EXPERIMENT 6 PREPARATION OF LAND CAPABILITY CLASS MAP

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1 EXPERIMENT 6 PREPARATION OF LAND CAPABILITY CLASS MAP Structure 6.0 Objectives 6.1 Intnxluction 6.2 Experiment 6.21 Deciding Factors for Land Capability Requirements 6.23 Procedure 6.3 Observations 6.4 Results 6.0 OBJECTIVES After completing this practical exercise, you should be able to: identify various type ofland classes; and classify the area into different capability classes. 6.1 INTRODUCTION Land and water being most precious natural resources need proper management fur their sustninable availability for different uses. India being a very vast country has a variety of land types available. Based on the certain conditions and thm1l.crerlsticsof the land, a criterion has been developed and accepted to identify the usability ofhmd which is called Land Capability Classification. It is a systematic ~ernent of different kinds of lands based on the properties that determine the ability of the land ID preduee crops on a virtually permanent basis. The grouping of soils into cap:abhityclasses is done primarily on the basis of their capability to produce common cuhivated crops and pasture plants without deterioration over a long period EXPERIMENT 6,.11 ~Cttllng Factors for Land Ca ability The major soil d'-:tractrerishcs of the lsnd include me texture of the lop 'SIoH,its effective depth, p'~bmty of the top suit and subsoil and associated land reatilil'es; ~.:g..'the 'S 'ope of lite l.an'd, the exrent of rerosiqn~the deg!'ee of wetness an'd S\il8'oep't~ibibit0'to ~vetf1lmvin,g.an-ar()'o\b.ng,

2 of use. The land-capability classes range from the best and most easily fanned land and to the land which has no value for cultivation, grazing or forestry, but which may be suited to wild-life, recreation or for watershed protection. They all fall into two broad groups. Preparation of Land Capability Class Map Group 1: Class I to IV: Land Suitable for Cultivation and other Uses Class-I (Green Colour): Soils in class-i have very few or no limitations that restrict their use. This type of land is nearly level and the erosion hazard is low. The soils are deep, well-drained, easily worked, hold water well and are either fairly well supplied with plant nutrients or highly responsive to the application of fertilizers. Soils in this class are suited to a wide range of plants and may be used for cultivated crops, pastures, forests, and wildlife, food and cover. These soils have slight limitations that restrict their use. Class-II (Yellow Colour): Soils in class-il have some limitations which reduce the choice of plants or require simple conservation practices. The limitations of soils in class ITmay result from the effects of one or more of the following factors: (i) a gentle slope, (ii) a slight susceptibility to erosion, (iii) less than ideal soil depth, (iv) occasional damaging overflow, (v) wetness which can be corrected by drainage, but existing permanently as a moderate limitation, (vi) slight to moderate salinity or sodium, easily corrected but likely to recur, and (vii) a slight climatic limitation on soil use and management. They may need one or more of the following practices: terracing, strip cropping, contour cultivation, water disposal area, covered with vegetation crop rotation, cover and green-manure crops, stubble mulching and the use of fertilizers, manure and lime. These soils may be used for growing cultivated crops, raising pastures, forests, and for wild-life, food and cover. These soils have moderate limitations that restrict the choice of plants or may require moderate conservation practices. Class-ill (Red Colour): Soils in class-ill have moderate limitations which reduce the choice of plants or require special conservation practices. When used for cultivated crops, the conservation practices are usually more difficult to apply and maintain. Factors responsible for these soils are: (i) a moderately sloping land, (ii) moderately susceptibility to water or wind erosion, (iii) frequent overflow accompanied with some crop damage, (iv) very slow permeability of the sub-soil, (v) wetness or continuing water-logging after drainage, (vi) shallow soil depth up to the bed-rock, hard-pan or clay-pan which limits the rooting-zone and water storage, (vii) low moisture-holding capacity, (viii) moderate salinity or sodium, and (ix) moderate climatic limitations. These soils have severe limitations that restrict the choice of plants or that require special conservation practices, or both. Class-IV (Blue Color): Soiis in class-iv have severe limitations that restrict the choice of plants and require careful management. The restrictions in the use of these soils are greater than those in class-ill and the choice of plants is more limited. When these soils are cultivated, very careful management is required and the conservation practices are more difficult to apply and to maintain. The use of these soils for cultivated crops is limited as a result of the effect of one or more of the permanent features, such as (i) steep slopes, (ii) severe susceptibility to water or wind erosion, (iii) severe effect of past erosion, (iv) shallow soil, (v) low moisture-holding capacity, (vi) frequent overflow accompanied with severe crop damage, (vii) excessive wetness or continuing hazard of water-logging after drainage, (viii) severe salinity or sodium, and (ix) moderately adverse climate. These soils 27

