Tropical Grasslands (2000) Volume 34, 16
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
N.P. STAMFORD, J.T. ARAÚJO FILHO and A.J.N. SILVA
UFRPE—Department of Agronomy, Recife, Brazil
A greenhouse experiment was conducted to evaluate the effects of applying elemental sulphur inoculated with Thiobacillus or gypsum, on dry matter production and nitrogen fixation of Leucaena leucocephala and Mimosa caesalpiniaefolia 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 the 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 NaHC03, NaCI, MgCl2, CaCl2, KCl), at three levels of electrical conductivity (0.2, 6.1 and 8.2 dS/m at 25°C), in a factorial combination. 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, and that M. caesalpiniaefolia was more susceptible than L. leucocephala to salinity promoted by the saline irrigation water.