Microbial transformation of nitrogen in cattle slurry as applied to an andisol grassland
2006
Mizota, C.(Iwate Univ., Morioka (Japan). Faculty of Agriculture) | ; Yamaguchi, Y. | ; Noborio, K.
Organic nitrogen compounds in the animal waste once applied to soil is followed by chemical modification. Microbial transformation of nitrogen in cattle slurry applied to an Andisol grassland with no-cattle grazing over 20 years in northeastern Japan was analyzed with a focus on temporal changes in chemical composition (ammonium- and nitrate-nitrogen) and the natural abundance of nitrogen isotopes, delta15N. Most urea and related metabolites, which were major organic constituents of nitrogen in cattle excreta, were hydrolyzed into ammonium-nitrogen during storage in an underground closed tank. Nitrification of the ammonium-nitrogen was largely delayed under lower soil temperature conditions with average air temperature (4-14 deg C), whereas rapid nitrification occurred under higher air temperature conditions (17-27 deg C). A coupled process of denitrification followed by nitrification was evidenced by a rapid decrease in the nitrate content with a simultaneous increase in the delta15N values of the residual. Such a process was facilitated by a combination of the high water retention property of the Andisol with an ample supply of organic matter.
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