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QUICK LINKS
Introduction to Soil Testing- What is It?
How to collect Soil Samples
Selecting a Soil Test Laboratory
Testing Methods
pH Tests
pH-Soil solution pH
Buffer pH
Phosphorous Tests including Sufficiency Ranges
Bray 1 (Weak Bray)
Bray 2 (Strong Bray)
Olsen
Mehlich 1
Mehlich 3
Morgan
Modified Morgan
Basic Cations/Nutrients Tests (Potassium, Calcium and Magnesium, also includes Sodium) including Sufficiency Ranges
Ammonium Acetate
Mehlich 3
Mehlich 1
Morgan
Modified Morgan
Micro-nutrient Tests including Sufficiency Ranges
DTPA
Mehlich 3
Mehlich 1
Morgan
Modified Morgan
Other Tests (Boron, Salinity, Bulk Density, Texture/Structure- Sand silt and clay, Saturated Paste, Cation Exchange Capacity-CEC, Organic Matter, Sulfur, and Soil Carbonate content.
Miscellaneous Tests

*Test methods that are listed in all categories (Mehlich 1 and 3, Morgan and Modified Morgan) are considered "universal" tests as they can extract all nutrients- major, secondary and micro. Susceptible to the "Jack of all trades, Master of none" argument.

THE CONDENSED VERSION FOR USING SOIL TESTS
A SIMPLE METHOD for Determining Fertilizer Rates and Nutrient Levels to Achieve Optimal Nutrient Levels for Phosphorous and Potassium

Quick Digest 8 Step:
Identify the Test method used by the Soil Test Laboratory.
In Most cases it will be Mehlich 3. Use the Mehlich 3 Sufficiency Ranges. If your CEC is Below 4, use the "Sand" ranges where noted.

Mehlich 3 Sufficiency Ranges for P and K:
P: 26-54
K: 75-176, 50-116 for sands

If Mehlich 3 wasn't used, Ammonium Acetate was most likely used for Potassium. Use the Ammonium Acetate Sufficiency Ranges. Bray 1 and/or Bray 2 was likely used to measure P if your pH is below 7. If your pH is above 7, Olsen was probably used for P. Use the appropriate (Bray 1 or 2, or Olsen) Sufficiency Ranges to be found in the thread that follows.

Ammonium Acetate Sufficiency Ranges for K
K: 100-235, 75-175 for sands

P Sufficiency Ranges
Bray 1 (Bray P1, Bray 1-P, Weak Bray)
Sufficiency Range (ppm): 15-30
Bray 2 (Bray P2, Bray 2-P, Strong Bray)
Sufficiency Range (ppm): 40-60
Olsen
Sufficiency Range (ppm): 12-28

Nitrogen is the driving force in the turf's usage of nutrients. For every unit of N the plant uses, it will use a proportionate amount of P and K. The following calculations will be based on ppm of elemental P and K with conversion to weights of P2O5 and K2O
For every pound of N applied to the lawn:
Cool season grasses will use approximately 0.3 lbs of P2O5 (or 3 ppm of P) and between .5 and .75 lbs of K2O (or 9-14 ppm of K).
Warm season grasses will use approximately .3 lbs of P2O5 (or 3 ppm of P) and .75 and 1 lbs of K2O(or 13-18 ppm of K).
1. Determine the Total pound of N you will be applying for the growing season.
2. Multiply the Total number of lbs of N by 3 to determine the total amount of P the turf will be expected to use for the season as ppm.
3. Multiply the Total number of lbs of N by 9 (for cool season turf) or 13 (for warm season turf) to determine the total amount of K the turf will be expected to use for the season as ppm.
4. Compare your soil test ppm for P and K to the appropriate sufficiency range.
5. a) If your soil test ppm value for P falls within the range, an adjustment value is 0, no adjustment.
5. b) If your soil test ppm value for P is below the sufficiency range, select a ppm value somewhere in the middle of the sufficiency range. Subtract the test report ppm value for P from your selected mid-range sufficiency range value. This value will be the P "addition" adjustment.
5. c) If your soil test ppm value for P is above the sufficiency range, select a ppm value somewhere in the middle of the sufficiency range. Subtract your selected mid-range sufficiency range value for P from the test report ppm value for P. This value will be the P "subtraction" adjustment.
6. a) If your soil test ppm value for K falls within the range, an adjustment value is 0, no adjustment.
b) If your soil test ppm value for K is below the sufficiency range, select a ppm value somewhere in the middle of the sufficiency range. Subtract the test report ppm value for K from your selected mid-range sufficiency range value. This value will be the K "addition" adjustment.
c) If your soil test ppm value for K is above the sufficiency range, select a ppm value somewhere in the middle of the sufficiency range. Subtract your selected mid-range sufficiency range value for K from the test report ppm value for K. This value will be the K "subtraction" adjustment.
7. Add the value calculated in step 2 to the value calculated in step 5 b (if applicable) or subtract the value calculated in step 5 c (if applicable) from the value calculated in step 2. If the result is zero or a negative number, the soil contains sufficient P and no P application is needed for the season. If the result is a positive number, then divide by 9. The result will be the total pounds of P2O5 fertilizer that needs to be applied for season to meet turf requirements and soil reserves. Do not apply more than 1lb/M of P2O5 within a 30 day period.
8. Add the value calculated in step 3 to the value calculated in step 6 b (if applicable) or subtract the value calculated in step 6 c (if applicable) from the value calculated in step 3. If the result is zero or a negative number, the soil contains sufficient K and no K application is needed for the season. If the result is a positive number, then divide by 18. The result will be the total pounds of K2O fertilizer that needs to be applied for the season to meet turf requirements and soil reserves. Do not apply more than 1lb/M of K20 within a 30 day period.

A more detailed, somewhat redundant, explaination. (The "Original Condensed/Simplified" version):
Soil testing was originally aimed at helping farmers improve crop yields. 70+ years or so ago when soil tests were being developed, farmers, by necessity, applied/fertilized all of the nutrients needed for that growing season prior to planting that year's crop. It was the only time the soil was available and the fertilizer could be tilled in to distribute it throughout the soil. One and done. Through studies, agronomists developed a data base that become the nutrient level ranges within which crops performed well. Regional testing by local University agronomists could narrow the spread of these ranges based on soil and climatic conditions particular to a region or State, but adjustments were still necessary to find the optimal nutrient level (defined as a point where further additions showed no further improvement) for each nutrient for a particular field and crop. Turf specialists have built on this model to develop turf grass sufficiency range levels.
The take away: range levels are intended to reflect the amount of nutrients needed to supply a crop/turf grass with sufficient nutrients for the WHOLE growing season.

Sufficient means acceptable, but not necessarily optimal. Optimal, the point at which increased amounts do not improve performance, can be defined as ensuring that the turf has all of the nutrients it needs for the level of performance we subjectively desire. How can we fertilize for optimal, avoid deficient, avoid excessive and be good stewards of the environment?

The Rational:

During my research, I kept coming across a turf grass fertilization method called the Minimum Level of Sustainable Nutrients (MLSN). Minimum? Sustainable? No thanks and I blew it off. A couple of years ago, I revisited the MLSN method (http://files.asianturfgrass.com/mlsn_cheat_sheet_us.pdf) and some tweaks suggested by a number of other specialists (like https://turf.unl.edu/NebGuides/g2265.pdf and more recently http://www.turfhacker.com/2018/03/mlsn-math-step-by-step.html) in depth.

It's simple and logical. It just makes sense.

Before we proceed with the Simplified method, we need to address a couple of points, including the not so simple issue of soil pH. Because pH has a massive influence on plant/turf nutrient availability, if it is or even CAN be modified, it should be the first thing adjusted. Generally, turf will perform well in a pH of 5.5 to 7.5 Even pH soil levels up to 8 can produce great turf. Nutrients are most available when soil pH is between 6 and 7. Refer to the in-depth guide below for guidance in making pH adjustments.

In order to keep the simplified method simple, it will address only those nutrients where optimal levels are most likely to have the greatest impact on turf performance. NP&K are used by all turf plants in far greater quantities than any other nutrient. Due to shear volume of usage, NP&K have the greatest influence on turf performance. That is why they are labeled the primary or major nutrients. More often than not, poor turf grass performance is due to shortages in one or more of the primary nutrients. Consequently, in the majority of cases, applying and maintaining sufficient quantities of the primary nutrients for the quantity of N applied will improve turf performance as well as provide the turf with the optimal amounts of major nutrients needed to achieve maximum turf grass performance.

As long as a soil test reports some value for the trace/micro/minor nutrients, leave them be for now. Do not adjust them unless there is some persistent visual indicator (deformed turf plants or unusual leaf color) that further researching indicates might be micro nutrient related. Even then I would confirm a micro deficiency with a tissue test prior to making any addition. Turf grasses are very efficient at extracting sufficient micros. In 17,000 soil tests, PACE turf never found a soil with detrimentally insufficient micro levels. If they are high, there isn't much of anything that can be done to lower the levels. Fortunately turf grasses are fairly tolerant to higher levels. Refer to the in-depth guide below for guidance in modifying micro/trace nutrients.

Ditto for making adjustments to improve soil tilth or for adjusting nutrient balance ratios, Those are items that will require referring to the in-depth portion of this guide for modification and don't qualify as simple.

Same for Ca and Mg. They are not included in the Simplified Method.
Ca and Mg are not commonly deficient but if they are, you will need to refer to the in-depth guide. Their correction can become a bit complicated as often the correction of another soil characteristic may involve adding Ca and/or Mg to the soil (pH as an example). In any case, they are not part of the simplified method.

Back to the simplified method:

That leaves us with N, P, K and S. These are the nutrients of greatest plant demand, most likely to deplete and be in need of replacement, and which are commonly contained within readily available fertilizers. We will also consider S, and Fe shortages as those nutrients are often contained in NP and K fertilizers and can influence which N, P or K fertilizers are selected, bought and applied. However, targeting and modifying for specific values for S or Fe, does not qualify as simple. Refer to the in-depth guide for guidance.

In a nut shell: Nitrogen is our primary turf grass growth regulator. Nitrogen applications increase the rate of growth, color, turf lushness and determine turf plant demand for the other primary, secondary and micro nutrients. Turf grass will use about 0.1 - 0.15 lbs of phosphorous and between .5 and 1 lb. of potassium for every pound of nitrogen that is applied (Note: Research has shown a direct relation between turf tissue N values and P and K values; those studies are the basis for these calculations and have proven to correlate quite well). The turf will draw these nutrients from what is already in the soil, from applied fertilizer or some combination of the two. Based on that relationship, If we apply 1#/M of nitrogen on May 30, September 1, October 1, November 1 and on December 1 (the winterizer) for a KBG lawn, that is a total of 5#/M of nitrogen for the season. Therefore, the turf should consume about .5#/M of phosphorous for the season (5#/M of N X 0.1 = 0.5#/M of phosphorous) and 2.5#/M of potassium (5#/M of N X 0.5 = 2.5#K/M). Those are the amounts that should be supplied over the season through fertilization to meet turf demand.

