Premium
Organic Nitrogen in Drainage Water from 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/jeq2000.00472425002900040029x
Subject(s) - drainage , environmental science , hydrology (agriculture) , nitrogen , fertilizer , lolium perenne , agronomy , chemistry , ecology , poaceae , geology , biology , geotechnical engineering , organic chemistry
Loss of organic N in land drainage may contribute to water pollution. This study was conducted to quantify the loss of organic nitrogen in drainage water from grazed grassland ( Lolium perenne L. cv. Talbot) swards receiving a range of fertilizer N inputs for 9 yr. Plots (each 0.2 ha) received 100, 200, 300, 400, or 500 kg N ha −1 yr −1 as calcium ammonium nitrate and were hydrologically isolated and drained to V‐notch weirs with automatic sampling of drainage water. For comparison, organic N loss was quantified in rivers draining six predominantly grassland catchments. The European Community maximum admissible concentration of total Kjeldahl N for drinking water of 1.0 mg N L −1 was exceeded in both land drainage and river water. Total organic N accounted for up to 54.7 and 20.2% of the annual N drainage losses from the plots receiving 100 and 500 kg N ha −1 yr −1 , respectively. Loads of soluble organic N were greater than particulate N but there was no significant relationship with fertilizer N input for either fraction. The average annual loss of total organic N in drainage water ranged from 3.5 to 9.1 kg N ha −1 . However, this loss cannot explain the large amount of unaccounted for N in calculations of nutrient balances where inputs invariably exceed outputs. In comparison, the average annual loss of organic N from the six river catchments ranged from 4.7 to 8.1 kg N ha −1 , which suggested that a large proportion of the organic N in river water was originating from land drainage.