This article throws light upon the eleven main types of soil problems faced in West Bengal. The types are: 1. Soil Depth Limitations 2. Soil Drainage Limitations 3. Water Erosion Problem 4. Soil Salinity Problem 5. Soil Texture Limitation 6. Waterlogging Problem 7. Surface Flooding Problem 8. Overall Soil Degradation 9. Soil Erosion 10. Land Slide Problem in West Bengal 11. Wasteland.
Type # 1. Soil Depth Limitations:
Effective soil depth governs root development and is a source of moisture and nutrient supply to the plants. The extent of depth classes which affect crop growth are shown in Table 11.2.
Type # 2. Soil Drainage Limitations:
Soils of West Bengal have been grouped into six drainage classes, of which four classes have been found to adversely affect soil and crop management. These are very poorly drained, poorly drained imperfectly drained and excessively drained, soils. Areas affected by these drainage classes are shown in Table 11.3.
Type # 3. Water Erosion Problem:
Erosion by water is a major soil degradation factor which should be taken into consideration. Areas affected by severe and moderate erosion hazards are shown in Table 11.4.
Type # 4. Soil Salinity Problem:
Soil salinity in West Bengal is mainly due to the inundation of tidal water in deltaic zone. The area affected by salinity limitation is shown in Table 11.5.
Type # 5. Soil Texture Limitation:
Soil texture is an important soil attribute governing crop production from initial stage up to the maturity of crops. The areas under the most important soil texture classes are shown in Table 11.6.
Type # 6. Waterlogging Problem:
Waterlogging is considered a serious limitation which adversely affects the yield and quality of crops. The areas in West Bengal affected by waterlogging are shown in Table 11.7.
Type # 7. Surface Flooding Problem:
Surface flooding is considered a serious limitation for crop production in West Bengal. Areas affected by moderate and severe flooding are shown in Table 11.8.
In Table 11.9, an attempt has been made to rank the types of problematic soils by area size.
Type # 8. Overall Soil Degradation:
Two major categories of soil degradation processes have been identified in West Bengal:
(i) Soil degradation due to displacement of soil material mainly through water erosion.
(ii) Physical and chemical deterioration of soil due to water logging, flooding and salinization.
As much as 30.9 per cent of the total geographical area of West Bengal has degraded soil cover.
Of this, 19.7 per cent of the area occurs mainly in Puruliya, Bankura and Darjeeling where the degradation is mainly due to loss of top soil by water erosion; 3.2 per cent of the degraded soil region occurring in South 24 Parganas and Medinipur have deteriorated due to salinization; 6.9 per cent of area occurring in 24-Parganas (North and South), Medinipur, Hugli, Nadia and Malda have been affected by water logging. This is shown in Table 11.10.
Type # 9. Soil Erosion:
The problem of soil erosion is a serious issue leading to decline in fertility and productivity value of the soil.
In a recent study conducted in Birbhum district of West Bengal a multiplicity of causes have been identified; these include low forest cover, ill-conceived canal irrigation without alignment of field channel, prevailing practice of leaving uncultivable land use-less, unrestricted grazing, improper bundling, excessive overland flow of irrigation water from barrages and cultural practices and lack of education.
Consequences of soil erosion, the study reveals, could be positively correlated with increasing waterlogging and uncontrolled irrigation; a land area with 40% being affected by erosion has 53% under waterlogging and 24% under uncontrolled irrigation; the effect, as a regression analysis, shows could lead to a coefficient of (-) 1.65 based on net value of crops per acre of gross cropped are (GCA) and proportion of soil eroded land.
This shows that for per unit increase in soil eroded land, about 1.65 unit of net value of crops would be decreased. The study further shows that cropping pattern is more diversified irrespective of farm size on unaffected land than on eroded land; productivity values of principal crop like paddy decreases by 25%-33% and potato by 47%-60%.
Type # 10. Land Slide Problem in West Bengal:
The Darjeeling Himalayan region is prone to natural hazards viz land-slides and associated stop failures especially after heavy monsoon rain. Impact of such hazards could lead to breach of communication, disruption of read traffic and supply of commodities, loss of lives, properties and tourist revenue.
Proper land use management plan in such areas calls for studies on land slide susceptibility. Identification of past and present slope failures, silts and determining geological, geomorphological and geotechnical condition may lead to the appropriate terrain classification.
