Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2000
Publication Date: November 1, 2000
Citation: Wilhelm, W.W., Varvel, G.E. 2000. Nitrogen uptake efficiency in grain crops. Agronomy Abstracts p. 122. Technical Abstract: Although N is one of the most abundant elements on earth, it is the second most critical substance (next to water) limiting crop production. Accept for very specialized cases, N must be in the relatively scarce forms of ammonium or nitrate, dissolved in the soil solution, and near an active root to be taken up. The difficulty in achieving truly ¿efficient¿ N uptake is underscored by the fact that concentrations of available nitrate and ammonium in soil and N in the plant differ by three orders of magnitude. Although diffusion and mass flow contribute to total N uptake, crops must rely upon active transport to take up sufficient quantities of N to support economically viable levels of yield. Active N uptake is fueled by ATP that drives ion pumps and opens ion channels in the plasmalemma. Improved N uptake efficiency may rely upon such creative approaches as use of mycorrhiza and genetic engineering to change uptake characteristics or be achieved through more classical breeding and management approaches. Classical possibilities include selection for genotypes with greater root surface area or uptake potential, managing tillage, water, and fertilizer so that greatest N availability coincides with maximum crop demand, and maintenance of a vigorous crop with a healthy root system capable of efficiently gleaning N from the rhizosphere.