Short-term Effects of N-fixing Legumes onSome Propertiesof Calcareous Salt-affected Soils

Cultivation of legumes in calcareous salt - affected soils may decrease soil sodicity. A field experiment was con ducted in Soba Research Station, 15 km south of Khartoum, to determine the potential of three N fixing legumes: guar ( Cyamopsis tetragonolobus ), hyacinth bean ( Dolichos lablab L. ) and cowpea ( Vigna unguiculata L) in amelioration of sodic soils. The treatme nts consist of control (without plant and gypsum), gypsum, cowpea; guar and hyacinth bean relying on either inorganic nitrogen or N fixation. Treatments were arranged in a Randomized Complete Block Design with four replications. Soil samples (0 - 25 and 25 - 50 cm depths) were taken before and after harvest and analyzed for pH, electrical conductivity (ECe), soluble cations (Ca 2+ , Mg 2+ , Na + , K + ), soluble HCO 3 - and sodium adsorption ratio (SAR). Results of the first season indicated that pH and ECe were not sig nificantly different among treatments whereas ; Ca 2+ , Na + and SAR were significantly (P ≤ 0.00 1 ) different among treatments. Total dry matter of hyacinth bean relying on N - fixation was higher than the hyacinth bean relying on inorganic N by 49.4%. In the second season, total dry matter of guar relying on N - fixation was 36% higher than that relying on inorganic N whereas hyacinth bean relying on N - fixation has increased soil soluble HCO 3 - 1 and decreased SAR. It may be concluded that cultivation of N - fixing plants in calcareous salt - affected soils could be a promising alternative to chemical amendments which may be expensive for small farmers.