GIS-based fuzzy membership model for crop-land suitability analysis T.R. Nisar Ahamed, K. Gopal Rao, J.S.R. Murthy * Department of Civil Engineering, Indian Institute of Technology, Powai, Mumbai 400 076, India Received 4 December 1998; received in revised form 16 May 1999; accepted 17 June 1999 Abstract Crop-land suitability analysis is a prerequisite to achieve optimum utilisation of the avail- able land resources for sustainable agricultural production. The Food and Agricultural Organisation [FAO, 1976. A framework for land evaluation (Soils Bulletin No. 32). FAO, Rome.] recommended an approach for land suitability evaluation for crops in terms of suit- ability ratings from highly suitable to not suitable based on climatic and terrain data and soil properties crop-wise. The assignment of a given area element (pixel) to any one suitability class is encountered with problems due to the variation of soil properties within the area as well as matching of the soil properties with more than one suitability class to dierent extents. The Boolean methods are designed to assign a pixel to a single class and no provision exists for assigning partial suitability to each of the appropriate suitability classes. In the present study the use of fuzzy (partial) membership classi®cation is used to accommodate the above uncertainty in assigning the suitability classes to the pixel. The evaluation of the spatial variability of relevant terrain parameters is carried out in a geographic information system environment while assigning the land suitability for crops in the study area of Kalyanakere sub-watershed in Karnataka. Nine parameters (eight of soil and one of topography) are con- sidered and suitability analysis is carried out by fuzzy membership classi®cation with due weightage factors included to accommodate the relative importance of the soil parameters governing the crop productivity. According to the ®eld information, the crop being grown in maximum area is ®nger millet. However, the crop-land evaluation results of the present study reveal that maximum area is potentially suitable for growing ground nut. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Land evaluation; Suitability criteria; Classi®cation; Fuzzy membership; GIS 0308-521X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0308-521X(99)00036-0 Agricultural Systems 63 (2000) 75±95 www.elsevier.com/locate/agsy * Corresponding author. Tel.: +91-22-578-2545; fax: +91-22-578-3480. E-mail address: jsrmty@civil.iitb.ernet.in (J.S.R. Murthy).