ABSTRACT
Gabon, and Vietnam ...................................................................................................... 347
23.2.1 Management of Acid Ferrallitic Soil Systems through
Direct Seeding on Permanent Soil Cover...................................................... 347
23.2.2 Initial Biomass Production to “Start the Pump”.......................................... 348
23.2.2.1 Use of Plant Species Able to Grow under
Adverse Conditions ......................................................................... 348
23.2.2.2 Liming and Fertilization.................................................................. 348
23.2.2.3 Soil Smoldering as a Means of Rapid Fertility
Improvement ..................................................................................... 350
23.2.2.4 Changes in Soil Characteristics Induced by Direct Seeding
and Soil Smoldering......................................................................... 351
23.3 Discussion........................................................................................................................ 354
References ................................................................................................................................... 355
Acid soils are widespread, especially in the tropics. Among the most acidic soils are
acid sulfate soils, which are estimated to cover over 24 million ha in the world. The
pH values of acid sulfate horizons measured in the field commonly range from 3.2 to 3.8
(Dent, 1986), but they can be even lower. In the Plain of Reeds, Vietnam, Verburg (1994)
measured the pH of soil solution to be as low as 2.75 at a depth of 40 cm on typic
sulfaquepts, while water pH in the irrigation/drainage canals could be as low as 2.2 at the
beginning of the rainy season.