Land Suitability for Irrigated Agriculture in Southern Tohama Plain, Saudi Arabia

Abstract

The Tohama plains are the important geomorphologic features in the south western region of Saudi Arabia, which receive relatively high quantities of runoff water from the surrounding hills. Soils of Southern Tohama plain are the most important source of available land resources. This research was carried out to evaluate the soils of the main landforms of Tohama plains for sustainable agricultural production, according to type, number and degree of agriculture limitations. Forty two soil profiles representing the main landforms were selected. Soil characteristics were rated for different systems of irrigation, irrigated agriculture and specific crops according to the recommended methods. Seven crops were selected for evaluation i.e. sorghum, mango, banana, pineapple, watermelon, tomato and green pepper. Generally, land suitability classes; highly suitable land (S1) is quite limited and represented by soil profile No. 31 (alluvial plain). Many crops are very suitable in these soils, such as; fruits; field crops and vegetables. Moderately suitable land (S2) have moderate limitations and represented by wadis (Profiles 25 and 34), pediplain with deep soils (Profiles 4, 5, 6, 7, 11, 13 and 18) and alluvial plain (Profiles 26, 27, 29, 35, 40 and 42). Most of these lands can be cultivated with following crops in the order: mango, pineapples, water melon, green pepper, tomato, sorghum and banana. Marginally suitable land (S3) have limitations which in aggregate are severe and represented by coastal plain (Profiles 2, 9, 16, 17 and 24), wadis (Profiles 3 and 30), pediplain with deep soils (Profiles 10, 12, 14, 19, 20, 21 and 22), alluvial plain (Profiles 28, 32, 33, 38, 39 and 41) and footslopes (Profiles 36 and 37). Most suited crops are in the order: mango, water melon, green pepper, pineapples, tomato, sorghum and banana. Currently not suitable (N1) have sever limitation and can't be corrected at currently acceptable cost, and represented by the dry sabkhas (Profiles 1, 8, 15 and 23), these soils require high input levels for leaching salts and improving drainability.