Published December 9, 2019 | By Mike Petersen
Couple different ways to test for part of the soil health of your soils
Do not get me wrong I am a advocate of all roots; living or deceased doing good for a healthy soil. But the big emphasis of being Cover Crops as the answer to soil health misses the many decks of a naval carrier like the USS Abraham Lincoln. What do you mean Mike? For a truly healthy soil a wider perspective of top soil health I suggest we look at soil structure, soil porosity (the importance of the varying soil pore sizes in the surface soil as well as subsurface and subsoil), pH, and what are the majority of the species of microbes (anaerobes, facultative anaerobes, aerobes). Not all are represented in your soil surface horizons to be of benefit to you. Firmacuties for instance when out of balance with other microbes in your soils can be of detriment to your soils be biologically in balance.
How do we find out what we have in my soils? That maybe your question. One can run the simpler soil tests that indicate respiration, fine when the soils are active and above 62-63 degrees Fahrenheit, but that does not give much indication who lives there and who is related to who. Yes I am partly having you consider an more expensive test at a speciality lab. Now not everyone is into such due to cost and then who knows what the dickens comes from the test, when to do it and where does one collect the sample(s) in the field. Mike, what other soil tests that you mentioned in the first paragraph for soil health will aid me in determining if my soils are healthy or so-so? Soil structure whether or not the soil aggregates are stable in a slaking tests which the NRCS can test with and for you. A true soil scientist can give you an indication of the soil structure if your soils from the surface or subsurface is moderate medium granular or subangular blocky. Having a soil test for bulk density can be done by some soil testing labs across the country. Or a look at the soil with a 10X to 15X hand lens on a 4″X4″ block of soil carefully pulled from the 1 to 5 inch area of the soil profile or 2 to 6″ zone. This kind of sample should be done in the spring or late winter before all the tillage is done. Besides, the soils should be moist not dry. Testing for pH is a standard tests from all soil testing labs whether private or University. The Haney test and other soil respiration tests can be done but they require some handling, and timing issues along with storage and shipping. Another suggestion; call your friendly NRCS office, speak to them about having an evaluation of your soil health by one of your states Soil Health guys or gals. Most are very apt and willing to do that for you.
Three different tests that will expand your knowledge about your soils on your farms. The Haney Test is one way as is the PLFA Microbial Community test. Many more dollars because they are looking at the DNA signatures of the bacteria in the soil sample at the time of the sampling. The Solvita tests is a one-time sample when the soils are warm (May into late August) to inform you if according to a standard how much CO2 is given off in a 24 hour period. All of these tests are usually from your surface 4 inches of the soil profile. If you would sample from 0-4 then 4-8 inches the numbers will be quite different but very informative. Then there is the ole grab a handful of the soil from the surface 4 inches and smell it with the nose. If there is that rich, earthy smell that is a little pungent – that is an aroma from the azotobacter and nitrosommonas little critters, a good thing but only broad brush look and smell. Do not get me wrong, these are qualitative but can be of some good news.
The PLFA tests require as I said some special handling and shipping steps. Those of you that want to really know will consider these tests. May I suggest go on-line and search out who does and gives a sound report of what is happening.
When I do Soil-Root Pit digs and evaluations I have done many of the physical tests at that time to inform you of all what I know from my 45 years of soils experience and learning. I can offer at the same time sampling for the other tests with a pit opened up.
Look into it folks. The Soils World is an amazing place to learn more about your farming practices and what you are dealing with each year.