Land is an important natural resource, which affect both humanity as well as for maintaining ecosystem. Land, the major input in agriculture, is getting reduced both in terms of size and its productivity.
Now only three per cent of the total geographical area is highly productive and around 19 per cent of the total area is low and medium productive. Every year we are losing about 5 to 7 million hectares agricultural land due to several natural and artificial (man made) factors. This shows the seriousness of land degradation.
At present, to meet the ever-growing demand for food, farmers are left only with intensive agriculture as the land available for cultivation is decreasing. This trend not only accelerates the land degradation but also narrows down the chances for increasing the food production.
Causes of Land Degradation
1. Water erosion
2. Wind erosion
3. Physical degradation, water logging, soil crusting, compaction, desertification etc.
4. Chemical degradation, salinization, sodification, acidification, nutrient removal, decrease of organic matter.
5. Biological degradation.
Causes of degradation: The major cause is the conversion of medium to low productive agricultural land to other uses like industries, brick kilns, road etc. The practice of intensive agriculture is also causing land degradation. The factors responsible are:
1. Climate: Higher evaporation than precipitation, drought, short duration rainfall with high intensity, high velocity winds, cyclones, storms etc.
2. Soil factors: Slope, coarse texture, impermeable and compact layers, seismic/volcanic eruptions etc.
3. Management factors: Unwise land use, improper cropping system with no conservation measures, excessive use of chemicals, exploitation of groundwater, indiscriminate deforestation, shifting cultivation etc.
4. Socioeconomic and policy factors: Population pressure, poverty, slow adoption of improved technologies, declining land: man ratio, land tenure system, ineffective land policies etc.
In India, it is estimated that out of 329 million hectares of geographical area, 175 million hectors is suffering from various kind of degradation. The report of National Bureau of Soil Survey and Land use Planning (1994) described that 57 per cent of the total geographical area of the country is suffering from different kinds of degradation of which a dominant part (45 per cent) is under water erosion and the rest 12 per cent is from wind, chemical and physical deterioration.
The extent of land degradation from one state to another depends upon topographical features, geological formations, soil characteristics, rainfall and other climatic parameters, land use, I measures of soil conservation management practices etc. Rajasthan (37 mha) tops the list followed by Madhya Pradesh (20 mha), Maharashtra, Andhra Pradesh, Karnataka and Gujarat (more than 10 mha each).
1. Water Erosion
Out of 69 mha estimated to be critically degraded in India approximately 43 mha are non- arable & barren, including 4 mha of ravine lands. The Himalayan Mountains with weak geological formation and poor physiographic conditions are under great stress and suffer from serious water erosion though water erosion is also rampant in the Western Ghats and other areas of high intensity rainfall. Water erosion not only removes the productive surface layer of soil but also reduces the storage capacity of reservoirs.
2. Wind Erosion
Wind erosion is more prominent in the hot arid region occupying 31.7 mha of which 61 per cent is found in western Rajasthan. Removal of vegetative cover and overgrazing enhance the intensity and extent of wind erosion and desertification. The sand movement causes calcine damage to the adjoining cultivated areas, roads, canals, buildings, etc.
3. Water logging
Water logging caused by rise in water table poses a great threat to soil productivity and environmental ecology, especially in the irrigated areas. Roughly an area of 100,000 ha is estimated to be affected by water logging annually.
Introduction of canal irrigation is the major reason for the once fertile lands to be affected by water logging (e.g., Hissar, Haryana). The menace of water logging has also taken place in the Indira Gandhi Nahar Project, which was initiated in 1961. The presence of hard layer especially gypsiferous in the profile accentuates the problem.
4. Salinization and Sodification
The development of soil salinity in India started long back and is more prominent in the arid and semi-arid areas though some coastal areas in the humid conditions also suffer due to the ingress of seawater.
Continuous use of poor quality groundwater for irrigation also leads to the development of soil salinity or sodicity, particularly in the slowly permeable soils. It is more serious in the Indo Gangetic Plain, black soil region, arid areas of Rajasthan and Gujarat and coastal areas.
The sodic soils possess high pH and exchangeable sodium percentage values, preponderance of carbonate and bicarbonate salts of sodium, deficient amount of organic matter, nitrogen, available calcium and zinc, presence of CaC03 (kankar) in the subsoil, impaired physical condition and poor moisture relations. Addition of a suitable amendment like gypsum is essential for reclamation of these soils.
The saline soils, on the other hand have high concentration of neutral salts mainly of chlorides and sulphates, lower values of pH and exchangeable sodium, better physical conditions etc. Many saline soils are often associated with high water table of poor groundwater quality. Provision of adequate drainage to lower the water table and leach out the soluble salts is imperative for amelioration of such saline soils.
5. Nutrient Loss
The factor greatly responsible for enormous removal of the plant nutrients is soil erosion. In India the nutrient loss to the tune of 5.37 to 8.40 million tonnes occurs through erosion every year.
This aggravates the problem of soil fertility depletion. The transformation from high internal input agriculture in the past to the present day high external input (fertilizers, pesticides) agriculture causes this problem. Here the removal of plant nutrients is sustainably higher than what in added through the fertilizers.
Agriculture in the past to the present day high external input (fertilizers, pesticide) agriculture causes this problem. Here the removal of plant nutrients is sustainably higher than what is added through fertilizers, thereby, resulting in a negative soil nutrient balance.