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This article in SSSAJ

  1. Vol. 35 No. 6, p. 997-1002
    Received: Dec 21, 1970
    Accepted: July 7, 1971

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The Influence of Soil-Fertilizer Geometry on Nitrification and Nitrite Accumulation1

  1. D. F. Bezdicek,
  2. J. M. MacGregor and
  3. W. P. Martin2



Nine granules (330 ppm N) of either urea, (NH4)2SO4, or diammonium phosphate (DAP) were spaced in a square pattern at distances of 0, 0.5, 1.0, or 1.5 cm on 30 g of soil. Samples were watered, incubated, and extracted with I N KCl. The extracts were analyzed for NH4+, NO2-, and NO3-. Generally NO2- accumulation for the three N carriers increased with granule spacing; the geometric effect was DAP > (NH4)2SO4 > urea. Nitrite varied from 140 to 265 ppm N. Increased NO2- accumulation with increased granule spacing was accompanied by a corresponding increase in NH4+ oxidation rate with little change in NO3-. Geometric effect with four granules (55 ppm N) spaced up to 2.5-cm apart showed that both NO2- and NH4+ decreased with increased granule spacing accompanied by increased NO3-. Single-granule studies suggested that the greater geometric effects of DAP resulted from the lower solubility and relatively low mobility of phosphate ions. The subsequent periphery pH decrease minimized outward movement of NH4+. These effects were less for (NH4)2SO4 and for urea.

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