Differences in nitrate leaching under variable and conventional nitrogen fertilizer management in irrigated potato systems
Whitley, K.M., J.R. Davenport and S.R. Manley . 2000. In Fifth International Conference on Precision Agriculture Proc., pp453-461. Bloomington, MN
Abstract
Over the past ten years there has been
increased attention to nitrate contamination of groundwater,
particularly to leaching associated with agricultural activities. In
the Pacific Northwest, nitrate in the groundwater is a concern in
potato (Solanum tuberosum L.) cropping systems. In this region
potato is generally grown under center pivot irrigation in coarse
textured soils. The combination of high fertilizer nitrogen (N)
requirements of potato and coarse soil texture lead to increased risk
of nitrate leaching. Site Specific Crop Management (SSCM) and Variable
Rate Application Technology (VRT) are potential tools to develop
strategies for environmentally sound nitrogen fertilizer management in
these systems. In this study, two adjacent fields were selected in row
crop rotations (potato as the 1999 crop). Each field was soil sampled
on a 61m x 61m grid to establish background soil N levels. One field
was fertilized with variable N rates while the other was fertilized
with a single N rate based on the field average. To evaluate field N
dynamics monitoring sites were established based on landscape position
(knoll, slope, valley) and soil test organic matter content (high,
low). Nitrogen flux was monitored with ion-exchange resin probes at
two depths, one in the root zone and one below the root zone. Soil
moisture and soil and petiole nitrate were monitored throughout the
growing season. This paper will discuss the leaching differences found
under the two fertilizer management strategies
Key Words
landscape position, soil organic matter, Solanum tuberosum L, VRT
