Silicon (Si)- and Zinc (Zn)-Solubilizing Microorganisms: Role in Sustainable Agriculture

Abstract

Across the world today, loss of the health of the soil is a key constraint causing reduced soil productivity and fertility, and also influencing crop yield, all major threats to food security. Intensive use of land by farmers, without undertaking appropriate nutrient management practices, results in the removal of more nutrients from the soil, which is connected to the decline in the productivity of crops. Plants need various nutrients in different ratios for their growth and development. The plants obtain these essential nutrients from soil, water, and air. Some of these nutrients are required in large amounts, whereas others are necessary in only small quantities for vegetative and reproductive growth of crop plants. As per recent speculation, reduced yield is mainly associated with reduction in the appropriate supply of nitrogen (N) by the soil, although total available N remains unaffected. In rice, silicon-solubilizing microorganisms have been noticed recently as more important for their role in the solubilization and mobilization of silicate minerals, rendering K (potassium) silicate and making potassium and silicon easily available to crop plants. Major causes of zinc deficiency in India are intensifying cultivation, unbalanced supply of nutrients, generally without zinc (Zn), and the predominance of lands with low organic matter content, calcareous nature, and high pH. Alternately, numerous microorganisms, especially those allied with roots, may increase the growth and productivity of plants. In the recent few years the use of Zn-solubilizing bacteria (ZSBs) as bio-fertilizers has acquired momentum, and bacteria are significant in improving soil nutrient content and sustaining crop production. ZSBs have been proven to have great ability to enhance Zn availability in the rhizosphere and to improve Zn supply to crop plants. Many genetically modified strains (GMSs) may be able to mobilize/solubilize more plant nutrients from the root zone. Development of GMSs with improved solubilization/mobilization of nutrients through genetic engineering and DNA technology is necessary to maintain an environmentally friendly and sustainable agriculture production system. Plant breeding strategies also appear to be a more reliable and cost-effective technique to enhance Zn content in plants. This chapter is mainly focused on silicon and zinc microorganisms, their role in the uptake mechanisms and solubilization activities in plants relative to nutrient dynamics, and the potential to apply this knowledge in managing a sustainable and eco-friendly agriculture system.