Silicon Nutrition and Sugarcane Production: A Review1

Silicon (Si) is one of the most abundant elements found in the earth's crust, but is mostly inert and only slightly soluble. Agriculture activity tends to remove large quantities of Si from soil. Sugarcane is known to absorb more Si than any other mineral nutrient, accumulating approximately 380 kg ha of Si, in a 12-month old crop. Sugarcane (plant growth and development) responses to silicon fertilization have been documented in some areas of the world, and applications on commercial fields are routine in certain areas. The reason for this plant response or yield increase is not fully understood, but several mechanisms have been proposed. Some studies indicate that sugarcane yield responses to silicon may be associated with induced resistance to biotic and abiotic stresses, such as disease and pest resistance, Al, Mn and Fe toxicity alleviation, increased P availability, reduced lodging, improved leaf and stalk erectness, freeze resistance, and improvement in plant water economy. This review covers the relationship of silicon to sugarcane crop production, including recommendations on how to best manage silicon in soils and plants, silicon interactions with others elements, and laboratory methodology for determining silicon in the soil, plant and fertilizer. In addition, a future research agenda for silicon in sugarcane is proposed. 1 Savant, N. K, Korndorfer, G. H., Datnoff, L. E. and Snyder, G. H. 1999. Silicon nutrition and sugarcane production: a review. J. Plant Nutr. 22 (12):1853-1903 2 To whom all correspondence should be addressed. E.mail: [email protected] INTRODUCTION Integrated management of 13 physiologically essential nutrients, namely six macronutrients [nitrogen (N), phosphorus (P), potassium (K), sulfur (S), calcium (Ca), and magnesium (Mg)] and seven micronutrients [iron (Fe), manganese (Mn), zinc (Zn), boron (B), copper (Cu), molybdenum (Mo), and chloride (Cl)] are generally considered by agronomists for increasing and sustaining crop yields. However, there are non-essential elements, that under certain agroclimatic conditions, enhance plant growth by promoting several physiological processes. Although not considered essential, these elements are said to be functional nutrients (Mengel and Kirkby, 1982). At times they are so important that they can be regarded agronomically essential to sustainable crop production. As far as rice (Oryza sativa L.) and sugarcane (Saccharum officinarum L.) crops are concerned, Si is such an element. Members of the grass family accumulate large amounts of Si in the form of silica gel (SiO2.nH2O) that is localized in specific cell types. The function of Si in plants has been proposed as i) support for cell walls (resistance to lodging); ii) deterrence to pest and pathogens; iii) reduction in water loss by evapotranspiration; iv) reduction in certain heavy metal toxicities, and v) an essential