# Soil Test Results - need input on P, K & Lime please!



## Awar (Feb 25, 2019)

So my soil test results came back this morning and I'm trying to figure out what to do next.

1. I'm due for monthly fertilizer in 2 weeks so I want to make sure I get P & K adjusted. Any input would be appreciated.
2. Zinc levels are low. Any input?
3. The backyard results say I need lime, do you agree with the recommendation of 28 lbs per 1000?
4. Should I apply the same P & K to the area I plugged 3 weeks ago in my front yard?

*FRONT*


*BACK*


Here's what my lawn looks like this morning. Almost fully recovered from leveling and maintained at 0.75" HOC.


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## Ridgerunner (May 16, 2017)

Need to know the testing methods used, or at least the name of the lab to see if we are familiar with the lab and their methods.
Is the soil sand or Georgia clay?


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## Awar (Feb 25, 2019)

Ridgerunner said:


> Need to know the testing methods used, or at least the name of the lab to see if we are familiar with the lab and their methods.
> Is the soil sand or Georgia clay?


@Ridgerunner I used Clemson University and I believe I read somewhere that they use Mehlich method. The soil is Georgia clay.


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## Ridgerunner (May 16, 2017)

Clemson uses M1 testing and a version of SMP for Buffer pH.
With a weathered clay with an CEC of 4, you're going to be challenged. The 4 CEC just isn't going to hold much in the way of nutrients. You'll want to be sure never to fall below MLSN values. Unfortunately they are based on M# testing. Your second issue is the clay soil. Although the soil wont hold nutrients (CEC), nutrients will not leach through the soil quickly which may somewhat offset the low CEC and help make nutrients available for a longer period. Keeping surface applied nutrients from running off (eroding) may be a major factor in fertilizing.
Having said that, you're lawn looks good, so whatever technique and schudule you are own is working.
For P and K, I suggest using the upper range of "sand" sufficiency levels as your guide, but that's up to you just remember your 4 CEC bucket is pretty small:
FYI
M1 sufficiency levels
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

Clemson reports tested nutrient levels in lbs/acre, to convert to ppm so you can compare to the above chart, divide lbs/acre by 2. The result is ppm.

To calculate the amounts of P and K fertilizer needed to get within range you can use the 8 step method found at the beginning of this thread: https://thelawnforum.com/viewtopic.php?f=24&t=1088

The 28lbs of lime per thousand is calculated to result in a pH of 6.2. 43 lbs/M would be needed to achieve 6.5, but many will tell you a pH of 6.2 helps reduce disease and can slightly help keep minor nutrients more available.


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## Awar (Feb 25, 2019)

Ridgerunner said:


> Clemson uses M1 testing and a version of SMP for Buffer pH.
> With a weathered clay with an CEC of 4, you're going to be challenged. The 4 CEC just isn't going to hold much in the way of nutrients. You'll want to be sure never to fall below MLSN values. Unfortunately they are based on M# testing. Your second issue is the clay soil. Although the soil wont hold nutrients (CEC), nutrients will not leach through the soil quickly which may somewhat offset the low CEC and help make nutrients available for a longer period. Keeping surface applied nutrients from running off (eroding) may be a major factor in fertilizing.
> Having said that, you're lawn looks good, so whatever technique and schudule you are own is working.
> For P and K, I suggest using the upper range of "sand" sufficiency levels as your guide, but that's up to you just remember your 4 CEC bucket is pretty small:
> ...


@Ridgerunner thank you so much for your response & guidance. I'm completely new to soil analysis but your response set me off to do some reading in your other thread and I learned a lot.

To recap what I learned, I divided the lbs/acre nos. from my soil test by 2 to get to ppm and compare with the upper range of sufficiency levels for Mehlich 1. At this time I only focused on P & K.

