Tropical Grasslands (1994) Volume 28, 146154
Grassland improvement in subtropical Guangdong Province, China.
D.L. MICHALK1, W.J. RYAN2 and HUANG ZHI-KAI3
1NSW Agriculture, Agricultural Research and Veterinary Centre, and
This paper reports a strategy for improvement of the acid Hapludult soils found in north Guangdong Province, China. These soils are so infertile that productive pastures cannot be developed without first improving the soil. Rebuilding soil fertility is a slow and costly process which requires manipulation of pasture species and fertiliser inputs to raise the soil organic matter level and thereby increase the cation exchange capacity. Three stages of soil improvement-pasture development are described through which individual paddocks may advance before high beef production can be realised. A molasses grass — round-leafed cassia mixture which responds to low rates of P and K is recommended for Stage 1 improvement on unlimed soil. This combination has low palatability 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, better quality species such as setaria sown with lotononis or Oxley stylo show promise for summer grazing by cattle on unlimed soil in Stage 2 improvement. Lime application may further increase the range of quality summer grasses and some temperate species during Stage 2. However, only after several years of rebuilding soil fertility and nutrient recycling under grazing can high producing Stage 3 subtropical and temperate species be sustained without high annual fertiliser and lime inputs. Cash crops and forage crops can be used in rotation with permanent pasture and strategic use of lime to diversify income, provide more cattle feed at critical periods, stop weed invasion and break insect and disease cycles. Changes in pasture composition (succession or retrogression) provide a useful guide to changes in soil fertility. While further research is required to refine the low-input, soil-improvement strategy described, this approach appears most likely to lead to sustained pasture development on the red soils in south China.