AMELIORATION OF SODIC SOILS BY TREES FOR WHEAT AND OAT PRODUCTION

Prolonged occupation of sodic soils by trees results in the latters' a melioration in terms of decreased pH and electrical conductivity and i mproved organic matter and fertility status. To assess whether sodic s oils reclaimed by tree plantations can be used for growing agricultura l crops, a greenhouse pot trial was conducted during winter of 1994-95 (November-April) at the Central Soil Salinity Research Institute, Kar nal, India. Wheat (Triticum aestivum, L; cultivar HD 2329) and oat (Av ena sativa, L. cultivar local) plants were grown in topsoils (30 cm) c ollected from 24-year-old plantations of Prosopis juliflora, Acacia ni lotica, Eucalpytus tereticornis, Terminalia arjuna and Albizia lebbek that had been established in 1970 on a highly sodic soil (pH(2) 10.2-1 0.5), and a reclaimed sodic soil from a farm field adjacent to the pla ntations. The organic carbon content and nutrient status of the soil u nder the 24-year-old plantations was much higher than that of a refere nce farm soil reclaimed through gypsum in 1974. Soil amelioration was highest under Prosopis canopies (pH 7.4 and organic carbon 0.89 per ce nt) in topsoil and minimum in Eucalytus canopies (pH 8.6 and organic c arbon 0.56 per cent). Reduced sodicity and improved fertility resulted in much better growth reference and productivity of the wheat and oat test crops grown on the five plantation soils, than in the reference farm soil. Grain and straw yields of wheat and oats were maximum in Pr osopis soil (wheat 61.7 g grains and 87.5 g straw and oats 87.9 g grai ns and 111.1 g straw per pot) and minimum in Eucalpytus soil (32.3 and 25.3 g, and 42.7 and 58.5 g per pot). Grain yields of both wheat and oats obtained in the Prosopis soil were 4.5 and 3.5 times more, respec tively, than obtained in the reference farm soil. The phosphorus conce ntration in whole plant tissues of wheat and oats was highest in Proso pis soils reflecting the prevailing phosphorus status and better resto ration processes of the soils. Potassium concentration was little affe cted due to different soil treatments. The study clearly indicated tha t prolonged afforestation of sodic soils by tree plantations, particul arly by Prosopis and Acacia trees, may restore the productivity of aba ndoned soils to much above the present agricultural production levels. The results further suggest that 24 years' occupation of sodic soils by trees, such as Prosopis, Acacia, Eucalyptus, Terminalia and Albizia , did not result in a build-up or accumulation of toxic allelochemical s which could be injurious to wheat and oats cultivation on such sails . (C) 1998 John Wiley & Sons, Ltd.