After reading this article you will learn about:- 1. Introduction to Soil Conservation 2. Identification and Description of the Problem 3. Some Results of Practical Value.
Introduction to Soil Conservation:
Soil and water conservation is essential to protect the productive lands of the world. In our country, where droughts, famines and floods cause crop damage almost every year, soil conservation will not only increase crop yields but also prevent floods and further deterioration of land.
Prior to the days of independence, while general problems of soil erosion were known, answers to them backed by scientific investigations were not known. Consequently, during the framing of the first year plan and early in the second five year plan, a chain of 9 Soil Conservation Research Demonstration and Training Centres were established (Table 12.1).
Broad objectives of these centres are:
(i) To identify erosion problems and conservation of land and water resources under different land use systems,
(ii) To evolve mechanical and biological methods of erosion control under different land use systems,
(iii) To evolve methods of control of erosion and reclamation of ravines stabilisation of landslides and hill torrents,
(iv) To evaluate hydrological behaviour and evolve techniques of watershed management under different systems,
(v) To set up demonstration projects for popularizing soil and water conservation measures,
(vi) To impart specialised training in soil and water conservation to gazetted and non-gazetted officers of State Governments.
All the above centres were under the control of Ministry of Food and Agriculture, Govt., of India up to September 30,1967. On October 1,1967, all of them excepting the Chattra centre were transferred to Indian Council of Agricultural Research, which continued to co-ordinate the research and training facilities up to October 1970 from New Delhi.
Finally, the responsibility of technical coordination of Research and Training was transferred to Soil Conservation Research, Demonstration and Training Centre, Dehradun, in October 1970. Later on April 1, 1974, the Indian Council of Agricultural Research established Central Soil and Water Conservation Research and Training Institute by restructuring Soil Conservation Research Demonstration and Training Centre, Dehradun and transferred whole technical and administrative responsibility of Soil Conservation Research and Training to it.
In addition to the above centres with head office at Dehradun, the work on soil and water conservation is also carried out directly by Central and State Governments.
For example, a Desert Afforestation and Soil Conservation Research Centre was established at Jodhpur in 1952 under the Forest Research Institute, which was later converted into Central Arid Zone Research Institute in 1959 with responsibility for the Rajasthan desert and arid zone research.
Similarly, a U.P. State Soil and Water Conservation Research and Training Centre was established at Rehmankhera near Lucknow to tackle the problems of ravine on the bank of Gomati river. Another Soil Conservation Centre was established at Hazaribagh to tackle the problems in the catchment of river Damodar (DVC).
Indian Council of Agricultural Research established ICAR Research complex for North-Eastern hill region in 1975 at Shillong to provide research base for the problems of shifting cultivation.
Its research centres were established in Nagaland, Tripura, Arunachal Pradesh, Mizoram, Assam, Sikkim, Andaman and Nicobar Islands, Goa and Lakshadweep. All India Coordinated Research Project was established in the 5th Five Year Plan, with mandate of research on increasing crop and forage production in dry lands by adopting soil and water conservation measures on watershed basis.
A brief account of the work done on soil and water conservation in India is being highlighted below, broadly as identification and description of the problem, some results of practical value, and projection of the problem.
The review is not exhaustive as it is beyond the scope of this book. For detailed information, the readers are advised to consult original publications of Central Soil and Water Conservation Institute.
Identification and Description of the Problem:
Since it is not possible to conduct detailed study on every piece of land, and soils of an area do have similarity with those of others, it was considered a first task to develop certain type of land sub-divisions and classifications.
This was necessary to enable transfer of certain type of conservation practices established for a particular location to another location associated with similar situations. This gave rise to sub-dividing country’s land into land resource regions and areas and other classifications based on their characteristics and other similarities.
Land Resources Regions and Areas of India:
Based on the informationâ€™s available on soil, water, climate, topography, vegetation and land use, etc., India has been divided into 20 land resource regions and 186 land resource areas.
