nitrogen transformations in cropland

We considered of N transformation processes among the three soil N pools (organic N, NH4+, and NO3−), namely gross N mineralization (oxidation of organic N to NH4+), gross heterotrophic nitrification (oxidation of organic N to NO3−), gross autotrophic nitrification (oxidation of NH4+ to NO3−), gross dissimilatory NO3− reduction to NH4+ (DNRA), gross NH4+ immobilization (the conversion of NH4+ to organic N), and gross NO3− immobilization (the conversion of NO3− to organic N). Additionally, we took into account plant NH4+ uptake (UNH4) and plant NO3− uptake (UNO3). Observations (upland/paddy) include N mineralization (334/114), autotrophic nitrification (199/109), heterotrophic nitrification (161/98), NH4+ immobilization (210/113), NO3− immobilization (194/23), DNRA (150/111), UNH4 (76/38), UNO3 (76/38). The UN (76/38) was also calculated as the sum of UNH4 and UNO3.