In the example in Table 2, banding the P at a lower rate resulted in the same yield as those based on crop removal recommendations.This illustrates the effect that banding P can have on reducing the corn crop’s overall P requirements. Most animal manure research interpretations indicate that approximately 60 to 80 percent of the total P is available to crops in the first year.ĭue to the chemical composition of other organic P sources such as bone meal, expect lesser amounts of plant-available P compared to total P.Ĭrop removal is common in many areas of the state. The combination of the organic-inorganic P ratios in the organic P sources and the soil environment affect the availability coefficient for organic P. The final decomposition product is orthophosphate P compounds. Much of the organic P is easily decomposable in the soil, but factors such as temperature, soil moisture and soil pH all have a bearing on the P mineralization rate. Organic P constitutes the remaining total P. Generally, 45 to 70 percent of manure-P is inorganic P. Consider P feed supplements and the fact that many could be considered P fertilizers as well. Chemical makeupĭiet fed to the animal has some control over this chemical makeup. Essentially, all inorganic P is in the orthophosphate form, which is the form taken up by growing plants. The P contained in organic P sources combines inorganic and organic P. More importantly, the processes have no effect on the availability of P to plants. The cost of converting rock phosphate to the individual phosphate fertilizers varies with the process. The P present in these two fertilizers is in the orthophosphate form. When ammonia is added to phosphoric acid that hasn’t been heated, it produces monoammonium phosphate (11-52-0) or diammonium phosphate (18-46-0), depending on the ratio of the mixture. The P in these products is present in both the orthophosphate and polyphosphate form. The 10-34-0 can be mixed with finely ground potash (0-0-62), water and urea-ammonium nitrate solution (28-0-0) to form 7-21-7 and related grades. The liquid, 10-34-0, is the most common product. Adding ammoniaĪmmonia can be added to the superphosphoric acid to create liquid or dry materials containing both nitrogen (N) and P. Upon contact with soils, polyphosphates revert back to orthophosphates. Polyphosphates consist of a series of orthophosphates that have been chemically joined together. The P in this acid is present as both orthophosphate and polyphosphate. The phosphate concentration in superphosphoric acid usually varies from 72 to 76 percent. The phosphoric acid produced by either the wet or dry process is frequently heated, driving off water and producing a superphosphoric acid. Orthophosphoric acidīoth the wet and dry treatment processes produce orthophosphoric acid, the phosphate form that’s taken up by plants. The impurities that give the acid its color haven’t been a problem in the production of dry fertilizers. The wet process involves treating the rock phosphate with acid-producing phosphoric acid – also called green or black acid – and gypsum, which is removed as a by-product. This treatment produces a very pure and more expensive phosphoric acid – frequently called white or furnace acid – primarily used in the food and chemical industry.įertilizers that use white phosphoric acid as the P source are generally more expensive because of the costly treatment process. In the dry process, an electric furnace treats rock phosphate. Figure 1: The process used to manufacture various phosphate fertilizers.
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