How will that result in optimum levels? What if those applied amounts aren't enough to be optimal for my turf? What if those applied amounts are more than needed?

This is where the results of the soil test are employed. A soil test reports the amount of each nutrient already present in the soil that is/will be AVAILABLE for the growing season (it is not a measurement of the total amount of a nutrient in the soil, again, I repeat, it is the quantity of nutrient available) to the turf for the growing season. As some soil specialists suggest, think of these soil test values as being stored in the soil. A "bank account", an insurance policy, or a rainy day fund from which withdrawals or deposits can be made. If the soil test nutrient values fall within the recommended sufficiency ranges (or at least above MLSN minimums) we are good to go. If the 0.5#/M of P or the 2.5#/M of K that we applied turns out to be insufficient for the turf grass demands, the turf will withdraw any shortage out of the soil "bank." In other words, the optimal value is always available to the plant. If the 0.5#/M of P or the 2.5#/M of K that we applied turns out to be more than what the turf grass needed, the excess amount will be stored/deposited in the soil "bank". Either way, a subsequent soil test will reveal if nutrients were taken out of the soil or deposited in the soil and we can make adjustments in next year's fertilizer application to keep the soil "bank" sufficient (within the ranges) to supply optimal nutrient levels to the turf and avoid any deficiency or excesses by staying within sufficiency ranges.

The EASY, SIMPLE Method, How to use:

1. The Soil Test



2. Determine the test extraction method used. In this case it is Mehlich 3
3. Pull the Sufficiency range values for the test method from the in depth guide.
In this situation:

Mehlich III (M3)
Ranges (ppm)

P: 26-54
Ca: 500-750
Mg: 70-140, 60-120 for sands
K: 75-176, 50-116 for sands
Na: unreported/N.A.
S: 15-40
Fe: 50-100
Cu: 0.4-2.5
Zn: 1-2
Mn: 4-8, 8-16 for pH >7
B: unreported/N.A. (update: per PACE and R. Carrow: 0.4/0.5- 1.5)

With a CEC of >16, this is not likely a sand, so we will not use "sand" values. If CEC is less than 6ish, then you the "sand" sufficiency ranges.

4. Compare the ppm values for each nutrient on the soil test report to the sufficiency ranges. Make note of all nutrients falling outside (above or below) range. If after achieving optimal P and K levels, the turf is still performing poorly, you will want to do further investigation of each deficient nutrient to eliminate it as the source of the issue. But:

Our goal is to determine the amount of fertilizer necessary to obtain optimal available primary nutrient levels and turf growth. Period, so we limit our focus to:

P: 26-54 Soil test reported value: 23, just slightly short of range--adjust.
K: 75-176, 50-116 for sands Soil test reported value: 80, within range, but at lower end. adjust?
S: 15-40 Soil test reported value: 9, low, adjust.
Fe: 50-100 Soil test reported value: 225, high, but not likely to be detrimental and no adjustment needed.

TMI: For reference when reading the paragraphs below: 1# of P2O5 = .44# of P (or lbs of P times conversion factor of 2.3 = lbs of P2O5, example: 0.5 lbs of P times 2.3 = 1.15 lbs of P2O5) and 1# of K2O = .83# of K (or lbs of K times conversion factor of 1.2 = lbs of K2O, Example 2.5 lbs of K times 1.2 = 3 lbs of K2O).
In addition, theoretically, the application of 1#/M of P2O5 will raise soil P test levels by 9 ppm and adding 1#/M of K2O will raise soil K test levels by 18 ppm.
The inverse is also true. Removing 1#/M of P2O5 from the soil will theoretically lower soil P levels by 9 ppm and removing 1#/M of K2O will lower soil K levels by 18 ppm.

For a total annual application of 5#/M of N, We need to supply the turf grass with 0.5#/M of P and 2.5#/M of K. They don't sell elemental P or K fertilizer. Fertilizer manufacturers sell in P2O5 and K2O equivalents. Therefor, we will need to apply 1.15/M of P2O5 equivalent fertilizer ( 0.5#/M of elemental P is the equivalent of 1.15#/M of P2O5, see above for formula) and 3#/M of K2O equivalent fertilizer (2.5#/M of elemental K is the equivalent of 3#/M of K2O, see above for formula). We could just apply a straight nitrogen fertilizer and just let the turf get its 0.5# of P or 1.15 lbs of P2O5 and its 2.5# of K or 3# of K2O from the soil, but that would lower the soil's P levels by 21 ppm (9 ppm X 2.3# of P2O5, see formula above) and the soil K levels by 54 ppm (see formula above). This would be fine if our P and K soil levels were excessively high and we wanted to lower them back into range, but our P and K levels are already on the lower end of the ranges and we do not want to drain the "bank", empty the rainy day fund, and have no insurance policy. In fact, as our P and K levels are on the low side, we want more insurance in this case.

Therefore, we will supply the turf with the 1.15#/M of the P2O5 it will use for growth this season PLUS we will apply an additional 1#/M of P2O5 to "bank" in the soil for additional insurance by adding 9 ppm to the rainy day fund. (Eventually, and there is no hurry, it would be good to raise soil P ppm levels in the mid to high 30s. over the next couple of years) That's 2.15#/M of P2O5 in total that we will apply this season. That can be broken up and applied however we like: into 5 applications of .43#/M of P2O5 or two applications of 1.1#.M (the general rule is no more than 1# per app within 30 days for any amendment, but an extra .1 is no problem). We will also supply the turf with the 3# of K2O it will use for growth this season PLUS we will apply another 1# of K2O to bank in the soil. (Eventually, and again, there is no hurry, it would be good to have soil K ppm levels at 100-120.) That could be applied in 4 equal applications of 1# of K2O.
To improve the S levels, we will look for sulfate content fertilizers like ammonium sulfate, potassium sulfate or sulfur coated urea.
Fe is high, so no modification is required. If it was low, we would look for an N,P or K fertilizer fortified with some iron content or consider the addition of iron from another source (FAS, or Iron sulfate for example).
To a great degree the source (whether a complete fertilizer, a TNPK, separate applications of SOP or TSP, and N or some combination of synthetics and organics) of the P and K and the rates (spoon feeding or max rates) and timing of application is not important as long as the total amount calculated gets applied during the growing season.
That's it. It really is much simpler in practice than it sounds. With a little practice, you can do it in your head.

 

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Use what follows from this point onward as a Quick Reference Encyclopedia of Terms and Concepts
Soil testing was primarily developed for food crops to get the greatest yield with the least amount of expense. Most of the data for soil nutrition reflects that goal. Fortunately, turf grasses are, on the whole, much more forgiving in their nutrient needs, so the nutrients levels determined "sufficient" for healthy crops encompass and are generally more than sufficient to meet the nutrient demands made by turf grasses. In addition, many university and independent agencies (PACE Turf) have more recently conducted and published studies specific to turf grasses that have refined turf nutrient requirements.

The purpose of soil testing is to attempt to measure how much of a nutrient will be available to the plant within a growing season period of time, That is, how much is in soil solution, the Solution Pool (and immediately available to the plant-a very small amount) plus how much more is being held (bound "tied up" in chemical complexes or on exchange sites on clay and humates/OM) within the soil where the bond "tie up" is weak enough (labile) to allow the nutrient to become available during that growth season time period, called the Active Pool. Some portion of nutrient is so tightly bound that it may not be available for years, called the Fixed Pool. The "goal" is to try and accurately measure both the Solution Pool and the Active Pool but not the Fixed Pool. The amount of nutrient that is measured depends on the strength of the extract used, weak extracts report lower amounts, stronger extracts will report higher amounts. Debate rises whether weak extracts are measuring enough of the Active Pool and whether strong extracts measure too much of the Fixed Pool. Much depends on the type of soil. The usefulness of the results depend on how well they have been calibrated to plant response through multiple studies that have resulted in the development of "sufficiency ranges" specific to each test extract method.

A number of reagents/extracts (chemical solutions) and tests have been developed to determine various soil characteristics and nutrient levels. The current most commonly employed soil test methods/procedures (associated by geographic region) can be found here and here and here and here. Some (see Mehlich series and Morgan) were developed to be "universal" reagents able to extract the broad spectrum of nutrients important to plant growth- the primary, secondary and micro nutrients, rather than using different methods to extract each type of nutrient. Some where developed for specific regional soil characteristics (pH, texture, CEC, OM content) and climates (See Generally: https://www.aces.edu/wp-content/upl...gSoilTestReportsFromCommercialLabs_071018.pdf). Many are still employed today as they have been judged superior to alternative methods at extracting accurate, repeatable and predictable levels of nutrients. Field tests have been conducted employing the data derived from these reagents extracts/tests to determine nutrient level ranges within which plants will acceptably perform.

In later posts I will provide the "SLAN sufficiency ranges" for each of the most common tests used by soil testing labs. Nutrient test values that fall within SLAN ranges (aka sufficient nutrient levels) are expected to result in sustainable turf grass growth. The SLAN or sufficiency nutrient ranges for each of the reagent tests have been selected to reflect levels at which there is a 50% expectation of turf plant growth response due to an application of a nutrient. Conversely, there is a 50% expectation that an additional application of a nutrient is not expected to result in turf plant response. (The soil science definition of OPTIMAL is: that level of nutrient at which an addition will not result in an improved/favorable plant response.) This 50/50 expectation is based on the provision of nutrient levels for at least one full season of plant growth.

That is to say: Of all the soils that fall within the sufficiency range, half are expected to be at less than optimal levels, but the other half are expected to be at, or above optimal levels.

The ranges are a baseline, a yardstick, against which nutrient additions can be measured and judged.

The "SLAN sufficiency" ranges for each of the different test methods that will be posted are based on the work of R. N. Carrow, professor and researcher in the crop and soil science department at the University of Georgia and credit is greatly acknowledged. After a number of years of collecting "ranges" from various sources with mixed results, special thanks to Virginiagal for directing me to Carrow's compilation.

Some labs use one "universal" reagent/test for extracting all of the nutrients [P, the Bases (Ca, Mg, K, and Na), and micro/trace nutrients] and some mix and match reagents/tests for the different nutrients. It is important to know which reagents/tests (and for which nutrients) the lab employed so that the correct "sufficiency level ranges" can be applied. If the test used is not identified on the test report, contact the lab and ask which test was used for Phosphorous, which for Sulfur, which for Buffer pH (if one was done), which for Base Cations (Ca, Mg, K, and Na), which for the micro/trace nutrients and which for soil solution pH.

Edits made to clarify the section defining nutrient ranges and SLAN sufficiency ranges. Thanks to Frontal and Monty for pointing out the need for this edit. Re-Edited 3/10/23

 

[Ridgerunner]

There is an axiom from the early days of IT: "[email protected] in, [email protected] out."
Providing the best data (sample) possible will provide the best useful soil test report.

