North Dakota Survey of Soil Copper, pH, Zinc, and Boron
Levels
Extension Report 52, February 1999
D.W. Franzen, Extension Soil Specialist
A survey was conducted in North Dakota to better understand
soil levels of certain nutrients based on landscape position.
Previous surveys have reported findings based on county averages
of composite samples, or regional averages based on composite
soil testing. Site-specific research during the last five years
has suggested that composite testing could mask deficiencies of
nutrients if they exist within fields by mixing high testing
areas with lower testing areas. This study was designed to reveal
soil levels from specific landscape positions, rather than field
averages or composite testing.
Three fields were sampled from each of the 52 counties in
North Dakota. Some of the fields were located with the assistance
of county agents, but many were taken while going door-to-door to
ask permission to sample. In each field, a separate 0-6 inch
sample was taken from an upland position (hilltop), slope, or
depressional area. In the Red River Valley, upland position is
more descriptive than hilltop. Each of the samples was a
composite of 10 sample cores taken within a 60 foot diameter in
the landscape position. From the entire sampling, 156 samples
were obtained from each landscape position. Samples were analyzed
for soil pH, zinc, copper, boron, and maps were made of the soil
levels separated into landscape position. There were 10 sites
with a history of manure. These sites have been eliminated from
the data set recorded in this publication.
RESULTS
Copper
Copper levels were generally greater in depressional areas
than on uplands and slopes (Figures 1-3). Levels were highest in
the Red River Valley, the Souris Basin, and in the traditional
dry bean growing area around Fessenden. Levels were particularly
low in the western half of the state, especially in Sioux,
Billings and Slope counties. Depressional areas were relatively
high (>1ppm) in copper, with the exception of the western two
tiers of counties. These results reinforce that some
site-specific sampling, such as separate samples from hilltops
and depressions, need to be taken in order to reveal the lower
copper levels most often seen in upper landscape positions.
Composite testing would likely lead to over-estimates of soil
copper levels on a field basis.
Figure 1. North Dakota copper
levels, ppm, non-manured sites, upland positions. (42KB color map)
Figure 2. North Dakota copper
levels, ppm, non-manured sites, sloping positions. (30KB color map)
Figure 3. North Dakota copper
levels, ppm, non-manured sites, depressional positions. (32KB color map)
Soil pH
Soil pH levels on upland positions were relatively high
(>7.0) in the eastern half of the state, the northwest and the
southwest. In the western one-half of the state, there was
relatively low pH (<7.0) in Sioux, Hettinger, Slope, Dunn,
McKenzie, McClean, Mercer, Oliver and parts of Kidder and Emmons
counties. The low pH area seems to follow the contours of the
Missouri Couteau region. Other low pH areas are found in La Moure
and Dickey counties and the beach ridge areas west of the Valley.
About 27% of acreage was found to be less than pH 7, but only
0.5% was found lower than pH 6.
On sloping positions, the lower pH areas are again in the same
areas of the western part of the state as in the upland position
sampling, following the Missouri Couteau region. Lower pH areas
are also found in eastern North Dakota in the glacial till plains
in the central and southern part of the state. About 35% of the
acreage on slopes was found to be lower than pH 7. About 3% of
the acreage was lower than pH 6.
Soil pH in depressional areas was lowest in the western half
of the state in areas similar to the extent of the Missouri
Couteau region. Other relatively low pH areas were found in the
south-central region and in some areas of the central glacial
till plain. About 50% of depressional areas tested less than pH
7. About 8% of areas tested less than pH 6.
There is a mistaken assumption that North Dakota does not have
significant areas of low pH. However, if the relative acreage of
hilltops, slopes and depressions in the state is equal, then
approximately 17% of the state acreage has a pH lower than 6.5
and conceivably could respond to limestone fertilization in
sensitive crops.
Figure 4. Soil pH levels, upland
positions, non-manured sites, 1998. (40KB
color map)
Figure 5. Soil pH on sloping
positions on non-manured sites, 1998. (41KB
color map)
Figure 6. Soil pH in depressional
areas, non-manured sites, 1998. (39KB color
map)
Zinc
Soil zinc levels were relatively low (<1ppm) in upland
positions except for some areas within the Red River Valley and
an area in Wells, Eddy and Foster counties where dry bean has
been a traditional rotational crop for many years. Approximately
93% of the hilltop acreage in the state has a soil zinc level of
less than 1 ppm, suggesting that zinc may nearly always be needed
for sensitive crops in most of the state.
