Effects of SalineSodic Water on Soil Chemical and Physical Properties

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Effects of Saline-Sodic Water on Soil Chemical
and Physical Properties
Kim Hershberger
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My Study

• Assess the effects of modestly saline-sodic water
  on soil chemical and physical properties of
  selected soil materials.
• Overall Goal-Determine the suitability of
  irrigating with modestly saline-sodic waters,
  while still maintaining the sustainability of the
  soil.
• Two laboratory experiments which subjected soils
  of varying clay content to diverse wetting/drying
  regimes using two water qualities.

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Irrigable Acreages within the Buffalo Rapids
Irrigation District
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TEXTURAL CLASSES 1- Clay 0-11 - Loamy Sand,
Sandy Loam, Loam 2- Clay 12-22 - Sandy Loam,
Loam, Silt Loam 3- Clay 23-33 - Loam, Clay
Loam, Silty Clay Loam 4- Clay 34 - Silty Clay
Loam, Silty Clay, Clay
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Baseline Chemistry Data
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Water Quality Targets

• POWDER RIVER
• EC 1.56 dS/m
• SAR 4.54
• pH 8.03

• CBM (PRODUCT WATER)
• EC 3.12 dS/m
• SAR 13.09
• pH 8.22

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Wetting Regimes

• 1X Wet/Dry with P.R.
• 1X Wet/Dry with CBM
• 5X Wet/Dry with P.R.
• 5X Wet/Dry with CBM
• 5X Wet/Dry with P.R. followed by leaching
• with 1 pore volume distilled water
• 5X Wet/Dry with CBM followed by leaching
• with 1 pore volume of distilled water

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Study of Soil Chemical Responses

• Treatment effect on soil chemistry was evaluated
  by monitoring the resultant saturated paste
  extract EC and SAR and comparing results with
  baseline conditions.
• Comparisons made by analyzing data based on their
  textural class.

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Methods

• Soil materials were saturated according to the
  water quality x wetting regime treatment
  combinations.
• 1X treatments-following wetting soils were oven
  dried.
• 5X treatments-intermediate drying cycles for 24
  hours at 95 deg F following fifth wetting soils
  were oven dried.

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• For 5Xd, after fifth drying to 95 deg. F, soils
  were placed on wire mesh racks where 1 pore
  volume of D.I. water was poured on the surface of
  each sample. Leachate water was allowed to drain
  for 24 hrs. Following drainage period, soils
  were oven dried.

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Resultant Mean Saturated Paste Extract EC and SAR
for Textural Classes (across all treatments)
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Resultant Mean Saturated Paste EC and SAR for
Treatment Combinations (across all textures)
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Ayers and Westcot (1976)
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Soil Chemistry Conclusions

• 1.Repeated irrigation with saline-sodic water
  will result in a general increase in the soil
  salinity and sodicity.
• 2.Repeated irrigation or dispersal of CBM product
  water to irrigable land is likely to result in
  elevated soil salinity levels substantially
  higher than published thresholds for some
  irrigated crops.

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• 3. Soil solution salinity will equilibrate at an
  EC value approximately 2-3 times the EC of the
  applied water soil solution SAR appears to
  equilibrate at a level comparable to the SAR of
  the applied water as long as leaching occurs.
• 4. Application of salt-free water following
  elevation of soil solution salinity and SAR
  through repeated wetting effectively reduced soil
  solution salinity while having little or no
  effect on sodicity.
• 5. The lowering impact of rainfall on EC and SAR
  is more predominant when salt concentrations are
  high, and in coarser-textured soils.

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• 6. The greatest increases in EC and SAR upon
  wetting with either CBM or P.R. water were in
  coarser-textured soils.
• 7.In few instances of this study were soil
  solution salinity x sodicity combinations
  measured which exceed these thresholds following
  single wetting events. In essentially all
  instances where saline-sodic water was repeatably
  applied, the resulting soil solution salinity and
  sodicity were significantly elevated to levels in
  close proximity to the previously published EC x
  SAR standards.

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• 8. Results of this study appear to be consistent
  with previously published reports of the
  relationship between exchangeable sodium
  percentage (ESP) and solution SAR, i.e., SAR
  0.8 x ESP (approximately). Utilizing an ESP
  threshold of 15, the majority of treated soil
  samples exceeding this value resulted from
  alternate wetting regimes with CBM product water
  followed by simulated rainfall.

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Soil Physical Properties Study
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Methods

• Soil water retention was measured at 1/10 - 15
  -bars of applied pressure.
• Water content was measured after soils had
  undergone treatment combinations (same as the
  soil chemistry study treatments.
• For 1X treatments, soils were saturated for 24
  hrs before pressure was applied.
• For 5X treatments, soils were placed on wire
  racks for wet/dry cycles and transferred to
  pressure plates for the final wetting period.

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Methods cont.

• 5Xd-Same procedure as the 5X
• Final wetting on the plate consisted of DI
  application

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Mean Gravimetric Water Content at Applied
Pressure Potentials for each Textural Class
(across all treatment combinations)
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Mean Gravimetric Water Content at Applied
Pressure Potentials for each Treatment
Combination (across all textures)
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Soil Physical Properties Conclusions

• 1. Water content associated with matric
  potential differed significantly due to
  predominant soil texture at all matric potentials
  investigated in this study.
• 2. Significant differences in water holding
  capacity of coarser-textured soils occur due to
  water quality treatment more often at greater
  matric potentials. In finer-textured soils
  differences in water holding capacity due to
  water quality treatment are more likely to occur
  at lower potentials.

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• 3. Significant changes in water holding
  capacity due to water quality treatment are only
  on the order of 0.02-0.04 g H20/g dry soil. The
  change reflected a decrease in water holding
  capacity in textural classes 1 2 and an
  increase in water holding capacity in textural
  class 3.
• 4. Reductions in water retention in
  coarser-textured soils are attributable to the
  loss of large pore spaces.

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• 5. The addition of saline-sodic water had the
  greatest effect on soil physical properties when
  the soil is near saturation. Changes in water
  holding capacity are likely to have
  non-discernible impact on irrigation suitability.
• 6. Successive wetting/drying cycles can cause
  aggregate coalescence and the loss of
  interaggregate porosity this appeared to occur
  more often in the coarser-textured soils.

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• 7. Although statistically significant
  differences were detected among water quality
  treatments, differences were not large enough to
  have a significant ecological impact.
• 8. CBM product water applied at these levels
  did not have a consistent significant impact on
  soil physical properties, i.e., water-holding
  capacity.

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Acknowledgements
ACKNOWLEDGEMENTS

• Committee Dr. Jim Bauder (chair), Dr. Douglas
  Dollhopf, Dr. Jon Wraith
• Funding Prairie County Conservation District,
  Buffalo Rapids Irrigation District, Department of
  Energy
• Bernard Schaff, Susan Winking, and Bauder Students