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.