Nitrate, organic, and ammoniacal N are all readily assimilated by rice, if growth factors, such as reaction, temp., and light, are kept uniform for all treatments. Denitrification resulted in losses of N from all farms of N used, although less was lost from ammoniacal forms than from nitrate or organic N. The concentration of nitrites found when denitrification was in progress was not large enough to be toxic to rice even when nitrates were the source of the N.