Consistency. Where did your consistency go?

Foremost, and the cardinal rule in soil testing is consistency of the sample. The first soil test is the baseline for future adjustment. Consistency in sampling, lab testing and application methods of amendments has a major influence in determining what amendments and what quantities need to be made in the future as soil texture, pH, climate and lawn care regimens (e.g. watering) have a major influence on how particular soil will react and change in response to amending. The less variation, the better because even n the best circumstances, test results from year to year can/will bounce around quite a bit, especially for residential lawns where the soil has been disturbed due to construction.

Why the change from 4" to 6" and why are you doing separate samples (F1 and B1)? Is there any observable difference between the soil in the two areas or is it just because it's two types of sod?

Enough knuckle rapping.

I'd be happy to guide and help YOU do your own analysis and recommendations if you are interested. Just let me know. :)

BTW, In this case, I agree with your initial assessment, It IS highly likely you have a "clay" soil.

??? How do you get clay with an TEC that low? Are there some clays that don't exchange cations? It looks to me like the bump in organic matter helped with the TEC.

Looks like you're chasing calcium. Your values are considerably higher, but the lab seems to have changed the goal. I don't know why that happens. Perhaps Ridgerunner can explain that. Maybe that is a function of the depth of the sample.

Brandon, aren't you the guy who's extremely happy with the change in your lawn from last year? If so, where are you going with this lawn? If you're going for best lawn in the state you are doing the right things.

Ridgerunner: Yeah, I tried to remain as consistent as possible. I would assume the primary determination of consistency is simply collecting enough samples from varied spaces in the area of interest. That I believe I did a good job of, so the other difference is sample depth. I changed my method of pulling soil samples, so last year I used a tool that pulled ~4" plugs from the ground. This year I just used a simple trowel to get to approximately 6". WIth the yard being fairly new, the roots were in completely different places from year to year. Additionally, the sand would have artificially changed the depth of my sampling anyway if I had used the same technique as in 2016. All this is to say, this yard was a significant work in progress in 2016, and it feels like the deviation from the soil sampling technique will be of secondary concern (unless their analysis of the soil differs depending on reported depth...maybe the difference in the target numbers like dchall said?). But point taken: consistency, consistency, consistency!

Yes, the F1 versus B1 is primarily because of the sod issue and whatever issues that brought with it. They've evened out in the last year, but it's still like I've got two different stands of grass I'm working with. Different weeds, different greenup, different onset of stress, etc.

Your recommendations would be welcomed.

dchall: Yeah, calcium has me scratching my head, as does the ph, but that's something of a derived quantity that's dependent on the exchangeable cations as I understand it.

And yes, I'm extremely happy with the change from last year! My goal is just to keep it strong and not backslide. Morpheus was obviously shooting for some targets in things like potassium, boron, etc. I just don't know what those targets were, or if I'm there yet.

Good questions.

??? How do you get clay with an TEC that low? Are there some clays
that don't exchange cations? It looks to me like the bump in organic
matter helped with the TEC.

There is a general relationship that can be made between CEC and soil texture (sand (CEC<6), silt (CEC 7ish to 13ish) and clay (CEC>15)), but it is not a rule as there are exceptions. Just as Brandon's observations are consistent with a clay soil, we know that other soil things can cause the same conditions (water penetration, rock hard when dry, etc.). So why do I think he has clay. Because he lives right smack dab in the middle of the Piedmont area of S.C. The predominant soil of the Piedmont is kaolinite clay which commonly has a low CEC in the range of 5. (google Piedmont, kaolinite and Clemson) I doubt OM did much to CEC. Only very stable OM has cation sites and it takes a long time for fresh OM to become stable OM.

Looks like you're chasing calcium. Your values are considerably
higher, but the lab seems to have changed the goal. I don't know why
that happens. Perhaps Ridgerunner can explain that. Maybe that is a
function of the depth of the sample.

It's hard to say what causes changes in soil test results. In this case, the calcium. It could be due to the depth having more calcium content or possibly, Brandon got an oversampling from the calcium from the lime apps.

