# davegravy's 2021 Waypoint results



## davegravy (Jul 25, 2019)

Front:



Rear:



For reference, here's my results from *last* spring (2020): https://thelawnforum.com/viewtopic.php?f=24&t=16343

Last season I did no P and hammered K and sulfur (same applied to front and back).


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## davegravy (Jul 25, 2019)

*pH*
No movement in the front but somehow a 0.2 drop in the backyard. Strange given I applied sulfur and AS evenly :search: Sampling error?

Is 7% lime a lot? Does it mean I shouldn't even try for temporary pH lowering?

*CEC*
Reduced from last season (S3M) with the SW3 analysis as expected - I think these numbers are more in line with my observation that my soil is somewhat sandy textured. I have no drainage issues, and I my soil dries out very quickly even after deep waterings.

*P*
Both M3 method values came down very slightly from last year but barely at all. Confused by the fact the BI method values suggest more P is needed whereas M3 suggests too much exists - why such a discrepancy and which should I follow?

*K*
Had a bit of an increase for both front and back - I'm happy about this. I'm surprised the recommendation is only for 3 or 4lbs this season compared to 5 from last season, given how little 5lb moved the needle. Any harm in applying 5lbs again this season?

*Mg*
Ca:Mg is a little high (IIRC 7 to 10 is optimal) 
Should I apply epsom salts and if so how much?

*Mn*
Should I bother with this?


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## Ridgerunner (May 16, 2017)

Thanks for posting a link to last year. It gives me a chance to catch my errors. Last year I explained that M3 can give inaccurate results for high pH soils, then I went on to analyze your P based on M3 results. Significant brain fart.



> pH
> No movement in the front but somehow a 0.2 drop in the backyard. Strange given I applied sulfur and AS evenly :search: Sampling error?


The multitude of variables existent in natural settings vs lab controlled settings makes chemical and microbiological influenced soil reactions a dynamic environment. (it's a game of horseshoes, not darts). And yes, there is always some inherent sampling error in the testing process.
The micro-life that produces acidity from sulfur is dependent on soil temp and moisture. Most assuredly your front and back lawns are not identical. 


> Is 7% lime a lot? Does it mean I shouldn't even try for temporary pH lowering?


Where is the 7% reported? What method was used? For a 7.4 - 7.6 pH soil that's a pretty high content. Soils with a 5% content often test at close to pH 8, but it can vary.
No mater the pH, I'm of the opinion that regularly acidifying with AMS, citric acid and sulfur, although not making a long term dent in pH, will acidify the soil solution for significantly long periods of time (10-14 days?) to result in improved nutrient availability. However, if you don't see an improvement, save yourself the effort. @Greendoc 


> CEC
> Reduced from last season (S3M) with the SW3 analysis as expected - I think these numbers are more in line with my observation that my soil is somewhat sandy textured. I have no drainage issues, and I my soil dries out very quickly even after deep waterings.
> AA vs M3. A truer reflection of CEC.





> P
> Both M3 method values came down very slightly from last year but barely at all. Confused by the fact the BI method values suggest more P is needed whereas M3 suggests too much exists - why such a discrepancy and which should I follow?


I'll try to keep this concise. Phosphorous is a very "reactive" anion. It will bind with almost all the different soil nutrient cations. In high pH soils it most commonly bonds with the excess Ca to form calcium phosphate (in low pH soils it most commonly bonds with Fe). The strength of these bonds vary. Over the period of a growing season, some are weak enough to be broken (labile) and the phosphorous becomes available to the plant. Some bonds are so strong that they may not be broken for years (non labile).
M3 extractant is a strong acid and will break stronger bonds resulting in measured P levels that would not normally be available in a high pH soil environment. BI (Olsen testing) extraction has been found to give more useful/dependable/accurate results of the amount of P that is or will become available to the plant. That is, BI is less likely to release non-labile forms of P.
Comparing BI levels to M3 levels can give you some idea of the proportion of P that is in the soil, but is non labile/ available or look at it as a general indicator of the proportion of each P application is going to end up unavailable/tied up. Otherwise discount the M3 reported levels.
The recommended sufficiency range for Olsen (BI) P is 12-28.
17 ppm for the back yard is a decent buffer reserve. I'd suggest you do maintenance application of P: for every pound of N, apply .25 lbs of P2O5.
12 ppm of P reported for the front is at the bottom end of sufficiency. Although that level would probably provide the turf with sufficient P for this season I would suggest you start the maintenance P program (.25 lbs P for every 1lb of N)and add an addition 1lb of P to build buffer reserves.
As P can quickly bind-up, spreading application (spoon feeding) over the season is recommended rather than applying in only one or two apps.
Regular acidifying soil solution (discussed above) can aid in keeping P available. It's the same theory behind using MAP in high pH soils.


