Enhancing the Productivity of Ultisols and Oxisols in Malaysia using Basalt and/or Compost

抄録

Ultisols and Oxisols in Malaysia are dominated by kaolinite and sesquioxides, having low pH and exchangeable bases, but high exchangeability for Al; hence, their productivity is low. Cocoa grown in these soils has poor yield. Studies were conducted in Malaysia to determine the effect of applying ground basalt and/or compost on the chemical fertility of the soils and the growth of cocoa. The results showed that basalt application improved the chemical fertility of Ultisols and Oxisols by increasing pH, Ca, Mg, K, and P content, and cation-exchange capacity. The increase in pH precipitated Al as inert Al hydroxides. The pH increase resulted from the hydrolysis of silicates when basalt disintegrated and dissolved in the soils. However, basalt takes time to disintegrate and dissolve completely, and its reaction with the soils resulted in the decrease of pHo, the pH at which the net charge is zero for the variable charge minerals. Because of the presence of variable charge minerals in the soils, the increase in pH and the concomitant decrease in pHo increased the negative charge of the soils, further improving soil productivity. A glasshouse experiment showed that basalt application improved cocoa growth. The improvement in cocoa growth due to basalt application has been confirmed by a field trial, and the best treatment was found to be combined application of basalt and compost.