The lab "goals" are based on the BCSR philosophy and are determined by simple calculations. BCSR recommends that the three cations Ca., Mg. and K should be in certain ratios to one another and each should hold a determined percentage of the total CEC. If a subsequent measurement of a soil sample shows an increase or decrease in one (or more) of three cations, then the calculated CEC changes and although the desired % of the new total CEC stays the same, the needed amounts to be held by each cation (Ca.) will change and so will the lbs amount of any reported shortage. For instance, in the earlier test, LL measured 965lbs of calcium and calculated a CEC of 5.72, LL calculated that 1036 lbs of calcium would occupy 68% of the CEC sites, so an addition of 71lbs of calcium would reach that % (the desired lbs/ac level). The same process holds true for the calcium in the new test based on the new CEC and measured amounts of calcium. The big question is why did the amount of calcium change so much. We kinda discussed some of the possible reasons above. That help any?

I fear I may have rapped too hard and made you a little defensive.

Unlike a garden or farm field, we don't incorporate amendments that will help them to more evenly distribute throughout a depth of soil. For lawns, we apply amendments to the surface and they work (leach) their way down deeper over time. Water soluble amendments move much quicker than insoluble amendments. Another major factor in how fast an amendment will move down through the soil is soil texture. Amendments will move down through coarse textured soils (sand) quicker than they will through a very fine textured soil (clay). Finally, but not of major import for this discussion point, CEC will influence the amount of amendment that gets "grabbed" by the soil as the amendment moves down through the soil, leaving less amendment to be "grabbed" by the soil at lower levels.

When taking a soil sample, if we sample and mix 1 cubic inch of the top inch of soil with 1 cubic inch of the second inch of soil with1 cubic inch of the 3rd lower inch of soil with 1 cubic inch of the 4th lower inch of soil depth, we should get a pretty accurate average of the amount of nutrient throughout the top 4" of soil.

When making recommendations, we calculate the total amount of amendment needed to
change the soil to a selected depth (with adjustments/tweaking based on a variety of factors). This is usually the depth of greatest mass
of turf root (4"). Because we surface apply amendments, when we retest, depending on the amendment, the top layers of soil tend to contain much more amendment than a lower level where the amendment may not yet have worked down to. We need to keep this in mind.

However, if we are not consistent with our sampling and we collect and mix two cubic inches of the top layer (where amendments are likely more concentrated) and mix it in with only 1/2 cubic inch of soil from the 3-4" level, our averaged amendment content is going to be skewed as a false high. The opposite is also true. If we take only 1/2 cubic inch of soil from the top inch and collect and mix that with 2 cubic inches from the 4" level, our averaged amendment content will be skewed falsely low. Taking soil two inches lower has the same effect, if the original sample was only to a 4" depth. It really is important. :)

I'm short on time right now, but I'll give you the common target ranges later and we can work through them.

Thanks for the detailed explanation, ridgerunner! I'll set up a new tab on the old lawncare spreadsheet, and post here when I've got a preliminary plan and questions.

Sounds like a good plan. :)

@Brandon: I have a selfish request. Would you put my curiosity out of its misery and go ahead with a soil jar test to show how much clay you have? I note in your thread from last year you mention twice that you should probably do it, but you never did. It's very easy to do and might be interesting.

I should say I was a bit confused recently because someone else did a jar test that showed very little clay. But then he had Logan do a soil particle size test that showed something like 20 or 30 percent clay content. I don't know if he did something wrong in sampling, or if the jar test isn't all it is cracked up to be.

Anyway, just curious!

52%

I think he's holding out on us, Ridge. :)

Out of town this weekend, but I think I'll have time to work up recommendations this weekend and hopefully get feedback on them. I'm already behind on lime and pretty much every thing for the yard this season.

I *really* do need to do that jar test :)

The jar test is not perfect. There was a soil professional on another forum for awhile. He seemed okay with the jar test, but according to him there are ways the certain types of clay will settle out quickly. I believe it has to do with particle size. Still it has practical application.

As an engineer, I live in the world of assumptions. As long
as they’re understood, all is well. However here, I’m making a LOT of
assumptions that I don’t understand very well at all, so I’m not too
comfortable with my conclusions. That is compounded by the inability to really
check the change from last year because of my lack of consistency (I know, I
know). After going through the numbers in detail, I now see just how helpful a
truly consistent measurement would have been.

