Spectrum Agronomic Library

Knowledge is key to using your analytic results to their fullest. The Spectrum Agronomic Library provides you with useful information that will help you to better understand the complex science of agronomy. Our agronomists will be continually adding original and reprinted articles, so check the library regularly for new information.

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Soil pH and Buffer pH

Spectrum Analytic Reporting Conversions

As of July 1, 2005, Spectrum Analytic began reporting P, K, Ca, and Mg results as unadjusted Mehlich 3 (M3) values in parts per million (ppm). Prior to this date, samples were extracted with the Mehlich 3 solution, and the results mathematically converted to their equivalents in the older tests of Bray P1 for soil P, and 1Normal ammonium acetate (1NAoAc) for K, Ca, and Mg.

The table below shows the correlation formula we used to convert M3-ppm to the lbs/a values.

Table 1: Correlation Formulas
Nutrient Formula Result
M3-P (Mehlich-3 ppm x 0.7) x 2 Bray P1 in lbs/a
M3-K (Mehlich-3 ppm x 0.84) x 2 1NAoAc K in lbs/a
M3-Ca (Mehlich-3 ppm x 0.75) x 2 1NAoAc Ca in lbs/a
M3-Mg (Mehlich-3 ppm x 0.88) x 2 1NAoAc Mg in lbs/a

For a complete explanation, see the original announcement of the change in Spectrum Analytic Reporting Conversions

Interpretation of Water Analysis for Livestock Suitability

Water is important nutrient to all livestock and poultry. As with feed ingredients, livestock water should meet the nutritional needs of the animal. Most minerals and dissolved solids found in water provide nutritional benefits when present within limited concentrations. This paper can be used as a guide to the recommended limits of certain substances commonly found in water used for livestock and poultry.

Guidelines for Evaluating the Quality of Water for Livestock
Quality Factor Threshold Concentration (ppm) Limiting Concentrations (ppm)
Total dissolved solids (TDS) 2500 5000
Calcium 500 1000
Magnesium 250 500
Sodium 1000 2000
Bicarbonate 500 500
Chloride 1500 3000
Nitrate (see table for more detailed listing) 200 400
Sulfate (see table for more detailed listing) 500 1000
Range of pH 6.0 to 8.5 5.6 to 9.0

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Effect of Soil Probe Lubricants On Analytical Results

A study by the University of Wyoming helps to answer the question of how lubricants affect soil test results. The study included five commonly used lubricants, two (motor oil and dish washing liquid) wiped on and three (WD-40, vegetable oil spray, and silicone) sprayed on the soil probe. Chemical composition of the lubricants is shown in Table 1.

Table 1. Chemical Composition of Five Commonly Used Soil Probe Lubricants
ppm
Lubricant % OM NO3 P K Fe Mn Zn Cu
WD-40 69 3 34 4 0.8 0.1 0.8 0.2
“PAM” Vegetable oil spray >70 9 34 1200 2.9 0.2 1.4 0.3
“Dove” dish washing liquid 30 205 44 2 0.2 <0.1 <0.1 <0.1
Synthetic motor oil 48 11 33 5 0.8 0.1 460 0.6
Silicone spray 2 37 2 3 0.9 0.1 0.3 0.4

Data shown in Table 1 indicates that lubricants can pose potential contamination problems. Their effects on test results for samples in the Wyoming study are shown in Table 2, and may be summarized as follows:

  1. Lubricants had no significant effect on soil test levels of organic matter, nitrate-N and K.
  2. Effects of lubricants on soil P tests were significant. WD-40, PAM and silicone increased soil P from 14 ppm in the control to approximately 16 ppm.
  3. Some lubricants significantly increased soil test values for micronutrients while others decreased these values. For example: WD-40 increased the test value for Fe, whereas reduced values for Fe, Mn, Zn, and Cu… possibly by complexing or precipitating these elements.
Table 2. Effects of Soil Probe Lubricants on Soil Test Results
ppm
Lubricant % OM NO3 P K Fe Mn Zn Cu
Control (no lubricant) 1.7 1 14 249 11.4 1.5 0.8 1.7
WD-40 1.6 1 16 248 13.2 1.8 1.0 2.0
“PAM” Vegetable oil spray 1.7 2 16 263 13.5 3.8 1.1 2.3
“Dove” dish washing liquid 1.7 3 14 280 10.1 1.3 0.7 1.2
Synthetic motor oil 1.6 2 16 265 12.5 1.4 0.9 2.0
Silicone spray 1.6 1 16 246 9.9 1.3 0.6 1.0

Conclusions:

  1. Lubricants significantly reduce the labor needed to sample soils with probes.
  2. The greatest benefit with probe lubrication are with depth samples, and with wet, clayey soils.
  3. Soil probe lubrication seems generally acceptable when sampling macronutrients.
  4. In this study, benefits realized from lubricants greatly outweigh the negligible nitrate-N contamination resulting from the lubricants used.
  5. Effects of probe lubricants on micronutrients could be considered significant since their concentration in the soil is low. However, benefits of using a probe lubricant outweigh the contamination risk if effects of the lubricant are taken into account when interpreting the soil test results.

Reference: Alan D. Blaylock, Lyle R. Bjornstead, and Joseph G Lauer, University of Wyoming. Taken from The Soil-Plant Council Analyst, The Soil and Plant Analysis Council, Inc. March 1996.

 
 
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