3 Practical Manual- Fundamentals of Watershed Management can be used for crops, pastures, forests, and wild-life food and cover. These soils have very severe limitations that restrict the choice of plants or that require very careful management, or both. Group 2: Land Not Suitable for Cultivation but Suitable for other Land Uses Class-V (Dark Green or Uncoloured): Soils in class V have little or no erosion hazard, but have other limitations, the removal of which is not practicable. They are used largely for pastures, forests, and wild-life food and cover. Such a land is nearly level and is not subject to more than slight wind or water erosion. Cultivation is not feasible because of one or more limitations, such as overflow, stoniness, wetness or severe climate. Examples of class-viand are (i) soils of lowlands subject to frequent overflows which prevent the normal production of cultivated crops, (ii) nearly level soils with growing season that prevents the normal production of cultivated crops,(iii) the level or nearly level stony or rocky soils and (iv) ponded areas where drainage for cultivated crops is not feasible but where soils are suitable for grasses or trees. Soils in class V are not suitable for raising cultivated crops but are suitable for perennial vegetation (grazing and forestry, with few or no limitation). Pastures can be improved and benefits from proper management can be expected. Physical conditions of soils are such that. it is practicable to apply pasture improvements, if needed, such as seeding, liming, fertilizing, and water control with contour furrows, drainage ditches, diversions of water spreaders. These soils are subject to little or no erosion but have other limitations, impractical to remove, that restrict their use mainly to pasture, rangeland, forestiand, or wildlife habitat, Class- VI (Orange Color): Soils in class-vi have severe limitations that make them un uitable for cultivation and limit their use largely for pastures, or forests, or wild-life food and cover. Soils in this class have continuing limitations which cannot be corrected, such as (i) steep slope, (ii) very severe erosion hazard, (iii) very severe effect of past erosion (iv) stoniness, Cv) shallow rooting-zone, (vi) excessive wetness or overflow, (vii) low moisture capacity, (viii) salinity or sodium, and (ix) severe climate. Soils in this class are subject to moderate limitations under grazing or forestry use. These soils have severe limitations that make them generally unsuitable for cultivation and restrict their use mainly to pasture, rangeland, forestland, or wildlife habitat. Class- VII (Brown Colour): Soils in class-vll have very severe limitations that make them unsuitable for cultivation and restrict their use largely to grazing or forestation or wild-life food and cover. The soils in this Class are subject to severe limitations or hazards under either grazing or forestry use. The physical condition of soils is such that it is not practicable to adopt pasture improvements and watercontrol practices. Soil restrictions are severe than those in the case of class-vi soils. These soils have very severe limitations that make them unsuitable for cultivation and restrict their use mainly to grazing, forestland or wildlife habitat Class- VIII (Purple Color): Soils and land forms in class- vrn have limitations that prevent their use for commercial plant production and restrict their use to recreation, wild-life food and water-supply, watershed protection or for aesthetic purposes. Significant rerum on site benefits from soils and land forms in class vm cannot be expected from management of crops, grasses or trees, although indirect benefits from wild-life, watershed protection or recreation may be possible. Bad lands, rocky outcrops. sandy beaches, marshes, deserts, river wash, mine tailings

