Growth and nitrogen fixation of Leucaena leucocephala and Mimosa caesalpiniaefolia in a saline soil of the Brazilian semi arid region as affected by sulphur, gypsum and saline water

A greenhouse experiment was conducted to evaluate the effects of applying e lemental sulphur inoculated with Thiobacillus or gypsum, on dry matter prod uction and nitrogen fixation of Leucaena leucocephala and Mimosa caesalpini aefolia grown in a soil with high sodium content and irrigated with saline water. An alluvial solodic medium texture soil, representative of the semi- arid region of Pernambuco, Brazil, was used. The treatments consisted of th e addition of elemental sulphur at two levels (0.3 or 0.6 t/ha), and gypsum at two levels (0.6 or 1.2 t/ha). Plants were irrigated with saline water ( containing NaHCO3, NaCl, MgCl2, CaCl2, KCI), at three levels of electrical conductivity (0.2, 6.1 and 8.2 dS/m at 25 degrees C), in a factorial combin ation. There was a treatment with no sulphur or gypsum applied. The results showed that elemental sulphur inoculated with Thiobacillus decreased soil pH and increased Al toxicity which harmed the growth of L. leucocephala, an d that M. caesalpiniaefolia was more susceptible than L. leucocephala to sa linity promoted by the saline irrigation water.