M. Vassanda Coumar

Soil Pollution - An Emerging Threat to Agriculture

Agriculture has always remained backbone of economy and sociopolitical stability of low and middle income countries, and employs largest work force in India. Maintenance of soil quality has been pointed out as one of the major contributing factors for sustainability of agricultural production. Rising contribution of industry to India’s GDP has been speculated to cause adverse impact on the precious land resources; though the issue has received less attention among the policy makers. There is a complex relationship of Indian economy with industry and agriculture, both of which competing for same natural resources with differential impact on land resources. This chapter highlights the need for reviewing different developmental activities having direct or indirect impact on agricultural productivity and the need for accelarating soil research to investigate upon migration of pollutants from source of generation and their impact on soil so as to devise strategies for protection and remediation of precious non-renewable soil resources.

Impacts of Soil Pollution and Their Assessment

Impact assessment of pollution is important step towards initiating appropriate remedial measures. However impact of soil pollution may not necessarily be uniform across the agro-ecological regions due to complex relationship among soil types, climate, crop types, nature and level of contamination as well as soil and crop management methodologies adopted. Moreover land resources are habitat of numerous organisms having varying degree of sensitivity towards contaminants. Hence, choosing right approach for assessing impact of pollution becomes important for satisfying various stakeholders affected by soil pollution. This chapter covers different types of impact of pollution on soil quality, economic yield of crop, food quality, biodiversity, fertilizer nutrient use efficiency, economy of the country etc. Pollution has already made adverse impacts on environment including soil in different countries. Widely cited instances of different types of pollution across the world and their impacts on soil and crop has also been discussed in this chapter.

Urban Activities in India Leading to Soil Pollution

Due to rapid growth in industry and service sectors, urbanization has seen phenomenon increase in many countries across the world with consequent rise in solid and liquid wastes. Per capita generation and nature of such urban wastes has been found highly related to level of economic activities of a country. Due to insufficient treatment facilities for these wastes, urbanization has been found polluting agricultural land considerably, particularly in lower and middle income countries. Unscientific processing of solid wastes as well as release of sewage effluents in environment and their use for benefit to crop production have been found an important route for contamination of agricultural land with toxic trace metals and organic pollutants. Safe and beneficial recycling of municipal solid wastes in agricultural land after appropriate processing and treatment is facing obstacles due to lack of appropriate quality and hazardousness of the end products. Widely prevalent marginal quality sewage water use for irrigation in agriculture in urban and peri-urban areas in developing countries like India has also been discussed in details through different perspectives like carbon sequestration, crop productivity, plant nutrient supply as well as risks from various pollutants and pathogens.

Remediation and Management of Polluted Sites

Soils perform several important ecosystem functions and therefore polluted land requires remediation and appropriate management for restoration of its life sustaining functions. Several technologies have been developed for their remediation based on clean-up, detoxification and risk minimization approaches. All of these technologies have both advantages and disadvantages in respect of the extent of applicability, side-effects on other components of environment, cost & ease of adoption, speed & effectiveness of remediation etc. While removal of contaminants and the risk minimization are the major approaches for heavy metal polluted soil, degradation to non toxic or less toxic compounds is the most common approach for soils polluted with organic pollutants. Plants, microorganisms, nanotechnology have also been used for remediation of polluted sites with varying degree of success. Waste products from agriculture, industries, city etc. have also exhibited their potential in minimizing risk from pollutants. Growers may minimize risks from polluted land through modification of soil, crop and nutrient managements. This chapter also discusses examples of a remediation approaches followed in case of different polluted sites worldwide.

Soil and Its Role in the Ecosystem

Soil is highly heterogeneous body in the terrestrial ecosystem that has evolved through thousands of years of natural processes and has remained habitat for enormous biodiversity. Due variability in seasonal temperature, rainfall, parent materials and vegetation, different types of soils have been found in India; and each of these soils have distinct mineralogical compositions, physical and chemical properties. Such heterogeneity has resulted wide variations in the response of soils to polluting activities which causes differential location specific impacts. To understand the interaction of pollutants with soil constituents and their impact on agroecosystems, basic knowledge on various aspects of soil resources and its functions are essential. This chapter describes in brief, the major soil types of India and their properties, role of soil constituents on its quality, different soil forming processes, inhabiting organisms and their role in different soil nutrient cycling processes affecting crop productivity.

Assessment of Heavy Metals Contamination in Soil

Several heavy metals are toxic to organisms including human and therefore their entry into food chain from polluted agricultural land is required to be controlled. Management and remedial measures of metal contaminated sites depend on the level and distribution of contamination. In view of high heterogeneity of soils in respect of heavy metals concentration, mere analysis of a sample may not confirm contamination due to polluting activities. This chapter describes various approaches for assessing heavy metals contamination of soil and expected degree of threat it may pose to the environment. Importance of baseline concentration in areas with high polluting activity is thoroughly discussed along with statistical significance. Degree of contamination and its threat has also been estimated by researchers through various models. Methods of assessment of risks to organisms due to heavy metals contamination in soil involving critical analysis of their translocation within plants and to human through various routes have also been described. Different countries have adopted regulatory limits to protect the land from contamination based on different approaches which resulted wide variations in their limiting values. Soil testing methods for rapid assessment of contaminated site has also been described in this chapter.

