Soil Fertility Enhancement in Mediterranean-type Dryland Agriculture: A Prerequisite for Development
Historically, the major factors dictating the growth of the various civilizations that flourished in the Middle East were the availability of water and fertile soils. Sustained cropping was only possible when the soils were rich in nutrients or where fertility was regenerated through flood-borne sediments. While the dominant constraint today to grow crops is still inadequate moisture, due to low and erratic rainfall and limited water supplies, economic crop production is not possible without an adequate supply of the essential nutrients, either from the soil or added as fertilizers or manures. As with soils elsewhere in the world, the native fertility of the Mediterranean region is insufficient to continuously support economic yields of modern crops. Research during the past three to four decades, a time when chemical fertilizers began to be used extensively in the region, has established the essential need for fertilizer nitrogen (N) in all but the most drought—stressed areas. Similarly, the calcareous nature of most soils in the region is such that native phosphorus (P) fertility is low, and thus without added P fertilizer only meager crop yields are possible. Fortunately, other important crop growth elements such as potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S) are well supplied in the region's weakly weathered and poorly leached soils. In recent years, awareness has developed of the importance of micronutrients for crop production, and deficiencies of iron (Fe) and zinc (Zn) are common, while both boron (B) deficiency can occur, as well as toxicity of the element. This brief overview of various aspects of soil fertility and plant nutrition in the primarily dryland Mediterranean region gives a chronology of developments in soil fertility and related plant nutrition and a “birds-eye” view of the main research accomplishments. While much of the work reported comes from countries of the region where the author has worked (Syria, Morocco, and Lebanon), the findings are applicable to the region as a whole, given the similarity of the region's soils and climate; indeed much of the work reported was from collaboration with scientists in other countries of the Middle East region (e.g., Libya, Tunisia, Algeria, Iraq, Iran, Jordan, Turkey, Cyprus, and Spain) through various research networks. Future soil fertility and fertilizer research will involve greater use of soil analysis to identify nutrient constraints; adaptation to the nutrient needs of improved crop cultivars and indeed new crop interaction of nutrients, especially N with soil moisture; more efficient use of fertilizers in a systems context and with conservation tillage; and an awareness of environmental and human health issues.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2004. . Copyright © 2004 by the Crop Science Society of America, American Society of Agronomy, 5585 Guilford Rd., Madison, WI 53711 USA