Management of tropical acid upland soil for sustainable food crop production in southern Thailand

A field trial was conducted in southern Thailand to develop and evaluate input technologies which could be employed for an opportunistic food crop production system on a Typic Paleudults under rainfed conditions. The trial compared 10 different input technologies for intercropping a rotation of groundnuts, upland rice, supersweet maize [sweetcorn] and mungbean [Vigna radiata] between young rubber [Hevea] trees for a period of four years prior to canopy closure. Results indicated that the highest yields of all crops were obtained in the high input technology which included application of lime and inorganic fertilizers containing N, P, K and Mg sufficient to meet crop requirements. The low input technology which applied minimal rates of N, P, K, Ca and Mg resulted in a lower yield, but was economically sound. Green manure (slashed Mucuna cochinchinensis, which had received 500 kg/ha rock phosphate once at sowing) did not sustain yields of rice and supersweet maize. Technologies which did not receive any inorganic fertilizer, viz. usual farmers' practices and organic residues, resulted in comparatively low yields of groundnuts and rice and an extremely low yield of maize.