Adequate sampling:
A couple of field studies have been done regarding the relationship between the number of samples taken and how well the total test area is represented by those samples.
In one field test, increasing numbers of samples were taken from a 3600sq ft plot. The results of the study indicated that when 3 or less samples are taken, there is a far less than 50% likelihood that the results of the soil test will reflect the entirety of the test plot. (i.e. that it would fall within 25% of the soil test nutrient levels of another sample taken within the test plot). However when 8 samples were taken, it was found that there was an 85-90% likelihood that soil testing of a mixture of the 8 samples would fall within 25% of the soil test results of any additional sample taken from the test plot. Adding more than the mix of 8 samples only slightly improved the relationship/likelihood. The magic number of samples for a 3600 sq ft plot appears to be 8 for improved accuracy of soil data.

Each individual sample
Most soil test labs, soil/turf specialists and agronomists commonly recommend that samples should reflect the soil profile within the root zone. For turf, they recommend that the sample extend from the soil surface to a depth of 4". It is recommended that the top of the soil sample be scrapped/cleaned off to remove contaminates like undissolved fertilizer prills and litter that could skew test results. Thickness and width of each sample should be the same between all samples to avoid over or under weighting a particular sample or strata in the final mix.
Separately sample, or avoid, any areas (former garden bed, play areas that were sand boxes or mulch covered, etc.) that are known to be unrepresentative of the test soil plot.

Tools
To eliminate/diminish contamination, use only clean stainless steel, quality steel or plastic shovels, trowels or buckets/containers when sampling. Avoid copper, brass and galvanized steel or dirty tools and containers.

 

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Soil Solution/Suspension pH. The most common reagent used for measuring soil solution pH is distilled or deionized water. Some/most labs use a 1:1 soil to water ratio and some use a 1:2 ratio. Testing done with a higher ratio/volumes of water will result in slightly higher pH values. Soil solution pH that falls between pH 5.5 and 7.5 are not considered detrimental to turf grass performance. Soil pH in the mid 6s is considered desirable as a compromise between nutrient availability, CEC and micro-life health. Soil pH fluctuates throughout the growing season and soil will generally be more acidic in the Fall than early Spring. For year to year comparisons, pH should be tested at the same time each year.
Although a number of test reagents (CaCl2, a common reagent for offsetting soil salt content) can be used to determine pH, most are usually only used upon request, as part of a client specified package, require an additional fee and are not regularly employed by most labs.

Buffer pH. There are a number of tests that can be employed by labs to determine the amount of total acidity present in soil. Current, Buffer pH testing methods are Shoemaker-McLean-Pratt (SMP), Watson and Brown, Woodruff, Adams-Evans, Sikora and Moore-Sikora, and the Mehlich and Modified Mehlich.

Acidic soils will have a large proportion of their acidity held in "reserve" on CE (Cation Exchange) sites and soil solution pH is a result of a balancing between the hydrogen in solution and the hydrogen held in "reserve." If hydrogen is removed from solution, "reserve" hydrogen will replenish much of the loss and settle into a new balance. Consequently, when adjusting pH, it is not enough to just neutralize the acidity in solution, a significant portion of the reserve must also be neutralized in order for the resulting re-balancing between solution and "reserve" to result in the desired final soil pH.

A variety of chemicals and solution ratios are employed depending on the specific Buffer pH test used. Which test is used should be based on the characteristics of the soil being tested as some tests are considered more accurate dependent on soil CEC, soil texture/parent material, soil (water) pH, and soil OM level. What they all have in common is a known initial test reagent pH and an ability to react with reserve acidity and display a soil's total acidity as a change in the pH of the test reagent. The measured value of the test reagent's pH after soil interaction is the "Buffer pH." Each particular test has a Lime Requirement (LR) chart that has been created to provide the amount of lime needed to raise pH to a desired value based on the Buffer pH value.
If you are unable to locate the LR chart for your soil test's Buffer pH and the lab does not provide or direct you to one, please feel free to contact me.

Note: Some labs report a value labeled as "Excess Acidity," "Hydrogen as a Percentage of Base," or "meq of Acidity or Hydrogen." These are not Buffer pH measurements, they are estimates based on calculations and are not accurate for determining lime applications.

 

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The Bray and Olsen tests are grouped together as they are (1) both are used solely for the extraction of Phosphorous and (2) they are companion P tests for the labs that employ them. (Bray, if the soil is acidic to neutral, (pH <7.2); Olsen, if the soil is alkaline, (pH >7.2. Note: However, Olsen is used for determining P by some labs for N.W soils if soil pH is >6.2 and by some labs for the SME -Saturated Media Extract test) Note: there are two Bray reagents/tests.

Bray 1 (Bray P1, Bray 1-P, Weak Bray) As the name implies, Bray 1 employs a weak reagent. Used to extract the P in solution and a small portion of readily available (highly soluble/most labile) forms of P present in the soil but not in solution. Bray 1 (vs Bray2) is the preferred reagent used for determining soil sufficiency levels.
Sufficiency Range (ppm): 15-30

Bray 2 (Bray P2, Bray 2-P, Strong Bray) Also, as the name implies, employs a stronger reagent. In addition to the P in solution and the portion of readily available/labile P extracted by Bray1, Bray2 also extracts an additional amount of P that is less soluble/available. (i.e. a significant portion of P that is considered less labile or "tied-up.") A comparison of results for the Bray1 and Bray2 test (some labs provide both) can be used to estimate the portion of a previous application of P that has remained readily available and the proportion that has become "tied-up" and unavailable.
Sufficiency Range (ppm): 40-60

Olsen
Sufficiency Range (ppm): 12-28

 

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Appropriate for a broad range of soils that have a pH <7.5.
It is considered a "universal" extractant as it can be employed to extract a number of soil/plant nutrients and can be used for a number of regional soils.
Mehlich 3 can be employed as an alternative to Bray and/or Olsen for the extraction of Phosphorous (P) and can provide useful (correlated) results over a wide range of soil pH levels. http://www.agronext.iastate.edu/soilfertility/info/ComparisonofMehlich-3OlsenandBray-P1Procedures.pdf

Ranges (ppm)

P: 26-54
Ca: >500
Mg: >70, >60 for sands
K: 75-176, 50-116 for sands
Na: unreported/N.A.
S: 15-40
Fe: 50-100
Cu: 0.4-2.5
Zn: 1-2
Mn: 4-8, 8-16 for pH >7
B: 0.4/0.5- 1.5

R. Carrow's unedited SLAN values:
P: 26-54
Ca: 500-750
Mg: 70-140, 60-120 for sands
K: 75-176, 50-116 for sands
Na: unreported/N.A.
S: 15-40
Fe: 50-100
Cu: 0.4-2.5
Zn: 1-2
Mn: 4-8, 8-16 for pH >7
B: 0.4/0.5- 1.5

*The Notation: unreported/N.A. indicates that the reagent is not considered appropriate for extraction of that nutrient or data was not available.

Pace Turf Minimum Nutrient Levels
Defined as levels above which turf does not poorly perform. Safe to assume that the converse is true?
All soils tested were low nutrient holding capacity soils with CEC <6.

pH: >5.5 to <8.5
P: 21 ppm
Ca: 331 ppm
Mg: 47 ppm
K: 37 ppm
S: 7

 

[Ridgerunner]

Primarily used for the Soils of the Southeastern United States but also for acid soils of the Northeast.

Ranges (ppm)

P: 15-30
Ca: 200-350
Mg: 50-100, 30-60 for sands
K: 90-200, 50-100 for sands
Fe: 50-100
Cu: 0.5-1
Zn: 1-3
Mn: 4-10, 10-18 for pH >7
B: 0.3-1

 

[Ridgerunner]

Used primarily for soils of the Northeastern United States, but also considered appropriate for the soils of the Pacific Northwest. SLAN turf ranges were not found for Modified Morgan; Modified Morgan ranges below are UMass, which "generally" comport to those of the University of Vermont and University of Maine recommendations, and should be employed with caution (advise that the recommendations provided specifically for your local and soil be obtained and employed). Modified Morgan was reportedly developed to improve nutrient extraction (particularly of K) in finer textured (clay content) soils. Modified Morgan substitutes ammonium acetate adjusted to pH 4.8 for Morgan's sodium acetate adjusted to pH 4.8. Unable to verify the appropriateness of either tests ability to extract additional nutrients than is reported below (Morgan and Modified Morgan/UMass) It does appear both reagents might be employed to extract Fe, Mn, Zn and Al and U of Maine states Modified Morgan used to extract nutrients they report.

Morgan

Ranges (ppm)

P: 10-20
Ca: 500-750
Mg: >100
K: 130-174
Micro-nutrient sufficiency ranges not found.

Modified Morgan

UMass Ranges (ppm)

P: 4-14, (UofVermont: 4-9.99)
Ca: 1000-1500
Mg: 50-120
K: 100-160

U of Maine "Optimal" Ranges (ppm)

P: 10-20
Ca: use 60-80% of Base Saturation
Mg: use 10-20% of Base Saturation
K: use 3.5-5% of Base Saturation
Na: <100
S: >15
Fe: 6-10
Cu: 0.8-1.2
Zn: 1-2
Mn: 4-8
B: 0.5-1.2

 

[Ridgerunner]

Ammonium Acetate reagent at pH 7 is commonly (and has been traditionally employed to determine Ca nutrient levels in high pH soils) used for the extraction of Ca, Mg, and K in all soils. Ammonium Acetate at pH 7 is also used to determine CEC/TEC. To avoid inflated Ca levels in calcareous soils when determining CEC/TEC, ammonium acetate at pH 8.1 is recommended (Addressed infra).

Ammonium Acetate pH7

Ranges (ppm)

Ca: 500-750
Mg: 140-250, 100-200 for sands
K: 100-235, 75-175 for sands
S: 30-60

 

[Ridgerunner]

DTPA (diethylenetriamepentenaacetic acid) is a chelating agent and is primarily used in the following reagents for extracting unbound metal soil nutrients.

DTPA-TEA (DTPA + triethanolamine to buffer to pH 7.3)
The most commonly employed reagent for the extraction of micro-nutrients.

Ranges in ppm

Fe: 10-15
Cu: >1
Zn: >2
Mn: 2-5, 5-15, if soil pH >7

AB-DTPA (Ammonium Bicarbonate and DTPA--Soltanpour and Schwab Ammonium Bicarbonate‐DTPA - Colorado)
Used for the Soils of the Southwestern United States to extract primary, secondary, and micro-nutrients. Reagent adjust to pH 7.6. See: https://extension.colostate.edu/topic-areas/agriculture/soil-test-explanation-0-502/

Ranges (ppm)

P: 8-11
Ca: unreported/N.A.
Mg: unreported/N.A.
K: 61-120
Fe: >10
Cu: >2
Zn: >1.5
Mn: >5

*The Notation: unreported/N.A. indicates that the reagent is considered appropriate/is employed for extracting that nutrient but data was not available.

 

[Ridgerunner]

This section Will be periodically updated.

