摘要：Many
studies have evaluated nitrate-N leaching from tile-drained agricultural soils,
but little longterm research has been performed on well-drained soils commonly
throughout the Midwest. Equilibrium tension lysimeters installed at a depth of
1.4 m were used to measure year-round (12 month) nitrate-N leaching below chisel-plow
(CP) and no-tillage (NT) continuous corn (Zea
mays L.) agroecosystems to determine the potential effects of common
agricultural practices on subsurface water quality. The corn systems were
fertilized at a rate of 10 kg N ha-1 of starter fertilizer and 180
kg N ha-1 as NH4NO3. For comparison, nitrate-N
leaching from a natural ecosystem was performed on a nearby prairie restoration
(PR). Drainage, nitrate-N leaching loss, and flow-weighted mean nitrate-N
concentrations for 8 years of data (1996-2003) are reported for the CP, NT and
PR ecosystems. Results show that 52%, 37%, 16% of cumulative precipitation was
collected as drainage, while 18%, 19%, 0.5% of the total N input was leached as
nitrate-N in the CP, NT, and PR, respectively. Nearly three-quarters of the
total nitrate-N was leached from each ecosystem during the period from 1 April
to 30 June. The 8-yr, flow-weighted mean nitrate-N concentration measured in
leachate was 9.5, 12.2 and -1 for the CP, NT and PR
treatments. Annual drainage volumes and nitrate-N leaching losses were highly
variable, stressing the importance of long-term studies capable of measuring
year-round drainage for understanding N leaching dynamics and evaluating
effects of cropping practices on potential groundwater quality.
关键词：Nitrate Leaching; Flow-Weighted Mean Concentration; Maize Agroecosystems; Prairie Ecosystem
