SILICON FERTILIZERS: AGRICULTURAL AND ENVIRONMENTAL IMPACTS - Fertilizers: Components, Uses in Agriculture and Environmental Impacts - page 184

heavy metal mobility in the soil-plant system and for reducing the heavy metal
accumulation in the crop. Finally, silicon fertilizers can be used for restoration of the
hydrocarbon polluted areas and for acceleration of the organic pesticide degradation in
the soil. At present, silicon fertilizers are successfully used in the USA, Canada,
Australia, Russia, China, India, and other countries. Annually the market of Si fertilizers
increases by 20%.
Keywords : Silicon fertilizer, soil chemistry, plant physiology, technology
I NTRODUCTION
One of important aspects necessary to provide sustainable agriculture, especially organic
farming, is related to the protection of cultivated soil against chemical, physiological, and
biological degradation. The conventional agriculture usually leads to soil degradation. To
transfer conventional agriculture to organic, high level of soil fertility should be formed.
Silicon is a constituent of many plants, but its role and functions in plant biology remain
poorly understood (Liang et al., 2007; Ma, 2003). Beginning in 1840, numerous laboratory,
greenhouse, and field experiments have shown benefits of Si fertilization for crop
productivity of rice ( Oryza sativa L.) (15-100%), corn ( Zea mays L.) (15-35%), wheat
( Triticum aestivum L.) (10-30%), barley ( Hordeum vulgare L.) (10-30%), sugar cane
( Saccharum officinarum L,) (15-40%), cucumber ( Cucumus sativus L.) (10-40%), strawberry
( Fragaria spp.) (10-30%), citrus ( Citrus spp.) (5-15%), tomato ( Lycopersicon esculentum
Mill.) (10-40%), grasses ( Stenotaphrum secundatum Kuntze, Cynodon dactulon L., Lolium
multiforum Lam, Paspalum notatum Fluegge) (10-25%), banana ( Musa paradisiaca ) (20-
40%; Matichenkov et al., 2011; Snyder et al., 2006).
Today Si fertilizers are successfully used in USA, Japan, China, India, Australia, Russia,
and other countries. During last 15-20 years, the volume of Si fertilizers and Si-rich soil
amendments was increasing by 15-20% annually. Hovewer, in spite of economical and
environmental benefits, Si fertilization is still rare in the world agricultural practice. The main
reason is low information about this element and its role in the soil-plant system.
Si Biogeochemical Cycle
Si is one of the most widely distributed elements in the Earth's crust. Soil is the most
silica-enriched layer of the Earth's crust: 20 to 35% of Si is tested in clay soils and 45 to 49%
in sandy soils (Kovda, 1985). Mainly, Si compounds in the soil are presented by crystalline or
amorphous Si dioxide and various alumosilicates. Quartz is the most distributed form of Si
substances on the Earth (Kovda, 1956). This crystalline kind of silica is characterized by high
stability to weathering (Russell, 2002). Together with coarse-crystalline silicates (feldspar,
plagioclase, orthoclase) and secondary or clay Si-rich minerals (kaolinite, vermiculite,
smectite) silica form a soil skeleton (Orlov, 1992). Fine clay minerals and amorphous silica
represent biogenic (phytoliths) and abiogenic amorphous forms or hydrated Si dioxide films
on the soil particle surface. They exhibit high geochemical activity and affect the chemical
soil properties (Kovda, 1985; Jacinin, 1994; Orlov, 1992). All natural waters, including soil