Pak. J. Agri. Sci., Vol. 44(3), 2007 401 PROPERTIES OF SALT AFFECTED SOIL UNDER EUCALYPTUS CAMALDULENSIS PLANTATION IN FIELD CONDITIONS Muhammad Nasim 1* , R.H. Qureshi 2 , M. Saqib 2 , Tariq Aziz 1 , Shafqat Nawaz 1 , J. Akhtar 2 and M. Anwar-ul-Haq 2 1 Sub-Campus University of Agriculture, Faisalabad at Depalpur, Okara 2 Saline Agriculture Research Centre, Institute of Soil & Environmental Sciences, University of Agriculture, Faisalabad-38040 Corresponding author’s Email: mnasimshahid@yahoo.com Plantation of salt tolerant trees on salt affected land is an environmental friendly and economically viable strategy to live with salinity where ground water is also highly saline. We studied growth response of eucalyptus camaldulensis on salt affected land and its impact on soil pH, EC, SAR, organic matter contents and infiltration rate. Two sites were selected with varying levels of natural salinity. Eucalyptus seedlings were grown on both sites for three years. A wide variation exhibited in growth of eucalyptus plants at each site. Sixteen plants were selected randomly on each site on the basis of visual growth differences. Among these selected trees, eight were categorized as good and other eight as poor plants. Growth parameters, such as plant height, tree girth and numbers of branches were recorded to monitor the effect of salinity on plant growth. Soil samples under the canopy of selected plants were collected up to the depth of 90 cm and analyzed for EC, SAR, pH, organic matter contents and infiltration rate. Growth of Eucalyptus plants at both sites was significantly affected by salinity as compared with other plantations grown on other fields (visual observation). All growth parameters were significantly more in good plants at both sites compared to poor plants. Sodium and chloride concentration was significantly more with lower K:Na ratio in poor plants than in good ones. Amelioration of salt affected soil by Eucalyptus plantation was assessed by comparing the soil chemical and physical properties before plantation and after three years. The soil pH was quite lower in soil under good trees than in soil under poor trees at all depths and at both sites. Sodium adsorption ratio (SAR) of soil under good plants at both sites was quite lower when sampled under the canopy of poor plants. Keywords: Eucalyptus spp, salinity stress, ion imbalance, sodium concentration INTRODUCTION Salinization of soil and water is an important factor for increased desertification in arid and semi-arid regions of the world (Szabolcs, 1992). About 6.3 million hectares of arable land in Pakistan is affected to varying degrees of salinity/sodicity. A number of strategies including use of chemical amendment and engineering approaches had been proposed for reclamation and revegetation of saline waste lands (Ashraf, 1994; Flowers, 2004). The high initial investment to purchase chemical amendment and low salinity tolerance of our major agriculture crops impels to develop and adopt more viable and economical strategies for highly salt affected lands. Saline agriculture is an environment friendly and economically viable approach to live with salinity as certain crop species and varieties are available with high salt tolerance (Aslam et al, 1993). A number of mechanisms have been proposed by which tree plantations can ameliorate the soil salinity and sodicity. These mechanisms include release of organic acids and complex energy sources by roots (Dormaar, 1988) and increase in partial pressure of CO 2 (Qadir et al., 1996) as well as a decrease in soil pH (Mashali, 1991; Qadir et al., 1996). Increased CO 2 concentration in soil releases Ca 2+ from dissolution of CaCO 3 . Physical movement of roots within soil also improves soil aeration and porosity favourable for plant growth on sodic soils. Under high salinity levels in the soil, many salt tolerant crops even fail to produce economic growth and yield, hence are not economical to grow on highly salt affected lands (Aslam et al., 1997). The development and maintenance of sustainable agro-ecosystem on highly salt-affected lands is an easier and more economical strategy with perennial plant species. The use of trees and shrubs to reclaim saline