Phosphorus limiting factors

Phosphorus (P) is one of the major limiting factors for plant growth in many soils. Plant availability of inorganic phosphorus (Pi) can be limited by formation of sparingly soluble Ca phosphates, particularly in alkaline and calcareous soils by adsorption to Fe- and Al-oxide surfaces in acid soils and by formation of Fe/ Al-P complexes with humic acids (94). Phosphorus deficiency can significantly alter the composition of root exudates in a way that is, at least in some plant species, related to an increased ability for mobilization of sparingly soluble P sources (29,31,71). 

Nutrients—Nutrients, such as nitrogen and phosphorus and other trace elements, are necessary for cell growth because they are key biological building blocks.52,53 Addition of nutrients as a supplement helps ensure that concentrations of nutrients do not become a limiting factor for bioremediation. 

Phosphorus accounts for 2 1% of the dry weight of living cells. The phosphorus content of the environment can be the life-conserving or life-limiting factor (Karl, 2000). 

Enhanced biorestoration is a means by which naturally occurring processes are deliberately manipulated to increase or enhance the rate of cleanup. Biological activity in the subsurface is controlled by the availability of one or more of the necessary metabolic requirements such as an electron acceptor or nutrient. Although electron acceptors are most often the limiting factor, inadequate availability of nitrogen, phosphorus, or micronutrients (such as potassium, copper, or even vitamins) can restrict optimum restoration. When the proper balance of these factors is established, the rate of chemical degradation is maximized. 

If you were use all the phosphorus, you will need 6 times that amount of moles of hydrogen because of the 6 1 mole ratio in the balanced equation. Multiply all the phosphorus (0.03) by 6 = 0.18 mole of hydrogen needed. But you have only 0.12 mole of hydrogen, so you cannot use all the phosphorus. This means that hydrogen is the only one you can use totally, and it therefore is the limiting factor. Just to be certain, if you use all the 0.12 mole of hydrogen, you will need one-sixth of that amount in phosphorus. One-sixth of 0.12 is 0.02 mole of phosphorus. Because the moles of phosphorus present is 0.03, you will have 0.01 mole left over. 

The data in Tables 34-1 through 34-4 show that the accuracy obtainable in the determination of an element is greatly dependent on the nature and complexity of the substrate. Thus, the relative error in the determination of phosphorus in two phosphate rocks was 1.1 % in a synthetic mixture, it was only 0.27%. The relative error in an iron determination in a refractory was 7.8% in a manganese bronze having about the same iron content, it was only 1.8%. In this example, the limiting factor in the accuracy was not in the completion step but rather in the dissolution of the samples and the elimination of interferences. 

Pitkanen, H., Tamminen, T., 1995. Nitrogen and phosphorus as production limiting factors in the estuarine waters of the eastern Gulf of Finland. Marine Ecology Progress Series, 129, 283-294. 

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