Phosphorus is an essential plant nutrient and is taken up by plant roots, usually as the dihydrogenphosphate ion, H2PO4-, derived from phosphoric acid, H3PO4. The manufacture of fertilizers that are used to rectify phosphorus deficiencies in soils depends on the availability of supplies of phosphoric acid. Application of phosphoric acid in agriculture: About 90% of the phosphoric acid produced is used to make fertilizers. It is mainly converted into three phosphate salts which are used as fertilizers. They are triple superphosphate (TSP), diamonium hydrogenphosphate (DAP) and monoammonium dihydrogenphosphate (MAP).
In the following, we will introduce you to the use of phosphoric acid in agriculture, which also includes plants and fertilizers.
Since phosphorous acid and its derivatives are not metabolized in plants, claims that phosphonate can contribute to P nutrient requirements for plant growth should be taken with much caution. Phosphours acid is used in agriculture but for a different purpose than phosphoric acid. Confirming other investiga-tions into the efficacy of phosphorous acid against oomy-cetes (a group of pathogens that include water molds and downy mildew), Förster et al. (1998) found that phosphite is capable of controlling Phytophthora root and crown roton tomato and pepper. The authors also tested the ability of phosphorous acid to act as a nutrient source for plant growth and found that P-deficiency symptoms developed when plants were grown hydroponically with phosphorous acid as the sole source of P (without phosphate). This means that although phosphorous acid can control oomycetes in a number of host-parasite systems, it is not a substitute for phosphate fertilization. The inverse is also true: Phosphate is an excellent source of P for plant growth but is unable to control pathogen attack by oomycetes, other than by improving the general health of the crop and, therefore, its natural defense system. At this point, no evidence exists to substantiate the claim that phosphoric acid provides for plant growth this is a Applications Phosphoric acid.
Both phosphoric acid (H3PO4) and phosphorous acid (H3PO3) are agrochemicals essential for crop production. Under normal plant growth conditions, both dissociate and exist as corresponding anions, phosphate and phosphite. A clear distinction exists between the two agrochemical compounds: The former is a nutrient source of P es-sential for plants, and the latter helps control agricultural epidemics of oomycetes. Phosphate and phosphite are not equivalent inside the plant. Phosphoric acid or phosphate cannot function as phosphorous acid or phosphite and vice versa. Since phosphites are systemic and very stable in plants, they should not be applied frequently. To help delay the development of phosphite-resistant oomycetes, care should be taken to alternate or mix phosphite with other effective fungicides. Phosphorus is an essential nutrient for plant growth, but uptake from soil can be difficult and an important limiting factor in achieving optimal yields in agriculture. Even when present in the soil in higher amounts, phosphorus availability to plants is often still problematic because of the phosphate-binding capacity of several types of soil. About 30 % of soil worldwide shows a high phosphate-fixing capacity.
Other application of phosphoric acid in agriculture, Some reports have suggested that almost 80 percent of the phosphoric acid that is produced is used in the production of fertilizer. Phosphoric acid is also used as an additive and flavouring agent in animal or poultry feed. Considerable phosphate fertilizer is used on soils of irrigated regions. If the behavior of liquid phosphoric acid after its incorporation with soil is such that it penetrates into the root zone and is otherwise as efficient as dry phosphate fertilizers in inducing favorable plant response, then it would seem practical to utilize the other advantages offered by applying the fertilizer in irrigation water. Commercial phosphoric acid (52% available P2O5) is produced by applying an excess of sulfuric acid to ground rock phosphate. This phosphoric acid is usually applied to an additional amount of phosphate rock to make concentrated superphosphate. A given quantity of phosphoric acid can yield more available phosphorus by applying it to rock phosphate than by using it directly as a fertilizer.
Because of its potential value in producing concentrated superphosphate commercial phosphoric acid has been used very little as a fertilizer. There is insufficient research in which the comparative value of the acid as a fertilizer has been investigated the purpose of the studies reported in this paper are, to compare: (A) the value of commercial phosphoric acid and concentrated superphosphate as fertilizers when applied in equivalent amounts, (B) the different methods of application and dilution of the phosphoric acid and, (c) Application of phosphoric acid in agriculture.