The Role of Silicon in Suppressing Rice Diseases

Some of these soil orders such as Ultisols and Oxisol account for 34% of the area of major soil orders in the tropics. These orders occupy great amounts of land (approximately 1,666 million hectares) in Africa and South and Central America (Fig. 2). Histosols and sandy Entisols also contain low levels of Si (57). As a result of Si leaching, the soluble Si content of tropical soils, such as Ultisols and Oxisols, is generally less than in most temperate soils (16). This might be one of the unidentified causes of lower rice productivity of many Fig. 1. A simplified acid weathering sequence in soils. Source: Friesen et al. (17). Reprinted from Advances in Agronomy, Vol. 58, Savant, N. K., Snyder, G. H., and Datnoff, L. E., Silicon management and sustainable rice production, p. 157, 1997, with permission from Elsevier.