Soil zinc levels in sloping positions were relatively high
(>1ppm) in some areas of the Red River Valley and the
northwest region of the state. Relatively low levels of zinc were
found in the rest of the state. About 98% of slopes tested lower
than the 1 ppm critical level for zinc in sensitive crops.
Soil zinc levels in depressions were relatively high in parts
of the Red River Valley, the Souris basin, the dry bean growing
areas and an area in Adams and Hettinger counties. The rest of
the state tested relatively low in zinc. About 91% of the
depressional acreage tested lower than 1 ppm, suggesting that
even in heavier, higher organic matter soils, response to zinc is
likely for sensitive crops in most of the state.
Figure 7. Zinc levels, ppm,
upland positions, 1998 survey. (32KB color
map)
Figure 8. Zinc levels, ppm,
sloping positions, 1998. (32KB color map)
Figure 9. Zinc levels, ppm,
depressional positions, 1998 survey. (40KB
color map)
Boron soil test survey results
Boron levels in the state were relatively low (<1ppm), with
upland positions generally lowest and depressional areas highest
in boron; however, most of the state tests under 1 ppm, which is
the southeast US critical level. Since few reports of boron
deficiency on very sensitive crops like sunflower and alfalfa
have been made, it is unlikely that the need for supplemental
boron is extreme. However, this survey makes it clear that
although the area north and east of the Missouri river are marine
sediment derived and should naturally be high in boron, only the
Red River Valley and the Souris Lake Plain soils appear to be
relatively high in that nutrient. Soils west of the Missouri
Coteau are particularly low in available boron.
Boron on upland positions was lowest from the Missouri Couteau
west, with highest levels in the Red River Valley and the Souris
Lake Plain. Over 75% of the samples tested below 0.5 ppm.
In sloping positions, over 60 % of the samples tested below
0.5 ppm. Boron levels were lowest west of the Missouri Coteau. In
depressional positions, boron was highest in the east and
northeast and lowest west of the Missouri Coteau.
It is important to note that although soil levels appear low
in boron, critical levels for boron application in North Dakota
have not been established. The line between not enough and too
much boron is very fine. Toxicity is a hazard of boron
application when adequate amounts are present for plant uptake.
Figure 10. Boron levels, ppm,
upland positions. (34KB color map)
Figure 11. Boron levels, ppm,
sloping positions. (39KB color map)
Figure 12. Boron levels, ppm,
depressional positions. (34KB color map)
SUMMARY
Soil copper, pH, zinc, and boron levels were surveyed
throughout North Dakota. Soil copper levels suggest relatively
low levels in the state, with nearly two-thirds of slopes and
hilltops testing below 0.6 ppm, but only about 10% of
depressional areas testing below that same level. Organic matter
and soil texture will eventually be determined on these samples
to further define probable areas of copper response on these
landscape positions.
Soil pH levels are relatively high, but 17% were found to be
below pH 6.5, mostly along the Missouri River and in areas of the
southwest. Although low pH may not directly impact small grains,
alternative crops, particularly legumes, may benefit from liming.
Crop responses to soil zinc in flax, potatoes, dry edible
beans and corn are well established. For other crops, response to
zinc when soil levels are low is unlikely. The survey shows that
generally soil zinc levels are low, and producers of zinc
sensitive crops should consider soil testing and zinc application
if levels are found to be low.
There is little if any data regarding boron response of
alfalfa or sunflower in North Dakota, as this element was
considered probably high as a consequence of the soils origin
from marine sediments. This survey suggests that levels are
relatively low. However, it
is not known if the current soil testing methods for this state
are valid. Only responses to boron application at known soil test
levels will contribute to the development of critical levels for
boron, if any, in the state.
Acknowledgements
Funding for this survey was received from Cenex Land O' Lakes and
Agrium, US.
Extension Report 52, February 1999
NDSU Extension Service, North Dakota State University of
Agriculture and Applied Science, and U.S. Department of
Agriculture cooperating. Sharon D. Anderson, Director, Fargo,
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