Nitrogen Contamination of Groundwater from Barnyards in the Central Sand Plain Aquifer of Wisconsin
File(s)
Date
1988-08Author
Travis, Micheal J.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
Nitrogen contamination of groundwater by barnyards
was monitored at five study locations in the Central Sand
Plain of Wisconsin. The study areas differed in size from
0.04 to 1.0 hectare. Cattle densities on these yards
ranged from 10 to 300 m^2 per animal. Management of the
yards' surfaces included: complete manure removal at the
smallest site; high organic accumulation at the three
midsize sites; and low accumulation on a vegetated surface
at the largest yard. Peizometers and multilevel wells installed
upgradient and downgradient of each barnyard were
used to monitor groundwater movement and quality in the
vicinity of the yard.
Potassium proved to be an excellent indicator of
animal waste influence in the shallow groundwater.
Concentrations of K+ were low or undetected in upgradient
water. Downgradient concentrations up to 725 mg/1 K+ were
observed in upper ports of downgradient multilevel
monitoring wells.
Groundwater flow analyzed at one of the study sites
indicated a complex system. Interaction of impermeable
and permeable areas affected recharge in the farmyard altering
local flow. In addition, variation in hydraulic
conductivity affected rate of flow and dispersion. Vertical gradients were noted and further complicated the
interpretation of contaminant flow.
Three aspects of nitrogen contamination of groundwater
by barnyards were noted: 1) direct infiltration within
the yard; 2) runoff from the yard and infiltration to the
groundwater in outlying areas; and 3) transformation of
nitrogen forms within the soil/water environment of the
barnyard. Groundwater nitrogen data was compared to soil
data obtained within the yards (Bowen, 1987). The low use
yard and the yard with regular manure removal contributed
nitrate to the groundwater system by direct infiltration.
The high use yards with manure accumulation restricted direct
infiltration by a compacted soil/organic layer which
encouraged runoff. Low density fencerows and areas surrounding
these barnyards accepted this runoff and were
suggested to be the most significant contributor to
groundwater quality degradation in these compacted barnyard
systems. Nitrate concentrations as high as 140 mg/1
NO3-N were detected in a well downgradient of one such
ponding area. Denitrification of N within the groundwater
was indicated at all sites by absence of 02 and detection
of NO2- in the groundwater. Changes of N species within
the contaminant plume indicated a dynamic chemical/
biological system established by a confined cattle facility.