This information is useful for:
(i) Determining national soil and water conservation needs;
(ii) Organising research;
(iii) Correlating technical soil and water management guides and manuals of different States; and
(iv) Transferring the research experience gained at one place to other similar places.
Considering these points in mind the Soil Conservation Research Centre, Dehradun prepared a land Resource Region and area map of India (Fig. 12.1).
The twenty land resource regions are as given below:
A. Northern Himalayas snow clad region
B. Northern Himalayas alpine grass and meadow region
C. Northern Himalayas forest region
D. Punjab, Haryana alluvial plains region
E. Upper Gangetic alluvial plains region
F. Lower Gangetic alluvial plains region
G. North-eastern Himalayas alpine grass and meadow region
H. North-eastern forest region
I. Assam valley region
J. Rajasthan desert region
K. Run of Kutch region
L. Gujarat alluvial plains region
M. Mixed yellow red black soil region
N. Black soil region
O. Eastern red soil region
P. Gangetic delta region
Q. Western delta region
R. Southern red soil region
S. Eastern coastal region
T. Andaman-Nicobar and adjoining islands regions
In the northern and north-eastern Himalayas, the vegetation has been given the main consideration in deciding the land resource region boundary. Northern Himalayas have been divided into three regions. Snow clad region (devoid of vegetation), alpine meadow and grass region and forest region. In northwestern Himalayas three regions viz. alpine, meadow and grasses; forest region and Assam valley region have been demarcated.
The rest of the divisions have been made according to soil like black soil region, mixed soil region, coastal soil region, etc. Alluvial Indo-Gangetic plains have been divided into three regions namely Punjab and Haryana alluvial plains region, upper Gangetic region and lower Gangetic region.
As the east and west coasts vary a lot in rainfall, coastal regions have been divided into western coastal region and eastern coastal regions. The red soil areas of the country have been divided into western red soil region and southern red soil region. All the islands of the country have been grouped into one region, i.e., Andaman-Nicobar and adjoining islands region.
Land use was taken to be the most important criterion for sub-dividing a land resource region into land resource areas. The land resource areas are, therefore, mostly based on the land use such as forest, irrigated or non- irrigated lands. The command area of each of the river valley project has been marked and numbered separately as one area except when it extends to two regions of different soil types.
The areas commanded by small ponds and tanks have not been considered except for those areas having an irrigation intensity of 80% or more. The non-irrigated agricultural lands have been sub-divided into different land resource areas depending upon rainfall and soil type.
The rainfall ones of 0-10,10-40, 40-80, 80-200 and 200-400 cm have been classified as arid, semi-arid, sub-humid, humid and per-humid, respectively. The eight Central Soil and Water Conservation Research Centres are expected to serve the following land resource regions of the country (Table 12.2).
Land Capability Classification:
In any soil and water conservation programme, it is desirable to first identify and classify the land according to its capacity. This is necessary to prepare and execute watershed plans to improve overall productivity of the land. The land capability classification is a systematic arrangement of different kinds of land according to their ability to produce on virtually permanent basis.
The land capability classification map is normally prepared by interpreting a standard soil survey map based on the specifications suggested by All India Soil and Land Use Survey Organisation (Soil Survey Manual). The Central Soil and Water Conservation Centre, Ootacamund has suggested the following land use classification for hilly areas (Table 12.3).
Similarly, a modified classification has been suggested for ravine lands by soil and water conservation centres (Table 12.4). In ravine lands, the slope of the land and gullies and distance of the land from the gullies are important and dominant factors influencing the land capability classification.
In India, where there is a great pressure of population and land hunger, it is not possible to retire all ravine lands to forests and grass lands. The main demand is to reclaim such lands for cultivation purposes. The classification includes these considerations.
Some Results of Practical Value:
1. Conservation Practices for Agricultural Lands:
The runoff and soil loss studies on 8% sloping land showed that up and down cultivation of maize as practiced by farmers in Doon Valley caused about 28.5 tonnes/ha soil loss which was reduced by 30% when the maize and cowpea were grown together across the slope.