To try to stay grounded in expertise, I’ve generally just
taken morpheuspa’s plan from 2016 and based on RidgeRunner’s ranges and
comments, tried to convince myself of whether I could justify using the same 2016
recommendations. So, my thoughts:

Assuming M III Phosphorus is what I’m adding with starter
fert, bag rate of scotts starter fert (24-25-4) is 0.75 lb/k Phosphorous, or
32.67 lb/ac. I added that 4 times in 2016 for a total of 131 lb/ac of P. Not
all of that hung around apparently, and since the B1 section increased by
47lb/ac and the F1 section only increased by 14lb/ac, it appears that the F1
section uses/loses P faster than the B1 section.

If the target is 200, seems like another season of about 4
starter fert applications would make sense, although in the B1 section it seems
like I’m cutting it close. Maybe I’ll apply a couple of the apps in that
section at 0.5 bag rate?

My Ca/Mg ratios are roughly in range (F1/B1 5.1/13.1) and
slightly up from 2016 (4.7/10.6), so that’s fine, but the Calcium saturation is
fairly far off. I’m assuming that this is what is causing my low pH values, but
not sure how that’s calculated. Also not sure how to calculate what my expected
increase in Mg saturation should be based on the fast acting lime. But since my
calcium is clearly low, at a minimum I can add the same calcium (lime) app I
did last year (F1: 3lb/k, B1: 1lb/k, spring and fall). The question would be
can I increase that app, particularly in the B1 section, and what should the
corresponding Mg app be? Since the Ca/Mg ratio is on the low side in F1 maybe I
should add less Epsom Salt than I did last year? Say, 1lb/k instead of 2lb/k?
Add the same or more in the B1 section to keep that ratio from becoming too
large. Say, 2lb/k again.

Potassium values seem to be low, and the saturation fell
significantly, which, based on morpheuspa’s statements, probably has to do with
the Calcium. Common lawn wisdom makes me think I should add in a potassium-rich
“winterizer” app in the fall to bump that number. But it again seems like I
need to add at least what I added of Potassium Sulfate in 2016 (F1: 3lb/k).
However, this time it looks as though adding 3lb/k to the B1 section also might
be a good idea.

I’ve been sufficiently warned about playing with boron in my
lawn to try to improve the number without very specific advice, so I’ll
probably just leave that alone this round.

I would have done the jar test, but I came home to a light
dusting of snow. Winter isn’t done with us yet, even in S. Carolina.

Or, you could just find morpheus and Andy on the other forum and ask him what to do for this year. Not exactly a "teach them to fish" kind of thing, but engineers also like to find the most simple solution that still achieves the goal. :o)

An excellent analysis and I'm very impressed.

As an engineer, I live in the world of assumptions. As long
as they’re understood, all is well. However here, I’m making a LOT of
assumptions that I don’t understand very well at all, so I’m not too
comfortable with my conclusions. That is compounded by the inability to really
check the change from last year because of my lack of consistency (I know, I
know). After going through the numbers in detail, I now see just how helpful a
truly consistent measurement would have been.

I'd say that's a pretty accurate description for soil analysis: a bunch of assumptions. This isn't a controlled lab situation and each year's soil sampling and test results can/will very sometimes significantly, so any variable we can control when sampling helps reduce those fluctuations.

To try to stay grounded in expertise, I’ve generally just
taken morpheuspa’s plan from 2016 and based on RidgeRunner’s ranges and
comments, tried to convince myself of whether I could justify using the same 2016
recommendations. So, my thoughts:

Why not? It's as good a place to start as any and better than starting from scratch.

Assuming M III Phosphorus is what I’m adding with starter
fert, bag rate of scotts starter fert (24-25-4) is 0.75 lb/k Phosphorous, or
32.67 lb/ac. I added that 4 times in 2016 for a total of 131 lb/ac of P. Not
all of that hung around apparently, and since the B1 section increased by
47lb/ac and the F1 section only increased by 14lb/ac, it appears that the F1
section uses/loses P faster than the B1 section.

