INTERACTION OF TREE CROPS WITH A SODIC SOIL ENVIRONMENT - POTENTIAL FOR REHABILITATION OF DEGRADED ENVIRONMENTS

Tree species of Acacia nilotica, Dalbergia sissoo, Prosopis juliflora and Terminalia arjuna were grown on sodic land for a decade at the Bio mass Research Centre, Banthra (of National Botanical Research Institut e, Lucknow) India (80 degrees 45'-53'E and 26 degrees 40'-45'N) with t he objective of discovering their relationship with the sodic soil env ironment to rehabilitate it for maximum fuelwood production. Results s howed a marked improvement in biogeochemical characteristics of soil b y increasing the water holding capacity (WHC), and by the addition of organic carbon, nutrients and fungal microflora. It was found that D. sissoo and P. juliflora were more efficient than were A. nilotica and T. arjuna in rehabilitating the land. Litter production by the first t wo was greater than that provided by A. nilotica and T. arjuna, which subsequently caused depletion in soil pH and exchangeable sodium perce ntage (ESP) values. It was found that there was a greater circulation of Ca, Mg and Fe than the other nutrients by all four tree species, wh ich was a desirable factor. Microbial activity was enhanced due to the accumulation of humus through decomposition of leaf litter and root d ecay. The potential extent of the biological rejuvenation of the sodic land was related to the distribution of tree roots in the soil profil e. To obtain better results a combination of such tree species should be selected in order to provide maximum and constant litter mulch thro ughout the year. This, in turn, would protect the land from desiccatio n. Thus, sodic lands could be rehabilitated effectively to restore deg raded environments through appropriate mixed tree cropping systems. (C ) 1998 John Wiley & Sons, Ltd.