Similarly, studies conducted at Agra Centre indicated that permanent vegetation with Dichanthium annulatum reduced soil loss to 2.3 tonnes/ha/year as against 14 tonnes/ha/year on a 2% slope.
Amongst the cultivated crops, bajra permitted the highest soil loss (10.4 tonnes/ha) which could be reduced to within the permissible limits by inter-cropping bajra with cowpea or moong. Cynodon dactylon has proved to be most efficient in providing protection to the newly formed terraces, bunds and other earthen structures.
Contour cultivation has been found to reduce runoff and soil loss in all the major soil groups of India. At Ootacamund, the runoff was reduced from 52 to 29 mm and soil loss from 39 to 14.9 tonnes/ha by adopting contour cultivation (Raghunath, et al., 1967). Similar results were also obtained at Dehradun and Kanpur (Table 12.5).
Construction of narrow based embankments at intervals across the slope (up to about 6%) along contour lines is an important soil and water conservation measure for arid and semi-arid area. The following cross-sections of bunds have been recommended (Table 12.6) for black soils in the dry areas of Maharashtra.
The spacing between bunds should not exceed 67.5 m horizontal or 1.5 m vertical drop whichever is less. For alluvial soils of Gujarat a vertical spacing of 1.83 m and cross-section of 1.3 m2 has been recommended for land with 6-12% slope and 0.9 to 1.2 m vertical spacing, and 0.9 to 1.3 m2 bund cross-section for slopes less than 6%.
Studies on graded bunding conducted at Kota centre on sloping cultivated lands (slope up to 4%) in the area showed that graded bunds of 1 m2 cross-section with 0.5 to 1.0 m vertical interval were suitable for checking soil erosion.
On flat lands, the provision of drainage channels was essential in kharif season due to low permeability of soils. Legumes, groundnut and black gram proved successful in controlling erosion, while maize gave the highest soil and water loss. Natural cover and Dub grass (Cynodon dactylon) were very effective in controlling soil erosion.
Graded bunding or terracing has been very useful in areas receiving more than 80 cm rainfall per year. In clay soil, it is successful even in areas receiving less than 80 cm annual rainfall. The graded terraces essentially consist of a wide low embankment constructed on the lower edge of the channel along the contour lines at suitable vertical interval.
A vertical interval of 0.3 (S/2 + 3) m, 45 cm top width, 55 cm height and 1.5:1 side slope has been found most satisfactory in Doon valley alluvial soils with 2-4% slope (s). In rainfed areas, bench terracing can be practiced on slopes from 6-33% with 60 to 180 cm vertical drop.
An alternative to contour bunding and graded bunding, the possibility of using contour ditches has been recommended in slowly permeable soils. Conceptually, contour ditching works on the principle that when suitably designed, it stores most of the runoff from a design rain storm and hence cuts off a vital portion of the runoff.
In construction, the contour ditch is essentially an inward form of a contour bund sunken into the ground, with flatter upstream side slopes provided for safety against scouring by the incoming runoff. Contour ditches could be 75 m spaced, 30 m long having cross-sectional area of 1.6 m2.
At Chandigarh it was found that the runoff reduced down to 10% of rainfall from the areas treated with staggered contour trenches (2.5 m x 0.45 m x 0.45 m) spaced 2 m apart and check dams.
Ridging and furrowing across the gentle slope, in soils with moderate to rapid infiltration rate, considerably reduced runoff (44 to 52%), soil loss (52 to 52.8%) and nitrogen loss (48.8- 50.9%) from cotton and tobacco fields. At Vasad, the ridge and furrow system adopted for Bajra reduced the runoff and soil loss up to the extent of 48 and 50%, respectively.
Mixed cropping of Jowar and Arhar, in alternate lines 30 cm apart has been recommended under dry farming conditions in black soil area of Kota (Singhal et al., 1977). This practice gave 36% more income as compared to growing Jowar alone (Table 12.7).
