Crop Nutrients for Sustainable Agricultural Production in the Drought-Stressed Mediterranean Region

Most areas of the world where rainfall is limiting are characterized by low agricultural output and, ironically, high population growth rates that generate increased food de-mand. Arid and semi-arid regions permit a range of vegetative biomass production, from rainfed crops to native pasture, and sparse steppe shrubs to true desert. Given the harsh climatic conditions in areas such as West Asia-North Africa, where less than ۱۰% of the land area is amenable to rainfed cropping, soil resources are fragile and cropping condi-tions precarious. Yet with appropriate manipulation of soil fertility and crop management within a systems context, including breeding of improved cultivars, conservation tillage, and rotations, substantial production increases can occur at the farmer's level. While irri-gation has increased considerably in the past few decades, having a major impact on crop yields, surface and ground water sources remain limited. Applied research specific to the region has shown that crop output can be considerably enhanced with adequate nutrition, most of which has to be added as commercial fertilizer. The substantial yield increases that have taken place in several countries of the region have been attributed to three fac-tors: water, fertilizers, and improved varieties. Technologies that potentially produce such high yield increases include identification of nutrient stresses and taking corrective action, and, where appropriate, adapting the plant to the soil conditions. If managed properly, innovative cropping systems to overcome these constraints can improve rather than de-grade soil conditions. Regardless of the advances in biotechnology, crop adaptation, and integrated cropping systems, chemical fertilizers will, in future, play an even greater role in the nutrition of both rainfed and irrigated crops in Mediterranean agriculture. Crop nutrition research will have to keep pace with agronomic developments. The future chal-lenge in soil fertility-crop nutrition lies as much in overcoming obstacles to technology transfer as in the generation of new knowledge. This selective review is based mainly on the author’s research experiences in the field of soil fertility and crop nutrition in the WANA region for the past ۳۲ years. It seeks to highlight research developments within the context of the region's crop production constraints, culminating in a perspective on future research challenges within the framework of cooperation between international in-stitutions and the region’s national research and development programs.

Keywords:

Irrigated cropping , Mediterranean agriculture , Micronutrients , Nutrient dynamics , Nitrogen fertilizer use , Phosphorus