Boron
https://www.borax.com/wp-content/uploads/2016/08/soiltestsforavailableboron-final-feb2012.pdf

Hot Water Extraction
Reagent: Water
Range (ppm) 0.5-1.0 (Recommendations vary greatly and are influenced by pH, higher pH makes B less available, and soil texture) e.g. See http://nmsp.cals.cornell.edu/publications/factsheets/factsheet47.pdf https://www.borax.com/wp-content/uploads/2016/08/soiltestsforavailableboron-final-feb2012.pdf (Note: Turf is not considered a high B demanding crop/plant) and http://corn.agronomy.wisc.edu/Management/pdfs/a2522.pdf

DTPA Sorbitol Extraction
Results correlate to within 96% of HWS,
Range (ppm) 0.4-2.0 (source Midwest Labs)
http://www.directseed.org/files/9514/8459/9380/Deciphering_Soil_Tests_Matt_Stukenholtz.pdf

Sulfur
Reagent: Monocalcium Phosphate Extraction
Range (ppm) 10-20

Organic Matter (OM)

Loss On Ignition (LOI)
Most common method employed by soil test labs. A measured quantity of soil is dried, weighed then subjected to furnace temperatures in excess of 360C (temperatures employed by individual labs can vary resulting in variable results). The high temperatures oxidize the OM converting carbon to CO2. The sample is re-weighed and the change/loss in weight is correlated to organic carbon/OM content that was present in the soil sample.
It is commonly assumed that OM is composed of 58% carbon. Conversion factor: of 1.72, but can be as high as 2.6 in subsoils. Formula: OM%= Organic Carbon (LOI)% X 1.72. Considered most accurate for soils with >6% OM.

Walkley Black (WB)
OM is determined by oxidation through a chemical reaction. Chromic acid is added to a measured quantity of soil and the amount of chromium6 that is converted to chromium3 is measured spectrophotometrically to determine the amount of organic carbon. Considered most accurate for soil with OM <2%. Historically, this method was the method of choice, but due to the Dichromate reagent's high toxicity and classification as a Class 1 hazardous chemical (carcinogen), its use is much less common than LOI.

Cation Exchange Capacity (CEC) aka Total Exchange Capacity (TEC)
Two methods are used for determining CEC/TEC: The Summation Method and the Measured Method.

The Summation Method
By far, the most commonly used method among labs. This method involves a calculation of the base cations (Ca, Mg, K and often Na) to determine their individual milliequivalent (meq) value:
Reported Ca. ppm /(divided by) 200 (or reported lbs of Ca / 400) = meq of Ca
Reported Mg ppm / 120 (or reported lbs of Mg / 240) = meq of Mg
Reported K ppm / 390 (or reported lbs of K / 780) = meq of K
Reported Na ppm / 230 (or reported lbs of Na / 460) = meq of Na
Note: reported lbs must be for an acre slice furrow (a depth of 6-7")

In addition, an meq value for minor of "other" cations (Fe, Mn etc), Al, and hydrogen (H, or H+) is estimated by employing a variety of formulas based on soil solution pH. Slightly more accurate estimates for hydrogen can be made using Buffer pH values. (Reminder: lime applications should be based on Buffer pH values only, not estimates.)

The sum of all meq values is reported as CEC/TEC.

Measured Method aka Direct Measure of CEC
This method is considered the most accurate for determination of CEC/TEC. Simplified, the most common method is a 24 hr soak of a measured quantity of soil in an ammonium acetate (AA) solution buffered to pH 7 (for greater accuracy for soils with a pH <5.5, unbuffered AA solution is recommended; for soils with pH >7.6, an AA solution buffered to pH 8.1 is recommended) to replace exchangeable cation soil sites with ammonium (NH4). The amount of NH4 is then measured by spectrometer to determine total soil cation exchange sites.

From USDA SARE program (associated with U of Maryland):
"A useful rule of thumb for estimating the CEC due to organic matter is as follows: For every pH unit above pH 4.5, there is 1 me of CEC in 100 grams of soil for every percent of organic matter. (Don't forget that there will also be CEC due to clays.) SOM = soil organic matter.

Example 1: pH = 5.0 and 3% SOM → (5.0 - 4.5) x 3 = 1.5 me/100g

Example 2: pH = 6.0 and 3% SOM → (6.0 - 4.5) x 3 = 4.5 me/100g

Example 3: pH = 7.0 and 3% SOM → (7.0 - 4.5) x 3 = 7.5 me/100g

Example 4: pH = 7.0 and 4% SOM → (7.0 - 4.5) x 4 = 10.0 me/100g"

Saturated Paste Test
Employed to monitor soil nutrient levels and ratios on a regular basis (often used every 6-8 weeks or less). It is considered a "snap shot" of short term changes. Results are variable with changes that occur based on fertilization applications, soil OM content, soil moisture content, soil microbiology and temperature. It is intended to reflect readily available plant nutrients; those that are in the soil water solution. (Also see the related "Soil Health" Test, the Haney Test and the Carbon Burst Test)
Reagent: Water

Ranges or "ideal" target values are ppm.
P: 1-3
Ca: 40-60 (55-60%)
Mg: 8-12 (12-20%)
K: 15-20 (9-10%)
Na: <20 (8-2%)
S: 5-10
Fe: 0.3 (+ or - 0.02)
Cu: 0.08 (+ or - 0.02)
Zn: 0.08 (+ or - 0.02)
Mn: 0.1 (+ or - 0.02)
B: 0.1 (+ or - 0.02)
Soluble Salt: <960
Bicarbonates: <50

Soil Structure aka Soil Physical Test

This test is used to determine the % of sand, silt and clay contained in a particular soil sample. Common test methods employed are the Hydrometer Method (suspending soil in an H2O based reagent and measuring the solution density to determine sand and clay fractions) and the Sieve Method (passing the soil sample through a series of every smaller mesh sizes to determine sand sub fractions).
The particle size make up of a soil can be used to draw conclusions/estimates regarding a soil's drainage rate, water holding capacity (both available and unavailable), CEC, aeration and pH buffering capacity. It can also be used to determine soil classification (sandy loam, loam, loamy clay, etc. and estimate bulk density based on classification)

Particle sizes and classifications:

>2.0 mm (2000 microns) = Gravel/Coarse fragment content (not used in classification)

Sand = 2.0 mm to 0.05 mm (50 microns)

• Very Coarse Sand = 2 to 1 mm

• Coarse Sand = 1 to 0.5 mm

• Medium Sand = 0.5 to 0.25

• Fine Sand = 0.25 to 0.10

• Very Fine Sand 0.10 to 0.05

Silt = 0.05 mm to 0.002 mm (2 microns)

Clay = <0.002 mm

Soil Classification tool (enter % sand and % clay and the tool will graph the soil's placement on the soil classification triangle):
https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/?cid=nrcs142p2_054167

Bulk Density

Bulk density reflects the weight of soil in a defined volume. It is reported as a the weight of a volume of soil divided by the volume, g/cm3. It is commonly employed to measure soil compaction which will impede root growth and water penetration, drainage and soil water holding capacity. Sands have higher bulk densities than clay soils as sands contain less air spaces (40%) than clay (58%).

Bulk Densities (not compacted) by soil classification.

Sand and Loamy Sands = 1.7 to 1.6
Sand Silt and Clay Loams = 1.6 to 1.3 (Loam = 1.4)
Clay = <1.3 to 1.1
Organic Soils can have bulk densities <1.0

Bulk Densities (compaction values that can impede root growth) by soil classification. Needs to be determined in the field. In general, any bulk density in excess of 1.6 can be expected to restrict root growth.

Sands = >1.75
Silt (and Loams) = >1.60
Clay = >1.4

A method for DIY bulk density determination:
http://soilquality.org.au/factsheets/bulk-density-measurement

Soil Salinity (The EC (Electrical Conductivity) Test)
High soil salt content can detrimentally affect osmotic pressure. In other words, the turf plant will suffer the effects of dehydration due to the inability to take up water. As increased salt content in water increases, the electrical conductivity of water also increases, Soil salt content is determined by measuring the electrical conductivity (EC) of the soil solution. A saturated paste solution is commonly used as the standard for EC measurement. However, be aware, some labs use a different proportion of water to soil solution for their tests and their EC results must be adjusted to a different standard. EC is measured in units of dS/m (decisiemens per meter) or mmhos/cm. Using the saturated paste test, a result of <4 dS/m or mmhos/cm is considered satisfactory for most plants. A reading of <2 is preferable for salt sensitive turf grass like KBG. Bermuda grass is much less sensitive and can withstand salinity levels up to a dS/m level of 6.9.

Soil Carbonate/Lime Content Test
Some labs offer a test to determine the amount of a soil's carbonate/lime content. The name of the test varies: Lime%, Carbonate%, Soil Earth Carbonates, etc. One lab even labels it the Fizz Test :roll: . Before requesting this test, verify that it is an actual measurement of the soil's carbonate content. This is not an inexpensive test.
One procedure labs use is the chamber test. A soil sample is placed into a sealed chamber (basically a bell jar with a pressure gauge). An acid solution is then applied to the soil sample. The acid reacts with any carbonate material (lime) in the soil and releases CO2. The CO2 increases the pressure within the chamber. The increase in pressure is measured and used to calculate the amount of carbonate/lime in the soil sample which is usually reported as a percentage.

Tissue Test for Nutrients

The values below are the most common ranges cited by numerous turf articles and University Turf programs:

via AgSource/Harris Laboratories

 

[Ridgerunner]

---gratuitous quotes:

A man once said, "There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns."

My father once told me, "People marry who they meet."



Calculations-The Math

The vast majority of soil test labs report nutrient values as parts per million (ppm). Some may, in addition, also report values in pounds per acre (an acre furrow slice).

An acre furrow slice is the amount of soil in one acre (43,560 sq ft) of land to the depth of 6.7" or 24,394 cubic feet. Assuming that a soil has a bulk density of 1.33 g/cm3, an acre furrow slice is estimated to weigh 2,024,458 lbs. For convenience and to simplify calculations, 6" rather than 6.7" is commonly used and 2,000,000 lbs rather than 2,024,458 lbs is used. Therefor, one acre furrow slice of any soil to the depth of 6" weighs 2,000,000lbs. In addition 43.5 is used as the number of thousand (M) square feet in one acre. (accept it, don't fight it).
These assumptions simplify conversion between lbs/acre (at a 6" depth) to ppm and ppm to lbs/acre (at a 6" depth). For instance, if there are 200 lbs of potassium reported in one acre of soil to a 6" depth (200lbs of K/2,000,000lbs of soil or a ratio of 200/2,000,000), dividing by a factor of 2 will result in the number of pounds of potassium (100lbs) in 1,000,000 lbs of soil (i.e. a ratio of 100/1,000,000) or 100 ppm. Conversely, if 100 ppm of potassium is reported (100/1,000,000) then multiplying by a factor of 2 will result in the number of pounds of potassium in an acre to the 6" depth (a 200/2,000,000 ratio or 200lbs of K/2,000,000lbs of soil). So, to convert ppm to lbs per acre, multiply by two. To convert pounds per acre to ppm, divide by two.

