Nitrate Reduction and Associated Microbial Populations in a Ponded Hanford Sandy Loam
1975
Volz, M. G. | Belser, L. W. | Ardakani, M. S. | McLaren, A. D.
A field plot of Hanford sandy loam was ponded for 2 weeks with a solution of KNO₃ and Ca(NO₃)₂ containing 100 ppm NO₃-N in order to measure short term denitrification rates as well as growth and distribution of bacteria capable of reducing nitrate to nitrite and/or N₂O and N₂. Denitrifying bacteria (10¹−2.9 × 10⁴/g soil) generally decreased in number with depth and time and were not as numerous as nitrate reducers (10¹−6.9 × 10⁵/g soil). In the top 60 cm of soil, the concentration of NO₂⁻-N in soil solution corresponded to minima in NO₃⁻-N, suggesting that NO₃⁻ reduction gave rise to the NO₂⁻. Denitrification rates calculated for the top 16 cm of water-saturated soil were estimated to range from 0.013 to 0.046 µg N/hour g⁻¹. The highest value was about 80% of that measured in a laboratory soil column studied previously. This difference in denitrification rates may be due to lower soil carbon content in the field.
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