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Agriculture / Soil
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GIS Based Model for Agro-Ecological Zoning: A Case Study of Chitwan District, Nepal
Madan P. Pariyar *, Gajendra Singh**
*Doctoral Student ,
**Professor
Agricultural and Food Engineering Program
School of Environment, Resources and Development
Asian Institute of Technology
Bangkok, Thailand
1.0 Introduction
Agro-ecological zone is a major area of land that is relatively uniform with respect to crop production possibilities. Since climate and soils are two most important natural resources which determine the ability of agricultural land to produce crops, agro-ecological zoning encompasses the delineation of land into regions or zones that are broadly homogenous with respect to climate and soil. The methodologies developed to date for agro-ecological zoning are applicable for rainfed agriculture mainly. Irrigation resource, one of the major resource bases determining crop production largely ignored. The concept of growing period calcuated from rainfall and evapo-transpiration, has been widely used in assessment of climatic resources. But as pointed out of Aggarwal (1993), in today's agriculture, when vast areas are irrigated and multiple cropping is practiced, growing period does not adequately describe the productivity of land.
The overall objective of this research was to demonstrate a methodology for agro ecological zoning using geographic information system. The specific objectives were:
- to develop a GIS based model for agro-ecological zoning; and
- to demonstrate the application of the model with a case study in Chitwan district of Nepal.
2.0 The study Area
The Chitwan district is located at South -Western corner of Narayani zone in Central Development Region of Nepal between longitudes 830 55' to 840 48' East and latitudes 270 21' to 270 46' sq. km. Physiographically, it si divided into Terai, Siwaliks and Middle Mountain Regions and Middle Mountain Regions. About three fourth of the area of the district is a vale whos lands have high agricultural potential and are relatively flat. Over 75% of the annual rainfall occurs during monsoon from June through September with average annual rainfall of 2000 mm
Forest, agricultural lands, pasture/grazing lands settlements and waste lands constitute the major land use cypes in the district. The agro climatic conditions are favourable crops, vegetables and fruits. There are three cropping seasons in a year viz. Monsoon (from June to September) winter (from October to February) and summer (from March to May). The important crops are paddy, maize and millet in monsoon, wheat lentil, potato and buckwheat in winter, and paddy and maize in summer. The cropping patterns are paddy-based in low lands and maize based in uplands.
3.0 Conceptual Framework
Agro ecological zoning includes the following:
a) Creation of a computerized inventory of land resources by bringing together two layers of information on physical environmental resources, viz climate and soil.
b) Creation of agro ecological zones based on climatic feature and soil characteristics which are note markedly influenced by changes in management (Carson 1992).
The conceptual GIS based model for agro-ecological zoning is shown in figure - 1
Fig 1 Conceptual GIS based model for agro-ecological zoning
4.0 Research Methodology
4.1 Creation of primary digital database
The primary databases were created by digitizing the land systems and land capability maps and scale 1:50,000. ARC/INFO version 3.4D plus was used for digitizing and geo-processing.
4.2 Creation of soil resources database.
The soil resources inventory was compiled from land systems report (LRMP, 1986). The various steps followed in the generation of the database were:
- Identification of soil mapping unit characteristics:
- Computer storage of soil data.
- Linkage of soil data to land systems database.
- Field verification of soil data.
- Creation of temperature regimes database.
The temperature regimes database was derived from the land capability coverage 'LANCAP' by grouping and classifying the polygon (land capability mapping units) based on their temperature related characteristics).
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