The results showed that gross rates of mineralisation (P<0.01), N[H.sub.4.sup.+] oxidation to N[O.sub.3.sup.-] (P<0.01), and dissimilatory N[O.sub.3.sup.-] reduction to ammonium (DNRA, P<0.05) significantly increased with elevated soil pH.
This study determined gross N transformation rates (nitrification, mineralisation, dissimilatory nitrate reduction to ammonium (DNRA) and N[O.sub.3.sup.-] immobilisation), and abundances of AOA and AOB under the pH treatments in a subtropical acid forest soil.
In the model, [M.sub.Nrec] = mineralisation rate of recalcitrant organic-N to N[H.sub.4.sup.+]; [M.sub.Nlab] = mineralisation rate of labile organic-N to N[H.sub.4.sup.+]; Total [M.sub.n] = the sum of [M.sub.Nrec] and [M.sub.Nlab]; Ratio of [M.sub.Nlab] = the ratio of [M.sub.Nlab] to the sum of [M.sub.Nrec] and [M.sub.Nlab]; [O.sub.NH4] = gross rate of N[H.sub.4.sup.+] oxidation to N[O.sub.3.sup.-]; [O.sub.Nrel]; = the gross rate of recalcitrant organic-N oxidation to N[O.sub.3.sup.-]; and DNRA = the gross rate of dissimilatory NO, reduction to ammonium.
1 a-d), whereas [sup.15]N enrichment of N[H.sub.4]' derived from [sup.15]N-N[O.sub.3.sup.-] did not change, indicating that transformations of N[O.sub.3.sup.-] via immobilisation and subsequent re-mineralisation or DNRA were low during the incubation period (Fig.
Office opened as part of the efforts by DNRA to provide access to its services across the rapidly growing city A VIP delegation from the Dubai Naturalization and Residency Administration (DNRA), paid an official visit to the full-service immigration office at the Dubai International Financial Centre (DIFC), which caters to the needs of the growing DIFC community.
Members of the high-ranking DNRA delegation included Lt.
The steady increase in soil N[H.sub.4.sup.+] concentration in wetland soil without added zeolite during the incubation further suggests DNRA
(Silver et al.
Nitrous oxide in wetlands is produced not only by denitrification but also by nitrification and DNRA (Stevens and Laughlin 1998; Hefting et al.
Given that denitrification was a minor pathway for N[O.sub.3.sup.-] transformation, the rapid N[O.sub.3.sup.-] removal observed in the first several hours following dosing may be attributed to several processes that we did not measure; specifically DNRA (Silver et al.
Abbreviations: BD, bulk density; DEA, denitrification enzyme activity; DNRA, dissimilatory reduction of nitrate to ammonium; I.D., internal diameter; LOI, loss on ignition; PVC, polyvinyl chloride.
Nitrous oxide production in soil is the result of key microbial processes (nitrification, denitrification, and DNRA) which can occur in a soil and sediment simultaneously and need substrate N[H.sub.4.sup.+]-N for nitrification and N[O.sub.3.sup.-]-N for denitrification and DNRA.
Soil pH is critical among the major known factors (such as available mineral N, soil water content, [O.sub.2] status, and the presence of available C), which affect nitrous oxide reductase and hence the production of [N.sub.2]O and [N.sub.2] through nitrification/denitrification or DNRA. For example, soil pH values from 4.5 to 6.5 have been reported to inhibit nitrous oxide reductase (Weier and Gilliam 1986; Flessa et al.