Recommendations for places to get a soil test?

[NewGrower2011]

So after prep'ing my soil and it's sitting there doing its cooking, I've been contemplating going ahead and shipping it off for a soil test. In my other thread there was an excellent example provided of a true lab test.

Can anyone recommend places to get a soil test? Especially a good thorough one that covers all the aspects we'd care about for this hobby. I'm hoping to find a modest price point where it's both accurate and thorough but not overly expensive.

From a turn-around time/mailing time, somewhere in the midwest is probably ideal.

 

[FamMan]

There is one on build a soil. Never used it thou

 

[rikdabrick]

The K3 test from Spectrum Analytics is the one to get if you're running a lightweight media. The K3 test is the only one I know of in the US where they actually weigh out the appropiate amount of media to be tested. Every other soil test uses a calibrated scoop thst is assumed to weigh a certain amount, but the scoop is made for field soil so the results are quite a bit different when you have a lightweight media. The K3 isnt on their website, but it exists and costs $51 which is kind of pricey for a soil test, but it'll give you accurate numbers for lightweight media. I don't use it because I grow in plain old dirt, but it's a good test. I also have silicon, molybdenum, selenium and cobalt tested for on the soil tests I get, but most people don't test for that stuff.

And don't be surprised if your numbers are through the roof especially potassium and sodium. It's a common problem with a lot of soil mix recipes. Fortunately a lot of people use a lot of aeration too otherwise their plants would be dead with some of the numbers I've seen.

 

[MistaRasta]

The K3 test from Spectrum Analytics is the one to get if you're running a lightweight media. The K3 test is the only one I know of in the US where they actually weigh out the appropiate amount of media to be tested. Every other soil test uses a calibrated scoop thst is assumed to weigh a certain amount, but the scoop is made for field soil so the results are quite a bit different when you have a lightweight media. The K3 isnt on their website, but it exists and costs $51 which is kind of pricey for a soil test, but it'll give you accurate numbers for lightweight media. I don't use it because I grow in plain old dirt, but it's a good test. I also have silicon, molybdenum, selenium and cobalt tested for on the soil tests I get, but most people don't test for that stuff.

And don't be surprised if your numbers are through the roof especially potassium and sodium. It's a common problem with a lot of soil mix recipes. Fortunately a lot of people use a lot of aeration too otherwise their plants would be dead with some of the numbers I've seen.

Logan weighs samples now, just request it after you send your sample in.

 

[greasemonkeymann]

So after prep'ing my soil and it's sitting there doing its cooking, I've been contemplating going ahead and shipping it off for a soil test. In my other thread there was an excellent example provided of a true lab test.

Can anyone recommend places to get a soil test? Especially a good thorough one that covers all the aspects we'd care about for this hobby. I'm hoping to find a modest price point where it's both accurate and thorough but not overly expensive.

From a turn-around time/mailing time, somewhere in the midwest is probably ideal.

just keep in mind a soil-test for organic soil isn't really a conclusive thing to base any adjustments on, remember the nutrient availability is going to change a LOT, especially since it's freshly made. As it breaks down it changes like crazy.
here is a link, read the first paragraph and ALWAYS keep that in mind, if you treat a soil test as 100% accurate & completely comprehensive, and then base your adjustments on that you will be chasing your ass all day long with organic soils

.

And don't be surprised if your numbers are through the roof especially potassium and sodium. It's a common problem with a lot of soil mix recipes. Fortunately a lot of people use a lot of aeration too otherwise their plants would be dead with some of the numbers I've seen.

Absolutely true, cannabis growers get a lil crazy with nutrients, plants do so well with so little...
extremely good advice. Cation issues affect a LOT of growers
another thing I see often is people adding nutrients to counter other issues, that nearly always ends badly...
that's why I've been preaching the importance of cation balance, aeration and proper watering techniques.
if you fully understand those three aspects of growing you'll be waaay ahead of most
why people overlook the importance of cation balance is beyond me
potassium tox will lock out all the cations, and the resulting defs will make most growers think it's a def (which it technically is, but adding any nutrients ain't gonna fix it)
damn near all the "cal-mag def" threads aren't really defs at all.
but hey, add more cal-mag right?

 

[rikdabrick]

Logan weighs samples now, just request it after you send your sample in.

They'll tell you the percentage of the scoop weight compared to the calibrated weight, but they still use the scoop. I usually send my normal mineral soil to them and get the scoop weight percentage too. My greenhouse soils weigh about 92% of the "normal" scoop weight which is close enough for me to not use the K3 test from Spectrum Analytics. Organic soil mixes could weigh 20% of the "normal" scoop weight, which is not close enough for me. I think they can get decently close on base cation distribution, but I don't think you'll get very accurate results with the actually ppm of the major cations and especially the micro nutrient minerals. I think you can get a good idea of what to do with your soil with their tests especially if you send in tests regularly and have a good eye for your plants' visual signs.