A couple of clarifications: 1) M III (M3) is the test that was used. It is a cocktail of chemicals that is used to extract nutrients for measurement. In this case the Phosphorous is reported as lbs per acre of P2O5. (Other labs may report it as ppm of elemental Phosphorous). The nice thing about reporting it as P2O5, is that P2O5 is the form of Phosphorous contained in fertilizers. So your assumption is right. 2) Phosphorous moves very slowly (down or otherwise) through the soil and phosphorous binds within days of application and can become unavailable to the plant. In acidic soils it binds to Aluminum and Iron. In high pH soils, it binds with calcium. An assumption: the difference between F1 and B1 may be due in part to the difference in pH between your two soils as reflected in the initial test.

If the target is 200, seems like another season of about 4
starter fert applications would make sense, although in the B1 section it seems
like I’m cutting it close. Maybe I’ll apply a couple of the apps in that
section at 0.5 bag rate?

I concur. As an alternative (based on your budget) Milorganite has reconfigured their formula to 5-4-0 from 5-2-0. Now only 10-20% might be organic P, but organic P is "slow" release and would help supply P to your turf better over time. (All of P2O5 is inorganic and although inorganic P is readily available to the turf plant, it also readily binds up.

I gave you the 200 range, because you had mentioned that you didn't know what target you had been given last year, 200 is his/a common target for a high maintenance lawn.

Some general points of clarification: 1) for every pound of N that a
plant uses (not every pound of N that is applied--but USED) the plant needs
and uses 1/2 pound of Potassium and 1/4 pound of of Phosphorous.
whichever is missing, is the limiting factor. 2)The ranges I gave you are the ones that soil scientist have found within which plants "appear" to do well. They are quantities averaged for soil types and plants. Research has shown that values below the range result in poor performance. That as you approach the low end, additions of that nutrient are more likely to show a visible improvement in the plant and as you approach the high end, additions of the nutrient are much less likely to result in any improvement. Values above the high end are very unlikely to show any improvement and at some point can be detrimental to the plant. (did I say this before?) Bottom line, as you progress with balancing your soil, if you reach a point within the range where you no longer see improvement, you've reached your optimum in regard to any nutrient.

My Ca/Mg ratios are roughly in range (F1/B1 5.1/13.1) and
slightly up from 2016 (4.7/10.6), so that’s fine, but the Calcium saturation is
fairly far off. I’m assuming that this is what is causing my low pH values, but
not sure how that’s calculated. Also not sure how to calculate what my expected
increase in Mg saturation should be based on the fast acting lime. But since my
calcium is clearly low, at a minimum I can add the same calcium (lime) app I
did last year (F1: 3lb/k, B1: 1lb/k, spring and fall). The question would be
can I increase that app, particularly in the B1 section, and what should the
corresponding Mg app be? Since the Ca/Mg ratio is on the low side in F1 maybe I
should add less Epsom Salt than I did last year? Say, 1lb/k instead of 2lb/k?
Add the same or more in the B1 section to keep that ratio from becoming too
large. Say, 2lb/k again.

This is when a buffer pH test would help- a lot IMO. If they still have your sample (30 days?) they could run that for about $10 per sample.

You are correct that base saturation reflects low pH readings and if you fill up all but 10 to 15% of the cation sites with Ca, Mg. and Potassium and leave the 10-15% to Hydrogen, you should end up with a pH in the 6's. But none of those nutrients neutralize the acidity. For soils, an addition of carbonate will do that. It's better to know how much carbonate/lime (an amount derived from buffer pH testing) is needed to raise pH than to estimate based on total base saturations. BSCR, CEC, lime and differences in lime products, etc. is a bit involved, but I'm happy to clarify any questions you have on them.

As it stands now, without a buffer test, as your pH is not really moving and/or dropping and as you want to avoid freeing up any more Aluminum (which can be toxic to the turf in addition to the P issue), you want to raise your pH using lime additions.

Your Mg is near sufficient levels, so it shouldn't be an impediment to your turf, however, if you wish to address the base saturation ratio, yes, 1#/k for B1 only of Epsom (considering the difference in sampling and to avoid over shooting) and mixed with the lime.

