Nutrients in fertilizers

Examples of the use of FIA with ISE detection involve the determination of nitrate and total nitrogen in environmental samples [48, 49, 125, 166], potassium, sodium [125], calcium [51] and urea [124] in serum or major nutrients in fertilizers [73]. An interesting combination of an ISFET sensor with the FIA principle [52] is shown in fig. 5.17. This is a simultaneous determination of potassium, calcium and pH in serum during dialysis on an artificial kidney. 

Although the most prominent use of saltpeter is for the production of black powder, potassium nitrate is also used as fertilizer. In the first half of the 17th century, Johann Rudolf Glauber (1604-1668) obtained saltpeter from animal pens and discovered its use to promote plant growth. Glauber included saltpeter with other nutrients in fertilizer... 

The oxy anions nitrate, sulfate and phosphate serve as important nutrient sources for plants. Chlorine is essential for plants in trace amounts. Nitrogen and phosphorus, together with potassium, are the most abundantly used nutrients in fertilizers (Bach et al. 1999). Sulfate and chloride salts accumulate in saline soils. 

M. Koshino, Determination of Major Nutrients in Fertilizers [in Japanese]. Bunseki, 11 (1978) 803. 

Secondary and Micronutrients in Fertilizers The great majority of farm fertilizers are produced, marketed, and appHed with regard only to the primary plant nutrient content. The natural supply of secondary and micronutrients in the majority of soils is usually sufficient for optimum growth of most principal crops. There are, however, many identified geographical areas and crop—soil combinations for which soil appHcation of secondary and/or micronutrient sources is beneficial or even essential. The fertilizer industry accepts the responsibiHty for providing these secondary and micronutrients, most often as an additive or adjunct to primary nutrient fertilizers. However, the source chemicals used to provide the secondary and micronutrient elements are usually procured from outside the fertilizer industry, for example from mineral processors. The responsibiHties of the fertilizer producer include procurement of an acceptable source material and incorporation in a manner that does not decrease the chemical or physical acceptabiHty of the fertilizer product and provides uniform appHcation of the added elements on the field. 

Plant nutrient sulfur has been growing in importance worldwide as food production trends increase while overall incidental sulfur inputs diminish. Increasing crop production, reduced sulfur dioxide emissions, and shifts in fertilizer sources have led to a global increase of crop nutritional sulfur deficiencies. Despite the vital role of sulfur in crop nutrition, most of the growth in world fertilizer consumption has been in sulfiir-free nitrogen and phosphoms fertilizers (see Fertilizers). 

Agriculture is the largest industry for sulfur consumption. Historically, the production of phosphate fertilizers has driven the sulfur market. Phosphate fertilizers account for approximately 60% of the sulfur consumed globally. Thus, although sulfur is an important plant nutrient in itself, its greatest use in the fertilizer industry is as sulfuric acid, which is needed to break down the chemical and physical stmcture of phosphate rock to make the phosphate content more available to plant life. Other mineral acids, as well as high temperatures, also have the abiUty to achieve this result. Because of market price and availabiUty, sulfuric acid is the most economic method. About 90% of sulfur used in the fertilizer industry is for the production of phosphate fertilizers. Based on this technology, the phosphate fertilizer industry is expected to continue to depend on sulfur and sulfuric acid as a raw material. 

The most productive wetlands are on mineral soils, often developed on alluvial deposits in fiuxial wetlands. Nutrients and fertile sediments seasonally flow into these areas under high rainfall and surface water flow. 

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