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Managing Nitrogen |
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All plants need nitrogen from their environment to grow. Nitrogen is the essential nutrient in synthesizing protein to build tissues that are used in repair and growth (Nutrient Pollution). In natural systems, nitrogen inputs and losses are balanced. Farms represent a managed environment, and the nitrogen cycle is altered. After each harvest, much of the nitrogen that the plant had in its tissues is lost from the immediate environment (the field). ... Excess nutrient application and soil erosion cause nitrogen and phosphorus to run off into waterways, where they cause many environmental problems (IFPRI). Like all other minerals, nitrogen has a cycle, from air to plant to soil and back. Here is a simplified diagram of the nitrogen cycle: (The Nitrogen Cycle) Although nitrogen is essential for healthy plant functioning and growth, excess nitrogen that runs off farms is a major problem, both for the farmer and for the environment. ... In particular, nitrogen causes pollution in water bodies by increasing the process of eutrophication. ... Nitrous oxide, another nitrogen product, is a greenhouse gas (OECD 120). ... Recognizing that nitrogen pollution is a serious problem, most countries have laws or voluntary regulations in place to help curb runoff. ... (NOTE: in the hard copy, I drew a diagram of a farm’s layout, using my own idea) Dairy farms often have levels of nutrients which are too high; these farms are termed “eutrophic,” the same term used for aquatic environments that have too much nitrogen and phosphorus. ... There are many things that could be done on the hypothetical farm that would help improve nitrogen use efficiency and thus reduce runoff. ... The Organization for Economic Co-operation and Development has created a simple diagram of nitrogen balance on the farm: (NOTE: in the hard copy, I drew a diagram derived from the one in the OECD book) The most significant inputs for a small farm are manure and biological nitrogen fixation. Although it is not entirely correct to assume that atmospheric deposition would equal nitrogen loss back into the air, for this model it is assumed that they are balanced. If the farm is properly managed, only negligible amounts of nitrogen will make it into the soil and water. Therefore, the farmer seeks a balance between manure input and leftover soil nitrogen from legumes and recycled crops (inputs) and the harvested crop (outputs). ... Or, the farmer could plant wheat in the field during spring through fall, and then plant clover during the winter to use as groundcover that protects the soil, to return nitrogen to the soil (clover is a legume), or for livestock to use as pasture. ... This works because legumes, such as soybeans, have beneficial bacteria that live in their roots and efficiently process nitrogen underground. The nitrogen gets left behind when the legumes are harvested, and future crops can use this nitrogen. ... Rotation using a cycle of grasses and legumes is the most effective way to build up the soil’s organic matter layer—the dense mat of roots from this system secures the soil during winter months, and the legumes replace some of the nitrogen content of the soil (Tivy 67). “It is estimated that a good legume crop will increase the nitrogen content in the soil by over 100-200 kg per hectare per year in temperate regions” (Tivy 68). ... Reducing erosion therefore ensures the retention of much of the soil nitrogen. ... Nitrate concentrations in polluted waters are highest during winter, because the nitrogen stored in the soil leaches out when precipitation begins to exceed evapotranspiration rates (Tivy 258). ... Disadvantages to organic fertilizers include: a varying nutrient content; soil retention of nutrients (1/3 of nitrogen is used right away, and the rest is locked up in the soil and then slowly released); and human sludge can contain toxic levels of unnecessary trace metals (Tivy 68). ... Incorporation or mixing into the soil greatly reduces losses of nitrogen to the air and keeps more in the soil where it is needed” (Georgia). ... Composting reduces odors and also stabilizes nitrogen from the unstable ammonia form, making it safer for household use (EPA 17). |
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Title: Managing Nitrogen
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