Can I Successfully Analyze Soil for N and K Without Commercial Test Kits?

[Swake]

I would like to analyse soil samples myself for N and K. Tried some commercial test kits and the results are good enough in terms of precision.

No idea what reagents are used in those kits. Is this something I can make myself knowing I have access to a minimal lab?

 

[SciencewithDrJ]

To my knowledge, you will need precision balances to weigh exact quantities, and distilled water, otherwise the results could be misleading.
Also, why only N and K? Phosphorus is critical also, and so is the pH measurement for healthy soil.
Commercial kits can only give you an approximate indication, but if you application needs precision, then a commercial lab would be best, since they analyze a wide range of cations and anions content of your soil.

 

[jim mcnamara]

I think doing that may be more complex than you want.
www.naptprogram.org/files/napt/north-central-states-methods-manual-2012.pdf

 

[Swake]

precision balances, distilled water

distilled water is not a problem. We have a 200gr calibrated scale that goes down to 0.05 gram and two not calibrated scales that go down 0.01 gram. Not top of the bill scales but I think I can thrust them enough for what I do with them.

Also, why only N and K? Phosphorus is critical also, and so is the pH measurement for healthy soil.

You are completely correct of course. pH measurement is being done. I'm in the process of validating my procedure, because I want to make sure I can thrust the measurement.
On this forum I found a thread about measuring P. I will try it out. Chances are I will need some help with it but let's first try and see

Very happy with approximate indications. Something like 'nothing - low - average - more that average - a lot'.
And possibility of comparison is important: 'the same - a little more than the other one - a lot more than the other one'.
This will allow recording evolution of the levels over time. No need for absolute figures. It would be fantastic to have them, but really not necessary.

@jim mcnamara thank you for this document, was searching for some time now and couldn't find anything like this on my own. At first sight it does contain lots of valuable information.

Thank you both for your answers. If it was only for a couple of tests I would send out the soil samples to a local lab. They perform analysis very well but they are expensive (it starts at 75€/$87 per test). This year I'll need about 20 tests only but as of next year probably a few hundreds of tests. And that represents a lot of money. Therefore it is worth some investigation. And anyhow I'm curious about how it is being done, I would love to have a relatively simple DIY method that is reproduce-able by many for cheap.

 

[jim mcnamara]

Some points:

First, most test kits are dumbed down, so that somebody who can read and is not color blind can do the tests well. But if you google you will find test kits that perform multiple sets of NPK and pH analyses, and are nowhere near as expensive. But a little harder to use. I think you may have done this already.

Next, you mention accuracy. You actually should get help from staff at a local agricultural facility - like an ag college or a government soils lab. Some places, this is not feasible Why get help? They have standard references and can assist you in tweaking validity of your tests. Example, where are you sampling from in the soil column?

Those facilities generally charge far less than $87 for their analyses. Plus, there may already be existing result sets for some areas.

Next, I assume you must be trying to do research. Are you aware of and actively using soil maps? You can sample the North end of a field, get result A, then walk to the South end and get result Q, because of local changes in soil. And wonder what you did wrong.

I could blather on, trying to guess. But no.

Bottom line: talk to a soil scientist from an agriculture college or from a Geology faculty. Consider a soils class as well.

 

[Swake]

The goal in one line: 1/ Maintaining pastures for horses in the most natural way possible. Fertilising is allowed but pesticides or 'chemical' products are banned. 2/ Optimising hay production on grassland. Same rules in terms of fertilisers and pesticides. There are many pastures, having many different situations.

I have been seeking help with some farmers and the local ancient wizards that remember the history of some pastures so we could do some research about the lands historical usage or its particularities. A school for horticulture has been helping with plans and tests and more. Very helpful.

It is true that soil can be very different only 25 meters further. And this is one of the things we're tracking.

The subject is certainly vast. And I'd like to keep the things simple where possible. First steps first. Now is the time to 'feed' the soil with the right things and in the right amounts. Let's track the changes as they occur. There is some room for experimentation. If and when we get bizarre results we'll of course fall back on specialists help.

 

[SciencewithDrJ]

The goal in one line: 1/ Maintaining pastures for horses in the most natural way possible. Fertilising is allowed but pesticides or 'chemical' products are banned. 2/ Optimising hay production on grassland. Same rules in terms of fertilisers and pesticides. There are many pastures, having many different situations.

I have been seeking help with some farmers and the local ancient wizards that remember the history of some pastures so we could do some research about the lands historical usage or its particularities. A school for horticulture has been helping with plans and tests and more. Very helpful.

It is true that soil can be very different only 25 meters further. And this is one of the things we're tracking.

The subject is certainly vast. And I'd like to keep the things simple where possible. First steps first. Now is the time to 'feed' the soil with the right things and in the right amounts. Let's track the changes as they occur. There is some room for experimentation. If and when we get bizarre results we'll of course fall back on specialists help.

It sounds like you have a big challenge ahead of you. I hope all goes well. Would be very interested to know how it goes and what solutions ultimately work out, so I would appreciate hearing how things go for you in the future on this undertaking.