Starting with NPK (Nitrogen, Phosphorous and Potassium). Then moving on to the other nutrients. NPK are used by the turf plant in far greater quantities than any of the other nutrients. For every pound of N used by a turf plant (used, not just applied), the turf plant will require and use 0.25 lbs of P and 0.5 lbs of K. Consequently, they have the largest influence on turf performance.

Nitrogen

Nitrogen is seldom included in soil tests as its level quickly changes. Best Practices: Use the schedules and quantities for N applications recommended for the particular type of turf being grown.

For the nerds : Nitrogen Toxicity. Some labs do routinely test for both nitrate (NO3) and ammonium-N (NH4). Studies have shown that total N values greater than 20ppm may result in poorly performing turf. As levels increase above 20 ppm (significantly at the 40+ ppm level), the greater the incidence of an effect similar in appearance to drought stress and die off. It is also recommended that NH4 values not exceed 7 ppm and that a NO3 to NH4 ratio of less than 3:1 be avoided as both situations have been found present in poor performing turf.


Potassium (K)

Example: A soil test reports a K value of 65 ppm via Mehlich III reagent testing and a CEC of 12.

1. As a CEC of 12 is >5 it is very unlikely to be a sand. Consequently we will employ the Mehlich III potassium sufficiency range for "other soils," 75-176 ppm (See Mehlich III value ranges supra).

2. We elect to increase our soil K level to a mid range value of 126 ppm.

3. Desired value (126 ppm) less current value (65 ppm) leaves a deficit (or the amount needed to be added to reach our desired level) of 61ppm.

4. 61 ppm, or a ratio of 61/1,000,000, multiplied by a factor of 2 results in a ratio of 122/2,000,000 or 122 lbs of elemental K per acre to a depth of 6 inches is needed to reach our desired potassium level.

5. Although potassium is available in a number of forms in fertilizers [e.g. potassium sulfate (SOP) or potassium chloride (MOP)], the amount of potassium contained in a bag of fertilizer is always reported as a K2O equivalent. (This is a holdover from the arcane days of chemistry when the oxide forms of chemicals where used in chemical formulas.) A bag of SOP fertilizer will report its contents as 50% K2O and a bag of MOP fertilizer will list its contents a 60% K2O.

6. K2O is 83% elemental potassium. To determine the amount of K2O needed to supply 122 lbs of elemental potassium, we multiply 122 by a conversion factor of 1.2, (122 X 1.2 = 146.4) resulting in the amount of 146.4 lbs of K2O. To determine how many pounds of potassium containing fertilizer needs to be applied to deliver 146.4 lbs of K2O, we divide 146.4 by the percent content of K2O listed on the fertilizer bag. In the case of SOP, the bag lists the contents as 50% K2O. 146.4 / .50 = 292.8 lbs of SOP. To determine the amount of MOP needed to apply 146.4 lbs of K2O, we would divide 146.4 lbs of K2O by 60%. 146.4 / .60 = 244 lbs of MOP. This is true for any potassium containing fertilizer. To determine the number of pounds of a 10-10-10 fertilizer that would be required to apply 146.4 lbs of K2O, we divide 146.4 lbs of K2O by 10%. 146.4 / .10 = 1464 lbs of 10-10-10.

7. To determine the amount to be applied to each 1000 sq feet (M) of soil to a depth of 6", divide by 43.5. For SOP: 292.8 / 43.5 = 6.8 lbs of SOP/M

8. The FORMULA: (Desired ppm level -(subtract) test reported level) X 2 X 1.2 / (percent of K2O listed on a fertilizer bag) / 43.5= total amount of fertilizer per M needed to reach the desired K ppm soil level to a 6" depth. e.g.: (176-65) X 2 X 1.2 / .50 / 43.5 = 6.8 lbs of SOP/M.

For the nerds :
General information for all "nerd" comments that follow: CEC, for our intents and purposes, is finite. [This is not to discount the portion of OM that is Stable Organic Mater (SOM or Humic Substance and its contribution to CEC, nor OM's soil structure, moisture holding capacity, or as a source of nutrients through decay). However, due to SOM's relative stability (over 100s, possible eons of years) and the extremely small changes to CEC attainable from additions of OM, or even humic substances, any variability to CEC due to changes in OM is herein considered inconsequential. (this is also an attempt to avoid the "Heisenberg Copenhagen experiment" argument regarding Humic and Fulvic acids. ] Increasing the amount of one cation on a CEC site means it must take the place of one of the other cations already present. Due to the dynamics of soil chemistry (valence, hydrated radius, etc.), this "exchange" between sites is not as predictable as it would seem (adding "X" quantity of a nutrient is unlikely to result in a calculable change in the number of CEC sites it will hold, or which other cations will be affected). Please find an excellent explanation of this CEC soil chemistry infra. In the case of potassium, its value to plant health and the quantity used by the plant outweighs any disadvantages in changes in calcium and magnesium held on CEC sites. Secondly, the addition of two units of potassium will only displace one unit of calcium or magnesium resulting in less impact to the % of CEC sites held by Mg and Ca.

Base Cation Saturation Ratio (BCSR). BCSR are recommended proportions on a percentage basis that Ca, Mg, P and Sodium (Na) and H+ should hold on the total CEC of soil. Total Base Saturation is calculated as the milliequivalents (meq) values of Ca+Mg+P+Na / Total CEC. Base Saturation % of each individual cation is calculated by dividing the meq for each nutrient by Total meq of all cations.

Example:

Ca reported ppm = 1360 ppm = 2720 lbs (2720 lbs / 400 = 6.8) meq of Ca = 6.8
Mg reported ppm = 180 ppm = 360 lbs (360 lbs / 240 = 1.5) meq of Mg = 1.5
K reported ppm = 195 ppm = 390 lbs (390 lbs / 780 = 0.5) meq of K = 0.5
Na reported ppm = 46 ppm = 92 lbs (92 lbs / 460 = 0.20) meq of Ca = 0.2
H+ reported as 1.0 meq

Total meq = 10

Thereby:
Total B. S. = 9 divided by 10 = 90%
B.S. of Ca = 6.8/10 = 68%
B.S. of Mg = 1.5/10 = 15%
B.S. of K = 0.5/10 = 5%
B.S. of Na = 0.2/10 = 2%
B.S. of H+ = 1/10 = 10%

Recommended BCSR percentages vary, but a common recent recommendation is:

Ca 65-80%
Mg 10-20%
K 3-8%
Na < 3%
H+ 10- 20%
BCSR percentages are often employed in addition to and as a companion to nutrient sufficiency adjustments to avoid nutrient imbalances.

Back to the potassium comments for nerds:

All of that BCSR explanation to clarify the following one point (although the info will be referred to in the nutrient discussions to follow):

B.S. percent of K should not exceed 10% as amounts greater than that may result in plant Mg deficiencies.

K to Mg ratios are another possible consideration. A growing number of agronomists are proposing, based on field trials and studies, that a 1:1 ratio (based on conversions/calculations made in consideration of differences in extraction methods) is favorable to plants. Proposed K to Mg ratios, based on soil texture, range from 1.2:1 for sand, 1:1 for loam, to 0.7:1 for clay. As both Mg and K are antagonistic to one another, the theory is that a 1:1 ratio allows both to be optimally taken up and used by the plant. Another possible advantage to achieving optimal uptake of Mg is an expected improved plant uptake of phosphorous due to Mg's synergy with P. (see Mulder's Chart of nutrient antagonism and synergy posted infra.)

In finer textured soils with Mg levels greater than 300 ppm and B.S. greater than 15%, high potassium levels can cause soil particle dispersion (compaction), damaging soil structure.

terraGIS Soil

Mulders Chart | PDF | Nutrients | Metals

Mulders Chart

www.scribd.com

Phosphorous (P)

Example: A soil test reports a P value of 6 ppm via Olsen reagent testing, a CEC of 9, and a pH of 8.1.

1. Checking the guidelines for the Olsen test, there is no separate guideline for sands, so we will employ the Olsen phosphorous sufficiency range for "all soils," 12-28 ppm (See Olsen value ranges supra).

2. We elect to increase our soil P level to a high range value/target of 26 ppm. (our operating theory is that at a pH > than 8, P is less available and also as this is newly plugged Bermuda, we hope to make P more available for root growth and spreading.)

3. Desired value (26 ppm) less current value (6 ppm) leaves a deficit (or the amount needed to be added to reach our desired level) of 20 ppm.

4. 20 ppm, or a ratio of 20/1,000,000, multiplied by a factor of 2 results in 40 lbs of elemental P per acre to a depth of 6 inches.

5. The amount of phosphorous contained in a bag of fertilizer is always reported as a P2O5 equivalent. (Like potassium (K2O), this is a holdover from the arcane days of chemistry when the oxide forms of chemicals where used in chemical formulas.) A bag of Triple Super Phosphate (TSP) fertilizer will report its contents as 0-45-0 or 45% P2O5. (A 10-10-10 fertilizer contains 10% P2O5)

6. P2O5 is 44% elemental phosphorous. To determine the amount of P2O5 needed to supply 40 lbs of elemental phosphorous, we multiply 40 by a conversion factor of 2.3 ( actual un-rounded off factor is 2.29), (40 X 2.3 = 92) resulting in the amount of 92 lbs of P2O5. To determine how many pounds of phosphorous containing fertilizer needs to be applied to deliver 92 lbs of P2O5, we divide 92 by the percent content of P2O5 listed on the fertilizer bag. In the case of TSP, the bag lists the contents as 45% P2O5. 92 / .45 = 204.4 lbs of TSP. To determine the amount of a Triple 12 (12-12-12) needed to apply 92 lbs of K2O, we would divide 92 lbs by 12%. 92 / .12 = 766 lbs of Triple 12.

7. To determine the amount to be applied to each 1000 sq feet (M) of soil to a depth of 6", divide by 43.5. For TSP: 204.4 / 43.5 = 4.7 lbs of TSP/M

8. The FORMULA:: (Desired ppm level -(subtract) test reported level) X 2 X 2.3 / (percent of K2O listed on a fertilizer bag) / 43.5= total amount of fertilizer per M needed to reach the desired K ppm soil level to a 6" depth. e.g.: (26-6) X 2 X 2.3 / .45 / 43.5 = 4.7 lbs of TSP/M.

For the nerds :
Phosphorous is most available between pH 6 and 8. Below pH 6, phosphorous tends to bind at increasingly greater rates with other elements (e.g. iron, Al. etc.), at pH greater than 8; phosphorous tends to bind at increasingly greater rates with Ca.

