lb/acre to ppm

[mayo]

For soil testing results, can lbs. per acre be converted to parts per million?

[beezer5477]

To convert from ppm to pounds
multiply by 2 and to convert from pounds per acre to ppm divide by 2.

[Guest]

Oh heavens no. Each element has a different conversion factor. Let me look them up, much more involved than by 2 or times 2.

[Guest]

Ok I was wrong in post 3 to say post 2 was wrong, but there is an issue and right now my mind is so frazzled I can't explain this logically.

I originally though it was wrong because I recently did calculations on how to raise ppm to a certain number.

Phosphorus - It takes 18 lb/acre to raise by 1 ppm
Potassium - It only takes 8 lb/acre to raise by 1 ppm

So on my quick rash reply I was thinking it's not as simple as just saying 2 lb.

I can't explain this logically, I just use the formulas, you would think if it was as easy as 2 then on application phosphorus and potassium would require the same amount, not one at 18 lb and the other only 8.

Maybe someone can logically explain this to me now.

Again, poster #2, I apologize for quickly saying you were wrong, I had these application conversions in my head.

[Guest]

So on my quick rash reply I was thinking it's not as simple as just saying 2 lb.

I meant simple as just saying 2. Not 2 lb.

[ThSimpson]

You are close on the soil ppm to lb/acre with using 2 BUT!!
All is based on an Acre furow Slice.
1 acre 6" deep =2 million pounds
1 Acre 3" deep= 1million pounds

If Soil test taken at 3' multiply by 1
6" x 2
7" x 2.33
9" x 3
12" x 4

Th

[gelbebrille]

some soil sample ppm are reported in mg / L....that is equivalent to saying ppm = g / 10^6 g water = g / 10^6 mL water = g / 1000 L water = mg / L water...ok? so it's based on g / million g and assumes density = 1 g/mL..anyway...
you have an area, let's assume a depth to get volume......1 ft...
(1 lbs / acre) x (1 acre / 43560 ft²) x (1 / 1 ft) x (1 ft / 12 in)³ x (1 in / 2.54 cm)³ x (1 cm³ / 1 mL) x (1000 mL / 1 L) x (454 g / lb) x (1000 mg / g) = 0.368 ppm
got that? 1 lb / acre = 0.368 ppm.

[toddw]

I do not know where you all got your information but, the conversion goes as this

1 acre inch = 3,000,000 lbs therefore

ppm * (0.3*sample depth in inches) = lbs/ac

example a sample was taken at a depth of 6 inches the nitrate came out at 14 ppm

14ppm (0.3 * 6 inches) = 25.2 lbs/ac

[williamblake621]

hmm i think your conversion format look pretty easier to understand !

[bredhedden1]

@toddw thanks for such decent format which help me a lot :)

[PatWilliams]

The main focus of soil fertility and management for crop generation is traditionally the tilled layer of the soil which goes back to the days. This 6-8 inch layer of soil is known as the plow layer. It is interesting that a plow layer weighs approximately 2 million pounds. In later years soil test labs have changed from reporting soil test results in pounds per acre but instead as parts per million (ppm).

Thanks
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