Premium
Inorganic Nitrogen in Drainage Water from Grazed Grassland in Northern Ireland
Author(s) -
Watson C. J.,
Jordan C.,
Lennox S. D.,
Smith R. V.,
Steen R. W. J.
Publication year - 2000
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2000.00472425002900010029x
Subject(s) - drainage , lolium perenne , hydrology (agriculture) , environmental science , fertilizer , interception , perennial plant , water flow , zoology , nitrogen , ammonium , agronomy , chemistry , ecology , soil science , biology , geology , geotechnical engineering , organic chemistry
The loss of inorganic N in drainage water from grazed perennial ryegrass ( Lolium perenne L. cv. Talbot) swards in Northern Ireland was studied for 9 yr. Plots (each 0.2‐ha area) were hydrologically isolated and artificially drained to V‐notch weirs with flow‐proportional monitoring of drainage water. Nitrogen, as calcium ammonium nitrate, was applied at 100, 200, 300, 400, or 500 kg N ha −1 yr −1 . The efficiency of flow interception by drains decreased on average by 39% during the 9 yr. Annual loss of NO − 3 in drain flow for the plot receiving 300 kg N ha −1 yr −1 ranged from 16 to 52 kg N ha −1 and was highest after a dry summer. In individual years, NO − 3 in drainage water was linearly related to fertilizer N input with 5 to 23% of the added N input being lost. The shape of the NO − 3 dose‐response curve did not change with time. Annual losses of NH + 4 and NO − 2 in drainage water were not related to fertilizer rate, and ranged from 0.2 to 4 kg N ha −1 and 8 to 540 g N ha −1 , respectively. Annual flow‐weighted mean NO − 3 , NH + 4 , and NO − 2 concentrations usually did not exceed the European Community maximum admissible limits for drinking water below a fertilizer N application rate of 300 kg N ha −1 yr −1 . However, the European Community guideline NH + 4 and NO − 2 concentrations in salmonid and cyprinid waters were exceeded at application rates ≥100 kg N ha −1 yr −1 .