Nanomaterials for Soil Reclamation

The demand for the development of eco-friendly, sustainable, and adaptable technologies for the disinfection of the environmental contaminants is increasing nowadays. Nano-bioremediation is one such technique that has made possible the use of biosynthetic nanoparticles for soil pollution remediation. It is an effective, efficient, and feasible method for revitalizing soil potential and rendering it pollution free. Pollutants present in soil are a great threat to soil biota, environment, and in fact human health. Nanomaterials exhibit the unique chemical and physical properties because of which they have always received attention in the growing era of bioremediation. Use of nanotechnology for bioremediation is one such technology as it focuses mainly on the interaction between the contaminants, the microorganisms, and the nanomaterials being used for both the positive (i.e., stimulating) and negative or toxic environmental effects. Thus, this chapter focuses on the need to recover the polluted soil and application of nano-remediation technology for restoring soil's cultivation capacity.

Microbes as Sustainable Biofertilizers

Across the globe, in both developed and developing countries, wheat provides the fundamental support for all other important foods. However, due to climate change, environmental stress, soil infertility, etc., the yield of wheat is affected. To overcome these issues, biofertilizers are recommended. They are eco-friendly, cost-efficient, and affordable by marginal farmers too when compared with chemical fertilizers. Biofertilizers are made up of living microorganisms that colonize the rhizosphere to promote plant yield and prevent plant disease. Pesticide degrading strains of bacteria are emerging as the best technique to overcome the negative effect of pesticides. Due to insufficient awareness among farmers, agricultural land and crops are cultivated through chemical fertilizers, which became a major threat to human health and agriculture. On the other hand, the government is implementing several measures in marketing bio-fertilizers for the betterment of agriculture and human health. In this chapter, the significance and future perspectives of biofertilizers have been covered.

Potassium Solubilizing Bacteria

Potassium (K) is one of the essential nutrients required for plants. Although the total pool of K in the soil is generally large, the bioavailable portion is meager. There are several mechanisms through which the insoluble K can be made available through soil microbes called “potassium solubilizing bacteria” or KSB. They play an important role in increasing the solubility of K for proper crop establishment under potassium deficient soils through the production of organic and inorganic acids, acidolysis, polysaccharides, complexolysis, chelation, and exchange reactions. Moreover, they also produce specific exopolysaccharides and biofilm that enhances the weathering of the K-rich minerals and increase the K concentration in the soil solution. Hence, the production and management of biological fertilizers containing KSB can be an effective alternative to chemical fertilizers. This chapter presents the underlying mechanisms and their role in providing sufficient K to the crops.

The Use of Micro-Algal Technologies for Soil and Agronomic Improvements

Microalgae are promising tools in improving soil fertility and agricultural production in the era of increased population and the need for food security, which is mostly hindered by climate change. The microbes have the ability to sequester atmospheric carbon dioxide, produce metabolites with many applications in addition surviving and growing in harsh environmental conditions. In this chapter, microalgae species of the cyanobacteria and green algae groups are established as good soil biofertilizers and conditioners which are crucial in nutrient cycling, improved soil structure, and increased soil microbial activity. These are requirements for better crop production. Microalgae are also crucial biocontrol agents that suppress and kill plant pathogens and pests, regulate the production of phytohormones, and in bio-remediation of polluted soils. Their use is therefore a road map to sustainable agriculture and food security. To ensure their optimal use, extensive research is necessary to understand the mechanisms of action behind the benefits.

Microbes and Their Role in Bioremediation of Soil

Soil is the Earth's shell and is getting polluted in a number of ways in the present scenario. Human activities are the root cause of different types of soil pollution, which is an alarming issue and has become a major obstacle that needs to be overcome to build a cleaner environment. The area of polluted soil is widening day by day by virtue of a sharp increase in people from all over the world. It has been expected that the global population will continue to increase up to 9 billion by 2050, and such prodigious population may be in need of advanced agricultural and industrial systems, which may inevitably cause soil pollution. Therefore, it is essential to control soil pollution, and fortunately, the solution for this is microbes that are the real creatures of life on Earth. In fact, microorganisms play a unique role in the detoxification of polluted soil environments, and in the last several years, this process has been called bioremediation. Remediation of polluted soils is necessary, and research continues to develop novel, science-based remediation methods.

