Delineating prime Farmland Module description

Land capability assessment is done to find out the general capability of the resources of an area for agricultural crops, forestry and other uses. In this assessment, the mapping units occurring in an area are grouped according to their limitations they pose for cultivation, the risk of damage if they are used for the identified use, and the way they respond to management interventions. Normally the criteria used in grouping the units don’t take into consideration any major and costly reclamation measures or conservation techniques that change the slope, depth or characteristics of the soils. This system is not aimed to find out the suitability of the land resources for specific uses or crops. Though the classification was evolved originally to help the soil conservation efforts, but now this system can be used for identifying priority areas, which requires immediate attention and development within a watershed or project areas.  

The capability grouping is based on the inherent soil characteristics, external land features and environmental factors that limit the use of the land for different purposes (I.A.R.I., 1971 and Soil Survey Division Staff, 1993). The following land and soil characteristics are used to group the land resources identified in an area into various classes, subclasses and units. 

          Soil characteristics:  Soil depth, texture, gravelliness, soil reaction, water holding capacity, calcareousness, salinity/ alkalinity etc.

          Land features:  Slope, erosion, rock outcrops and drainage.

          Climate:  Rainfall distribution and length of growing period. 

In the capability system, mapping units are generally grouped at three levels – capability class, subclass and unit. Depending on the level of available information, grouping can be done at any one of the above levels. If the information available for an area is of general nature, then the classification can be done only up to class or subclass level and if it is detailed and site-specific then the classification can be done up to the unit level, which is an equivalent of a management unit for the survey area. Since site-specific and comprehensive database is generated through the Land Resource Inventory for all the watersheds in the project districts, the land resources can be grouped into various land capability units for each watershed area.

Structure of the classification

Capability classes, the broadest groups, are designated by roman numerals I to VIII. The numerals indicate progressively greater limitations and narrow choices for practical use. The eight classes used in the classification are: 

Capability subclasses are formed based on the dominant limitations observed within the capability class. They are designated by adding a lower-case letter like e, w, s, or c, to the class numeral. For example, in subclass IVe, the letter ‘e’ shows that the main hazard in class IV land is the risk of erosion. Similarly, the symbol ‘w’ indicates drainage or wetness as a limitation for plant growth or cultivation (in some soils the wetness can be partly corrected by artificial drainage); the symbol ‘s’ indicates shallow depth, calcareousness, salinity and sodicity or gravelly nature of soil as limitations and ‘c’ indicates climate or rainfall with short growing period as a limitation for plant growth.

The land capability subclasses have been divided into land capability units based on the kinds of limitations present. Ten land capability subclass units are used in grouping the resources of an area, which are indicated below with their symbols 

• Stony or rocky
• Erosion hazard (slope, erosion)
• Coarse textures (sand, loamy sand, sandy loam)
• Fine texture (cracking clay, silty clay)
• Slowly permeable sub soils
• Coarse underlying material
• Salinity or alkali
• Stagnation, overflow, high groundwater
• Soil depth
• Fertility problems

Capability units have almost similar soil and other land characteristics that influence the use of the land resources at the field level. Accordingly, each capability unit is expected to respond uniformly to a given level management. (Note: Under Sujala project, land capability assessment is done only up to land capability subclass and not up to land capability unit levels)

By following the Land capability classification system, the phases mapped or the map units identified at the watershed level can be grouped into various land capability classes, sub classes and land capability units. The various parameters to be considered and their ratings to be used in grouping the land parcels/areas into land capability units are given in the table below. 

Source:

1. United States Department of Agriculture (USDA), 2012, Soil Survey Manual, Handbook No:18, USDA, USA.
2. Natarajan, A., and Dipak Sarkar, 2010, Field guide for soil survey, National Bureau of Soil Survey and Land Use Planning (NBSSLUP), ICAR, Nagpur, India.
3. IARI (1971) Soil Survey Manual, IARI, New Delhi

Table  Parameters and their ratings to be used for land capability units/classes

Step By Step Process

• The web page will have the drop down for selecting District, Taluk, Village, Watershed name, Survey Number.
• User will select the District, Taluk, Village, Micro Watershed and Survey number.
• System will Fetch the information related to selected Survey number.
• System will fetch the Slope, Erosion, Drainage, Soil depth, Texture, Rock out Crops, EC, pH, Permeability for the respective Survey Number.
• System will fetch climate_data to find the climate condition for the respective area.
• System will execute the query on Master Land capability Table to find
  • Class for Climate category against Climate value.
  • Class for Slope category against the slope value.
  • Class for Erosion category against Erosion value.
  • Class for Drainage category against Drainage value.
  • Class for Soil Depth category against Depth value.
  • Class for Soil Texture category against Texture value.
  • Class for Gravels category against Gravel value.
  • Class for Rockout crops category against Rockout_Crops value.
  • Class for EC category against EC Value.
  • Class for pH category against pH Value.
  • Class for Permeability category against Permeability Value.
• If the for all Class Value comes as ‘I’ then update the LCC as ‘I”.
• If any class value is greater than ‘I”, Get highest class value from all above for deciding the LCC. And add the lower case letter like e, w, s, or c to the Class number. e.g, IIIw  , the letter ‘w’ shows that the drainage or wetness is limitation in class III land. Below symbols will be used to show the limitations.
  • e – Erosion limitation
  • w – Drainage Limitation
  • s - Depth, Texture, gravel, rockout crop, EC,pH, Permeability limitation
  • c – Climate Limitation         

• Save the result in Land_Capability Table with Id, Cadastral_ID, LCC, Limitation.
• Fetch the Farmer Name from Land_Parcel_Information table against the selected survey Number. This table will be populated using the web service from BHOOMI.
• Display the result in a table showing the information such as Survey number, farmer Name, area in hectare, Land Capability Classification, Limitation, Arable/Non Arable.