Nitrogen plant uptake

I. Ortas, P. J. Harris, and D. L. Rowell, Enhanced uptake of phosphorus by mycor-rhizal sorghum plants as influenced by forms of nitrogen. Plant and Soil 7774 255 (1996). 

Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002).

Chemical fertilizers are used in most parts of the world, although less so in developing countries because of the high cost. The nitrogen content in chemical fertilizers is known, and application rates can be determined accurately, These may vary depending on the cropping system used. Nutrients are more immediately available for plant uptake in chemical fertilizers than in manure however, they may be more easily leached into groundwater if used in excess. Slow-release fertilizers reduce this loss,... 

Oxelfelt, F., Tamagnini, P., Salema, R. and Lindblad, P. (1995). Hydrogen uptake in Nostoc strain PCC 73102 effects of nickel, hydrogen, carbon and nitrogen. Plant Physiol. Biochem. 33,617-623. 

Simulation of Nitrogen Movement, Transformation and Plant Uptake in the Plant Root Zone", U.S. Environ. Prot. Ag. EPA-600/3-78-029, 1978 106 pp. 

Column 3 shows the approximate annual plant uptake per hectare (ha) of the elements, assuming an annual dry matter production of 10 000 kg ha-1. The amounts of calcium, potassium, and nitrogen absorbed greatly exceed plant absorption of the other elements. 

Schiniel, J. P. and Chapin, F. S. III. (1996). Tundra plant uptake of amino acid and NH nitrogen in situ Plants compete well for amino acid N. %y 77, 2142-2147. 

There are three primary elements in fertilizers that require analytical determinations nitrogen (N) available phosphate (AP) for plant uptake expressed as P2O5 and water-soluble potassium expressed as K2O. Procedures are examined to determine values based on the best methods available for the primary elements, secondary elements, micronutrients in fertilizers, and other trace elements. Uniform methods can eliminate problems associated with fertilizer analyses, resulting in agreement between laboratories on a given sample. By following the exact procedures as outlined in an acceptable method, one can expect a reliable and reproducible chemical analysis. 

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