[attachment=5150]

---

Prepared by:
M. Dhakshinamoorthy, Professor, IMTI, Trichy

---

Introduction

India is blessed with a wide array of soil types that would have developed in the subcontinent as a direct consequence varying climatic conditions and vegetations. According to the National Bureau of Soil Survey and Land Use Planning (NBSS & LUP), taxonomically eight out of twelve Soil Orders in the world exist in India. The Inceptisols (alluvial soils) cover nearly one-third of the geographical area of the country. The arable land available per head has been reduced by 50% in the past fifty years from 0.34 ha (1950) to 0.16 ha (1998-99). The land available for cultivation is shrinking 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 utmost essential to promote the soil productivity in order to maintain the achievement already made in realizing self-sufficiency in food grain production. India has been exposed to a very high degree of soil degradation within the club of developing countries. According to the latest estimate, 187.7 million hectares (57.1%) 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). In this paper, various soil degradation hazards and their impacts on agro-ecosystems and suggested policies to be orchestrated in order to prevent further deterioration.

[attachment=9885]
SOIL DEGRADATION
 When plants (trees & shrubs) are cleared from a site, soil is exposed to sunlight and the eroding effects of wind and water. Soil aeration is increased and the rate of weathering increases.
 Apart from erosion, the proportion of organic matter in the soil gradually decreases, through the action of microbes in the soil which use it as a source of energy unless the new land use provides some replacement.
CAUSES OF SOIL DEGRADATION
FORMS OF SOIL DEGRADATION
IMPACTS
• The main impact of soil erosion is the reduction in soil quality which results from the loss of the nutrient-rich and fertile upper layers of the soil, and the reduced water-holding capacity of many eroded soils. In other words, 'Erosion removes the cream of the soil' (soilerosion.net). Therefore soil erosion is one of the most serious threats to soil fertility. Even low erosion rates which are almost invisible can over the years have a severe impact on soils. It is therefore of vital importance to protect the soil from erosion. Especially organic farming fully depends on maintaining the natural fertility of the soil.
• Soil erodibility is an estimate of the ability of soils to resist erosion, based on the physical characteristics of each soil. Generally, soils with faster infiltration rates, higher levels of organic matter and improved soil structure have a greater resistance to erosion. Sand, sandy loam and loam textured soils tend to be less erodible than silt, very fine sand, and certain clay textured soils.
Soil conservation measures
• Certain conservation measures can reduce soil erosion. Soil / land management practices such as tillage and cropping practices, directly affect the overall soil erosion problem and solutions on a farm. When crop rotations or changing tillage practices are not enough to control erosion on a field, a combination of measures might be necessary. For example, contour plowing, strip cropping, or terracing may be considered.
Types of conservation measures:
• Agronomic: such as plant / soil cover, conservation farming methods, contour farming
• Vegetative: such as planting barriers (vegetative strips), live fences, windbreaks
• Structural: such as Fanya Juus, terraces, banks , bunds, cut off drains, barriers
• Overall management: such as area closures, selective clearing