Yes, I'd increase the lime app. As both areas are near the same pH, fast acting lime at 9lbs/k (B1 and F1) would be indicated and even that may not make for much movement in pH on a future test. It should help the available P values to raise.

Potassium values seem to be low, and the saturation fell
significantly, which, based on morpheuspa’s statements, probably has to do with
the Calcium. Common lawn wisdom makes me think I should add in a potassium-rich
“winterizer” app in the fall to bump that number. But it again seems like I
need to add at least what I added of Potassium Sulfate in 2016 (F1: 3lb/k).
However, this time it looks as though adding 3lb/k to the B1 section also might
be a good idea.

Agree, in fact, I'd suggest increasing to three apps of 3#/k this year. Avoid applying within 2-3 weeks of any lime app.

I’ve been sufficiently warned about playing with boron in my
lawn to try to improve the number without very specific advice, so I’ll
probably just leave that alone this round.

That's up to you, based on the soil tests and your previous app,, you could apply 2 tablespoons of Borax per k again to raise values into the optimal range. Your decision.

I would have done the jar test, but I came home to a light
dusting of snow. Winter isn’t done with us yet, even in S. Carolina.

Hope that makes sense. Feel free to ask for any clarifications. Once again, nice job.

Or, you could just find morpheus and Andy on the other...

Andy is still active. I believe morph is taking time to work on other hobbies for awhile. He seems to have a lot going on.

Excellent, I very much appreciate the detailed feedback Ridgerunner. I'll get back with questions as soon as I digest all of the info. Slowly learning here and I'm definitely seeking out as much expertise as possible. To that end, that's a good suggestion danielj. There's a range of engineering personalities, going from super practical plug-n-chug get-er-done types, to those who (over)analyze everything and would rather not do anything if they don't understand why it works. I'm closer to the (over)analysis side of that spectrum, for better or worse :)

The lime is still the most confusing to me. Last night when trying to figure things out I tried to interpret the calcium content on my Encap lime label which led me down a confusing rabbit hole that ultimately I decided to just back away from. So help understanding BSCR, CEC, and lime apps in general would be helpful.

Also, re-reading my 2016 thread, I remember how difficult getting a uniform app of lime was in the F1 section because it was so small (~1k). I wonder how much that affected my results. I'm getting a new smaller spreader this season, so I hope that improve uniformity for light apps in the future (like the pot ash).

Cation: an atom or molecule possessing a positive charge. For our soil purposes: Ca, Mg, K, Na and to a much lesser extent by %, ammonium and many of the micros. Aluminum is a cation, is not a nutrient (in fact can be toxic to plants) and can be present in soil in significant amounts.

Anion: an atom or molecule possessing a negative charge. For soil purposes: Phosphorous which is a nutrient and present in significant amounts.

Clay and "stable" OM (humate) possess negatively charged surfaces. These negative charges on their surface attract and lightly hold/bond cations. The more negative sites, the greater the number of cations that can be held on each stable OM (humate) or clay particle. The more humate and/or clay particles, the more negative sites and the greater the number of cations that can be held. Sand soils have little clay or humate content and have fewer negatively charged sites to hold/bond cations. The higher the clay (or humate) content in a soil, the greater the negatively charged sights and the more cations that can be held in the soil. The number of sites and the quantity of each nutrient cation held on those sites and their proportions has become the measure by which to judge the fertility of a soil and the basis for determining whether or not a soil contains enough of each nutrient cation to be sufficient for plant health.

The bond between a cation and a neg soil site is not structural, it is a weak attraction of two opposite charged particles, so the bond is relatively easy to break, allowing the nutrient cation to be available for plant use. Because the bond is so easy to break, the cations are classified as "exchangeable". However, although they are all "exchangeable", some cations (the ones most commonly found in the largest numbers on negative sites) possess a greater capability for attraction than others; Al > Ca > Mg > K > Na > H+. Although a single H+ can be dislodged by any other cation, H+ is a wildcard, as, in significant numbers (such as exists in a low pH soil) H+ atoms can "gang up", exert enough collective "force" and dislodge any other cation from a negative site.