Then I went through the 8 step method:

1) 6 lbs of N per season (I bag clippings)
2) P = 6 x 3 = 18 ppm
3) K = 6 x 13 = 78 ppm
4) My Front Yard P = 10 lbs/acre = 5 ppm vs. 30 ppm upper range
My Front Yard K = 119 lbs/agree = 60 ppm vs. 100 pm upper range
5.b) P is low, adjustment = 30 - 5 = 25 ppm
6.b) K is low, adjustment = 100 - 60 = 40 ppm
7) P = 18 + 25 = 43 ppm (divide by 9) = 4.7 lbs per k per season
8) K = 78 + 40 = 118 ppm (divide by 18) = 6.5 lbs per k per season

I understand that those are the P & K numbers that I need to add by fertilization this season, but they're too high to put down during the summer, and just from basic understanding of my low CEC I'm not sure my soil will hold much nutrients.

So I'm thinking of adding some P & K to my normal fertilization program (say 2 lbs) this season and if anything it'll help, then next season I'll do another soil test early spring and see where I stand. Thoughts?


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## Ridgerunner (May 16, 2017)

> I understand that those are the P & K numbers that I need to add by fertilization this season, but they're too high to put down during the summer, and just from basic understanding of my low CEC I'm not sure my soil will hold much nutrients.


Exactly. Apply using reason in determining quantities, re-test next year and re-calculate based on the results. [BTW: I'm afraid I got to typing faster than I was thinking and failed to proof read. By "using the upper range of "sand" sufficiency levels" I intended that to apply only to K and not P (there is no sand range for P) and by "upper", I meant anywhere between 75-100.] As long as you're applying the calculated usage, 18 ppm for P and 78 ppm for K, your turf should at least get what it needs. Anything added above that (an extra pound or so) will go to soil reserves (limited by CEC). There is no rush on building reserves and kudos for applying common sense in determining that 4.7 lb/M of P might be too much to apply for one year. 
What do you mean "1 bag clippings" in


> 1) 6 lbs of N per season (I bag clippings)


?


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## Awar (Feb 25, 2019)

Ridgerunner said:


> > I understand that those are the P & K numbers that I need to add by fertilization this season, but they're too high to put down during the summer, and just from basic understanding of my low CEC I'm not sure my soil will hold much nutrients.
> 
> 
> Exactly. Apply using reason in determining quantities, re-test next year and re-calculate based on the results. [BTW: I'm afraid I got to typing faster than I was thinking and failed to proof read. By "using the upper range of "sand" sufficiency levels" I intended that to apply only to K and not P (there is no sand range for P) and by "upper", I meant anywhere between 75-100.] As long as you're applying the calculated usage, 18 ppm for P and 78 ppm for K, your turf should at least get what it needs. Anything added above that (an extra pound or so) will go to soil reserves (limited by CEC). There is no rush on building reserves and kudos for applying common sense in determining that 4.7 lb/M of P might be too much to apply for one year.
> ...


Perfect!

I was saying that i bag the grass clippings when I mow so I need to put down a little more nitrogen than those who keep their clippings to compensate. I expect to apply 6 lbs of N per k per season in total which may appear to be on the high side so I was trying to explain that I bumped the no. up to compensate for bagged clippings.


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## Awar (Feb 25, 2019)

@Ridgerunner so for the long term how do I fix my my soil so it can better store nutrients? I've been applying Humic Acid for 2 seasons now and would consider other products to enhance my soil.


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## Ridgerunner (May 16, 2017)

CEC (indicative of a soils ability to hold nutrients) arises from the presence of 1. clay and 2. organic matter (humates- the soil science's version of UFO). Although you have a clay soil, it's a weathered clay which means it has lost much of it's ability to hold nutrients (CEC). You didn't test for OM, but based on your calculated CEC, it's probably very low which is common for soils in a Southern climate. So you could increase CEC by replacing your weathered clay with a younger high CEC clay (NOT) or by increasing your soils humate content. Soil OM is calculated on the basis that it is 58% carbon, so to increase OM by 1%, you would need to apply 267 lbs/M of carbon. Humic acid is about 58% carbon. If you applied 459 lbs/M of pure humic acid, that should produce a 1% increase in OM.
Once you know the % of OM in the soil, you can guesstimate the aount of CEC it will contribute. See the section on CEC in my thread or my post here: https://thelawnforum.com/viewtopic.php?f=9&t=18293&p=271874&hilit=sare#p271874
Personally, I'd rather raise healthy turf and let root cycling and mother nature create OM and humates even if it takes 2-10 years.
Just adjusting your pH may be more effective than adding HA.


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