Fertilizer and soil amelioration trials on inland and coastal soils in Malaysia

Results of a three NPK factorial trial on an inland soil in Malaysia (Jerangau series) showed that pod and wet bean productions increased significantly within a year of application of rock phosphate (RP) to three and half year-old cocoa. In the third year, a significant yield response to muriate of potash applications was recorded. Improved production attributable to RP and muriate of potash applications was maintained until termination after six years. There was no response to application of nitrogen. In contrast, in a similar trial on coastal clay soil in Malaysia (Bernam Series), cocoa planted under Malayan Tall coconuts responded favourably to nitrogen manuring and superior yields were recorded throughout a period of nine years from planting. Application of RP and muriate of potash did not result in any improvement in growth nor pod production. As application of calcium limestone had been found to raise the pH of coastal clay soil and improve cocoa growth and yields, three small-scale trials were established to monitor changes in the acidity levels of Bernam and Sedu series soils following applications of ameliorants: calcium limestone, oil palm bunch ash and quicklime. At four and half years after the commencement of the trial, it was observed that annual applications of limestone and bunch ash at 0.27 km/m2 raised topsoil pH from 4.3 to 5.4 and 5.2 units respectively. Effects of the ameliorants on sub-soil pH were less pronounced. Of the three ameliorants, limestone appewered the most desirable on account of its faster action, cheapness, availability and less detrimental side effects. Fresh bunch ash and quicklime were considerably more difficult to apply as they were hygroscopic and caustic