IMPROVEMENT OF DRY TROPICAL RANGELANDS IN HAINAN ISLAND, CHINA .1. EVALUATION OF PASTURE LEGUMES

During 1981-83, we studied some legumes for potential improvement of d ry tropical (1,001 mm annual rainfall) rangelands in Hainan Island, Ch ina. The productivity and persistence of 16 pasture legumes were teste d on sandy (<5 mg/kg available P) and loam (12-25 mg/kg) soils under c utting in a randomized block design with plots split for sequential so wings in 1981, 1982, and 1983. Dry matter yield, sward composition, an d legume density were measured at the end of the wet and dry seasons e ach year. Thirteen legumes established with density averaged over 3 se quential sowings >1 plant/m2 on 1 or both soils, but only 5 perennial stylos (Stylosanthes), siratro [Macroptilium atropurpureum (D.C.) Urba n], and centro (Centrosema pubescens Benth) (loam soil only) persisted through 2 dry seasons and yielded more than 0.5 metric tonne(t)/ha in 3-year-old swards.S. guianensis (Aubl.) Sw. cv Cook yielded best on b oth soils, but proved less tolerant to fire than cv Graham, which is t he common stylo recommended by this study as a companion for Siratro f or improvement of loam soil rangeland. Siratro was the only non-stylo to produce >2 t/ha and show relative stability with sward age, but car eful grazing management and regular fertilization are needed to mainta in siratro content above 40% in commercial sowings. Tolerance to fire, low P requirement, and high yield in 2- and 3-year-old stands makes S . scabra Vog. cv Seca the most suitable legume for sandy soil, but sin ce it is slow to establish, a mixture of S. scabra and S. hamata (L.) Taub. cv Verano which is noted for its quick establishment and prolifi c seed production is recommended for range improvement of low P soils.