> K
> Had a bit of an increase for both front and back - I'm happy about this. I'm surprised the recommendation is only for 3 or 4lbs this season compared to 5 from last season, given how little 5lb moved the needle. Any harm in applying 5lbs again this season?


Cool season turf will use about 0.5 lbs of K for every 1lb of N. AA sufficiency range is 100-235. 150-175 would be a good buffer reserve value if doing maintenance applications. To help you calculate: every one pound of K2O/M will theoretically add 18 ppm. Suggest .5 lbs for every pound of N for maintenance and apply additional K to build reserves. Beware of applying K after September to avoid snow mold if that's an issue and limit rates to 1-2 lbs/M in any one monthly app. and target application prior to Sept.


> Mg
> Ca:Mg is a little high (IIRC 7 to 10 is optimal)
> Should I apply epsom salts and if so how much?


I'm not a proponent of chasing Ca;Mg ratios unless there are soil texture issues.
AA sufficiency levels for Mg: Mg: 140-250, 100-200 for sands. Increasing Mg a little is fine as Mg is an important nutrient for photosynthesis. Rather than Epsom, you could use K-Mag for some of your K. Suggest you target 150-175ish ppm for Mg.


> Mn
> Should I bother with this?


M3 sufficiency levels are 8-16 for high pH soils. I see no reason to adjust.


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## smartbutpoor (Mar 12, 2021)

@davegravy which test did you opt for? I am in the same region as you and took soil samples yesterday. I was thinking S3M and sending the samples to Tennessee.

I see SW3 recommended a lot in the forums but Waypoint website recommends it for Texas and Southwest US.


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## g-man (Jun 15, 2017)

@Ridgerunner I think he asked for an excess lime (fizz test) in the front lawn. The 7% shows on the right side. Basically, doing elemental sulfur will be pointless to actually change the 6in of soil pH.

@smartbutpoor Do the SW1.


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## davegravy (Jul 25, 2019)

g-man said:


> @Ridgerunner I think he asked for an excess lime (fizz test) in the front lawn. The 7% shows on the right side. Basically, doing elemental sulfur will be pointless to actually change the 6in of soil pH.


@Ridgerunner Huge thanks for the response, I am still digesting it and may need some more clarity. To answer your Q, I selected the % Lime test.



Given what @g-man said above, I take this to mean I'm basically peeing on a forest fire and shouldn't expect any significant permanent pH change. Question is if what you wrote about having a chance of changing the pH of the top bit of soil for a few days after each app still rings true? CA and Sulfur's not that expensive, I'll probably just try and see.


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## Ridgerunner (May 16, 2017)

Permanent change of soil pH in high pH (>7.2ish) is pretty futile.
See the numbers in this post for the theoretically values involved:
https://thelawnforum.com/viewtopic.php?f=24&t=26675
And here are the real-life results of a test conducted by Agvise when theory meets reality:
https://www.umanitoba.ca/faculties/afs/agronomists_conf/media/LEE_MAC_2017_soil_amendment_poster.pdf


> changing the pH of the top bit of soil for a few days


Not changing pH of the top SOIL layer (will avoid a discussion of the science involved) but the soil SOLUTION (i.e the water in soil) through which the plant gets much of the nutrients it takes in and where many of the chemical interactions occur. Reportedly, lowering soil solution pH can improve nutrient availability in high pH soils. @Greendoc has extensive experience in this technique. That's why I tagged him for his insights.
I don't have a lot of confidence in determining specific numeric content derived from a fizz test. It's just observational. Basically adding vinegar to soil and judging content based on how active the reaction (fizzing) is. Non existent, some or a lot? Ok, but a specific number like 7.2%? I think not.


