Soil physico-bio-chemical properties as influenced by varying tree densities in poplar (Populus deltoides Bartr. ex Marsh.) based agroforestry system

Abstract

The present investigation was carried out at old site of Agroforestry Research Centre, Patharchatta, G.B. Pant University of Agriculture and Technology, Pantnagar, during 2010-11 to study the effect of tree densities on soil physico-bio-chemical properties under ten year old poplar based agrisilviculture system. Poplar tree density classes showed significant effect on soil physico- chemical and biological properties. The soil bulk density was significantly lower under trees compared to sole crop. The soil chemical properties viz., organic carbon, available nitrogen, available phosphorus, exchangeable calcium, DTPA extractable zinc, copper and manganese were significantly higher under trees than sole crop. However, soil EC improved under sole crop. The soil pH, available potassium, exchangeable magnesium and available sulphur were not significantly influenced by tree density classes. However, significantly higher amount of nutrients were recorded in surface layer i.e. 0-15 cm which decreased significantly with successive increase in soil depth except for Mg²⁺ which was higher in 15-30 cm soil depth. The soil biological properties were significantly influenced both by tree densities and soil depths. Significantly higher dehydrogenase and phosphatase activities were recorded under 1000 and 500 trees/ha, respectively as compared to sole crop, whereas both activities decreased with increase in soil depth. Overall it is concluded that soil properties were significantly improved under poplar based agroforestry system in comparison to sole crop, and 500 and 1000 trees/ha proved to be the best tree density for improving soil health depending on the trade-off between tangible outputs (crop yield and wood) in the system.