Introduction
India is blessed with a great soil diversity soils. Taxonomically eight out of twelve Soil Orders in the
world exist in India. Due to variety of reasons the arable land available per head has been reduced by 50 percent from 0.34 ha (1950) to 0.16 ha (1998-99) and is shrinking further at an alarming rate due to the exponential growth of urbanization that commensurate with increasing proportion of lands unsuitable for cultivation of crops (Yadav, 2002).It is essential to promote the soil health in order to maintain the achievement already made in realizing self-sufficiency in food production.
United Nations Organization declared 2015 as the International Year of Soils with a great ambition of
enhancing awareness on soil health and promoting healthy soil management practices. The central and state governments, Indian Council of Agricultural Research and the farm universities in India planned several initiatives to enhance the awareness about soil health among the farmers, general public and the policy makers throughout the year with great zeal but there is a need to continue the same tempo beyond 2015.
Constraints faced by Indian soils:
Indian soils have been exposed to a very high degree of soil degradation according to an estimate, 187.7 million hectares (57.1percent) of the total geographical area (329 million hectares) is degraded. The degraded land encompasses water erosion (148.9 million ha), chemical hazard (13.8 m ha), wind erosion (13.5 m ha), water logging (11.6 m ha), salinization (10.1 m ha) and nutrient depletion (3.7 m ha).
Soil and Life:
Soil is one of the most diverse habitats on earth that contains thousands of different organisms that
interact and contribute to the global cycles that make all forms of life possible. Soil biodiversity that refers to the variability existing among living organisms of the soil such as micro-organisms (mainly bacteria, fungi, protozoa and nematodes) and meso-fauna (e.g. acari and springtails), as well as the more familiar macro-fauna (e.g. earthworms and termites). These diverse organisms interact with one another and with the various plants and animals in the ecosystem forming a complex web of biological activity. Soil organisms contribute a wide range of essential services to the sustainable function of all ecosystems. These services are not only essential to the functioning of natural ecosystems but constitute an important resource for the sustainable management of agricultural systems. Soil biodiversity is unique as it hosts quite densely packed soil biota which cannot be
found anywhere in the nature.
Healthy Soil: A typical, healthy soil might contain several species of vertebrates, many species of
earthworms, 20-30 species of mites, 50-100 species of insects, tens of species of nematodes, hundreds of species of fungi and perhaps thousands of species of bacteria and actinomycetes. Soil contains the organism with the largest area. A single colony of the honey fungus, Armillariaostoyae, covers about 9 km2.
This soil biodiversity transform energy, create and modify their habitat, influence soil health, and aid in the regulation of greenhouse gases. In a similar vein, one might see the ‘biological universe' in a single gram of fertile soil, approximately a teaspoon in size, containing all the domains (Bacteria, Archaea and Eukarya) and elements of life. The majority of life on earth is dependent upon six critical elements: hydrogen (H), carbon (C), nitrogen (N), phosphorus (P), oxygen (O), and sulfur (S) that pass through, and are transformed by, soil organisms.
Agricultural Practices and Soil Degradation:
The agricultural practices such as ploughing, unscientific fertilizer application and pesticides usage have affected biological soil functions. Several factors influence the soil biodiversity. The important ones are (i) Various farming activities exert tremendous pressure and influence soil biodiversity and activity of individual organisms in the soil. (ii) Deforestation and practices such as shifting cultivation or clearing of grasslands affects soil environment and reduces the number and species of soil organisms. (iii) Reduction in quantity and quality of plant residues leads to a reduction in range of habitats and foods for soil organisms. (iv) Different farming systems affect the soil biota and the response may be either positive or negative depending on which part of the soil biotais affected. (v) Intense tilling of soil will reduce the number of fungal hyphens, because soil aggregates, which are held together by these hyphens, are broken down. (vii) Contamination of soil brought about by
addition of industrial wastes and use of contaminated ground water.
Soil health and soil biodiversity:
Soil organisms serve numerous roles and the most critical function is the regulation of biogeochemical transformations. Soil functions mediated by the soil biodiversity are, (1) Formation and turnover of soil organic matter (OM) that includes mineralization and sequestration of carbon, (2)Nutrient cycling, (3) Disease transmission and prevention, (4) Pollutant degradation, and (5) Improvement of soil structure (Gupta et al. 1997).
The ability of microorganisms to recycle carbon can provide indirect health benefits to plant communities. Soils that contain larger amounts of organic matter and microbial biomass tend to have higher rates of microbial activity and as such, some organisms may have the ability to out compete other organisms including plant pathogens. Soils that contain high levels of organic matter may also support specific antagonistic microorganisms that have an explicit means of suppressing pathogens
such as the production of antibiotics. Microorganisms also interact directly with plants through symbiotic relationships that provide nutrients to plants while supplying Carbon to the microorganism(s).
Ecosystem functions of soils:
Soils store water and filter water increase food security and our resilience to climate change impacts such as floods and droughts. The important ecosystem functions played by soils include, (a) Nutrient cycling (b)Habitat for organisms (c) Regulation of floods (d) Source of pharmaceuticals (e) Source of genetic resources (f) Foundation for human infrastructure (g) Provision of construction materials (h) Cultural heritage (i) Purification of water (j) Production of food, fodder, fibre, fuel and (k) Regulation of soil contamination and more importantly the carbon sequestration.