4 and other nearly barren lands are included in class-viii in order to protect other more valuable soils to control water or for wild-life or for aesthetic reasons. These soils and miscellaneous areas have limitations that prevent commercial plant. production and restrict their use to recreational purposes, wildlife habitat, watershed, or esthetic purposes. Preparation of Land Capability Class Map Note: The land-capability class is indicated on the maps by romanynumerals I to VIII or by standard colours or by both. ~ Example : The Land capability map of Himachal Pradesh Description Class Area Area Limitations Potentials (000' ha.) (0/0) III Moderate problems Moderately good cultivable IV Moderately steep lands Fairly good land VI Steep lands subject to Well suitable for grazing, severe erosion, forestry and plantation VII Very steep land subject For grazing or forestry, not to erosion arable VIII High erodible gullies Suited only for wild life Requirements and badlands Topographic sheet of study are,a (preferably oflarger scale i.e. 1:250,000) having varying topography; Soil map of the area if possible; Tracing sheet, pencils of different desired colours etc.; and Planimeter, scale etc. for taking areal and length measurements. 6,2.3 Procedure Draw the base map of the study area on tracing sheet with the help of topographic sheet in the background; ~ r. 29

5 Practical Manual- Fundamentals of Watershed Management Identify/delineate the areas/sub-watersheds having different category of general slopes; Calculate the general slopes of these areas and reflect the figures in the respective area polygons; Thus the slope map for the different areas within the study area is prepared; Overlay this slope map over the soil map of the area to identify the soil types/ soil depth etc. in the areas delineated; If soil map is not available and soil properties of the area are available in the table or other form or the soil map is on different scale which is difficult to overlay, the soil properties of area may be extracted/ extrapolated/interpolated and assigned to the delineated area polygons accordingly; Based on the criteria of land capability classification explained above, assign the class for to the delineated areas; Assign/fill the standard colours (specific to the class as mentioned above); and Put the proper legends to complete the land capability map for the study area. Measurements Measure the area of the area delineated under different classes with the help of a planimeter (ern"); Add up the area under same class to get the area under different capability classes; Convert the map area to the geographical area by applying proper scale factor; and Tabulate different classes of the study area with their per cent coverage. 6.3 OBSERVATIONS Area conversion 1 ern" (map): = 0.25 km-on ground (1: 50,000 Scale Topo-sheet) Area conversion 1 cm' (map): = 6.25 km2on ground (1: 2,50,000 Scale Topo-sheet) Example 6.1 A study area of 6,80,625 ha was considered for classification as per the standard capability classes. The areas under different classes measured through a planimeter on map were 234 cm? under class-ill, 457 cm' under class-iv and 398 cm? under class-vi. Calculate the geographical area of these classes in ha and identify the percent area occupied by these classes. Scale of classified map is 1: 250, Solution Scale: 1: 250,000 1 cm? (map): = 6.25 km2(geographical area) = 625 ha (geographical area)

6 S.No. Class Area on map (cm') Geographical Per cent area Area (ha) under class Preparation of Land Capability Class Map 1 III 234 1,46, N 457 2,85, VI 398 2,48, Total 6,80, RESULTS For the sustainable use of our land and other natural resources, it is of utmost importance to understand the limitations of our land and geographical areas. In the same context, the present exercise of understanding the principle and methodology involved in classifying a geographical area into different capability classes was taken up. The procedure of understanding the limitations of the land area and identifying the suitable class category was followed to classify the area under study. The geographical area and perc ent area under different classes was also calculated to have the broader idea of land usability of area under study. 31

Land Capability Classifications

Land Capability Classifications Unit: Soil Science Problem Area: Basic Principles of Soil Science Student Learning Objectives. Instruction in this lesson should result in students achieving the following