Productivity and profitability of intercrops under four tree species throughout their rotation in north-western India

In an experiment, different crops, viz. pearlmillet [Pennisetum glaucum (L.) R. Br.], wheat (Triticum aestivum L), potato (Solanum tuberosum L), Egyptian clover (Trifolium alexandrinum L.) and annual turmeric (Curcuma longa L.) were evaluated during 2005 to 2011 at Ludhiana, Punjab under 4 agroforestry tree species, viz. necklace poplar (Populus deltoides Bartr ex. Marsh.), eucalypt (Eucalyptus tereticornis Sm.), M. composita Willd. and toon (Toona ciliata M. Roem) during first to sixth year of tree age. Tree growth parameters, growth and yield parameters of intercrops and sole crops, soil organic carbon, nutrient status and economics of agroforestry systems were determined. The diameter at breast height (DBH) and height of poplar and eucalypt were higher than the other species after 6 years of age. The fresh stem biomass was the lowest (73 t/ha) in toon and the highest in eucalypt (213 t/ha). The growth and yield of all the crops declined under tree plantations with the increase in growth of trees during each subsequent year. Toon plantation had the minimum adverse effect on understorey crops, whereas eucalypt caused the maximum reduction in yield of all the intercrops. When grown as intercrops under tree block plantations, productivity of turmeric and wheat was better than the other crops under tree species. Amongst different tree-crop combinations, intercropping of turmeric with poplar and eucalypt gave the maximum net returns (16, 22, 225 and 14, 62, 065/ha respectively) followed by poplar-wheat (14, 30, 000/ha). Agroforestry systems also improved the soil fertility status. Soil organic carbon, six years after planting, was the highest under Melia, i.e. 21.2% increase over its initial level (2.83 g/kg). Available N and P were the highest under Melia (139.1 kg/ha) and poplar (15.65 kg/ha) based agroforestry system, respectively, at the end of the experiment.