Nitrate leaching potential under variable and uniform nitrogen fertilizer management in irrigated potato systems
Whitley, K.M. and J.R. Davenport. 2003. HortTechnology 13:605-609
Abstract
Potato (Solanum tuberosum) production
in Washington State's Central Columbia Plateau faces nitrogen (N)
management challenges due to the combination of coarse textured soils
(sandy loam to loam) and hilly topography in this region as well as
the high N requirement of potato. Potato growth and development
can vary with the N availability across the field. In this
2-year study, two adjacent potato fields were selected each year (1999
and 2000). Each field was soil sampled on a 200 ft (61.0 m)
grid to establish existing soil N content. One field was
preplant fertilized with variable N rate while the other was
conventionally preplant fertilized, applying a uniform rate across the
field based on the field average. During the growing season,
each field was monitored for nitrate leaching potential using ion
exchange membrane technology. Soil and plant nutrient status
were also monitored by collecting in-season petiole and soil samples
at two key phenological stages, tuber initiation and tuber
bulking. Overall this research showed that variable rate
preplant N fertilizer management reduced N leaching potential during
the early part of the growing season, but did not persist the entire
season. Since preplant N accounted for only 40% of the total
seasonal N applied, it is possible that further gains could be made
with variable rate in-season N application or with variable rate water
application.
Key Words
ion exchange membrane. landscape position, soil organic matter, Solanum tuberosum, spatial variability
