[biggreg]

The at home lime requirement test:

Peat soils have a widely variable lime requirement to bring the acidity up into plant happy range. 3 to 4 grams per L typical up to 15g per L for the really broken down mucky mucks.

Measure out 3 or more 1 Liter samples of soil and weigh in increasing amounts of lime. I weigh 38% Ca micronized lime into a tared glass of distilled water and add it to the sample. Then rinse out the glass with more water to be sure all the lime goes into the soil.Mix sample well and incubate the sample at garden conditions ( temp and moisture)for a week or so until ph is stable. ) I get a stable reading after 3 or 4 days , stirring soil daily, but wait at least a week or longer to be sure. With those ph readings, we can graph the linear response and get the amount in grams needed to hit a target ph.

[biggreg]

Base Cation Saruration Ratios (BCSR) can be manipulated in our mixes working in soil mass ppm or mass volume ppm

Or

If you ain't into BCSR, and rather look at Suffiency Levels of Applied nutrients (SLAN), then mass per volume ppm is what you need
Convert your soil mass ppm test numbers to mass per volume ppm numbers with your a bulk density test. This reframes the soil mass ppm numbers into numbers that match mineral soil data and are compareable to one another.

[biggreg]

Let's say your lab weighed in your sample and reported in mg/kg or ppm soil mass. Your Ca is 6000ppm. Is that enough or too much?
Your bulk density is .2g/cc
Your ppm - mg/l is 6000x.2= 1200ppm. Right In the suffiency range With equal grams of Ca per container as a mineral soil weighing 1g/cc with a 1200ppm -soil mass.

Plants grow in a volume of soil, not a mass of soil.

[biggreg]

If you have a soil test in which the lab "weighed"your organic soil sample with a mineral soil scoop, your report is neither in mg/kg or mg/L. The numbers on that wrongly executed test can only show a general direction of the soil. Those numbers do not reflect the grams of the elements in the mass of the soil nor the grams of the elements in your volume.

[biggreg]

Labs performing Mehlich 3 extractions differ on calculating the CEC. If you're playing with BCSR ratios, the reccomended method is a total CEC calc including Ca+Mg+K+Na also accounting for other bases and exchangeable acidity. Logan Labs uses this method to give a TEC as they call it. See attached. In their equation, divide the lbs/acre number by 2 to add it up in ppm (soil mass)

Or use this calculator
https://growabundant.com/calculate-tcec/

[biggreg]

Lets look at a side by side of the same soil and the same lab both by mass and volume:

Check out the attachment for the test results in ppm mass per volume of extract solution. This number is equal to the soil mass ppm if 2g of soil is correctly measured in the test. We have no idea what the mineral soil scoop weighed in, we just know it's less.
Here is the soil mass equation,from the SERA lab manual, used to convert units mg per L in the test extract to ppm soil mass, mg/kg on the final report:

[biggreg]

Let's look at the BCSR ratios calculated in the brookside/Logan labs TCEC method. I didn't test Na by mistake so we will call it zero

2g sample. = TCEC 44.95, 69.3% Ca, 13.6% Mg, 4.69%K
"2g" scoop. = TCEC 32.51, 70.86% Ca, 12.48%Mg 4.25%K,

The ratios are close but the CEC is off on the scoop to weigh sample

[biggreg]

Now let's convert from soil mass to mass per volume and look.
A cubic centemeter of this soil at field moisture that has been dried weighs .363g.

If Ca is 6230 mg/kg and bulk density is .363g/cm3, then the soil has 2261 mg Ca/L

If Mg is 734 mg/kg, then the soil has 266 mg/L

K is 823 mg/kg then we have 298 mg/L

The TCEC is 16.31 meq/100cm3 this soil has the cation exchange capacity equal to 16.31 meq/100g mineral soil.

[biggreg]

Let's convert the "2g" scooped sample.

Ca 1672 mg/L
Mg 176 mg/L
K 195.6 mg/L
TCEC = 11.79 meq/100cm3

Misweighed sample reads low all around

[biggreg]

Once we convert to mg/L we can look at Mehlich 3 calibrated for mineral soil suffiency levels.

The weigh in test has very high Ca, slightly high Mg, and adequate K

The scooped version has high Ca, adequate Mg and just barely moderate K