AN EUCALYPT AND BHABAR GRASS PLANTATION SYSTEM TO OPTIMIZE RESOURCE USE FOR BIOMASS PRODUCTION IN THE FOOTHILLS OF SUB-TROPICAL NORTH INDIA

Abstract

In a replicated field study conducted for eight years (1984-91) on an eroded alluvial soil of semi-arid tropics (Udic Ustocrept), bhabar, a commercial grass (Eulaliopsis binata) was uniformly intercropped under Eucalyptus tereticornis planted at 2500 ha"1 for pole wood in a north-south oriented paired rows system allowing better canopy adjustment and light conditions. The response to six eucalypt planting treatments, usual pits of 0.3 m³ (Tl), shallow augerhole SAH (6x 60cm) (T2), deep augerhole DAH (6x 120 cm) (T3),DAH filled with 1 kg farm yard manure (FYM) (T4), DAH filled with 1 kg of rice husk (RH) (T5), and DAH+FYM+RH (T6), was studied to find out the best practice that promotes tree growth and minimizes competition for moisture. After seven years, the best and the worst treatments of DAH + FYM (T4), and pit planting (Tl) recorded a survival of 84 and 53%, DBH of 9.7 and 8.6 cm, pole biomass of 67.1 and 28.5 air-dry tonnes, marketable number of poles 2109 and 1328 and annual net returns from trees and grass Rs 10 659 and Rs 6239 ha^-1 y¹ respectively against Rs 700 ha'1 y ' from rainfed field crops. DAH without FYM (T3) and SAH (T2) followed the best treatment. Rice husk (high CN ratio) seriously depressed tree growth. FYM filled in DAH helped in the development of a vigorous deep root system to exploit moisture from lower soil layers and hence alleviated the effect of droughts. The grass yield under tree planting treatments was almost uniform, and varied from 11 t ha^-1 in good to 2 t ha^-1 in poor rainfall years with annual mean of 4.07 t ha^-1 from the November and 0.99 t ha^-1 from the June cuts. The plantation improved infiltrability of the soil and hence ensured less runoff and efficient use of rainwater resource for biomass production.