Spectrum will actually weigh out the amount of soil they use for the Mehlich 3 and ammonium acetate pH 8.2 tests on the K3 test. They use a 1 gram scoop for their "normal" soil tests and actually weigh out 1 gram of soil for the K3 test which will give you more accurate results because all the soil tests are supposed to be based on the weight of the soil.

 

[rikdabrick]

just keep in mind a soil-test for organic soil isn't really a conclusive thing to base any adjustments on, remember the nutrient availability is going to change a LOT, especially since it's freshly made. As it breaks down it changes like crazy.
here is a link, read the first paragraph and ALWAYS keep that in mind, if you treat a soil test as 100% accurate & completely comprehensive, and then base your adjustments on that you will be chasing your ass all day long with organic soils


Absolutely true, cannabis growers get a lil crazy with nutrients, plants do so well with so little...
extremely good advice. Cation issues affect a LOT of growers
another thing I see often is people adding nutrients to counter other issues, that nearly always ends badly...
that's why I've been preaching the importance of cation balance, aeration and proper watering techniques.
if you fully understand those three aspects of growing you'll be waaay ahead of most
why people overlook the importance of cation balance is beyond me
potassium tox will lock out all the cations, and the resulting defs will make most growers think it's a def (which it technically is, but adding any nutrients ain't gonna fix it)
damn near all the "cal-mag def" threads aren't really defs at all.
but hey, add more cal-mag right?

@NewGrower2011 greasemonkeyman makes a couple good points here. I do think you can get reliable numbers and do appropriate adjustments from an appropriate soil test over time, but like greasemonkeyman said, if it's a new mix it's going to change quite a bit. I usually tell people to mix it up and let some water move through it and wait for 3-4 weeks before you send in a(nother) test. It takes a little time and water for the cations and anions to find their place and kick out some of the other minerals. Another good point he makes is that most deficiency symptoms come about from too much of another element, not because of an actual deficiency of the element that the plant is showing signs of.

And @greasemonkeymann you're right about too much potassium. Too much K messes up everything and it's a common mineral to get abused, e.g., just about any commercial fertilizer. Plants can always catch up on a K, Mg or N (and maybe some other elements that I can't think of off the top of my head) deficiency so it's not necessary to have too much. Plants can never fix cells built without enough calcium which is one reason why I'm pushing Ca base saturation to 85% now. Most of the rest of the stuff is easy to fix if there's enough Ca.

I can't say I'm familiar with Ca-mag, but I would assume that should help push K off the cation exchange sites in a soil. I use fine ground (passes through 100 mesh sieve) oyster shell flour or ag lime to knock out K in acidic soils, gypsum in alkaline soils and either gypsum or 50/50 gypsum and lime in soils with a good pH range. Dolomite would work to knock K out of the soil too, but I'd only consider it's use to get to the amount of Mg for the CEC percentage that I want, which is 8-10%. I usually just use MgSO4 for my Mg requirements though. If Cal-mag isn't working to knock out excess K then it's PROBABLY either because people aren't letting enough water run through their soil with the Cal-mag or they're not using enough would be my guess. Potassium has a weaker charge than Mg and Ca so either of those two minerals will push out excess K. Gypsum with it's Ca and sulfur is particularly effective to push K off the exchange sites.

 

[NewGrower2011]

So I haven't done my search homework yet, but this term 'cation balance' is new to me. I've heard of the CEC numbers and understand more is better - correct? So how does CEC relate to balance? I guess I'm off to go on a search next.

 

[rikdabrick]

So I haven't done my search homework yet, but this term 'cation balance' is new to me. I've heard of the CEC numbers and understand more is better - correct? So how does CEC relate to balance? I guess I'm off to go on a search next.

Having a higher CEC soil can be better. It doesn't matter too much if you know what you're doing. There's people who farm in sand soils with really good results and those soils can have a CEC of 4-10. 10 isn't too bad, but 4 is low. A higher CEC soil is going to take more minerals to get it to where you want it; it can hold a lot of minerals so it has a bigger battery basically and you can let plants run it in for quite awhile without having to do much which is nice. The downside to higher CEC soils is that is takes more minerals to get to where you want it and it's harder to turn it around if it's wonky and if you mess up in your amending it's more difficult to fix. High CEC soils are like a huge cargo ship. They carry a lot of goods but take a long time to turn around if they make a wrong turn. Low CEC soils are like a speed boat. They don't hold much, but it's easy to change coarse of necessary. One of my greenhouses has a CEC of 11.32 and the other one has a CEC of 16.18 which I think is a good range. It can hold enough minerals to get me through a grow and it's not difficult to make changes when I amend. That's normal field/mineral soil which is probably equivalent to a organic soil with a CEC of 40-60 (because organic soils are usually not nearly as dense)

And balancing your cations is just getting your base cations where you want them. In general I'd say having Ca at 68-75%, Mg at 8-10%, K at 4-6% and Na at 0.5-1.5% is a good start.