Significance Of Siliconaccumulating Grasses For Integrated Management And Remediation Of Metalliferous Soils

Silica is the second most abundant element in the Earth's crust, so it would be useful for amelioration of aluminum (Al) toxicity in acidic soils. Ranking of silicon accumulation in the subfamilies of Poaceae is shown in Figure 21.2. Subsoil acidification is a serious global environmental concern. Acid soils occupy nearly 30% (3.95 ha) of the arable land area in tropical and temperate belts. In addition to the natural processes, farming and management practices such as high use of nitrogen fertilizers, removal of cations by harvested crops, and leaching and runoff of cations resulted in acidification of soils. In many industrialized areas, the atmospheric deposition of sulfur and nitrogen compounds is a major source of proton influx to soils. More than the low pH of the soils, the major problem associated with acid soils is the toxicity of Al and manganese and the deficiency of phosphorus, calcium, magnesium, and potassium.

In addition to these nutritional factors, the acid soils are also characterized by low water-holding capacity due to compaction of soils. Apart from mineral toxicities, soil acidification is also known to change the species spectrum of the forest soils by changing the microbial activity of the soils. Acidification is also known to reduce the degradation of soil organic matter and alters cation and nutrient flow in the ecosystem. In general, most of the acid soils have low exchangeable bases (e.g., Ca, Mg, and K), mainly because of the low cation exchange capacity (CEC) of the soils. The oxides of Al and Fe in wet acidic soils fix large fractions of the phosphate, making it unavailable to plants

Enhanced photosynthesis, stimulate growth, prevent Mn/Fe toxicity

Enhanced photosynthesis, stimulate growth, prevent Mn/Fe toxicity

Enhanced assimilation of NH4-N

4"

Enhanced supply of carbohydrates

Enhanced supply of cell wall materials

Enhanced assimilation of NH4-N

Improve Improve tolerance tolerance to to bacterial, fungal, heavy N insect pests and

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