positive nitrogen balance Quick reference
The Oxford Dictionary of Sports Science & Medicine (3 ed.)
... nitrogen balance A condition in which the rate of protein synthesis is greater than protein breakdown or loss, resulting in tissue growth. A positive nitrogen balance is the normal situation for children and expectant mothers. Anabolic steroids accelerate protein synthesis and tend to create a positive nitrogen balance...
positive nitrogen balance
balance
balance Quick reference
A Dictionary of Food and Nutrition (4 ed.)
... With reference to diet, positive balance is a net gain to the body and negative balance a net loss from the body. When intake equals excretion, the body is in equilibrium or balance with respect to the nutrient in question. Used in reference to nitrogen (protein), mineral salts, and energy. A balanced diet is one containing all nutrients in appropriate...
nitrogen balance Quick reference
A Dictionary of Food and Nutrition (4 ed.)
... balance ( N balance ) The difference between the dietary intake of nitrogen (mainly protein) and its excretion (as urea and other waste products). Healthy adults excrete the same amount as is ingested, and so are in N equilibrium. During growth and tissue repair (convalescence) the body is in positive N balance, i.e. intake is greater than loss and there is an increase in the total body pool of protein. In fevers, fasting, and wasting diseases the loss is greater than the intake and the individual is in negative balance; there is a net loss of protein...
Nitrogen Cycle Reference library
The Oxford Companion to Global Change
...cycle of nitrogen (Figure 1). The most abundant form of nitrogen on Earth, N 2 , is the least reactive species. Nitrogen fixation converts atmospheric N 2 to one of the forms of “fixed” nitrogen that can be used by biota (e.g., NH 4 + and NO 3 − ). Nitrogen-fixing species are most abundant in nitrogen-poor habitats, where their activity increases the availability of nitrogen for the biosphere. At the same time, denitrifying bacteria return N 2 to the atmosphere, lowering the overall stock of nitrogen readily available for life on Earth. The balance between...
Microbial Ecosystem Processes Reference library
Jessica L. M. GUTKNECHT
Berkshire Encyclopedia of Sustainability
...or low-nutrient soils (such as those on former mining sites). Nitrogen mineralization is the process where organic compounds are broken down, releasing inorganic forms that can be used by plants and microbes. Nitrogen immobilization is the process by which any soil organism takes up nitrogen so that it’s no longer available for other organisms. High rates of immobilization can be positive in that less excess nitrate nitrogen (nitrogen combined in a nitrate ion, as opposed to nitrogen in the form of ammonia, nitrites, etc.) leaks into lakes, rivers,...
Atmospheric Chemistry and Composition Reference library
Encyclopedia of Climate and Weather (2 ed.)
...to increased CO 2 levels is expected to act as positive feedback, producing a further increase on top of direct anthropogenic emissions. Substantial uncertainty exists in the role of the world's oceans in removing atmospheric CO 2 , especially the process of mixing of surface water into the deep ocean. Nitrous oxide (N 2 O), another greenhouse gas, is fairly abundant among atmospheric trace gases. Through oxidation to nitric oxide ( NO ), it serves as the main source of stratospheric NO X , or odd nitrogen, which is in turn plays a major part in chemical...
atmospheric electricity Reference library
The Oxford Companion to the Earth
...conditions Charges are released and exchanged in air even in the absence of local thunderstorm activity. There are several sources of this free charge, or ionization. Air molecules such as nitrogen, oxygen, and water vapour are split by collisions with high-energy radioactive particles, producing charged fragments or molecular small ions. Small ions may be positive or negatively charged. Another source of ionization (particularly at high altitudes) is cosmic rays (high-energy nuclei). Near the surface, however, the radioactivity released by natural rocks...
Ozone Reference library
The Oxford Companion to Global Change
...The ozone balance in the stratosphere is maintained by destruction of ozone through catalytic cycles that involve nitrogen, hydrogen, chlorine, and bromine species. The chemistry of the stratosphere, with respect to the production and catalytic destruction of ozone, is thus a complex system, involving a large number of chemical reactions. Ozone in the Stratosphere Ozone plays a major role in the Earth's atmosphere because it absorbs solar radiation at wavelengths shorter than 300 nanometers that is not absorbed by molecular nitrogen (N 2 ) or molecular...
Ozone Reference library
Encyclopedia of Global Change
...radiation. The ozone balance in the stratosphere is maintained by destruction of ozone through catalytic cycles that involve nitrogen, hydrogen, chlorine, and bromine species. The chemistry of the stratosphere, with respect to the production and catalytic destruction of ozone, is thus a highly complex system, involving a very large number of elementary chemical reactions. Ozone plays a major role in the Earth's atmosphere because it absorbs solar radiation at wavelengths shorter than 300 nanometers that is not absorbed by molecular nitrogen or molecular oxygen,...
