Soil Fertility Testing: A timely summary of historical database trends

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Soil Fertility TestingA timely summary of
historical database trends
Ann Wolf, Ag Analytical Services Lab Douglas
Beegle, Crop and Soil Sciences Pennsylvania State
University
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Soil test summarieswhat can they tell us?

• Assess nutrient management practices
• Target areas for improved nutrient mgt and
  environmental protection

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Goal over time Keep soil nutrients in optimum
range
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Goal over time Keep soil nutrients in optimum
range
Below optimum Increase inputs
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Goal over time Keep soil nutrients in optimum
range
Above optimum Decrease inputs
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Todays talk

• Historical trends in soil pH, P, and K in PA over
  time (county, state-wide and national)
• Recent trends in Cu, Zn and S

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pH
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Importance of pH and benefits of liming

• Nutrient availability of macro and trace elements
• Decreased phytotoxicity of Al, Mn
• Microbial activity
• Pesticide activity

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Percent of Pennsylvania soils with low pH (lt
6.0) over time
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Soil pH
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Soil pH
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Soil pH
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Soil pH
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Although lt 25 of soils in several SE counties
test low in pH (lt 6.0), the trend of increased
number of low pH soils in these counties is
similar to other counties in PA
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Similar trend of increasing pct of low pH soils
observed in North Central and a number of
Southeastern states
Soil pH trends in other states (Potash and
Phosphate Institute, 2001)
Soil pH trends in other states
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Al,Fl,
Ga
,
Nc
,Sc
50
Ar
,Ms,
Tn
40
Percent of soils with pH lt 6.0
Pa
North Central
30
20
Wi
10
0
1980
1985
1990
1995
2000
2005
2010
Year
Il, In, Ia, Ks, Ky, Mi, Mn, Mo, Oh
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North America ave 34
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Factors contributing to soil acidity

• Natural weathering processbases leached from
  soils
• Acid rain (S emissions)
• Crop removal of basic cations
• Organic matter decomposition
• Nitrogen (ammonium) fertilizers

Not enough attention being paid to liming
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Ag Lime Consumption in PA
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pH Summary

• Over the last 30 years, the number of low pH
  testing soils in PA has more than doubled.
• Approximately 30 of PA soils test low (lt 6.0)
  in pH
• The trend of increasing number of low pH testing
  soils over years is evident in all PA counties.
• Greater attention needs to be paid to liming PA
  soils.

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PHOSPHORUS
Low P testing soils (Crop production concerns)
High P testing soils (Pollution concerns)
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Phosphorus
Mehlich 3 soil test
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Change in percent of PA soils testing low (lt 30
ppm) in P over time
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PhosphorusTrends at county level
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PhosphorusTrends at county level
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PhosphorusTrends at county level
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Low/medium soil test P trends in states with
high manure density
PPI Soil Test Summary, 2001
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Low/medium soil test P trends in states with
high manure density
PPI Soil Test Summary, 2001
IA, IL, IN, MN, NE, OH
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Phosphorus inputs
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Imbalance between manure nutrients and crop
requirements
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Imbalance between manure nutrients and crop
requirements
Example Dairy manure and corn
Manure rate based on N crop requirements
Manure nutrient
Crop nutrient need
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Imbalance between manure nutrients and crop
requirements
Example Dairy manure and corn
Manure rate based on N crop requirements
Excess P
N
Manure nutrient
Crop nutrient need
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Imbalance between manure nutrients and crop
requirements
Example Dairy manure and corn
Manure rate based on N crop requirements
Manure rate based on P crop requirements
N
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High P testing soils
Pollution potential
P index required when soil test P gt 200 ppm
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Change in percent of PA soils testing 150 ppm in
P over time
150 ppm limit used since data for soils with P gt
200 ppm not available for years 1971-1986.
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l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
Counties with highest rates of manure P generated
per acre of crop land (2002)
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50 of Pa soils test greater than optimum (gt 50
ppm P) 7 of Pa soils test greater than 200 ppm P
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Phosphorus Summary

• Steady decrease in low P testing soils from the
  1970s to early 1990s consistent with other
  states with high manure density.
• Approximately 30 of PA soils currently test low
  in P.
• Elevated soil test P levels have been increasing
  steadily in PA over the years.
• Highest soil test P levels are greatest in
  counties with high animal densities and can be
  attributed to the imbalance between manure
  nutrients and crop nutrient needs.
• 50 of Pa soils test higher than optimum and 7
  of Pa soils test higher than 200 ppm

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POTASSIUM
Low k testing soils (Crop productivity concerns)
High k testing soils (Animal health concerns)
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Potassium soil test interpretations
Mehlich 3 soil test
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Soils testing low in K (lt 100 ppm K) are
decreasing
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Similar trend of decreasing of low-K testing
soils observed in other states with high manure
density
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Imbalance between manure nutrients and crop
requirements
Example Dairy manure and corn
Manure rate based on crop N requirements
Manure rate based on crop P requirements
N
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Soils testing greater than optimum K (gt150 ppm K)
are increasing in PA
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Concerns with excess K in soils

• Suppress Mg uptake
• Grass tetany in grazing animals
• Excessive K uptake
• Milk Fever in dairy cattle

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Potassium soil test trends summary

• Low testing K soils (lt 100 ppm K) have been
  decreasing and high K test soils(gt 150 ppm K)
  have been increasing in PA over the last several
  decades
• Highest soil test K levels are greatest in
  counties with high animal densities and can be
  attributed to the imbalance between manure
  nutrients and crop nutrient needs.
• Soil testing should be used as a tool to monitor
  K levels in soils for optimum fertility and to
  avoid animal health issues.

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Cu, Zn, S
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Mehlich 3 Cu distribution in PA soils
Concern with high levels from
dairy foot baths
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Mehlich 3 Zinc Distribution in PA Soils
Occasionally deficient in soils with high pH and
high P from fertilizer (no manure) additions
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Mehlich 3 S distribution in PA soils
Not currently a common deficiency but could be in
the future if acid rain is reduced
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Acid rain over time
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Acid rain over time
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Summary

• PA soil test trends and needs
• Number of low-pH testing soils continues to
  increase. Need to pay more attention to liming
  soils
• We have done a good job of reducing number of low
  P and K testing soils concerns now focused on
  high P and K soils in areas of high animal
  density.
• No evidence of problem areas with Zn,Cu,S
  deficiencies/toxicities. Pay attention to
  potential decreases in soil S and increases in
  soil Cu over time.

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