The improvement of acid sulphate soils for crops other than padi

Draining non-calcareous pyritic material, which commonly occurs in recent marine and estuarine deposits, leads to oxidation of pyrite and consequently to extreme acidification of the soil, and often to crop failure. Complete oxidation of the pyrite and removal of the resulting sulphates takes many years; the quantities of lime necessary to raise the pH of the resulting Al-soil are prohibitive, as is the difficulty of liming to the required depth. Previous attempts to reclaim acid sulphate soils by leaching and liming have only intensified the problem. Waterlogging the pyritic horizon(s) by raising the water table dramatically increased the yields of established oil palms, the extent of the recovery being greater the shorter the period the palms had suffered free drainage. Raising the water table 2 years after planting on acid sulphate soil increased the yields to values comparable with those obtained from palms of the same planting on freely-drained non-acid soil. For the 5th and 6th years of growth, average annual yields of 10 tons or more FFB/acre were obtained from palms on acid sulphate soil in which the pyritic zone was flooded from the time of planting. Oil palm seedling roots scarcely penetrate freely drained pyritic horizons, but once these are waterlogged the pyritic zone is explored as extensively as freely-drained non-acid soil. It seems that coconuts also benefit from waterlogging of the pyritic horizon