-east India

Tree growth, survival and crop yield under agrisilvicultural practices were analyzed over a seven-year period in a split plot experiment on acid alfisol under rainfed conditions at ICAR Research Farm, Barapani (Meghalya), India. Three indigenous species including a fruit plant, and one introduced tree species formed the main plot treatments and three crop sequences were the sub-plot. The tree species were mandarin (Citrus reticulata), alder (Alnus nepalensis), cherry (Prunus cerasoides) and albizia (Paraserianthes falcataria), and the crop sequences were (a) soybean (Glycine max)-linseed (Linum usitatissimum) for three years, then groundnut (Arachis hypogea)-mustard (Brassica campestris) for three years followed by soybean-linseed in the seventh year, (b) groundnut-mustard for three years, then soybean-linseed for three years and groundnut-mustard in the seventh year, and (c) sole trees ('tree only'). A positive effect of intercropping on height and diameter growth, crown width and timber volume was observed in alder, albizia and cherry but no appreciable differences for these parameters were observed in mandarin between the two situations. Alder and albizia attained maximum growth and woody biomass followed by cherry and the minimum growth was recorded by mandarin. The better growth and timber volume in the 'tree+crop' situation was mainly due to the application of fertilizers and weeding. Crop yield reduction was observed with alder, mandarin and cherry and as the distance from tree increased, yield also improved. However, in albizia the proximity of tree did not reduce crop yield. The implications of the results are discussed in the context of the suitability of the species in this region and their usefulness in agroforestry systems.