Plant nutrients chemical sources

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. 

Since the chemical composition of alluvium obviously depends upon the source of the material, one can only make general statements about plant nutrient contributions that are related to alluvial processes. Soils vary widely as to their plant nutrient contents, as shown in Table 9.4. It should be recalled that, at most, only 5 to 10% of these totsil amounts is likely to be solubilized in any given year. Using the figure of 0.45 Tg of sediment per day carried by the Mississippi River at St. Louis, and assuming 5% dissolution of plant nutrients contained in the sediment, an estimated 90—2000 Mg of available nutrients is transported daily by this river alone. The sediment plus contained nutrients is either laid over or extends existing deposits. For example, the Po River extends its delta by about 8 X 10 m y". ... 

It is often implied that nutrients used in organic cropping systems are natural as opposed to the s5mthetic or chemical sources used in conventional systems. Actually, any effort to difierentiate foods from a nutrient source standpoint is of limited use because, whether the source of nutrients is organic or inorganic, all nutrients are chemical . .. all are natural and exist in nature. .. and all nutrients are absorbed by the plant in the soluble inorganic form. The natural versus s5mthetic distinctions are not defensible on the basis of science. 

Air, water, soil, and food are all unavoidable components of the human environment. Each of those elements influences the quality of human life, and each of them may be contaminated. Food is not only the elementary source of nutrients, but may also contain natural chemical substances with toxic properties, e.g., cyanogenic glycosides (many plants), solanine (green parts of potatoes, sprouted potatoes, and potatoes stored in light), industrial pollutants (heavy metals), biogenic amines (fish), or mycotoxins (moldy foodstuffs). 

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