Fig. 1 Relative contributions of added ammonium-N, ryegrass-N and soil native N to the extractable organic nitrogen (EON) and microbial biomass N (MBN) in soil with ammonium (80 mg N kg-1) and/or ryegrass (160 mg N kg-1) addition. Numbers on bars are contributions of related sources, which are not shown when < 5%.
Fig. 2 Relationships among the transformations of extractable NH4+ and NO3-, extractable organic nitrogen (EON), microbial biomass N (MBN), mineral fixed NH4+ (MFN) and non-microbial organic N (NMON) after 15N-ryegrass and/or 15NH4+ addition. The solid blue lines indicate the known pathways. The dotted red lines indicate the unclear pathways.