SOIL DEGRADATION: A THREAT TO INDIAN AGRICULTURE
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06-10-2010, 12:40 PM



.doc   SOIL DEGRADATION.doc (Size: 71.5 KB / Downloads: 154)

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.
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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
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SOIL DEGRADATION: A THREAT TO INDIAN AGRICULTURE


.doc   SOIL DEGRADATION.doc (Size: 71.5 KB / Downloads: 20)

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.

SOIL EROSION

Soil erosion is the surface removal of productive soil by means of water, and wind that is the prime environmental costs in agriculture. Soil erosion alone constitutes 86.5% of land degradation that is considered the most serious hazard (Table 1). Approximately 5334 million tonnes of productive soil is being carried away by erosion that accounts for 16.4 t/ha/year. The eroded soils leaches out valuable plant nutrients to the tune of 5.0 to 8.4 million tonnes every year which accounts for Rs. 6,100 to 21, 600 crores of estimated loss of money. The removed soil gets accumulated in the reservoirs and thereby reducing their storage capacity by 1-2% every year. Erosion has been accelerated in recent times by vegetation removal, over exploitation of forest cover, excessive grazing and faulty agricultural practices.

Policy Suggestions to Prevent Soil Erosion

The erosion being the monstrous factor associated with soil degradation, it is appropriate to develop holistic strategies to minimize the erosion hazard and conserve soil productivity
• Well-defined database and mapping of various types of soil degradation hazard is very much required to develop strategies that maybe widely adoptable. This task can be accomplished using Geographical Information System (GIS) and Remote Sensing Techniques.
• Encourage rural population and tribal communities to utilize the non-conventional energy sources such as biogas plants in order to prevent overexploitation of forest cover

NUTRIENT IMBALANCE IN INDIAN SOILS

In the past fifty years, the fertilizer consumption has increased exponentially by 6 times from 3 (1950) to 18 million tonnes (2000) that commensurate with four-fold increase in food grain output. It has been observed that the indiscriminate use of nitrogenous fertilizers appears to affect the quality of crops through nitrate pollution in the groundwater. A holistic approach is to be adopted in order to maintain the balance between the crop removal and addition of fertilizers. Balanced fertilizer application is imperative for sustained productivity. In India, the problem is compounded by imbalanced fertilizer use, leading to widening of NPK ratio from 5.9: 2.4: 1 in 1991-92 to 10: 2.9: 1 in 1996-97 as against the optimum ratio of 4 : 2: 1 (Yadav, 2002). Most of Indian soils are deficient but excessive use of N alone fails to produce sustainable yields over a long period. Achieving balance between the nutrient requirements of crops and the nutrient reserves in the soils is essential for maintaining high yields and soil fertility, preventing environmental contaminations and sustaining agricultural productions over the long-term.

MICRONUTRIENT STATUS OF INDIAN SOILS

In India, the continuous cultivation of crops with high analysis straight fertilizers has pronounced a sharp decline in availability of micronutrients in soils and this associated with a reduction in nutritional qualities of agricultural produce and crop yields (Anon, 2003). It has been reported that the occurrence of micronutrients deficiencies in Indian soils to an extent of 46%, 9%, 5% and 4%, Zn, Fe, Cu and Mn, respectively (Singh and Saha, 1995). Consequently, both the production and consumption of micronutrients have increased by 30% in three years during 1999 - 2001. Correction of micronutrient disorders is gaining importance and of utmost need for sustainable farm production. Among the micronutrients, Zn appears to be deficient in most soils in India at varying intensities with the exception of acidic soil regions where the Zn status is at the moderate level. The inherent ability of the soil to supply boron and sulphur is at the declining trend and requires replenishment. Augmentation or restoration of lost soil fertility and productivity can be achieved only through addition of micronutrient fertilizers and mobilization of their residual effect through proper nutrient cycling. The applied micronutrient in the soil is often unavailable to the crop plants due heavy fixation in soils. Consequently, the micronutrient use efficiency by plants is extremely lower. To make the situation more complex, multiple micronutrient deficiencies are more prevalent than as a single nutrient deficiency.

Suggested policies in micronutrient management

Delineation of micronutrient deficiencies in India should be done to create a database as a reference tool for policy making. The ICAR has 15 micronutrient centres of which Tamil Nadu Agricultural University, Coimbatore, is one of the oldest Centres carrying out micronutrient research for the past 40 years. The data from various centres can be used to develop database on micronutrient status of Indian soils. The GIS technology may be employed to map the micronutrient deficient regions at the micro and macro levels.

ORGANIC FARMING

In India, there are also efforts to return back to the organic agriculture in order to improve the quality of food production and to promote nutritional security and ensure sustainability. It’s the concept of “Merry Go Around”. Organic production system largely excludes the use of synthetically compound fertilizers, pesticides, growth regulators and livestock feed additives. To the extent possible, organic farming rely on crop rotation, crop residues, animal manures, biofertilizers, botanicals and biopesticides to maintain soil productivity and tilth, to supply plant nutrients and to control weeds and pests. The organic agricultural products fetched US $ 17 billion in the global market in the year 2000 that is likely to double in five years reaching a figure of US $ 31 billion in 2005. Over 50% of the global share comes from the USA that gains $ 8 billion through the sale of organic produce. Inside this market place, India’s share is meager 0.001%. India is ranking 75th position in the global organic agriculture scenario. Why there is a vertical shift required from inorganic to organic? The Indian agriculture is beginning to show a sign of yield stabilization, imbalance in soil nutrient status, loss of nutritional security and livelihood of people. India’s organic production has touched 14,000 tonnes in 2002, of which 11,000 tonnes had been exported.

CONCLUSIONS

The soil degradation is increasing at the alarming proportion and needs to be circumvented to sustain agricultural production in India. Among various factors responsible for soil degradation, erosion appears to be the first and deserves governmental and non-governmental agencies to take immediate steps to minimize the hazard. Currently, several policies are in place without much impact at the large scale. Maintenance of soil nutrient status may be possible by adopting recently developed innovative site-specific nutrient management approaches. Micronutrient fertilization seems to contribute one-fifth of the total agricultural output deserves much more significance in the years to come. Timely identification and ameliorative measures are required to minimize the loss in crop productivity. Organic movement is gaining momentum in India and its applicability is more rationale and reasonable for export oriented agriculture. Sustainability in food security in relation to organic farming is yet to be established.
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