CEC: Cation Exchange Capacity or TEC: Total Exchangeable Cations are a measure of the number of cation sites present in a measured unit of a particular soil. Each unit of TEC/CEC represents 6.022 X 10 to the 20th power of sites. The higher the TEC/CEC, the more cations (nutrients) that the soil can hold and the more fertile the soil is judged to be. Sands commonly have a low TEC/CEC (<6). Pure clay can have a TEC/CEC of 40-60. Organic soils (humate) can have TEC/CEC much greater than 100. There are exceptions, as with very old and weathered clays. Due to structural changes those clays can lose negative charge sites, resulting in lower TEC/CEC than would normally be expected of a clay.

Base Saturation: For most reports. it is a measure of the total negative sites held by the cations Ca, Mg, K, sometimes Na.

BSCR: Base Saturation Cation Ratios. Is a measure of the portion of the negative sites held by of each of the individual cations Ca, Mg, K, H+, Na and sometimes a mishmash of "other" minor cations. BCSR is based on testing of the most fertile world soils and sets a desired "standard" relationship between the cations (a set number/% of sites that should be held by each of the individual cations) to produce/replicate the most fertile soils and the healthiest, most productive crops. Over time the desired "set standard" has become a "range" of the amount of sites that each cation should/can fall within to produce a fertile soil. For those that are guided by BCSR philosophy, the goal is to fill the CEC/TEC sites with the proper amount of each cation and the soil will be in "balance" and at the proper pH.

To be continued?...up to you Brandon.

ridge said: Each unit of TEC/CEC represents 6.022 X 10 to the 20th power of sites.

Exchange capacity is measured in units of meq/100 g dry soil. Are you saying that 1 meq/100 g dry soil equals the 6.022 x 10^20 sites/100 g dry soil? I'm not questioning it, just wondering where you found that. This number is close to, but not quite equal to, Avogadro's number.

@davidj

I'll have to look to find the citation, I'll link it if I do.

It is Avogadro's constant: 6.022 x 10^23, or 1 mole, well, kinda pretty much.

Not having a background in science, (it's been nearly 50 years since I had even any college science), it took me a while to understand CEC/TEC: Moles (mol), Ions, that a mole was the equivalent to 12grams of carbon atoms (12 grams?!??-huh, 12??), molecular mass, meq, etc.

Anyway, I struggled for quite a while with why the number of CEC charges per unit varied from Avogadro's constant (number). Then I had my DUH moment-how dumb my itty bitty mind : 1 meq is 1000th of a mole, so 6.022 x 10^23 / 1000 or (1 x 10^3) = :)

The only point I was trying to make is that it is a big number. :)

Here's a cite, that I have bookmarked as "CEC: I wish I'd found this a long time ago, woulda saved a lot of research" Lol

http://www.public.iastate.edu/~teloynac/354meq.pdf

I think it gives a much better explanation than what I gave.

Sorry I missed your question but I got sidetracked with Avogadro's number. I didn't recognize the term until I googled it and it brought back all those memories.

Are you saying that 1 meq/100 g dry soil equals the 6.022 x 10^20 sites/100 g dry soil?

Yes.

Interesting catch BTW.

Oh, (and don't ask me to produce the citation) I remember coming across an article that stated the reason for reporting CEC as meq rather than moles was just because someone felt a CEC reported as a whole number like 18 meq was just simpler than reporting it as 0.018 mol. :/ EDIT: NM, the linked article says that.

Don't feel bad. I'm a chemical engineer in a former life and still had to look up exactly what a milliequivalent was. I've seen the term in the past but never needed to use it. It isn't commonly used unless you are in medicine (I guess) or soil science.

Thanks!

Brandon,

If you're still around.

Encap Fast acting lime calcium content is 36%. Are you going to use that or another Encap product?

If you're trying to balance the Ca deficiency to match the "desired" value on the LL test in an effort to raise pH, keep in mind that those TEC numbers are estimates, and consequentially, so is the reported base saturation hydrogen % (look at the differences in your Ca and TEC numbers between years.) When adjusting for pH, it's best to work off a buffer pH which is an actual measurement/test done by the lab to determine the carbonate needed to neutralize the soil acidity.

Brandon,

If you're there :) and you'd just rather that I do the recommendations and timing, just let me know.