2. Gully, Torrents and Landslide Control:
It has been shown that gully erosion can be controlled by:
(i) Closure to grazing and biotic interference which results into regeneration of trees and grasses leading to a forest;
(ii) Providing contour/graded bunding in the catchment of gullies and peripheral bunds near the gulley heads;
(iii) Providing gully plugs to reduce the velocity of runoff water and encourage silting.
Small gullies (depth 3 m) can be reclaimed by clearing, minor levelling by bulldozer and putting up series of contour bunds at vertical interval of 0.9 m with pipe outlets in diagonally opposite manner to get maximum length of land for runoff water.
At the end of the gully, a composite earthen check dam with spillway of brick masonry should be constructed. The practice at Vasad centre showed that the cost is repayable in five year with a balanced crop rotation. Plantations of Arundo donax, Agave americana, Ipomea cornea and Vitex negundo are most successful. Some of the specifications for gully plugging are given in Table 12.8.
A medium gully (depth 3-9 m) can be reclaimed by clearing and levelling the bed, constructing a series of composite earthen and brick masonry check dams with suitable water disposal structures, at a vertical interval of about 1.5-2 m and bench terracing with side slopes 8-15%. The side and branch gullies should be plugged.
The cost of reclamation is repayable in 7-8 years with irrigated agronomical or horticultural crops. Dendrocalamus, Agave, Arundo donax, Acacia and Prosopis spp., and Dalbergia sissoo may be planted in stabilized gully beds. Construction of staggered trenches on irregular ravine terrains has been found highly beneficial.
Vegetative barrier of Ipomea carnea near the bank of river helps the soil to resist from being eroded easily by the flowing water. Also, the plantation of Taramarix dioica, Prosopis juliflora near the bank of river resists the silt laden flowing water and results into silt deposition.
In classes V and VI lands along the banks of torrents in Doon valley, it has been found economical to grow Dalbergia sissoo, Acacia catechu for fuel and Chrysopogon for grass and Eulaliopsis binata for fibre. For all treatment combinations the benefit-cost ratio was more than unity. For fuel wood purposes, the trees at a closer spacing of 4.55 m x 4.55 m or 9.15 m x 9.15 m was found more profitable.
Three varieties of pine apple namely Queen, Kew and Giant Kew were found successful at Dehradun. Vegetative covers like Kudzu vine (Peuraria hirsuta), Dichanthium annulatum, Chrysopogon fulvus and Eulaliopsis binata provided good protection to soil on 11% slope.
Landslide can be successfully controlled through mechanical measures such as gabion, check dams with wide aprons, inward sloping and projecting masonry spillways.
Biological measures such as contour witling, mulching and planting of Ipomea carnea, Vitex negiindo, Napier for quick covers and Erythrina suberosa, Dalbergia sissoo and Acacia catechu for permanent covers have been found suitable for stabilisation of landslides. The technology is available for transfer.
Torrent beds and old river beds which are unfit for cultivation of agricultural crops have been profitably used for growing hybrid napier (NB-5 and NB-21). Trees such as Prosopis juliflora (on hump and side slopes), Acacia nilotica (on side slopes) and Dendrocalamus strictus (on beds) and grasses such as Dichanthium annulatum have been found useful for ravine control.
3. Conservation Practices for Non-Agricultural Lands:
Erosion is serious problem on land classes V, VI, VII and VIII due to limitations of slope, stoniness, rockiness, shallow depth, wetness, etc. Establishing vegetative cover is one of the most effective ways of soil and water conservation in such soils.
Soil and water conservation research centres all over the country, therefore, have endeavored to select grasses and trees which will not only protect the land but will produce fodder, fibre, fuel and timber (Table 12.9).
A number of tree species, such as those given below (Table 12.10), have been introduced by Soil Conservation Research Centres for protective and productive purposes in denuded and eroded areas.
