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Massachusetts

At the end of October I collected my fall soil sample. Multiple samples at a depth of 10-12 inches. I mixed the sample well and divided it into 2 ziplok bags. Mailed priority mail at the same time. pH and CEC and some other values were similar from the 2 labs BUT look at the readings below (one lab vs the other).

Phosphorus 3 ppm and 25 ppm
Potassium 49 ppm and 94 ppm
Calcium 532 ppm and 1128 ppm
Manganese 0.6 ppm and 6 PPM !!
Copper 0.4 ppm and 2.2 ppm
Iron 2.5 ppm and 45 ppm !!

Both are reputable labs that are commonly discussed on this board. Has anyone else seen this kind of disparity in values? Whenever the values were far apart, all of the low values came from the same lab and all of the higher values from the other lab. Any opinions on what to do for the future? Do you think it could be handling on my part?

As is said "A man with 2 watches never really knows what time it is"

1/16/2013 7:17:38 PM

Torrance, Ca.

Wow! That's a bummer!

Going to be nice to hear others input............ I am getting ready to take two samples from my new patch, one from all the areas the cover crop looks great and another from the areas the cover crop is a little yellow. From the looks of your report,,,, seems like it would be different anyways........

1/16/2013 8:00:13 PM

South East

choose a lab and stick with it. Never use two diffrent labs in a singel season, its only gonna make you doubt them. If you doubt numbers or think somethings wrong, call the lab and ask for an explanation.

1/16/2013 8:20:14 PM

East Jordan, MI

There can be many reasons for the disparity.
people errors
dirty equipment
input errors

Samples taken too soon after adding amendments can make "hot spots" so if even a single piece of a raw nutrient gets in the sample that sample will show extrememly high. Likewise the lower one could be that low because the nutrients haven't had time to do any good yet.

That said. Extraction methods differ from lab to lab which can cause differences. Even the same sample redone in the same lab can have some differences -- dirty equipment, operator error, errors in pH buffer added (which really affects micronutrients).

Also some labs report in lbs/acre (divide by 2 to get ppm) Are you sure the higher one is in ppm?

1/16/2013 8:21:20 PM

Massachusetts

I have been very careful to digest the reports. All values are ppm. (BTW, I think it is divide by 3 to get ppm from lbs./acre). I used one lab (Frank) all 2012 season. It happens to be the one that gave the lower values in the Oct analysis. I was considering using a new lab for the 2013 season so I thought that dividing a sample and sending it to both labs was a very reasonable thing to do as a transition. Troublesome to me actually. Troublesome that one lab would be consistently low in a number of areas and the other would be consistently high in those same areas. I think that rules out the hot spot thought (Cecil).

1/16/2013 9:07:13 PM

Glosta

Lbs per acre is based on a 6" furrow slice which equates to 2,000,000# of Soil. Ppm therefor is 1 ppm per 2# per acre. Some Labs use an 8" or 12" depth and would state such on the report or in their method disclaimer. Since you used 2 different Labs you need to look at their methods before you make any comparison. Best bet would be to call the Labs.

1/17/2013 4:02:15 AM

Corryton, TN

Got my results back yesterday with similar issue. Been using a lab that results at 6", new lab at 10". Knowing that old lab was at 6 and I worked ground down to 12", I ammended a new patch accordingly. First test on a new patch in Aug, made ammendments, planted buckwheat, Oct tilled in buckwheat, second test - most values came up and getting close to where I wanted them (both at old lab). Ammended again for 12" depth and planted winter rye & wheat. Tested last week to depth of 10" with stainless steel soil probe made for taking soil samples as instructed by new lab. Results were way out of balance but generaly way lower. Example in pounds/acre: Test 1-Boron-1.47, T2-Boron 2.32, Test 3 Boron 1.2 with recommendations to add more. Test 2 results were in the VERY HIGH range. Where is the toxic level for Boron? What if it was a human error? I don't need my lab doing that, I've got that covered myself! LOL Phone call going out today

1/17/2013 5:59:08 AM

Germany

I know that german and american soil analysis results are totally incompatible because they use other extraction methods plus other measuring unit system. And most times the analysis methods are not exactly described in the results. So it seems to be necesary to ask the labs about their methods.

1/17/2013 6:45:22 AM

Corryton, TN

Got an answer from the main dirt person at the "New to me" lab.

Short answer: the extraction method used is different. New lab claims their results are closer to what the plant can extract from the soil

1/17/2013 1:11:01 PM

President - GPC

Don't trust the ammonium acetate test to give accurate numbers for the metals like Mn, especially in neutral or alkaline soils.
The Mehlich 3 extractant will give a better picture of what is potentially available there is what I have been told.

1/17/2013 1:23:55 PM

Corryton, TN

I don't know what's best but after talking to more lab people looks like I've been seeing result from Mehlich 1, Mehlich 3, Olsen-P and AB-DPTA. Thought I had a handle on this dirt thing but it just slipped through like warm jello. More reading required!

1/17/2013 2:35:39 PM

East Jordan, MI

Given your responces I'd have to agree with the different extraction methods used. Only way to find that out is to call them, tell them the delima and get the agronomist to explain it to you. They are usually very freindly and patient.

1/17/2013 8:43:13 PM

Massachusetts

So I would offer this as a practical solution....If you want to compare your soil to say, Ron Wallace's soil report, you need to use the same lab as Ron. Right?

1/28/2013 9:21:49 PM