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The Effects of Several Herbicides on Nitrification in a Field Soil Under Laboratory Conditions
Published online by Cambridge University Press: 12 June 2017
Extract
The process of biological nitrification in soil is a two-step oxidation of the ammonium ion to nitrite and thence to nitrate and is largely caused by the autotrophic bacteria in the genera Nitrosococcus, Nitrosomonas and Nitrobacter. The biochemical activities of these soil microorganisms can be studied by using the percolation technique of Lees. When studying the nitrifying organisms, an ammonium salt solution is bubbled under air pressure through a lift tube to the surface of a soil sample in a suitable container from whence it percolates downward through the soil and drains back into the reservoir from which it came. Air and moisture are thus constantly replenished in the soil and water logging is avoided. The value of the method lies in the fact that any substance introduced into the percolating fluid which affects the metabolism of the nitrifying organisms causes a change in the rate of conversion of the ammonium ions to nitrate ions. When the nitrate in the percolating fluid is in equilibrium with the nitrate in the soil, measurements of the nitrate nitrogen in aliquots of the percolating fluid are a measure of the rate of nitrification in the soil.
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- Copyright © 1957 Weed Science Society of America
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