Nutrient Availability Chart According to pH

I saw this earlier and thought it would be good to have here to reference.

www.thelawnforum.com

The most effective reduction method for phosphorous binding in low pH soils is to raise pH. However, lowering pH is often unrealistic for high pH soils; improved P availability may be achieved in part by spoon feeding P or through application of an organic P source (manure).
Arbuscular mycorrhizal hyphae (fungi) have a symbiotic relationship with turf roots/plants. They are a major supplier of turf plant phosphorous. Mycorrhizal hyphae not only supply turf with P, but also water and with the water, micro-nutrients. It is also considered a major contributor to soil structure (ped) development. When soil phosphorous levels exceed 100ppm (via Olsen), Mycorrhizae hyphae root infection drops off dramatically and at levels >140 ppm, it is virtually absent. Mycorrhizal hyphae is also related to root resistance to disease. Some numbers: there is approximately 100 meters of mycorrhizal hyphae in a gram of soil, 1.5 miles in a cm3, and 7-8 miles in a teaspoon of soil. Mycorrhizal hyphae is 100 times more efficient at extracting and delivering nutrients than roots and 10 times that of hair roots. Mycorrhizal hyphae allow the turf to access up to 100,000 times the soil as roots can access alone.

UAF/CES Publications :: Home

http://amazingcarbon.com/PDF/JONES-MycorrhizalFungiEVERGREEN%28Sept09%29.pdf

https://www.researchgate.net/publication/270338608_Contribution_of_Arbuscular_Mycorrhizal_Fungi_to_Soil_Carbon_Sequestration

The Secondary Nutrients (Calcium, Magnesium and Sulfur) These nutrients are used by the turf plant in lesser amounts than the Primary Nutrients of NPK, but are used in much larger volumes than the Trace/Micro-nutrients.

Sulfur (S)
Sulfur is the overlooked nutrient. It is important to plant health, photosynthesis, other important processes and winter hardiness. Unless elemental sulfur has been applied to the soil within the past two years (Sulfur is often used in an attempt to lower pH, more on this supra), the vast majority of the sulfur reported as ppm on the soil test (and the form in which nearly all S exists in the soil) is in the form of sulfate. Sulfate is the only form of S that the turf plant uses. Sulfate will NOT result in lowering soil pH.
Soil Sulfur (sulfate) should be adjusted to the values given for the particular extraction method used (see guidelines supra.). Adjustment amounts are calculated the same way as amendment amounts for any other nutrient:
The FORMULA:: (Desired ppm level -(subtract) test reported level) X 2 / 43.5= total amount of lbs of S per M needed to reach the desired S ppm soil level to a 6" depth. Divide that amount by the % S listed on the bag of fertilizer amendment to determine the total amount of that amendment needed to reach the desired value. If using elemental sulfur (advised against) do not exceed 2#/M every 6 months.
Although Elemental Sulfur can be used, it is suggested that any S deficiency be made up by applying fertilizer amendments such as sulfur coated urea, or even more preferably, a sulfate containing amendment such as ammonium sulfate or when adjusting other nutrients, by applying gypsum, potassium sulfate, magnesium sulfate or K-mag and retesting for S in a subsequently scheduled nutrient soil test.

For the nerds : 1. Elemental sulfur will lower soil pH BUT Sulfate does not lower soil pH. 2. In very unusual situations, sulfate buildup can create a black layer. This occurs in humid high temperature climates where anaerobic conditions may arise due to excess water and soil compaction and poor soil drainage. This has been observed on some golf courses where intensive sulfate containing fertilizers are applied and due to excess soil water, microbes use the oxygen in the sulfate and replace it with hydrogen producing hydrogen sulfide (rotten eggs) creating toxic conditions.

Calcium (Ca)
Please see comment that follows the Magnesium discussion (infra),
If Ca levels are below the guidelines (see guidelines supra.), then adjustment (addition) should be made:
The FORMULA:: (Desired ppm level -(subtract) test reported level) X 2 / 43.5= total amount of lbs of Ca per M needed to reach the desired Ca ppm soil level to a 6" depth. Divide that amount by the % Ca listed on the bag of fertilizer amendment to determine the total amount of that amendment needed to reach the desired value. For instance, Gypsum (calcium sulfate) is approximately 22% Ca so divide by a factor of 0.22 to determine the total amount of gypsum needed to raise the Ca content to the desired level.
Another neutral pH Ca source is calcium nitrate (20% Ca).

Magnesium (Mg)
Please see comment that follows,
If Mg levels are below the guidelines (see guidelines supra.), then adjustment (addition) should be made:
The FORMULA:: (Desired ppm level -(subtract) test reported level) X 2 / 43.5= total amount of lbs of Mg per M needed to reach the desired Mg ppm soil level to a 6" depth. Divide that amount by the % Mg listed on the bag of fertilizer amendment to determine the total amount of that amendment needed to reach the desired value. For instance, Epsom Salts (magnesium sulfate) is approximately 10% Mg so divide by a factor of 0.10 to determine the total amount of Epsom Salts needed to raise the Mg content to the desired level.
Another neutral pH Mg source is K-Mag (11% Mg).

For EVERYONE : Lime should not be used as a source for Ca (calcitic lime) or Mg (dolomitic lime). Lime should ONLY be used to raise soil pH (see section on adjusting pH to follow). Once sufficient lime has been applied to achieve the desired pH, then any further additions of Ca or Mg that are needed should be derived from a neutral pH source (gypsum or calcium nitrate for Ca or Epsom Salts or K-Mag for Mg).
Adjustments to Ca and Mg is a game of whack-a-mole. An increase in one will result in some amount of decrease in the other and a much more dramatic decrease in potassium on the CEC sites.
Your primary goal is to provide enough Mg and Ca to attain the recommended values in the guidelines supra.
For the nerds : A secondary goal is to balance the Ca to Mg ratios (Base Saturation percentages) Once sufficient Mg is present to meet guideline values, Ca can be increased to achieve desired Ca:Mg ratios. Although the "ideal" Ca:Mg ratio for greatest Mg and Ca availability is considered to be 8:1, a wide range of ratios have been found to be NOT detrimental (per studies: 0.25:1 all the way to 30:1) and a large segment of agronomists consider anywhere between 6:1 and 10:1 to be an "ideal" range. Another goal is to keep Mg:K ratios within the ranges discussed in the section regarding potassium supra. Again, most important is curing deficiencies/raising values to the guideline ranges. If an excess of Ca is present and Mg levels are sufficient per guideline ppm values, it is best to leave it be rather than attempt to raise Mg to reach some "ideal" ratio.

Adjusting Soil pH
This section will be in two parts: Raising pH and Lowering pH. The "Ideal" pH range for the best balance between maximum overall nutrient availability and an environment conducive to microbial activity is 6.5-6.8, However, soil pH ranges between 5.5 and 7.5 have not been found detrimental to most cool or warm season turf grass' performance. Generally, high pH soils will have a less detrimental impact on turf plants than a very low pH soil. In addition, a number of turf specialists suggest maintaining soil pH below 6.5 to help reduce disease on cool season grasses grown in transition zones and in climates where warm season grasses are otherwise commonly recommended. Another consideration is that various turf species (particularly some warm season turf grasses) will perform fine in pH ranges outside of 5.5 to 7.5. For example: Centipede performs best at soil pH between 5.0 and 5.5 and will perform satisfactorily at even lower soil pH, but does very poorly in soil pH at 6.5 and higher.

Raising pH in Low pH Soil
Excess soil acidity is neutralize by applying a carbonate source. Lime is used as the source of carbonate for soil pH adjustments. The results from a Buffer pH test are used to determine the total amount of lime needed to raise the soil pH to a desired pH value. (see supra discussion on pH for explanation of the Buffer pH test).
When a Buffer pH is done by a lab, the soil test report will provide an amount of lime to be applied to raise soil pH (a common target is pH 6.5, but verify with the lab if this is not stated on the report).
A second note of caution: Some labs make recommendations for only one year of application, so if the amount of lime recommended on the report is for only one year's application, it may not be the total amount of lime needed to raise the soil pH to the desired value. (Once again, if this is not clarified on the report, check with the lab or see the "For the nerds" comments below.)
A third note of caution, lab recommendation amounts are based on a lime quality CCE number. (If the report does not state the CCE value of their recommendation, verify with them what that CCE number is.) For instance, a soil report might recommend that you apply 100 lbs/M of a 70 CCE lime but the store you go to only carries 80 CCE lime (Bags of lime will always have a CCE value on the bag label) or the report recommends 90lbs/M of a 100 CCE lime but the store only carries 75 CCE. How do you know how much 80 or 75 CCE lime to buy and apply? To convert test CCE amounts of lime to another equivalent amount of lime of another CCE value: divide the test report CCE value by the lime bag being purchased CCE value. Then multiply the test report recommended lime quantity by the result.

For example: report recommends 100 lbs/M of a 70 CCE lime and the store carries 80 CCE lime.
70 divided by 80 = 0.875. Then 100lbs X 0.875 = 87.5 lbs/M. You need to buy and apply 87.5 lbs/M of 80 CCE lime to get the same acid neutralizing effect as 100 lbs/M of a 70 CCE lime.
For example: report recommends 90 lbs/M of a 100 CCE lime and the store carries 75 CCE lime.
100 divided by 75 = 1.33. Then 1.33 X 90 = 119.9 lbs/M of the 75 CCE. That is the equivalent of 90 lbs/M of a 100 CCE lime.

Lime is used to adjust pH, NOT Ca and/or Mg levels. Calcitic lime will necessarily raise Ca levels and dolomitic lime will raise Ca and Mg soil levels, but the sole purpose of lime is to adjust pH. The addition of Ca and or Mg is an unavoidable side effect of lime and not the goal. Fortunately, many low pH soils need an increase of Ca or both Ca and Mg. Select calcitic or dolomitic lime based on the soil Ca and Mg levels but only secondarily to pH adjustment. After desired pH is attained, stop using lime and apply gypsum or Epsom Salts to make up any Ca or Mg shortage.
Bag directions for lime application rates should always be followed, otherwise, for Aglime (non-fast acting lime), do not apply more than 100 lbs/M total per year and never more than 50 lbs/M at one time, once in the Fall and once in the Spring (or 25lbs/M every three months, etc)

For the nerds : The results from a Buffer pH test are used to determine the total amount of lime needed to raise the soil pH to the desired pH value by employing a corresponding Lime Table (see supra discussion on pH for explanation of the Buffer pH test).
Most lime Tables use rows and columns. Not all Lime Tables are configured the same. Some tables will list Buffer pH values in columns and the desired pH value in rows or vice versa. Other Lime Tables will have a separate table for each desired pH value and each table will then have the Buffer pH values in columns and the current pH value in rows or vice versa. Whichever, the tables are basically used the same way: the cell at which the appropriate Buffer pH value and the appropriate soil pH (either desired or current pH) intersect, is the amount of lime as tons or pounds of lime required per acre or thousand square feet to achieve the desired final soil pH.
The amount of lime required as displayed by the table is also dependent on the the type of lime upon which the Lime Table is based. State Universities that provide soil testing services will base their Lime tables on the quality of the lime available in the state (due to shipping costs, most lime supplied to a region come from the closest mine regardless, within reason, of lime quality) and according to minimum standards pursuant to individual state law. Minimum standards of lime quality E.g. carbonate content and granular size) are set by each individual state. In order to correctly use a Lime Table, it is important to know the lime quality (CCE) standard upon which it is based.
CCE is a reflection of lime quality, Pure calcitic lime would contain 100% calcium carbonate and would have a CCE of 100.

