Phosphorous levels in different types of playa lake bottoms

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Phosphorous levels in different types of playa
lake bottoms

• John Davis
• Shawn Gales

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Methods of collecting samples

• Tools used
• Depth of samples
• Location of samples
• Number of samples

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Location of Samples
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Types of Samples Collected

• Creek Bottom Flow from Feedyard
• Playa with runoff from irrigated crop land
• Playa with runoff from irrigated crop land using
  waste water
• Playa with runoff from rainfall with all native
  grass surroundings

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LABORATORY PROCEDURES

• By
• Shawn Gales and John Davis

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Laboratory Procedures for determining Phosphorus
in soils using Mehlich III Extracting Solution
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24 Soil samples were tested. The samples were
ground and sifted through a 2mm sieve. 2 grams
were then used from each sample. 20ml of Mehlich
III was added to each sample.
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The samples were shaken on a rotative shaker for
5 minutes. The soil was filtered through a 6
Whatman filter paper. The samples were decanted
and collected into vials.
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• 4 reagents were prepared.
• Sulfuric Acid Solution 5N
• Ammonium Molybdate Solution
• Antimony Potassium Tartrate Solution
• Sodium Hydroxide Solution 2N

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Color reagents were also prepared daily. The mix
color reagent contains 50ml of the 5N Sulfuric
Acid Solution, 5ml of the Antimony Potassium
Tartrate Solution and 15ml of Ammonium Molybdate
Solution.
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Dissolved into the mixed color reagent was 0.528
grams of Ascorbic Acid and 30ml of deionized
water. Standards were prepared using Mehlich
III Extractant.
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10 Standards were prepared at 500, 250, 125,
62.5, 31.25, 15.6, 7.81, 3.91, 1.96, 0.98ppm of
Phosphate. For the 500 standard half Mehlich III
and half 1000ml Phosphate was used and repeated
for the other standards.
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• Procedure
• Pipette 0.4 ml extract soil sample solution into
  a 10ml test tube.
• Added 5.9ml deionized water.
• Added 2 drops of 2N NaOH.
• To this 1.2 mixed reagent and agitate was added
  for 5 seconds on a vortex shaker.

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• Let stand for 15 minutes.
• A colorimeter(spectronic 21) was used with a wave
  length of 685nm to analyze for Phosphate
  concentrations.
• Calibrated the colorimeter with Mehlich III
  Solution.
• Recorded results of the 24 samples.

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ResultsIrrigated Cropland (Meador)

Results in ppm.
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ResultsNative Grass (Pender)

Results in ppm.
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ResultsWastewater Irrig. (Clymer)

Results in ppm.
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ResultsCreek Bottom (Irwin)

Results in ppm.
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Average Results
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Summary

• P levels were typically higher in playa bottom
  and bench positions.
• P levels were higher adjacent to feedyard, or
  when wastewater was used
• P levels were low in the creek bed (flowing water
  carries sediments and therefore, P)