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## Ridgerunner (May 16, 2017)

Here's the Agvise study in the form of an article. Makes understanding it a little easier to understand and more informative: https://www.agvise.com/adjusting-high-soil-ph-with-elemental-sulfur/


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## Kaba (Mar 29, 2019)

Dave your numbers are looking quite good, congrats!!

The little bit I know the guys already covered and then some.

My only 2 cents is kmag would be my choice from an economical perspective as you can get a bit bigger k buffer and boost your mg in one bag.

I forget what I paid for my 50lbs bag of Epsom, but it was over $20 anyways from BY. Your Ca is within order compared to being closer to the escarpment, but from my understanding it's pretty hard/not worth it to fix that ratio when the soil is so calcitic.


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## jaykrooze (Mar 30, 2020)

All this pH talk has me down in the dumps. Loading on the ES just isnt going to cut it... Damn!


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## davegravy (Jul 25, 2019)

Ridgerunner said:


> > K
> > Had a bit of an increase for both front and back - I'm happy about this. I'm surprised the recommendation is only for 3 or 4lbs this season compared to 5 from last season, given how little 5lb moved the needle. Any harm in applying 5lbs again this season?
> 
> 
> Cool season turf will use about 0.5 lbs of K for every 1lb of N. AA sufficiency range is 100-235. 150-175 would be a good buffer reserve value if doing maintenance applications. To help you calculate: every one pound of K2O/M will theoretically add 18 ppm. Suggest .5 lbs for every pound of N for maintenance and apply additional K to build reserves. Beware of applying K after September to avoid snow mold if that's an issue and limit rates to 1-2 lbs/M in any one monthly app. and target application prior to Sept.


To be clear, applying K *in* September is ok, just not after? Remember I'm in (southern) Canada where the season is typically a little shorter than much of the US.

I've been applying 1.25lb K/M monthly and am sitting at 4lbs currently, which I understand nets me a 36ppm gain on my reserves assuming I hit my 4lb N target this year. Thinking I'll push it to the max 2lb K/M monthly the rest of the year.


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## g-man (Jun 15, 2017)

https://mobile.twitter.com/djsoldat/status/833702016652365824


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## davegravy (Jul 25, 2019)

g-man said:


> __ https://twitter.com/i/web/status/833702016652365824


Ok, so just don't do high K lol.


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## Ridgerunner (May 16, 2017)

Nothing is a certainty. It's just statistical probabilities. So it's not that K after September will result in snow mold damage, it's just that studies have shown higher probability of damage. (While were on the topic the calculated 36 ppm increase is only technically true. We're dealing with a lot of environmental variables. Still, it's the best we have to guide us.) In Ohio I've continued to follow the old advice of late Fall K winterizer and in over 40 years I've only had snow mold once back in the 70s when we had an exceptionally heavy snow and the lawn was under snow pack for over a month in late winter. If you're in the Lake Huron snow belt, it might be prudent not to apply K after the end of August/1st of Sept and don't go overboard on that last application. At the rate your currently applying, you're building reserves. There's no rush to get it done in just a couple of years as it's just insurance and won't make a difference to turf that's receiving maintenance K applications.


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## g-man (Jun 15, 2017)

^ +1

It becomes a risk vs reward analysis that you need to do. Is adding more K worth of a risk to you? Are you seeing an issue that k will address? What will be the issue with not adding K this year and just working on it next year?


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## davegravy (Jul 25, 2019)

g-man said:


> ^ +1
> 
> It becomes a risk vs reward analysis that you need to do. Is adding more K worth of a risk to you? Are you seeing an issue that k will address? What will be the issue with not adding K this year and just working on it next year?


Thanks you two. At least for the front yard which has the lowest reserves and the poorest turf health once the heat hits in the summer (partly due to old cultivars) I think it's worth pushing the K.

Next spring we're starting house renos and I expect the front lawn will be a mess from construction equipment trampling it anyways. Snow mould damage will fit right in, and so it's an opportunity to boost the K reserve without worry.


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