Sub- theme - III LAND QUALITY

Sub-Theme- III
LAND QUALITY

Our land resources perform various functions like providing base for vegetation, water bodies, habitat for human, animals, birds and other organisms; producing food and fibre; maintaining or enhancing water quality; partitioning water flow and sequestering carbon. Land quality is defined as the capability of land to perform these functions without becoming degraded. Majority of these functions of land are, however, determined by the quality of soil. Maintaining and improving the quality of the Nation’s soils can increase farm productivity, minimize use of nutrients and pesticides, improve water and air quality, and help store greenhouse gases.
Soil quality is defined as the continued capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain biological productivity, promote the quality of air and water environments and maintain plant, animal and human health. In short, soil quality can be defined as the “fitness for use” or “Capacity of the soil to function”.
There are several interacting processes occurring among the components of soil as well as with atmosphere. Soil is the storehouse of major, secondary and micronutrients required for plant growth and also for growth of soil micro-flora and fauna. Through different chemical, biochemical and microbial processes, these nutrient elements are released slowly as per the requirement of plant and other organisms. Plant is incapable to take up nitrogen directly from atmosphere even though it contains about 77% nitrogen. Some of the bacteria living in soil fix atmospheric nitrogen to make it available for higher plants. Similarly, soil contains significant amount of phosphorus, but in unavailable form. Various chemical and biochemical processes (mediated by phosphorus solubilizing bacteria) make this nutrient available to plant. Thus status of various nutrient cycling processes indicate the health status of soil.
Soils of the land area perform filtering action for water and therefore, its capacity to filter determines the quality of surface and ground water bodies. Concentration of carbon dioxide has been constantly increasing due to its emission from burning of fossil fuel, deforestation and large scale disturbance for urbanization. Soils also act as a sink for carbon. The vegetation including forests and agricultural crops fixes atmospheric carbon in leaves, shoots and roots through photosynthesis. These carbonaceous materials are temporarily locked in the soil profile on its decay and thereby help in reducing carbon-di-oxide concentration in the atmosphere and global warming. However, soils differ in such carbon storing capacity (Carbon sequestration) depending on their characteristics. Soils of the land also act as a sink for several toxic pollutants generated due to anthropogenic activities. Metals play an important role in our daily life. To meet out increasing demands, metals are continuously mined out from deeper layers of earth crust. After serving human purposes, these metals are ultimately disposed on the land surfaces in the form of industrial effluents, solid wastes etc. Each soil has a definite tolerable limit (loading limit) for pollutants. Once these limits exceeded, pollutants contaminate food chain and ground water bodies, affect adversely the plant growth and soil biota.
Thus the land care and soil quality management assume great significance for ensuring agricultural sustainability which is inevitable to feed the burgeoning population not only in India but across the world. In order to evaluate land quality, we need to identify the key attributes represent the health of land.
Indicators to assess land quality
Land use
Land use is an indicator reflecting how and to what extent society is responding to meet its changing needs and goals or to adapt to changing environmental conditions. Ideally, it is recommended that our geographical land area should have 33% forest cover. However due to increase in demographic pressure, the area under forests and agriculture is reducing continuously; consequently, area under dwellings and industry is increasing. Over the years, such interference of anthropogenic activities is considered as the major cause of land degradation. About 85 million ha of agricultural land are reported to be suffering from various degrees of soil degradation processes such as erosion, salinization, alkalization, water logging, desertification, loss of organic matter, loss of nutrients, soil compaction, entry of toxic pollutants etc.
About 45% of total geographical area of our country is affected by various kind of land degradation. In these degraded land area, erosion of soil caused by water flow contributes maximum to the degradation processes (about 63%) followed by acidification (about 11%), water logging (about 10%), erosion of soil by wind (about 6%) and salinization of soil (about 4%).
Information on aspects such as nature and density of vegetation or nature and productivity of crops; conditions of the land surface (slope, runoff, erosion rates and salinity); hydrological conditions (flooding incidence, groundwater dynamics); and physical, biological and chemical conditions (toxins, nutrients) of the soil helps in explaining various degradation processes. Such monitoring information, superimposed on a baseline soils and terrain database, will allow the estimation of potential productivity changes of land under different main uses and of suitability changes for different purposes such as conservation of native vegetation or animal populations.
Soil Quality
Since all agricultural activities are directly or indirectly, affected by how the “soil is handled”, its health becomes the prime concern before one can address human and livestock health issues. Managing soil is a formidable challenge to ensure productivity, profitability and national food security. Soil quality can be assessed by a number of physical, chemical and biological attributes / processes. Relevance of one or more unfavourable soils conditions for long periods leads to un-sustainability of agricultural system. Major issues of soil quality include:
i) Physical degradation – where, physical properties of soil such as bulk density, structure, water holding capacity, depth etc. are changed un-favorably. Physical degradation of soil are caused by compaction due to use of heavy machinery like combined harvester, tractor, laser leveller, intensive cultivation, puddling, water logging and soil erosion.

ii) Chemical degradation – where chemical properties like pH, electrical conductivity, soil organic matter content, available plant nutrient status, base saturation, cation exchange capacity, phosphate fixing capacity etc. are affected resulting in decline in soil fertility. Chemical degradation is caused by wide nutrient gap between nutrient demand and supply, imbalanced use of fertilizers, emerging deficiencies of secondary and micronutrients, limited / no use of organic manures, acidification and aluminium toxicity in acid soils, salinity and alkalinity. While salinity problems are often associated with irrigation, salinity problems can also occur in dry land areas where rainfall is insufficient to leach salts from the soil.

iii) Biological degradation of soil – where biologically mediated soil processes like nitrogen fixation, phosphate solubilisation, nutrient mineralization etc are affected. Biological degradation due to organic matter depletion caused by rise in soil temperature, loss of biodiversity due to agricultural chemicals like herbicides, pesticides, fertilizers etc. Biological degradation is perhaps the most serious form of soil degradation because it affects the life of the soil and soil may not be able to cycle nutrients and transform harmful chemicals or substances to nontoxic waste or to combat plant pests and diseases. The microbial community is continually adapting to the environment, and can function as indicators of changes in soil quality.

iv) Soil pollution from industrial wastes, excessive use of pesticides and heavy metal contamination resulting in deterioration of water and crop produce quality.
Remedial measures:
Remedial / corrective measures for degraded land could start after identifying the constraints. These can be broadly categorized as following:
Changes in land use pattern: Cultivation of crops having profuse foliage and cover can control soil erosion during rainy season. Plantation of trees and developing grassland with profuse deep root system on the barren and degraded land minimizes soil erosion and prevents degradation of water quality.
Modifying soil conditions by applying amendments: Management of acid soils should aim at raising pH through application of lime which improves nutrient availability and inactivated iron, manganese and aluminium toxicity. Alkali soils can be reclaimed by applying gypsum, which lowers down the pH and exchangeable sodium.
Salinity in the soil can be reduced by leaching down the salt with good quality of irrigation water. Sub-surface drainage technology can mitigate the twin problems of soil salinity and water logging. Growing green manures and addition of organic manures such as farmyard manure and compost improve soil properties.
Avoiding setting up of industries on a land with low fixing capacity for pollutants can prevent contamination of food chain and water bodies and protect crops, soil micro-flora and fauna.