Subsurface (Tile) Agricultural Drainage Reference library
Gary R. Sands, Srinivasulu Ale, Laura E. Christianson, and Nathan Utt
The Oxford Encyclopedia of Agriculture and the Environment
...nitrous oxide emissions have been shown to be a fairly small percentage of the nitrogen balance across a bioreactor, and start-up strategies to mitigate the impact of high organic outflows have been suggested, much work remains to further optimize bioreactors to maximize nitrogen removal and minimize pollution swapping ( Healy et al., 2015 ). Constructed Wetlands. When constructed wetlands are placed to intercept subsurface drainage, substantial reduction in nitrogen loadings are possible (e.g., 50%). Wetlands remove nitrate from water primarily via the...
Acid Rain Reference library
Encyclopedia of Climate and Weather (2 ed.)
...(SO 2 ), nitrogen oxides (NO X ), and volatile organic carbons (VOCs). Coal-fired power plants and gasoline-powered motor vehicles are the major sources of these pollutants in industrialized regions. Sulfur gases are emitted mainly from point sources involving the combustion of fossil fuels. Natural sources of sulfur gases include sea spray, volcanoes, and biological activity; these sources, however, are less productive by at least a factor of 10 than human-caused emissions in major industrial countries such as the United States. Nitrogen gases result...
Agricultural Nitrogen and Phosphorus Pollution in Surface Waters Reference library
Marianne Bechmann and Per Stålnacke
The Oxford Encyclopedia of Agriculture and the Environment
...occur in a nitrate reduction zone, which can capture nitrate and prevent it from reaching the stream. However, nitrate transported in the tile drains will bypass the nitrate reducSource: ion zones and be leached directly to the stream. Mitigation of Nitrogen Losses From Agricultural Soils Nitrogen Surplus. Nitrogen losses to water can be reduced by reducing the N surplus in agricultural production over time. A reduction in N losses is a long-term process since any N loss to water in the course of a year is dependent on the actual weather. For example, high...
Soil Quality as Affected by Intensive Versus Conservative Agricultural Managements Reference library
Luigi Badalucco
The Oxford Encyclopedia of Agriculture and the Environment
...with integrated pest management (IPM), which resorts to alternative pest control methods not affecting the functional diversity of soil biota ( Lamine, 2011 ; Leake, 2003 ). Moreover, the inclusion of symbiotic nitrogen-fixing varieties in a rotation enriches soil in nitrogen, thus reducing the need for energy-intensive production of nitrogen fertilizers ( Herridge, Paoples, & Bodder, 2008 ). Also, legume-based rotations are considered crucial for maintaining soil fertility as they can promote C sequestration in soil, especially in semi-arid environments....
Organic Farming Reference library
Theodore J. K. Radovich
The Oxford Encyclopedia of Agriculture and the Environment
...solved but may be addressed in part by approaches such as breeding crops under organic conditions for traits such a high nitrogen use efficiency and weed tolerance, as well as adjusting consumer diets to consume less meat ( Lammerts van Bueren & Myers, 2011 ). Conclusions Although there has been valid critique of the potential sustainability of organic farming, it remains an important example of ecological agriculture that attempts to balance the need for productivity in the near term with a conservation of resources required to ensure those needs are met in...
Gaia Hypothesis Reference library
The Oxford Companion to Global Change
...For example, nitrogen maintains much of the atmospheric pressure and serves to dilute oxygen, which at 21% of the atmosphere is just below the level at which fires would disrupt land life. Yet oxygen is sufficiently abundant to support the metabolism of large respiring organisms such as humans. Both oxygen and nitrogen are biological products—oxygen is the product of past photosynthesis, while the gaseous nitrogen reservoir is largely maintained by the actions of denitrifying organisms (which use nitrate as a source of oxygen and release nitrogen gas)....
Gaia Hypothesis Reference library
Encyclopedia of Global Change
...example, nitrogen maintains much of the atmospheric pressure and serves to dilute oxygen, which at 21 percent of the atmosphere is just below the level at which fires would disrupt land life. Yet oxygen is sufficiently abundant to support the metabolism of large respiring organisms such as humans. Both oxygen and nitrogen are biological products—oxygen is the product of past photosynthesis, while the gaseous nitrogen reservoir is largely maintained by the actions of denitrifying organisms (which use nitrate as a source of oxygen and release nitrogen gas)....
Modeling of Natural Systems Reference library
Encyclopedia of Global Change
...fluxes of mass (matter), especially carbon, nitrogen, and oxygen. The Earth's natural system is also clearly extremely heterogeneous. There are many subsystems that interact with one another to produce feedback effects—which occur when a portion of the output from the action of a system is added to the input and subsequently alters the output. The result of such a loop system can either be an amplification of the process or a dampening, and such feedbacks are labeled positive and negative, respectively. Positive feedbacks enhance a perturbation, whereas...
sea water Reference library
The Oxford Companion to the Earth
...are also gases, which in order of their relative abundances are nitrogen, oxygen, and carbon dioxide. By volume dissolved nitrogen accounts for about 64 per cent of the total gases dissolved in sea water. This nitrogen is biologically unimportant, as most organisms cannot directly make use of it. Sea water contains a substantially higher concentration of dissolved oxygen than the atmosphere (34 per cent as opposed to 21 per cent). The supply of oxygen to the surface ocean reflects a balance between the input of oxygen across the air–sea boundary and...