4. Projection of the Problem:
The Central Soil and Water Conservation Research and Training Institute and its regional centres during the last two and half decades have provided many solutions to local problems and developed techniques for not only conserving the production base but also increasing production of food, fodder, fuel, fruits, fibre, timber, etc. from all land uses.
The techniques for conserving and increasing production from agricultural lands in the watershed comprise of contour cultivation, contour bunding, graded bunding, bench terracing, grassed waterways, watershed harvesting, water storage and water application.
While accomplishments are substantial, looking at the problems, there would be heavy pressure on land-water-plant system by human and cattle in future. The human population which increased from 361 million in 1951 to 548 million in 1971 will be 931 million by the year 2000 A.D. The net area per capita, which decreased from 0.9 ha in 1951 to 0.6 ha in 1971, will further decrease to 0.35 ha by 2000 A.D.
Though the cultivated area increased from 119 million hectares in 1951 to 140 million hectares in 1971, the per capita availability of land for production of food, fibre and other needs shrank from 0.33 to 0.29 ha and this will further be decreased to 0.18 ha by the year 2000 AD.
It is projected (Table 12.11) that if the cost of development is kept at the sixth plan price and provision is made for an increasing target of 3.5 million hectares in every 5-year plan, we shall be able to treat only 90 million ha of land by the end of Tenth Five Year Plan at the cost of 66741 million rupees.
These projections do not take into account the cost of maintaining or rebuilding the work, the life of which is generally estimated to be 15 years under field conditions. To achieve this level of development, it will also be necessary to train sufficient manpower.
Conservation of soil and water cannot be achieved without considering practically all the art and science involved in agriculture. Factors in general include physical, biological and economic interwoven such that any change in one usually effects a change in the other.
Two types of basic informationâ€™s must be developed for efficient application of a conservation practice. The first type relates with the knowledge of the forms of manifestation, natural distribution, intensity, frequency of occurrence, etc. of natural forces and resistances to be dealt with, as well as the range of variation within which each can be manipulated.
The second type of information deals with the analysis and evaluation of the effects and interactions of forces and resistances. An analysis of these forces and resistances will help segregate the elements of the problem and furnish leads to the research necessary for its solution. Following is an outline of fundamental factors in soil and water conservation.
I. Forces involved in soil erosion, sedimentation, runoff and water management:
Form, distribution (seasonal, annual, cyclic), intensities, amount, impact characteristics (drop size and velocity)
B. Solar Radiation Affecting:
(1) Temperature: (a) air; (b) soil; (c) water; (d) plant (governing evapotranspiration)
(2) Photosynthesis (rate of cover development)
(3) Permeability: (a) Surface; (b) sub-surface
(4) Moisture: (a) form; (b) content; (c) tension
C. Gravity Affecting:
(1) Water movement: (a) Surface â€” sheet and channel; (b) sub-surface movement; (c) fluid properties
(2) Ice movement: (a) in stream; (b) mass
(3) Soil movement; (a) in mass; (b) in flowing water; (c) deposition
D. Molecular Forces Affecting:
(1) Soil: (a) swelling; (b) shrinking; (c) slaking; (d) dispersion; (e) drying; (f) cementation
(2) Water: (a) evaporation; (b) capillary
(3) Soil solution: (a) base exchange; (b) leaching and flushing
(1) Velocity and turbulence
(3) Distribution and duration
II. Resistance to forces involved in soil erosion, sedimentation, runoff and water use and management
(1) Size of particles: (a) dispersed (texture); (b) aggregated
(2) Structural stability: (a) cohesion and adhesion
(1) Snow: (a) insulation; (b) moisture absorption; (c) flow retardation
(2) Vegetal: (a) growth characteristics; (b) density; (c) seasonal protection; (d) evapotranspiration
C. Watershed Characteristics:
(3) Slope â€” concave or convex, steep or flat, long or short
(5) Drainage pattern and density
D. Channel Characteristics:
(1) Shape and area of cross-section
(4) Erodibility of bed and bank