Favorable Soil Microbes for Sustainable Agriculture

Beneficial microbes are used as the best alternative against the synthetic fertilizers and pesticides. The beneficial microbes not only help with plant growth, nutrition uptake, nitrogen fixation, but also help in acquiring the ions, not freely available to plants to uptake; these microbes also guard the plants by secreting toxic chemicals by inducing defense systems against pathogens. These microbes can provide best choice to look forward to sustainable agriculture and sustainable ecosystem. The addition of soil inoculants in the form of microorganisms or bio stimulants promise more environmentally friendly approaches for augmenting crop yields. The crop becomes less reliant on chemical fungicides and herbicides as many strains of microorganism have abilities of controlling pests. In this chapter, the interaction of beneficial plant bacteria, bio stimulants, effects on native microbial communities, and bacteria influencing economically important crops are discussed.

Multifaceted Potential of Plant Growth Promoting Rhizobacteria (PGPR)

Plant growth-promoting rhizobacteria (PGPR) is a unique group of bacteria that colonize the rhizosphere and roots of plants. They are involved in a plethora of interaction with the host plant and benefit the host plant from nutritional and pathological point of view. The beneficial role of PGPR extends from fixation of atmospheric nitrogen, solubilization of phosphates, siderophore production, synthesis of plant growth regulators, and conferring protection to plants through production of antibiotics and ultimately helping the plants in acquiring resistance. The microbes are also being used for bioremediation purposes and thus act as an eco-friendly cleansing agent. PGPR has gained immense interest in the scientific community and have emerged as a very reliable tool for eco-friendly and sustainable approach for crop production. PGPR is a potent candidate of bioprospection for sustainable use in agriculture and bioremediation process for the overall benefit of mankind.

Role of Bacillus spp. in Agriculture

The advent of the industrial revolution and intensified agricultural practices have posed irreversible impairment in the soil by accumulating various xenobiotic compounds. Soil, being a core constituent of Earth, not only supports plant growth but also acts as a water filter, buffering pollutants and conserving myriad microorganisms. Untreated industrial effluents, dumping of plastics, and overuse of pesticides are some of the major contaminants enrooted for soil pollution causing severe threats to living beings and the biosphere. Bioremediation using microbes has been recommended as a safe and viable method for the soil fertility restoration due to their adaptive nature modulated by the environment. Among the microbes, Bacillus sp is considered as an effective bioremediating agent as they are the warehouse of copious enzymes, eco-friendly products, and plant growth-promoting metabolites that play a key role in agriculture, textile, food, leather, and beverage industries and thereby ensure soil sustainability.

Quorum Quenching for Sustainable Environment

Quorum quenching is the process that prevents quorum sensing through the disruption of signalling cascade and bacterial communication among themselves mediated by the degradation of the signalling molecules. Therefore, quorum quenching has a considerable contribution in the negative regulation of threatening diseases and eventually increasing soil reclamation through different mechanism mediated by microorganisms in reclamation of soil. Quorum sensing has a significant contribution in enhancement of soil quality through microbial-based enzymes and mechanism in the versatile fields which are a component of the environment. The current chapter discusses the details of various direct and indirect mechanisms mediated by microbial systems that have a significant role in soil reclamation for the sustenance of the environment.

Rhizosphere Engineering and Soil Sustainability

Soils are a vital part of agricultural production. Soil health plays a significant role in the best crop production. Nowadays, our lands are under immense pressure. This pressure may be in the form of climatic changes that affect crop productivity or may be due to population increment that forces our current food system to produce more food to meet consumer needs. Climatic changes affect soil sustainability in the wrong way. Salinity, drought, and heavy metals disturb land structure badly. As the population increases, it dramatically impacts the current production system to fulfill the present needs. In all these situations, agricultural soil sustainability is a challenging factor for soil scientists to make our agriculture sustainable because agricultural sustainability couldn't be possible without maintaining soil health. Many approaches are available to improve soil structure and health. Among these, plant growth-promoting rhizobacterium is a good option. It not only improves soil structure but also helps the plants under abiotic stress conditions.