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Dissimilatory nitrate reduction to ammonium (DNRA), denitrification, anaerobic ammonium oxidation (anammox) and biological N2 fixation (BNF) can influence the nitrogen (N) use efficiency of rice production. Whilst the effect of N application on BNF is known, little is known about its effect on NO3 - partitioning between DNRA, denitrification and anammox. Here, we investigated the effect of N application on DNRA, denitrification, anammox and BNF, and on the abundance of relevant genes in three paddy soils in Australia. Rice was grown in the glasshouse with (150 kg N ha-1 ) and without N-fertiliser for 75 days, and the rhizosphere and bulk soils were collected separately for laboratory incubation and quantitative PCR analysis. Nitrogen application reduced DNRA rates by >16% in all the soils regardless of the rhizospheric zone but it did not affect the nrfA gene abundance. Without N, the amount and proportion of NO3 - reduced by DNRA (0.42-0.52 µg g-1 soil day-1 , 45-55%) was similar or higher than that by denitrification. However, with N the amount of NO3 - reduced by DNRA (0.32-0.40 µg g-1 soil day-1 ) was 40-50% lower than the NO3 - reduced by denitrification. Denitrification loss increased by >20% with N addition, and was affected by the rhizospheric zones. Nitrogen loss was minimal through anammox, while BNF added 0.02-0.25 µg N g-1 soil day-1. We found that DNRA plays significant positive role in paddy soil N retention as it accounts for up to 55% of the total NO3 - reduction, but this is reduced by N application. [ABSTRACT FROM AUTHOR]