Geological Survey of India has undertaken extensive study along main road alignment in Kurseong, Darjeeling and east Sikkim districts during 1993-94 and later years. A total of 200 sites of slope failures have been identified based on aerial photo interpretation and extensive ground checking.
Of these 131 number of failures (59.6%) were recorded between 20Â°-30Â° slope zone, followed by 66 failures (30%) between 30Â°-45Â° slope zone, while no failure was recorded on slopes less than 10Â° (GSI, 1995).
Analysis of seven geological formation exposed in the area revealed at more than 30Â° angle are most susceptible to land slide and granular non-plastic to low plastic soils are more slide prone than fine silty soils especially on slopes between 30Â°-45Â°.
Further it is observed that deforested and locally cultivated, irrigated lands are maximum slide prone. A slope failure susceptibility map has been prepared by GSI. The said map may be used for future land use planning and slope management; the study area could also be demarcated from highly susceptible to low susceptible zone.
The human activities identified as contributory factors to land slide include, unplanned construction, inadequate and improper sewerage system in the built up areas on slopes, large scale deforestation and clandestine coal mining in many areas on the slopes in Gondowana terrain.
(i) Rambe to Jorebunglow via Mongpoo,
(ii) Teestabazar to Jorebunglow via Peshok-two vital links connecting Darjeeling to Kalimpong and Gangtok,
(iii) Rangpo to Risruthang along northern bank of Rongpochu river
(iv) Hill Cart Road from Rongtong to Kurseong were studied for the above assessment.
Type # 11. Wasteland:
India has shown an alarming rate of decline in the man-land ratio; while it was 1.25 hectare per capita in 1921, its sharp decline to 0.48 hectares per capita was noted in 1986. Besides the man-land ratio, the problem of overuse and abuse of land resources led to the formation of Wasteland Survey and Reclamation Committee by the Govt. of India as far back as in 1960-62.
However, it is only in 1985 that a National Wasteland Development Board was constituted with the objective to achieve a quantum leap in afforestation activities and to place greater emphasis on the development of fuel wood and fodder.
In West Bengal, the total wasteland area has been divided into 3 major parts viz. Barren and uncultivable land, fallow lands other than current fallow, and cultivable wasteland. In Table 11.11 has been shown comparative data on these 3 parameters between 1984-85 to 1994-95.
On the other hand the above figure does not reflect the estimate of saline and alkaline land as also water eroded wasteland area; the same has been estimated by Bhumbla and Khare (1984) as shown in Table 11.12.
The above data when compared with the figures on soil erosion in West Bengal shows that there is a difference between the two which could be attributed to non-inclusion of saline wasteland. In terms of soil erosion the district of Medinipur tops the list with 2,32,932 hectare followed by Bankura with 2,15,500 hectares and Puruliya with 1,65,200 hectares (ERCWDP, Jan., 1991).
While soil erosion of the area under forest sector amounts to 4,37,045hectares (4.94 per cent), that under the non-forest sector stands at 6,65,000 hectares (7.52 per cent). It is reported that steps are being taken to treat the area under soil erosion and nearly 30% of the area has been treated by 1991. This is shown in Table 11.13.
A special mention should be made of the mining areas located within the western district of Bardhaman, Birbhum, Bankura and Puruliya. The most important mining area in the state is the Ranigunj coal field which covers an area of 1,53,000 hectares; of these nearly 6,000 hectare of degraded land due to coal mining could be identified.
The major degradation could be attributed to the subsidence’s through underground mining (5,094 hectares). An area of 370 hectares is also degraded due to the presence of over-burdened dump in open cast mine area.
An environmental master plan for Ranigunj coal field has been prepared which indicates the possible reclamation of the vast wasteland area, in this mining sector of eastern India. It is estimated that as much as 5,065 hectares out of 5,954 hectares of mined wasteland could be reclaimed through a proper management strategy. The total area affected by soil erosion is shown in Table 11.14.
The other problem is erosion due to river. Of these the erosion affected area on the right bank of Ganga below Farakka and some stretches of Bhagirathi near Jiaganj in Murshidabad district need special mention. At present the annual volume of erosion along Bhagirathi is estimated at 8.5 million cubic metre and the annual land area loss is about 220 hectares.
Another problem identified in West Bengal with regard to wasteland is due to quarrying of pit sand in the Hugli district. The damage extends to 6 blocks e.g. Dhaniakhali, Singur, MograChinsurah, Pandua, Balagarh and Jungpara. An area of 163.92 hectares is estimated to have been converted to non-agricultural land due to sand extraction.
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