Quick-release fertilizers

Quick-release fertilizers Water soluble Slow-release fertilizers Combinations of plant nutrients that are slow to dissolve in water... 

Since urea is relatively quickly metabolized, so-called controlled release fertilizers have been developed. Examples are crotonylidene urea (I) (from urea and acetaldehyde) and isobutylidene urea IBDH (II) (from urea and isobutyraldehyde). The most important are, however, the urea-formaldehyde products of which 191 lO-M were produced in the USA in 1993. 

Phosphate chemistry in soils has been studied more intensively than that of any other element save nitrogen. Phosphate added to soils is first adsorbed quickly and is later fixed into increasingly less soluble states as time increases. Despite this great effort, quantitative predictions of phosphate concentrations in soil solutions are poor and no techniques have been devised to release the large amounts of unavailable phosphate in soils, nor to prevent fixation of fertilizer phosphate by soils. The uncertainties about soil phosphate chemistry and the difficulty of increasing phos-... 

Films of poly(ethylene oxide) are also used to manufacture water-soluble packages for preweighed quantities of fertilizers, pesticides, insecticides, detergents, dyestuffs, and the like. The packages dissolve quickly in water, releasing the contents. They eliminate the need for weighing and offer protection to the user from toxic or hazardous substances. 

The choice of a fertilizer depends on its use and convenience. A fertilizer can be prepared as crystals or a powder, in a liquid solution, or as a gas such as ammonia. The ammonia and ammonium fertilizers are water soluble and quick-acting. Other forms may be made to slow-release by enclosing water-soluble ammonium salts in a thin plastic coating. The most commonly used fertilizer is NH4NO3 because it is easy to apply and has a high percent of N by mass. 

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