In addition to reporting the Buffer pH value which is used in conjunction with the Lime Rate (LR) Charts as discussed above to determine lime applications for pH adjustment, some labs will use the Buffer pH results to calculate soil hydrogen content and report the soil hydrogen content as meq and/or a percentage of Base Saturation (B.S.). This soil hydrogen value is used to calculate Total Cation Exchange Capacity (CEC/TEC).
When a buffer pH is not performed, labs will estimate soil hydrogen content using a formula. This estimate should not be used for determining lime application. As an example, Logan labs uses the following formulas for estimating hydrogen content and calculating total CEC:

http://loganlabs.com/doc/tecformulas.pdf

1 meq = 6.022 X 10 to the twentieth power of electrical charges.
1 meq of hydrogen is 10 ppm or 20 lbs of hydrogen per acre furrow slice.

Significant values for pH adjustment:
Atomic weight of hydrogen is approximately 1.
The atomic weight of calcium carbonate is approximately 100.
The atomic weight of sulfur is approximately 32.

Raising pH
1 molecule of calcium carbonate (CaCO3) will neutralize 2 atoms of hydrogen creating Ca + H2O + CO2.
Consequently, 50 lbs of CaCO3 will neutralize 1 lb of hydrogen.

Lowering pH
1 atom of sulfur (S) will produce (through biological processes) 2 atoms of hydrogen. 2 atoms of hydrogen will neutralize 1 molecule of CaCO3.
Consequently, 1 lb of sulfur can be used to neutralize 3.12 lbs of calcium carbonate.

Other acidifying sources:
Indexed common fertilizer acidifying effects (the amount of CaCO3 that one pound of product will neutralize):

Sulfur coated Urea (38-0-0): 1.18
Ammonium Sulfate (21-0-0): 1.10
Urea (46-0-0): 0.81
Ammonium Nitrate (34-0-0): 0.60

Higher numbers indicate greater acidifying effect. For example 1# of Ammonium Sulfate (21-0-0) will neutralize 1.10 pounds of 100 CCE limestone and 5# of 21-0-0 (equal to an application of 1.05 lbs/k of N) would neutralize 5.5 lbs of 100 CCE of limestone.

Resource (see Mechanisms that Control pH):

http://www.agronext.iastate.edu/soilfertility/presentations/soilphliming04.pdf

For the DIYer, who likes to shoot from the hip (USE AT YOUR OWN RISK):
Although I try not to post links so as to not clutter up this thread with links that are likely to go dead, Here are some links to charts and methods for calculating lime or Sulfur (or other acidifying source) based on soil solution pH:

Charts:

http://msue.anr.msu.edu/uploads/files/Lowering_Soil_pH_with_Sulfur.pdf

http://www.plantstress.com/articles/toxicity_m/soilph%20amend.pdf

http://www.aces.edu/timelyinfo/Ag%20Soil/2008/April/S-04-08.pdf

https://articles.extension.org/pages/13046/raising-soil-ph-and-soil-acidification#Neutral_to_Slightly_Acid_Soils

Soil Acidification: How to Lower Soil pH

Many plant species require acid soil conditions to thrive. Throughout Ohio and many other parts of the Midwest surface soils are neutral to slightly alkaline. Elemental sulfur can be applied as a soil amendment to decrease the pH or acidify such soils. Due to the cost, the application of sulfur...

ohioline.osu.edu

http://grounds-mag.com/mag/grounds_maintenance_managing_soil_ph/

More:

http://www.veoliawatertech.com/crownsolutions/ressources/documents/2/21951,Water-pp393-394.pdf

http://www.bh-ec.org/Docs/Turfgrass-Rutgers.pdf

Lime Recommendations - Turf (Penn State College of Agricultural Sciences)

Limestone recommendations are made based on the pH goal and the amount of exchangeable acidity measured by the Mehlich Buffer soil test.

agsci.psu.edu

ph value and lime requirements

www.aglime.org.uk

http://lawr.ucdavis.edu/classes/ssc102/Section5.pdf

https://people.ucsc.edu/~wxcheng/envs161/Lecture7/Ch9acid_alkalinity_Salinity.pdf

ADJUSTING THE MICRO/TRACE NUTRIENTS (Boron (B), Manganese (Mn), Copper (Cu), and Zinc (Zn)

As amounts of Trace Nutrients are so small, conversion to ounces (or grams) from pounds is recommended.

The FORMULA:: (Desired ppm level -(subtract) test reported level) X 2 (to convert ppm to lbs) X 16 (to convert lbs to ounces) / (percent of the trace element listed in the product source) / 43.5= total amount of product per M needed to reach the desired trace nutrient ppm soil level to a 6" depth.
For example:
Soil Test reports a Boron level of 0.3
You wish to raise the soil level of Boron to 1.5
Twenty Mule Team Borax (a common source) contains 11% Boron.
Therefore:
1.5 (desired ppm value) - .03 (test reported value) X 2 (to convert ppm to lbs) X 16 (to convert lbs to ounces) / .11 (% of pure element in source product) / 43.5 (to calculate for 1000 sq ft.) = 8 oz of Twenty Mule Team per M

For Everyone : It is strongly recommended that a tissue test be performed before amending micro-nutrients. (On page 3 of this thread there is a post regarding "Tissue Test" with a chart of expected tissue nutrient values.)Trace Elements are almost never deficient/absent in soil. In over 17,000 soil tests done by PACE Turf, they report that they have never found a deficiency of an element. The trace elements are usually present, the problem is that due to pH, they can be unavailable to the turf plant. Although deficiency is very uncommon, deficiency is most likely to occur in very low CEC (<5) soils (e.g. Light colored sands which also allow increased loss of micro-nutrients due to leaching; and low OM soils as OM, in addition to being a source of CEC is a repository of trace elements), and in soils in climatic regions with higher rainfall (leaching) and warmer temperatures (loss of OM and soil weathering). Testing of Trace Nutrients and adjustment should only occur once any pH adjustment has been completed. For High pH soils, where pH adjustment to make trace elements more available is impracticable, fresh OM and chelated forms of trace nutrient elements should be used.

APPLICATION RATES (Now that you have calculated the total quantity for each nutrient to achieve desired values, can it all be applied at once: How much and how often should it be applied?)
If it is new construction where soil has been trucked in and maintaining soil structure and avoiding settling issues are not a concern and the soil can lay barren to cook for 3-6 months before planting,, most nutrients can be applied in their total calculated amounts if incorporated into the soil (tilled in),
However, in the vast majority of cases, the lawn is already established (or we do not want to disturb the existing soil structure) and all amendments are by necessity surface applied. Surface applied nutrients leach down from the surface into ever greater depths of the root zone. As nutrients percolate down they enter the soil solution and over time, attach to cation sites to be held in reserve for latter entry into the soil solution.
Some things to keep in mind (although some of this might be better placed in a "for nerds" section,):
The sufficiency/recommended ranges used for determining desired nutrient target levels and for calculating total nutrient additions are based on the total reserve (CEC) ability of a soil. Research based on decades of studies indicate a direct relationship between reserve nutrient levels and healthy plants. Achieving a nutrient's level within the recommended reserve range is expected to sufficiently replenish the soil solution with the nutrients necessary for healthy turf plant growth demands for a year or more. Of the pounds of nutrient calculated using the above formulas, only a small fraction ( a couple of ounces/M) is needed to achieve sufficient soil solution nutrient levels, which can be sufficient for a month or so, the rest (the lion's share) is intended to be held in reserve.
As a surface applied nutrient leaches down, it will by necessity create high saturation levels of that nutrient in the upper levels. Not until the soil has had time to "cook" (in some cases and with some nutrients, a year and possibly longer) will the soil and nutrients balance and the root zone achieve homogeneity. Also, adding more will not make it leach down or change the balance any faster.
Over application can also result in temporary imbalances between nutrients (see Mulder's Chart).
In sum, there is no advantage in applying nutrients in as a short period of time as possible, As people are loathe to say, "it's a marathon, not a sprint." It's better for the turf and soil to take a little extra time than to try to achieve the desired levels quickly.

In all cases, follow product package directions first. Also consult Mulder's chart for nutrient antagonism. Generally, the greater the amount of time between application of antagonistic (or, for that mater, any two nutrients that don't come pre-mixed in the bag) nutrients, the better (2-3 weeks at a minimum). Examples (including, but not limited to): Apply nitrogen fertilizer 2-3 weeks prior to any lime application if possible. Apply any potassium fertilizer 2-3 weeks prior to applying any magnesium product if possible. Avoid applying a phosphorous source and a calcium source within 3 weeks of one another if possible. Etc. NOTICE: Failure to follow antagonistic nutrient application guidelines will not kill/poison the soil or turf.

Suggested MAXIMUM rates for soil application per one thousand square feet:

Calcium and Magnesium
When applying lime (calcitic or dolomitic):
No more than 50# (25# is preferred max) of Aglime in any single application, no more than 100# total in a calendar year and evenly space applications over the year. The suggested application schedule for either the max 50#/M or the preferred 25#/M rate of Aglime is 2X per year (e.g. Late Fall and Early Spring).
(Discussion of Aglime and Fast acting lime for another time)

When applying gypsum:
Use the lime application guidelines. 50# (25# preferred) per individual application. 100# max. per calendar year.

When applying Epsom Salts
No more than 0.45#/M of elemental magnesium or 4#/M of Epsom Salts per any single application (1-2# of Epsom is preferred) , no more than 8#/M of Epsom Salts total in a calendar year and evenly space applications over the year.

Nitrogen
Follow university turf site recommendations for your turf.

Phosphorous
No more than 1-2#/M of P2O5 per application, not more than one application per 30 day period and not more than 4-6#/M total per season (best to apply higher rates after aeration to incorporate and reduce loss through erosion/run off). Do not apply if less than 30+ days prior to ground freeze.

Potassium
No more than 1#/M of K2O per application, not more than one application per 30 day period and not more than 4-5#/M total per season (applying after aeration will aid in incorporation into root zone). Do not apply if less than 30 days prior to ground freeze and avoid application during periods of drought stress.

Sulfur
Sulfur coated nitrogen fertilizer or sulfate fertilizers (e.g. SOP when potassium is called for) are recommended sources.

Micro/Trace Nutrients
Suppliers of golf course products are sources of Trace Nutrient products (most are for foliar application, but some can be used for soil surface application. Follow package recommendations for application guidance. Chelated forms are preferred especially for higher pH soils, but should usually be applied at lesser rates than sulfate based micro-nutrient products. It is strongly recommended that a tissue test be performed before amending micro-nutrients. (On page 3 of this thread there is a post regarding "Tissue Test" with a chart of expected tissue nutrient values.)

