# ScottW 2021 soil test w/ comparison to 2020



## ScottW (Sep 16, 2019)

This will show last year's (2020) soil test & recommendations, then I will show what I applied during the 2020 season to address deficiencies, then show my recent 2021 report. Analyses performed by Waypoint in Richmond, VA.

First, the 2020 report:









There was low K and very low S. Recommendation was to apply 3 lbs of K per 1000 and 0.63 lbs of S. With pH being slightly high I used ammonium sulfate for most of the N, which also adds S and can gradually reduce pH.

To keep the view uncluttered I'm only showing K and S (the deficiencies) on this graph, but this was what I applied during 2020:









That was 4.25 lbs of K per 1000 (recommendation was 3). Applied 1 lb at a time roughly every 4-5 weeks starting late March and ending mid-July when I had hit/exceeded the target recommendation. I alternated products between muriate and sulfate of potash so they went MOP-SOP-MOP-SOP.

There was ~3.5 lbs of S per 1000 (recommendation was 0.63) added throughout the year. That came from a combination of the SOP apps listed above and from using ammonium sulfate for most of my N.

This is my 2021 soil analysis, hot off the presses:









First off, pH is down to 6.9 from 7.2, which is nice.
K is still low. I applied ~35% more than the target recommendation and it barely made a dent in ppm value and no change in % saturation. 
I also see OM is up slightly from 7.1% to 7.2% and CEC increased from 13.8 to 15.4. Normally I would think these would be good. Does this mean some/more of the K is bound up, or would this be extracted and reflected in the ppm value?
FWIW I mulch the vast majority of my grass clippings (aside from the rare debris cleanup mow) as well as my leaves in the fall, so I'm not bagging & removing large amounts of nutrients.
I sampled cores to about a 4" depth. Is K mobile enough in the soil that a bunch got leached away between my last app (July of last year) and when I pulled these cores ~10 days ago?

I applied roughly 5x the recommended amount of S, which got it up into the "medium" range, which is still lower than "optimum."

I think the report looks pretty good overall and my fert routine doesn't need to change drastically from last year. But my perception is that I need to significantly exceed the recommended amounts in order to make any real improvement in the low nutrients. I'm pondering applying 1 lb of K per month (roughly) and keeping that up all through the fall. Does this seem reasonable?


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## g-man (Jun 15, 2017)

Very interesting. I dont have an answer. At first I though, maybe a sampling error, but looking at the other numbers, I dont think it is. Your Ca and sulfur increased, but that's mainly it. I would continue doing more K and using AMS and see what happens next year.


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## VALawnNoob (Jun 9, 2020)

Scott, I have VA clay soil and spread 2 50# bags of Lesco 0-0-50 SOP last year from SiteOne on 2 different occasions and it brought up my K from 114-131ppm in the front and 57 to 151ppm in the rear. both also received 18-24-12 lesco starter fert as overseeding as well as CX throughout the season.


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## Easyluck (Feb 5, 2019)

How much nitrogen did you apply?


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## ScottW (Sep 16, 2019)

VALawnNoob said:


> Scott, I have VA clay soil and spread 2 50# bags of Lesco 0-0-50 SOP last year from SiteOne on 2 different occasions...


So if I'm reading that right, you applied 4 bags total on your 22K sqft? I applied a bit less than the equivalent of 1 full bag on my 5K, so our amounts per sqft would be similar.



Easyluck said:


> How much nitrogen did you apply?


Total of 3.25 lbs N per 1000 throughout the season. A majority of that (2 lbs) was applied during the fall.


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## Lawn Whisperer (Feb 15, 2021)

Interesting, it seems like the basic cation saturation ratios (BCSR) remained somewhat the same with the exception of the additional hydrogen. Could the BCSR and CEC be a limiting factor?


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## Easyluck (Feb 5, 2019)

This study may send you down a rabbit hole.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1126&context=undergradresearch_symposium

Maybe the high iron had an impact on raising K levels.

https://acsess.onlinelibrary.wiley.com/doi/epdf/10.2136/sssaj2016.12.0420


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## ScottW (Sep 16, 2019)

Those sources indicate several factors influencing K fixation, but it's still not entirely clear to me why my tests show basically no increase in K year over year _unless_ the S3M test methodology doesn't fully extract the portion of K that has become more permanently fixed (I don't know). We do have significant clay content in our soils but I don't know about vermiculite versus other forms.

Prior to 2019 or 2020 I hadn't gotten a soil test since 2014, so I was not keeping on top of things, plus I was bagging my clippings a lot prior to 2019 thereby removing a lot of nutrients including K. Perhaps the soil K reserves got so depleted that it had the capacity to fix a bigger fraction of what I applied last year into a less extractable form (which remains a question) and will take a while to gradually build up again. Otherwise, where'd it go? I didn't remove clippings, and K doesn't evaporate away. Presumably lost via leaching.

What was also mentioned is that fert recommendations are based on the needs of your crop (grass in my case) that year and not necessarily with the goal of building up soil reserves. Presumably if my soil had sufficient K the recommendation would have been 2 lbs instead of 3 lbs, to go along with that 4 lbs N recommendation, since plant tissue analyses show a 2:1 ratio of N:K.

I'm not super worried about it, just curious where the K went. I'll follow my plan and see how it looks next year. Marathon, not a sprint. I started the K apps around this time last year, and the lawn did look pretty good overall.


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## Lawn Whisperer (Feb 15, 2021)

It seems that you've optimized Ca/Mg for the CEC of your soil, therefore limiting the amount of K that your soil can retain.
"Too much calcium and magnesium can cause a potassium deficiency"
https://www.cannagardening.com/interactions_between_nutrients


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