The management of soil acidity for sustainable crop production

The Australian Centre for International Agricultural Research (ACIAR) has funded a 4-year project to develop sustainable food crop production systems on acid, low fertility soils. Field trials were commenced in mid-1986 at four sites in Malaysia to evaluate crop responses to amelioration of acidity in three Ultisols and one Oxisol, and to relate these responses to both solid and solution phase soil chemistry. Ground magnesium limestone (GML) (21% Ca, 12% Mg) was applied at rates up to 8 t ha−1. The UPM trials involved rotation cropping of groundnut and sweet corn, with two crops per year. The RRIM trials involved these two crops and grain corn, intercropped with young rubber trees for 2 to 3 years before canopy closure. Liming gave strong responses in crop yield. Initial applications of 4 and 8 t ha−1 were effective after 3 years in the UPM trials. Yield responses of all crops occurred up to the maximal rate of 2 t ha−1 in the RRIM trials. Rubber tree growth benefitted from the intercropping and earlier commercial tapping has occurred. Application of GML to groundnut and sweet corn was economically viable, while earlier rubber tapping has further economic benefits.