Much has been learned about the proper and judicious use of fertilizers. Fertilizer application by farmers has grown from an art to a science. As food producers have strived to increase crop yields by overcoming nutrient deficiencies the use of fertil izers has increased dramatically. This has created a large chemical industry capable of supplying the needed plant food elements. A more complete understanding of soil chemistry and plant nutrition has led to greater fertilizer use with improved fertilization methods and crop cultural practices. Improved fertilizer technology has led to the production of more efficient forms of fertilizer. The modem fertilizer industry and with it fertilization practices began in the humid countries of the world. The use of fertilizers in arid and semiarid regions was later in development, although agriculture had its beginning in semiarid and arid regions. The development offertilizer use is parallel to industrial development in various areas of the world.

Problems of irrigated regions. Soils of arid regions. Soil and water relations. Soil, water, and plant relations. Plant relations to saline and alkali soils. Evaluating land for irrigation. Source and quality of irrigation water. Measuring irrigation water. Field application of water. Irrigation practices for various crops. Effects of irrigation on soil characteristics. Drainage. Reclamation and management of saline and alkali soils. Control of the physical properties od soil. Control of the biological properties of soil. Maintaining available phosphorus in soil. Potassium. Mixed fertilizers. Principles of fertilizer practice. Soil management in fruit production. Special problems in vegetable crop production. Soil management around the home.