Phosphorus is an essential nutrient for plants as no other nutrient can replace it in its roles in plant growth. It plays a key role in several plant processes but its primary purpose is to store and transfer the energy produced by photosynthesis. When phosphorus is deficient the plants will be stunted and can have a darker green colour than normal. Since it is also involved in the transformation of starches and sugars, under deficient conditions sugars can accumulate and create reddish-purple blotches.
Figure 1: The terrestrial phosphorus cycle [Source: http://upload.wikimedia.org/wikipedia/en/9/91/Phosphorus_Cycle_copy.jpg]
Phosphorus has a permanent place on fertilizer recommendations as it is regularly found to be deficient. The most common source is mined rock phosphate which is processed to produce the fertilizer that is spread on fields. It comes either as solely phosphorus (Superphosphate) or combined with Nitrogen (MAP or DAP). After application the phosphorus has several fates, as shown in Figure 1; it can leach down, be taken up by plants and then off the field with the crop, or it can be removed through run-off or erosion.
While a useful nutrient for growing terrestrial plants, phosphorus is also the limiting nutrient in aquatic ecosystems. An increased concentration supports a larger population of algae which can cause problems for other organisms. When the algae die off, the oxygen that is used during the decomposition is no longer available for plants, fish, or animals.
While a useful nutrient for growing terrestrial plants, phosphorus is also the limiting nutrient in aquatic ecosystems. An increased concentration supports a larger population of algae which can cause problems for other organisms. When the algae die off, the oxygen that is used during the decomposition is no longer available for plants, fish, or animals.
Figure 2: The aquatic phosphorus cycle [Source: http://upload.wikimedia.org/wikipedia/en/e/eb/Phoscycle-EPA.jpg]
A study completed by Winter et al. (2007) evaluated the major sources of phosphorus to Lake Simcoe from 1998 to 2004 which included septic tanks, urban runoff, sewage effluent, atmospheric, the Holland Marsh, and tributaries. Of these sources the Holland Marsh, an intensive area of agriculture, contributed the least amount, between 1 and 5%, over the studied years in comparison to the other sources (Figure 3).
Figure 3: The major sources of total phosphorus to Lake Simcoe for hydrologic years 1998/99-2003/04 (Winter et al., 2007)
References
- MSU Extension Service. (2014, August 21). Why is my young corn stunted and purple?. In Corn in Mississippi. Retrieved from http://msucares.com/crops/corn/corn_stunted.html
- Plant and Soil Sciences eLibrary. (2014). Importance of Phosphorus to Plants. In Soils - Part 6: Phosphorus and Potassium in the Soil. Retrieved from http://passel.unl.edu/pages/informationmodule.php?idinformationmodule=1130447043&topicorder=2&maxto=15&minto=1
- Rehm, G., Schmitt, M., Lamb, J., Randall, G., & Busman, L. (2002). Understanding phosphorus fertilizers. In University of Minnesota Extension. Retrieved October 9, 2014, from http://www.extension.umn.edu/agriculture/nutrient-management/phosphorus/understanding-phosphorus-fertilizers/
- Winter, J. G., Eimers, M. C., Dillon, P. J., Scott, L. D., Scheider, W. A., & Willox, C. C. (2007). Phosphorus inputs to Lake Simcoe from 1990 to 2003: Declines in tributary loads and observations on lake water quality. Journal of Great Lakes Research, 3(2), 381-396.
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