Medium-term response of peat drainage water to changes in nitrogen deposition from the atmosphere

A 12-month glass-house simulation experiment has been used to investigate the response of drainage water solute chemistry of Calluna and mixed grass moorland peat microcosms to elevated deposition of ammonium- and nitrate-N. Uptake for both N deposition species was greater for grass than for Calluna vulgaris turfs. Nitrification was negligible for the elevated ammonium-N treatments, which did not therefore enhance nitrate leaching, but did result in substantial increases in ammonium leaching for both vegetation types. However, the elevated nitrate treatments resulted in dramatically enhanced ammonium-N leaching and a more modest enhancement in the leaching of organic-N. The biological uptake minimises the acidification effect of the enhanced N depositions, with ca. 70% of the additional H+ inputs as HNO3 being consumed in N transformation reactions.