In field trials at Changhua (slightly alkaline slate alluvial soil) and Taichung (strong acidic red earth) in 1988-91, 10 or 20 t pig manure/ha or chemical fertilizers at rates recommended for the individual crops or both pig manure and chemical fertilizer were applied to a sorghum/ratooned sorghum/maize cropping sequence. Pig manure either alone or with chemical fertilizer increased plant height, spike weight, 1000-grain weight and grain yields. In some cases the higher rate of pig manure was more effective than chemical fertilizer alone. Maize gave the best response to 20 t pig manure + chemical fertilizer, while sorghum and ratooned sorghum responded best to 10 t pig manure + chemical fertilizer. Pig manure increased root density of maize at a depth of 30 cm.