Carbon Regulation by Soils:
The carbon cycle is the exchange of carbon (in various forms, e.g., carbon dioxide) between the atmosphere, ocean, terrestrial biosphere and geological deposits. Most of the carbon dioxide in the atmosphere comes from biological reactions that take place in the soil. Carbon sequestration occurs when carbon from the atmosphere is absorbed and stored in the soil. This is an important function because the more carbon that is stored in the soil, the less carbon dioxide there will be in the atmosphere contributing to climate change. Plants use carbon dioxide from the atmosphere, water from the soil and sunlight to make their own food and grow in a process called photosynthesis. The carbon they absorb from the air becomes part of the plant. Animals that feed on the plants pass the carbon compounds along the food chain. Most of the carbon the animals consume is converted into carbon dioxide as they breathe (respiration), and is released back into the atmosphere.When the animals and plants die, the dead organisms are eaten by decomposers in the soil (bacteria and fungi) and the carbon in their bodies is again returned to the atmosphere as carbon dioxide. In some cases, the dead plants and animals are buried and turn into fossil fuels, such as coal and oil, over millions of
years. Humans burn fossil fuels to create energy, which sends most of the carbon back into the atmosphere in the form of carbon dioxide.
Climate regulation by soils:
Climate change is one of the most spoken subject from the recent past as it represents a serious threat to farming and to the global food security. Soils have a significant role in helping the universe from the impacts of climate change. Soils help to combat and adapt to climate change by playing a key role in the carbon cycle. Healthy soils provide the largest store of terrestrial carbon. When the soils are managed scientifically and in a sustainable way they can play an important role in climate change mitigation by storing carbon (carbon sequestration) and decreasing the emission of greenhouse gases in the atmosphere.
When the soils are not managed scientifically or if the management of soils is very poor or if the soils are cultivated through unsustainable agricultural practices, soil carbon can be released into the atmosphere in the form of carbon dioxide (CO2), which can contribute to climate change. Due to increasing human population the steady conversion of grassland and forestland to cropland and grazing lands over the past several centuries has resulted in historic losses of soil carbon worldwide and India is not an exception to this phenomenon. However, by restoring degraded soils and adopting suitable and scientific soil conservation practices, there is possibility to reduce or decrease the emission of greenhouse gases from agriculture, enhance carbon sequestration and build resilience to climate change.
Changes in temperature and rainfall patterns can have a great impact on the organic matter and processes that take place in the soils, as well as the plants and crops that grow from them. In order to meet the related challenges of global food security and climate change, agriculture and soil management practices must undergo fundamental transformations. Improved agriculture and soil management practices that increase soil organic carbon, such as agro-ecology, organic farming, conservation agriculture and agroforestry, bring multiple benefits. They produce fertile soils that are rich in organic matter (carbon), keep soil surfaces vegetated, require fewer chemical inputs, and promote crop rotations and biodiversity. These soils are also less susceptible to erosion and desertification, and will maintain vital ecosystem services such as the hydrological and nutrient cycles, which are essential to maintaining and increasing food production. The scientific practices help in increasing the productivity and resilience to climate change (adaptation), while reducing and removing greenhouse gases whenever possible (mitigation). The integrated natural resource management through watershed based approach is being tried on a more systematic way where land resources are studies in detail and scientific decision support systems are developed for sustainable soil management as done in Sujala-III project in Karnataka.
Soil degradation hazards have serious implications and impacts on agro-ecosystems.The erosion of soils by means of water, and wind is the prime environmental costs in agriculture. Soil erosion alone constitutes 86.5 percent of land degradation that is considered the most serious hazard. According to some studies approximately 5334 million tonnes of productive soil is being carried away by erosion that accounts for 16.4 t/ha/year. The eroded soil leaches out valuable plant nutrients to the tune of 5.0
to 8.4 million tonnes every year which accounts for INR. 61000 to 21 6000 million of estimated loss of money. The removed soil gets accumulated in the reservoirs and thereby reducing their storage capacity by 1-2 percent every year. Erosion has been accelerated in recent times by removal of vegetation, over exploitation of forest cover, excessive grazing and faulty agricultural practices. There is an urgent need to address these issues.
Policies for Soil Governance:
Governing of soil requires international and national collaboration between governments, local authorities, industries, private sector, farming communities and the general public to ensure implementation of coherent policies that encourage practices and methodologies that regulate the usage of the soil resource in a sustainable way without any conflicts between users. Soil governance need to be geared towards promotion of sustainable agriculture practices. The need to monitor
and avoid the negative effects of agricultural land use such as soil erosion. There is a need to use science and technology tools for soil management and soil governance along with suitable policies, strategies and the processes of decision-making by the governments on how the soil is utilized. There is need to focus on (a) Developing database and mapping of various types of soil degradation hazard to develop strategies that maybe widely adoptable. (b) Encourage farming community and tribal groups to utilize the non-conventional energy sources such as biogas plants in order to prevent overexploitation of forest cover (c) Provision of incentives may be a cost effective measure to encourage farmers to adopt soil conservation practices (d) More research on sustainable integrated farming practices.(e) The land use policy should form the basis for integrated approach comprising of land, soil and water (f) Need to develop detailed land resource inventory and database of other natural resources to help farmers and policy makers with Decision Support System for sustainable land management so that the government programs and development plans are directed by scientific basis
for the state investments.
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