Potassium chloride in fertigation

The rapid proliferation of fertigation in modern agriculture has brought about a growing demand for factory mixed fertilizer solutions, as well as wide-scale dissolution of solid fertilizers by farmers in the field. Rules of chemistry and physics control the rate of dissolution and, hence, the nutrient content in the fertilizer solution. Potassium chloride (KCl) is the cheapest potassium-containing fertilizer. Data concerning the dissolution of potassium chloride and other potassium sources are presented below. Introduction Fertigation is the application of solid or liquid mineral fertilizers via pressurized irrigation systems, creating nutrient-containing irrigation water. Although the practice of commercial fertigation started only in the mid 20th century, there is evidence that the concept of irrigation with dissolved nutrients in water was well known in the past. The first reported example dates back to ancient Athens (400 BC) where city sewage was used to irrigate tree groves (Young and Hargett, 1984). One of the major factors in promoting modern fertigation was the development of micro-irrigation systems (MIS) such as drip irrigation, jets and micro-sprinklers. Field experiments in Israel in the early 1960s showed that when localized sections of a field are irrigated, as in MIS, standard broadcasting of fertilizers is ineffective. The limited root zone and the reduced level of mineralization in the restricted wetted zone are the main reasons for the reduced nutrient availability to the plant. When this was recognized, fertigation was integrated in almost all MIS. Israel is an unmatched example of the use of fertilizers by fertigation. The Israeli farmer uses an average of 100, 55 and 75 kg/ha/y of N, P2O5 and K2O, respectively. Over 50% of the N and P2O5 is applied by fertigation. Of the 33,000 tons used annually, approximately 10,000 tons are applied as clear liquid N-P-K, N-K or P-K solutions or soluble complex fertilizers, and another 5,000-10,000 tons are applied as solid KCl dissolved in the field. Fertigation is by far the most common, and in some cases the only, method of fertilizing in greenhouses, orchards, vegetables and drip irrigated field crops such as cotton, maize, jujube, etc. Various sources have shown the advantage of applying K through irrigation water. Potassium ions are adsorbed at the cation exchange sites of soil colloids, but it was shown that lateral and downward mobility of potassium occur