Agriculture, Soil and Environment

Agriculture has always remained backbone of economy and socio-political stability of low and middle income countries, and employs largest work force in India. Maintenance of soil quality has been pointed out as one of the major contributing factors for sustainability of agricultural production. Rising contribution of industry to Indias GDP has been speculated to cause adverse impact on the precious land resources; though the issue has received less attention among the policy makers. There is a complex relationship of Indian economy with industry and agriculture, both of which competing for same natural resources with differential impact on land resources. This chapter highlights the need for reviewing different developmental activities having direct or indirect impact on agricultural productivity and the need for accelarating soil research to investigate upon migration of pollutants from source of generation and their impact on soil so as to devise strategies for protection and remediation of precious non-renewable soil resources.

Enhancing N Use Efficiency and Reducing N 2 O Emission by Coating Urea with Newly Identified Bio-Molecule (C 20 H 30 O 2 ), Nano-Zn Oxide and Nano-rock Phosphate

The increasing use of nitrogenous fertilizer and its importance in Indian agriculture has attracted the attention of environmentalists. There is a greater concern that nearly 30–60% of applied N is lost in the form of ammonia from the agricultural soils through volatilization. To reduce such loss, urea can be coated with pine oleoresin, a novel coating material, for making slow release urea with minimal cost using the solvents like petrol. The POR-coated urea releases N slowly by the action of a physical barrier and increase N availability by inhibiting urease activity through antibacterial properties and reduces volatilization loss by acidifying alkaline micro-sites in soil. It also improves the biomass yield, nitrogen uptake and nitrogen use efficiency. Keeping in view of the above, the current investigation was aimed to coat urea with nano-ZnO (<100 nm) and nano-rock phosphate (<48.6 nm) using pine oleoresin (POR) as a coating agent and to study their effect on nitrous oxide (N2O) emission. Significant improvement in N use efficiency ranging 10–20% was observed in greenhouse studies. Further, the results clearly demonstrated that further encapsulation of POR coated urea with nano-Zn oxide (<50 nm) and nano-rock phosphate (<100 nm) reduced nitrous oxide emission by 30–40%. Nano-ZnO coated urea showed the least N2O emission (0.28 μg N2O mg−1 N) followed by 35% nano-RP coated urea (0.30 μg N2O mg−1 N). The results thus indicated that coating urea with 2% nano-ZnO and 35% nano-rock phosphate could be used as a potential means to reduce N2O emission from fertilizer N.

Soil, Landscape and Nutrient Management of Ravine Areas for Enhancing Crop Productivity and Livelihood Security

Ravine formed from intricate network of gullies because of localized physical degradation due to surface runoff affecting the friable unconsolidated material in the formation of perceptible channels resulting in undulating terrain with fragile ecosystem. Over-exploitation of this vast tract of existing ravine lands coupled with improper management practices has led to deterioration of soil health and poses threat to adjoining productive agricultural lands. Under ravine landscapes, soil undergoes various changes due to accelerated erosional processes. With rapidly shrinking per capita availability of land, there is a growing need for restoration of these areas for productive land uses. Maintenance of soil organic carbon is one of the most important factors for aggregate stability, soil structural durability and nutrient availability in ravine areas. Deficiency of nutrients and poor water retention are two major causative factors of stagnation in crop productivity in ravine lands. In this chapter, an attempt has been made to consolidate various best nutrient management practices for soils under ravine region for increasing crop productivity and improving soil health. Also, there is a need to harness and manage the indigenous technical knowledge and fine-tune them to suit the modern needs. Overall, the twin aspect of devising strategies for leveraging resources to tackle the challenge of enhancing soil health and carbon sequestration will help in combating climate change without compromising economic development in ravine areas. The future R&D strategies for maintaining soil health, crop productivity and environmental sustainability in degraded ravine land have also been included.

Spatial Distribution and Baseline Concentration of Heavy Metals in Swell–Shrink Soils of Madhya Pradesh, India

Defining and understanding the current abundance and spatial distribution of metals in soils are essential and reliable information on this aspect are needed for proper legislation. To estimate the baseline concentrations and spatial distribution of heavy metals (HMs) in Swell–shrink soils Sehore and Vidisha districts, 100 surface soil samples (0–20 cm) were randomly collected across the two districts and their physico-chemical properties and total HM contents were analysed. Spatial distribution maps of HMs were prepared and influence of soil parameters on HMs was studied. Most of the soils in the region had neutral to alkaline pH (6.58–8.60), non saline (EC 0.11–1.3 dS/m), medium organic carbon (0.6%), CaCO3 0.2–11.5% and clay >40%. The baseline concentrations of HMs (mg kg−1) were Cu, 178.1; Cd, 0.7; Pb, 24.4; Cr, 116.9; Ni, 81.8; and Zn, 85.2; respectively. The concentrations of Cd, Pb and Zn in all the samples were within the safe range but the concentrations of Cr, Cu and Ni were a little high.