NITROGEN NUTRITIONAL STATUS AND FATE OF APPLIED N IN MANGROVE SOILS

摘要

Fluctuation of inorganic N content in mangrove soils of the Tamshui estuary, northwestern Taiwan, showed that ammonium concentrations ranged from 0.15 to 17.10 mg N kg(-1) soil, while nitrate ranged from trace amounts to 2.54 mg N kg(-1) soil. Geographic and edaphic factors caused the difference of inorganic N between the sites. These levels were much higher than values reported elsewhere. Pot experiments showed the added N-15 labeled ammonium (6 mg N per pot) disappeared rapidly. The N-15 residues remaining in the soil were mostly in the organic form. N uptake by Kandelia candel was 13.1% after one month and 19.6% after three months. Recoveries of applied N after three months were 40.3% in planted treatment and 32.6% in unplanted treatment. Most of the N loss, occurring in the first month, can be attributed to denitrification. The large N loss suggests a high potential for mangrove soils to remove high input of N from the river through denitrification.