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Nitrate Levels in Shallow Groundwater under Pastures Receiving Ammonium Nitrate or Slow‐Release Nitrogen Fertilizer
Author(s) -
Owens L.B.,
Edwards W.M.,
Van Keuren R.W.
Publication year - 1992
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/jeq1992.00472425002100040014x
Subject(s) - nitrate , groundwater , fertilizer , zoology , urea , environmental science , hydrology (agriculture) , ammonium , nitrogen , watershed , chemistry , agronomy , ecology , biology , geology , geotechnical engineering , organic chemistry , machine learning , computer science
This study examined the impact on groundwater quality of conventional and slow‐release N fertilizer to small, grazed watersheds in eastern Ohio. Three small watersheds (each less than 1 ha) received 56 kg N/ha annually as NH 4 NO 3 for 5 yr. For the next 10 yr, one watershed received 168 kg N/ha annually as NH 4 NO 3 and two others received the same amount of N as methylene urea, a slow‐release fertilizer. Shallow groundwater samples were collected from springs and analyzed. After the 5‐yr prestudy period, NO 3 ‐N levels in the groundwater from the three watersheds were in a 3 to 5 mg/L range. Groundwater NO 3 ‐N concentrations increased slightly during the first 3 yr at the higher N fertilizer rate, though they remained in the 3 to 5 mg/L range. Nitrate‐N levels increased more sharply during the rest of the study. Although these NO 3 ‐N levels varied more between the growing and dormant seasons than when lower rates of fertilizer were applied, they eventually reached a slower rate of increase. During the 9th and 10th yr of the high application, seasonal NO 3 ‐N levels in groundwater ranged from 10 to 16 and 7 to 14 mg/L from the watersheds receiving NH 4 NO 3 and methylene urea, respectively. This study showed that 168 kg N/ha was too much for this system, regardless of whether conventional or slow‐release N was used.