1. Introduction
1.1. General
The term “Oases” was initially applied to small areas in Africa and Asia, typically supporting trees and cultivated crops with water supply from springs and from water seepage, originating at some distance (Gad, 2008). The main objective of this study is to develop a GIS based model for land capability classification in the western desert Oases.
Land Capability is the “quality” of land to produce common cultivated crops and pasture plants without deterioration over a long period of time (FAO, 1983). Wells (2001) defined land capability as “the ability of land to support a particular type of use without causing permanent damage”. Land capability classification categories are subdivided into capability classes and subclasses. The soil, as the main component of land capability classification system, takes into consideration soil limitations, risk of damage when soils are used, and the way in which soils respond to treatment. Capability classes range from Class I soils, which have few limitations for agriculture, to Class VIII soils, which are unsuitable for agriculture. The land capability classification provides a guide for the assessment of soil constraints and land management recommendations for use at a range of scales including state, catchment and the property planning level ( Murphy et al., 2004).
The first land capability classification (LCC) was developed, in USA, by Soil Conservation Service (now called the Natural Resource Conservation Service) in the late 1930’s and early 1940’s. The LCC is a three level classification, consisting of capability class, capability subclass, and capability unit. Land was placed in a class based on landscape, slope, soil depth, texture and acidity. Subclasses were identified for special limitations such as erosion, excess wetness, problems in the rooting zone, and climatic limitation. Land capability units were identified as grouping of soils with similar levels of yield and common requirements for land management. Procedures to classify soils, according to the LCC, needs an elaboration of detailed soil survey in addition to information on slope, erosion, and land use.
There are many approaches in land capability classification according to the collected samples and land cover data. The earliest formal systems, based on scores for soil and land properties, were developed in Germany in the 1930’s. In recent studies, the collected soil samples are chemically and physically analyzed while some soil parameters are measured in the field or interpreted from the enhanced ETM+ images. These parameters include climatic condition, texture, soil depth, CaCO3%, gypsum%, gravel%, salinity, alkalinity, slope and drainage pattern (Stori, 1964, Sys, 1991 and Arnous and Hassan, 2006). These parameters are assessed by applying remote sensing and GIS techniques (Panhalkar, 2011), as they are powerful tools for collecting information at a very low cost and high accuracy. Moreover, the use of GIS lies in its capability for modeling, constructing models of the real world from the digital database and using the models to simulate a given scenario.
Progress in GIS technologies allows to process large amounts of spatial data and to provide more accurate and accessible information about the land (Arnous and Hassan, 2006). The use of spatial analyses techniques, in evaluating the land capability, support the production of multi-thematic maps. The created database would help in outlining the limiting factors, accordingly suitable suggestions for sustainable agricultural use (Ali et al., 2007).
บทนำ1.1. ทั่วไปพื้นที่เล็ก ๆ ในแอฟริกาและเอเชียมาที่ระยะห่างบาง (กาด 2008) สนับสนุนต้นไม้และน้ำ จากน้ำพุ และ จากการไหล ซึมของน้ำ ปลูกพืชโดยทั่วไปเริ่มใช้คำว่า "เครื่องเทศ" วัตถุประสงค์หลักของการศึกษานี้คือ การพัฒนา GIS ที่ใช้รูปแบบการจัดสามารถที่ดินในทะเลทรายตะวันตกเครื่องเทศที่ดินมี "คุณภาพ" ของที่ดินในการผลิตพืชปลูกทั่วไป และทุ่งหญ้าพืชไม่เสื่อมระยะยาวเวลา (FAO, 1983) การ ความสามารถที่ดินบ่อ (2001) กำหนด "ความที่ดินสนับสนุนบางชนิดใช้ไม่ก่อให้เกิดความเสียหายถาวร" ที่ดินสามารถจำแนกประเภทจะถูกแบ่งออกเป็นความสามารถในการเรียนและระดับ ดิน เป็นส่วนประกอบหลักของดินสามารถจำแนกระบบ ที่นำมาพิจารณาข้อจำกัดดิน ความเสี่ยงของความเสียหายเมื่อมีใช้ดิน และวิธีการที่ดินที่ตอบสนองต่อการรักษา ช่วงชั้นความสามารถจากระดับฉันดิน ซึ่งมีข้อจำกัดบางอย่างสำหรับการเกษตร ดินที่ระดับ VIII ซึ่งไม่เหมาะสำหรับการเกษตร การจัดประเภทความสามารถที่ดินให้คำแนะนำสำหรับการประเมินข้อจำกัดดินและคำแนะนำการจัดการที่ดินเพื่อใช้ช่วงของเครื่องชั่งรวมทั้งสถานะ ลุ่มน้ำ และลักษณะของการวางแผนระดับ (เมอร์ฟี et al. 2004)The first land capability classification (LCC) was developed, in USA, by Soil Conservation Service (now called the Natural Resource Conservation Service) in the late 1930’s and early 1940’s. The LCC is a three level classification, consisting of capability class, capability subclass, and capability unit. Land was placed in a class based on landscape, slope, soil depth, texture and acidity. Subclasses were identified for special limitations such as erosion, excess wetness, problems in the rooting zone, and climatic limitation. Land capability units were identified as grouping of soils with similar levels of yield and common requirements for land management. Procedures to classify soils, according to the LCC, needs an elaboration of detailed soil survey in addition to information on slope, erosion, and land use.There are many approaches in land capability classification according to the collected samples and land cover data. The earliest formal systems, based on scores for soil and land properties, were developed in Germany in the 1930’s. In recent studies, the collected soil samples are chemically and physically analyzed while some soil parameters are measured in the field or interpreted from the enhanced ETM+ images. These parameters include climatic condition, texture, soil depth, CaCO3%, gypsum%, gravel%, salinity, alkalinity, slope and drainage pattern (Stori, 1964, Sys, 1991 and Arnous and Hassan, 2006). These parameters are assessed by applying remote sensing and GIS techniques (Panhalkar, 2011), as they are powerful tools for collecting information at a very low cost and high accuracy. Moreover, the use of GIS lies in its capability for modeling, constructing models of the real world from the digital database and using the models to simulate a given scenario.Progress in GIS technologies allows to process large amounts of spatial data and to provide more accurate and accessible information about the land (Arnous and Hassan, 2006). The use of spatial analyses techniques, in evaluating the land capability, support the production of multi-thematic maps. The created database would help in outlining the limiting factors, accordingly suitable suggestions for sustainable agricultural use (Ali et al., 2007).
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