Nk. Patni et al., GROUNDWATER QUALITY UNDER CONVENTIONAL AND NO-TILLAGE - I - NITRATE, ELECTRICAL-CONDUCTIVITY, AND PH, Journal of environmental quality, 27(4), 1998, pp. 869-877
The use of conservation tillage is increasing in North America, but in
formation on its effect on water quality in cold climatic regions is l
imited. To obtain such information, the effect of no-tillage (NT) and
conventional tillage (CT) treatments on nitrate-nitrogen (NO3-N) conce
ntration, specific electrical conductivity (EC), and pH in shallow gro
undwater (1.2, 1.8, 3.0, and 4.6 m depths) was studied over four succe
ssive crop years in corn fields (loam soil) of approximately 3 ha each
, located in eastern Ontario, Water table elevation was also monitored
during three crop years. Average NO3-N concentration at the 1.2, 1.8,
and 4.6 m depths was consistently higher under CT than under NT in ev
ery crop year and every season. However, the effect of tillage was not
significant at P < 0.05. Nitrate concentration decreased significantl
y with depth. It was about two to three times the drinking water limit
of 10 mg/L as NO3-N at the 1.2, 1.8, and 3.0 m depths. At the 4.6 m d
epth, NO3-N concentrations were mostly low but increased with time. Ch
anges in water table elevation appeared to affect NO3-N concentrations
at the 1.2 m depth under NT only. At a given depth, EC and pH of grou
ndwater were not affected by tillage treatment. However, within each t
illage treatment, values increased significantly with depth, Results f
rom this study indicated a large spatial variability in NO3-N and EC v
alues in groundwater, which could have masked small tillage effects, M
ore intensive temporal and spatial sampling may be required to establi
sh tillage treatment effects, if any.