Conservative (very) recommendations for surface (per M- 1000 sq ft)sulfate (e.g. copper sulfate, etc) products NOT chelate applications:

Boron
No more than 0.1 oz of the elemental nutrient content is advised for any one application based on review of Boron supplement product recommendations. (For perspective, some specialists recommend maximum rates as little as 0.011 oz/M for foliar application to turf).
Additional applications should be spaced 90 days apart.

Manganese
No more than 0.8 oz of the elemental nutrient content is advised for any one application.
Additional applications should be spaced 90 days apart.

Zinc
No more than 0.3 oz of the elemental nutrient content is advised for any one application.
Additional applications should be spaced 90 days apart.

Copper
No more than 0.4 oz of the elemental nutrient content is advised for any one application.
Additional applications should be spaced 90 days apart.

http://www.extension.umn.edu/garden/yard-garden/soils/soil-test-interpretations-and-fertilizer-management/#micronutrients-commercial

http://archive.lib.msu.edu/tic/mitgc/article/1972110.pdf

Organic Matter

Percent OM is an estimate/quesstimate calculated by measuring the carbon content of soil and applying a factor of 1.72 based on the assumption that Carbon content of OM is 58%:
About 5-25% (a common estimate is <15%) of organic content in soil is fresh organic material. (animal and plant). It is a good source of plant nutrients (particularly Nitrogen). Plant tissue is 45-50% carbon content.
It can take anywhere from days to two years for fresh organic material to decay to the point that it is no longer recognizable under a light microscope as plant or animal structures/material/cells. At this stage it is still a very significant source for nutrients as it continues to further decay over the next 10-40 years.
After about 30 years, it reaches the point where it is highly resistant to further decay and is classified as humic substances (humin, Humic acids and fulvic acids) which can remain in the soil for centuries.. Humic substances are the source of OM's water holding capacity, soil aggregate capabilities, and CEC.
Consequently:
1% soil OM content is approximately 460 lbs/M of OM or 267 lbs/M of soil carbon.
It is estimated that it would require the addition of 4600 lbs/M of organic material (grass clippings, tree leaves, alfalfa pellets, etc) to produce 460 lbs/M of OM or a 1% increase of soil OM.
1% soil OM content will result in 2 meq of CEC.
See:

https://humates.com/pdf/ORGANICMATTERPettit.pdf

What Does Organic Matter Do In Soil?

Organic matter serves as a reservoir of nutrients and water in the soil, aids in reducing compaction, and increases water infiltration. Yet, it's often ignored and neglected.

www.noble.org

What is soil organic carbon? | Agriculture and Food

Soil organic carbon is a measureable component of soil organic matter. Organic matter makes up just 2–10% of most soil's mass and has an important role in the physical, chemical and biological function of agricultural soils. Organic matter contributes to nutrient retention and turnover, soil...

www.agric.wa.gov.au

The importance of soil organic matter

Keys to Understanding Soil's & Soil Testing for Sustainable Soil Management

 

[Fronta1]

 

[Fronta1]

I would be interested to know what the "sufficient", "optimum", and "excessive" levels are for p,k,ca, and mg in ppm of you know. I've seen a variety of different suggestions but not sure which one to go with. And also the amount in ppm each is raised per pound added. You touched on this once before in another thread of mine but would be useful here as well. Thanks.

 

[monty]

In later posts I will provide the "sufficiency level" mid-ranges that are expected to result in satisfactorily performing turf grass for each of the most common tests used by soil testing labs. The "sufficiency" ranges for each of the different test methods that will be posted are based on the work of R. N. Carrow, professor and researcher in the crop and soil science department at the University of Georgia and credit is greatly acknowledged. After a number of years of collecting "ranges" from various sources, special thanks to Virginiagal for directing me to Carrow's compilation.

Thanks for this post and I'm looking forward to the subsequent ones! Very interested in the topic.

 

[Ridgerunner]

There is no "universal" labeling method (Edit: to my knowledge). Some labs use none at all in their reports. The ranges assigned to any particular label are made by the test labs or the authors of studies who created them. There is no universal definition that assigns a certain label as a specific ppm range, nor could there be considering the variety of test reagents in use. Each lab/author usually provides descriptions explaining what their classifications mean.

As an example, I offer this explanation provided by Midwest Laboratories for their Rating System:

"Most soil test readings on the report are given a rating of very low (VL), low (L), medium (M), high (H) or very high (VH). The purpose of these ratings is to provide a general guideline for determining optimum nutrient levels for crop growth. Upon request, an unrated form can be obtained. Optimum levels may vary slightly from those shown on the Soil Analysis Report, however, the actual value that is best is dependent on many factors such as crop, yield potential and soil type."

Perhaps you'll find a more satisfactory answer after I complete this series for the individual test reagent SLAN ranges.

The only test for which I have a ppm level for expected turf nutrient "deficiency" is Mehlich III. I do not have any additional "deficiency" or "excess" ppm levels for other soil tests.

Adding 1#/k of P2O5 will add 9.5 ppm of phosphorous to the soil. However, that total amount may not be reported on a subsequent soil test due to soil chemistry, leaching, run-off etc, and due to the limitations of a particular test's reagent to extract non-labile forms.

Adding 1#/k of K2O will add 18 ppm of potassium to the soil. Once again, that's not to say that a subsequent soil test will reflect that amount of increase, but it's the best we got.

 

[Ridgerunner]

I would be interested to know what the "sufficient", "optimum", and "excessive" levels are for p,k,ca, and mg in ppm of you know. I've seen a variety of different suggestions but not sure which one to go with. And also the amount in ppm each is raised per pound added. You touched on this once before in another thread of mine but would be useful here as well. Thanks.

Frontal,
I added the PACE TURF minimum levels to the Mehlich III section. Hope that helps some.
I should also qualify that the ppm numbers per of P2O5 and K2O are for a 6" soil depth. The ppm values for 4" would be a third higher:

Adding 1#/k of P2O5 would (theoretically) add 12.6 ppm of phosphorous to the soil to a 4" depth.
Adding 1#/k of K2O would (theoretically) add 24 ppm of potassium to the soil to a 4" depth.

Please feel free to let me know if I can/should clarify any other areas.

 

[Fronta1]

Wow, RR, I had not realized you had updated this. This belongs in the a&faq for sure.

 

[monty]

You've successfully sent me down a rabbit hole of reading...what can you tell me about Mehlich 3 ICP as opposed to the Mehlich 3 ranges you listed above? Penn State uses Mehlich 3 ICP and their optimal ranges are very different.

PSU Optimal Ranges for Mehlich 3 ICP results

 

[Ridgerunner]

Monty,
You and Frontal are asking great questions that tax my knowledge base. Keep in mind that I'm just a hobbyist and without a professional background, but I'll do my best within my limits. Anytime someone wants to add something from their knowledge base, please feel free. (I'd name someone, but it would be uncouth and unfair to volunteer a person without permission. So I wont name any names of people associated with any universities in Ohio)

You've successfully sent me down a rabbit hole of reading

Welcome to the rabbit hole. Sorry about that.

...what can you tell me about Mehlich 3 ICP as opposed to the Mehlich 3 ranges you listed above? Penn State uses Mehlich 3 ICP and their optimal ranges are very different.

PSU Optimal Ranges for Mehlich 3 ICP results

M3 reagent should be M3 reagent irrespective of the lab. The ICP in "Mehlich 3 ICP" identifies the instrument [Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), aka the ICP-Optical Emission Spectrometry (ICP-OES)] used to analyze (identify and quantify) the amount of chemicals/nutrients in the extraction solution (Mehlich III reagent in this case). Some labs still employ the Atomic Absorption Spectrophotometers (flame and furnace) instruments (AAS, aka FAAS). A few labs have reportedly begun to employ new technology: Microwave Plasma Atomic Emission Spectroscopy (MP-AES)... and that is the extent of my knowledge.

I was planning on addressing SLAN and the differences between labels, ranges, definitions and philosophies/tactics in a "summation," but this is as good a place and time as any.

The difference of ranges is in the definitions of the labels employed: sufficiency and optimal. When I was attempting to compile my own list of ranges for each reagent, I was stymied by the differences I was finding between labs, universities and regions- even for the very same reagent. The ranges I listed above are the work product of Prof. Carrow. I reorganized them for simplicity. He has classified the listed SLAN ranges as "common sufficiency ranges, (i.e. the "medium range")." "Medium" levels of nutritients are levels at which there is a 50% expectation of plant growth response (in this case turf plants as this collection is specifically targeted at turf) from an application of that nutrient. "Sufficient" is most often defined by SLAN proponents as "sustainable." It is a philosophy developed from an economic and environmental perspective.
Beyond that, they have proven useful in establishing the baseline level for healthy turf from which adjustments for can be made to achieve desired results. SLAN, in conjunction with BCSR can be employed to determine "optimal" nutrient levels.

Although soil test labs and soil programs are not restricted by these definitions, definitions have been developed by Regional Soil Test lab associations.
Examples:
Definition published by Rutgers:

"Below Optimum (includes Very Low, Low, Medium)
The nutrient is considered deficient and
will probably limit crop yield. There is
a high-to-moderate probability of an
economic crop yield response to
additions of the nutrient.

Optimum (High)
The nutrient is considered adequate and
will probably not limit crop growth.
There is a low probability of economic
crop yield response to additions of
nutrient.

Above Optimum (Very High)
The nutrient is considered more than
adequate and will not limit crop yield.
There is a very low probability of an
economic crop yield response to
additions of the nutrient. At very high
levels there is a possibility of a negative
impact on the crop if nutrients are added."

And this from "Recommended Soil Testing procedures for the Northeastern United States", by Douglas Beegle:

"Below Optimum (Very Low, Low Medium)
Same Definition as above.

Optimum (Sufficient, Adequate)
Same definition as above.

Above Optimum (High, Very High, Excessive)
Same definition as above.

Generally, Optimum levels are based on research done in the field (an average over years in numerous sites within the state or region) to determine a level of nutrients at which further additions show no further improvement in plant growth. A "That's all she'll take, cause she can't take no more," if you will.

The take away: SLAN sufficiency ranges are calculated to be borderline Below Optimal/Optimal. A level at which turf growth is sustainable/"healthy," but additions of nutrients are likely to improve turf plant growth. They are not intended to be a "target level" other than one at which turf will be sustainable. SLAN levels can be employed with BCSR as a baseline from which to determine optimal levels for a specific soil, climate and turf plant. Optimum levels are more predetermined and not as tailored to a specific soil and turf plant. There is little to no chance that an addition will improve plant growth. Penn's Optimal level is calculated for Pa. soils, climate and cool season grasses in general and although more accurate than a range intended for all N.E. Regional soils, they may or may not be optimal for any specific lawn and turf type established in Pittsburgh or Harrisburg. SLAN levels or Optimal levels: just a matter of philosophy and tactics. SLAN is more DIY, Optimum levels are more "pre-built."

I hope somewhere in there I gave you an answer.