Soil samples...

[farmaholic]

We have never been big soil samplers so some of this is foreign to me.
On Phos....am I understanding this correctly?

We have two Phosphorus results. One using the Bi-carb(Olsen?) method and the other Bray-P1. From what I understand the Bray doesn't provide the most accurate results for basic ph soils, which we have, we are just above neutral to up to a point higher.

To convert test results from ppm to lbs/ac websites say multiply the results by 2 to get soil P then multiply that by 2.2913 to get P2O5.

Is that assuming all the soil P needs to be converted to P2O5, so all the soil P isn't plant available until coverted.

Is the soil test really telling me anything regarding available Phos"FATE" or is it only telling me how much Phos"FOR-US" is in the Soil?

[ColevilleH2S]

In North America most soil lab reports list Phos in terms of P2O5, so that last multiplication should not be needed.

Same as with fertilizers sold here, that 11-51-0 is 51% P2O5

[farmaholic]

H2S...

A&L Canada Lab is reporting only the test results for N and S analysis in both ppm and lbs/ac, all other nutrients are only reported in ppm.

All the recommendations are suggested in lbs/ac.

[GDR]

H2S...

A&L Canada Lab is reporting only the test results for N and S analysis in both ppm and lbs/ac, all other nutrients are only reported in ppm.

All the recommendations are suggested in lbs/ac.

Every few years i test a couple fields then wonder why i was dumb enough to spend the money. Has never changed my mind on my fertility plan and if i put on the N rates they recommend my yield would be zero because it would be flat and burnt corner to corner.

[farmaholic]

We normally don't either but we thought it was time for a "cheque up".

Yup...recommended rates for target yeilds would be insane. We've grown decent crops here without excess fert. Our usual limiting "nutrient" is H2O 💦💧💦💧💦....and unless you're irrigating...you can't buy that shit.

[blackpowder]

For $125/ field, I find it my cheapest input.

[WiltonRanch]

I soil test very seldom. With my variable terrain unless we were into the variable rate and mapping I think it’s a waste. My soil test involves asking my neighbours who grow the best crops what they did. Every time I soil tested made me feel like a shitty farmer for mining nutrients but I’d ask around and find my package wasn’t too far out. Still though it’s nice to get an idea of long term trends of nutrient levels, changes in ph, cec, and om.

[grassfarmer]

Got my first ever positive surprise from a soil test this fall. Grew and grazed corn 2 years running with 80lbs N each year. Same field this year we grew corn again without any fertilizer as we missed the window to get it on then it was so dry it wouldn't have helped. Silaged about 9 ton/acre and when we tested I was assuming it would be severely depleted. Lo and behold it came back showing 143lbs N and the P and K were both very high too. Recommendation for growing a 15 ton corn silage crop next year was zero inputs. Money saved on this field would pay for many years of soil testing.

[farmaholic]

Got my first ever positive surprise from a soil test this fall. Grew and grazed corn 2 years running with 80lbs N each year. Same field this year we grew corn again without any fertilizer as we missed the window to get it on then it was so dry it wouldn't have helped. Silaged about 9 ton/acre and when we tested I was assuming it would be severely depleted. Lo and behold it came back showing 143lbs N and the P and K were both very high too. Recommendation for growing a 15 ton corn silage crop next year was zero inputs. Money saved on this field would pay for many years of soil testing.

Grassy, that almost seems hard to believe but I guess those first two years was alot of nutrient cycling but this year's 9 tonnes taken off and no call for nutrients next year is what is surprising me. Were you intercropping with a legume that you forgot to mention?

[Guest]

Got my first ever positive surprise from a soil test this fall. Grew and grazed corn 2 years running with 80lbs N each year. Same field this year we grew corn again without any fertilizer as we missed the window to get it on then it was so dry it wouldn't have helped. Silaged about 9 ton/acre and when we tested I was assuming it would be severely depleted. Lo and behold it came back showing 143lbs N and the P and K were both very high too. Recommendation for growing a 15 ton corn silage crop next year was zero inputs. Money saved on this field would pay for many years of soil testing.

Well done and no carbon tax to pay on N next year. Regen farming, don't forget to leave the gly out

[helmsdale]

Soil testing has more than paid for itself around my operation...

On year's where we get skunked on moisture, it's been astounding to see what sort of nutrients are left over for the following year. Fert bill can often get cut by 1/3 to 1/2. After a banner year, it's equally astounding to see what little is left.

Have also gps'd every sample point in every field, so results year to year are directly comparable. Has been nice to track OM, EC, and PH changes.

[grassfarmer]

Grassy, that almost seems hard to believe but I guess those first two years was alot of nutrient cycling but this year's 9 tonnes taken off and no call for nutrients next year is what is surprising me. Were you intercropping with a legume that you forgot to mention?

Yeah, it surprised me too. No legume, only corn. The physical transformation in the soil is remarkable - from dead concrete like clay to nice mellow stuff full of worms. Organic matter went from 3.4 to 4.3 in 3 years too. We haven'd used glyphosate on it as we seek out good non-GMO corn varieties but the previous farmers used glyphosate and NH3 regularly in their wheat/canola rotations.

[bigzee]

You have to take soil testing with a “grain of salt”. Firstly, like anything you have to believe what you are doing is not a waste of money. I test for the
most part of every year. In 16 we pulled off massive yields, like most. The tests showed very little nutrients left which they should have. So in 17 pumped the ground full very dry conditions, tested results shows very high levels of everything. Nitrogen numbers seemed a little fictitious so had some fields retested, results came back a little lower but still very high .. over 100 lbs available.
Was happy to have tested or else I would have put down a lot that wasn’t needed.
Most guys don’t soil test they put down their regular amounts and go. Phos is the one that’s tricky.
Fert prices are through the roof, commodity prices are crap, be interesting to see if there will be guys cutting back and changing rotations.

[Guest]

Got my first ever positive surprise from a soil test this fall. Grew and grazed corn 2 years running with 80lbs N each year. Same field this year we grew corn again without any fertilizer as we missed the window to get it on then it was so dry it wouldn't have helped. Silaged about 9 ton/acre and when we tested I was assuming it would be severely depleted. Lo and behold it came back showing 143lbs N and the P and K were both very high too. Recommendation for growing a 15 ton corn silage crop next year was zero inputs. Money saved on this field would pay for many years of soil testing.

I would re take that one
we haven't done many over the years , because we don't follow them , but decided we would check them all this year . one came back with 70 lbs on N . told them to re take it and came back at 15 lbs N

[farmaholic]

Kinda a crap year in 2015, a bin buster in 2016, another kinda crappy one in 2017 and a respectible 2018. Wheat most of those years was almost always the best, it must be mining out the nutrients.

N is dismal in my fields. How much mineralization(?) can I count on? There is enough residue on some fields and has been for a while, I would think it has to be cycling for years already. Residue doesn't build up on flax years, and not much in lentils, but that may only be 1 out of 4 or 5 years in the rotation. You may think peas don't leave much but it is generally smashed to smithereens....unless the crop suffered field wide root rot inhibiting a healthy crop stand.

So what's the deal on the Phos results in the opening post of this thread?

This us what the report states:

Phosphorus-P ppm
Bicarb- X value
Bray-P1- X value

No where in the results section is there a lbs/ac value...only in the recommendation section do the "prescribe" X lbs/acre of P for target yields.