GRASSLAND IMPROVEMENT IN SUBTROPICAL GUANGDONG PROVINCE, CHINA .3. STRATEGY FOR IMPROVEMENT OF ACID SOILS

This paper reports a strategy for improvement of the acid Hapludult so ils found in north Guangdong Province, China. These soils are so infer tile that productive pastures cannot be developed without first improv ing the soil. Rebuilding soil fertility is a slow and costly process w hich requires manipulation of pasture species and fertiliser inputs to raise the soil organic matter level and thereby increase the cation e xchange capacity. Three stages of soil improvement-pasture development are described through which individual paddocks may advance before hi gh beef production can be realised. A molasses grass - round-leafed ca ssia mixture which responds to low rates of P and K is recommended for Stage 1 improvement on unlimed soil. This combination has low palatab ility to cattle, but the yields of above 11 000 kg/ha DM top and root growth should significantly increase the level of soil organic matter. With moderate P and K inputs and some soil improvement in Stage 1, be tter quality species such as setaria sown with lotononis or Oxley styl o show promise for summer grazing by cattle on unlimed soil in Stage 2 improvement. Lime application may further increase the range of quali ty summer grasses and some temperate species during Stage 2. However, only after several years of rebuilding soil fertility and nutrient rec ycling under grazing can high producing Stage 3 subtropical and temper ate species be sustained without high annual fertiliser and lime input s. Cash crops and forage crops can be used in rotation with permanent pasture and strategic use of lime to diversify income, provide more ca ttle feed at critical periods, stop weed invasion and break insect and disease cycles. Changes in pasture composition (succession or retrogr ession) provide a useful guide to changes in soil fertility. While fur ther research is required to refine the low-input, soil-improvement st rategy described, this approach appears most likely to lead to sustain ed pasture development on the red soils in south China.