Fertigation: An overview of some practical aspects

Fertigation is herein defined as the application of solid or liquid (fluid) mineral fertilizers via pressurized irrigation systems, thus forming nutrient containing irrigation water. Although the practice of fertigation only started commercially in the mid 20th century, there is evidence that the concept of irrigation with dissolved nutrients was well known in the past. The first reported example dates back to ancient Athens (400 B.C.) where city sewage was used for the irrigation of tree groves (Young and Hargett, 1984). Liquid ammonia was probably the first commercially produced liquid fertilizer (New York, 1921), but in modern fertigation the use of ammonia as the nitrogen source is negligible. The increased production of ammonia and other nitrogen solutions led to the development of direct application of these solutions into the soil by mechanical means i.e. through drills, knives and injection tubes etc. This mode of application, although probably used on larger areas than fertigation, will not be discussed in this paper. Fertigation with phosphoric acid was demonstrated by Shell Chemical Company in 1943, and ten years later the first NPK solution was made by mixing phosphoric acid, neutralized with ammonia and with an addition of potash to create ‘4-10-10’ grade solution (Young and Hargett, 1984). One of the major factors to promote modern fertigation was the development of Micro-Irrigation Systems (MIS) which includes drip, jets and micro sprinklers. Field experiments in Israel in the early 1960’s showed that when only part of the field area is irrigated, as in MIS, the use of standard broadcast application of fertilizers is ineffective. The limited root zone and the reduced amount of mineralization in the restricted wetted zone are the main reasons for the reduced nutrient availability to the plant. Recognition of these facts led to the installation of fertigation facilities with almost all applications of MIS.