JustinM

Justin Morris
During the Soil for Water film premiere held in February, two questions were asked regarding different types of soil health testing.

Question: Can you explain the PLFA and Haney soil health tests?

Answer: PLFA is an acronym for Phospholipid Fatty Acid test. Since all organisms in the soil have a phospholipid membrane, this type of test can differentiate the different types of phospholipid fatty acids in different types of bacteria, fungi, protozoa and nematodes. A PLFA test will give you a pretty good indication of the general groups of organisms in the soil along with their approximate populations so you can analyze their relative ratios to each other. The Haney test doesn't tell you who's there like a PLFA test, but it does tell you how healthy your soil is by using many measurements of health. These measurements include: water extractable organic carbon, water extractable nitrogen, water extractable organic nitrogen, carbon to nitrogen ration, solvita microbial activity test, inorganic nitrogen, inorganic phosphorus, and inorganic potassium. Here is a link to a presentation done by Rick Haney that talks about the test he developed: https://www.youtube.com/watch?v=qQ3tI-KwgEE&t=4s.

Question 2: Have different farmers/ranchers found that the Haney soil health test results change with changes in soil management?

Answer: Agricultural producers have found that the results of the Haney Test change with changes in soil management. Crop producers have noticed that their soil health calculation (SHC) improves as they disturb the soil less, keep the soil covered, increase cropping diversity and strive to keep a live root in the ground as much throughout the year as possible.
 
During the Soil for Water film premiere held in February, two questions were asked regarding different types of soil health testing.

Question: Can you explain the PLFA and Haney soil health tests?

Answer: PLFA is an acronym for Phospholipid Fatty Acid test. Since all organisms in the soil have a phospholipid membrane, this type of test can differentiate the different types of phospholipid fatty acids in different types of bacteria, fungi, protozoa and nematodes. A PLFA test will give you a pretty good indication of the general groups of organisms in the soil along with their approximate populations so you can analyze their relative ratios to each other. The Haney test doesn't tell you who's there like a PLFA test, but it does tell you how healthy your soil is by using many measurements of health. These measurements include: water extractable organic carbon, water extractable nitrogen, water extractable organic nitrogen, carbon to nitrogen ration, solvita microbial activity test, inorganic nitrogen, inorganic phosphorus, and inorganic potassium. Here is a link to a presentation done by Rick Haney that talks about the test he developed: https://www.youtube.com/watch?v=qQ3tI-KwgEE&t=4s.

Question 2: Have different farmers/ranchers found that the Haney soil health test results change with changes in soil management?

Answer: Agricultural producers have found that the results of the Haney Test change with changes in soil management. Crop producers have noticed that their soil health calculation (SHC) improves as they disturb the soil less, keep the soil covered, increase cropping diversity and strive to keep a live root in the ground as much throughout the year as possible.
Hi Justin!

Thank you for sharing that video. I think Dr. Haney does a great job at explaining how complex and variable soil testing can be and the difference between Soil Organic Carbon (SOC) and Soil Organic Matter (SOM). Which brings me to what I call " The SOM crash". In recent work I started noticing that people starting to implement the 5 soil health principles in semi-arid, arid regions sometimes see a SOM crash, while describing a visually healthier soil. At first it made me really question the validity of testing for SOM but then I started thinking that it was possible that very happy soil microbes where consuming it. What are your thoughts? Should land managers start focusing more on SOC metrics rather than SOM?
 
Luz,
I just saw your response and questions regarding arid region SOM crash and what it means. I have been working with soil health measurement processes for several years and continue to work to find low cost and quick measurement tools to help all growers better understand what is taking place in their soil. Having worked with soil respiration, CO2, I find that even with 2 identical soils with moderate soil health, soils exposed to higher temperatures will consume or respire more carbon as well as mineralize more soil nutrients due to the temperature alone. The Arhennius Equation will rule the rate of microbial respiration, The Arrhenius equation describes the relationship between the rate of reaction and temperature for many physical and chemical reactions.
For soil microbes for every 10 C increase or decrease in temperature, the rate of respiration will double.
This is one reason semi-arid and arid soils usually have less OM or carbon present, it is metabolized more quickly. For those interested, I have found that using soil respiration in conjunction with microbial biomass measurements can provide some unique insights to what your soil is doing, both can be performed in real-time and at low cost. I am bench testing some areas to help growers focus on the critical growth stages of crops and plants using irrigation with high dissolved oxygen water, very promising.
 

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Hi Justin!

Thank you for sharing that video. I think Dr. Haney does a great job at explaining how complex and variable soil testing can be and the difference between Soil Organic Carbon (SOC) and Soil Organic Matter (SOM). Which brings me to what I call " The SOM crash". In recent work I started noticing that people starting to implement the 5 soil health principles in semi-arid, arid regions sometimes see a SOM crash, while describing a visually healthier soil. At first it made me really question the validity of testing for SOM but then I started thinking that it was possible that very happy soil microbes where consuming it. What are your thoughts? Should land managers start focusing more on SOC metrics rather than SOM?
Hello Luz,

SOM crashes come about from not providing enough carbon into the system where the carbon to nitrogen ratio of the cover crops they're using is too low. When the carbon to nitrogen ratio gets to be less than 24:1 as a general rule, residue will quickly disappear because the microbes will be eating the relatively low carbon, high nitrogen material very quickly. In contrast, when we have higher carbon residues where the carbon to nitrogen ratio is higher than 24:1 especially as we get into corn or wheat residue, these types of residues generally decompose very slowly. In arid environments this is even more pronounced since water is a limiting factor and water helps to drive biological reactions. So, when there's a SOM crash, yes, the microbes begin consuming the very glues that help give soil it's structure and pore space. This is why paying attention to the species of plants in the cover crop and when it should be terminated is of crucial importance in maintaining enough residue until the next cash crop canopies over to protect the soil. As far as SOC versus SOM, I don't think it really matters. You can convert SOM to SOC simply by dividing by 2 or multiplying by 0.5 since roughly 50 percent of SOM is carbon. Beyond using SOM or SOC to track progress, I'm still a fan of using WAS (Wet Aggregate Stability) to get a better overall picture of soil health. WAS is likely the best overall indicator of soil health because it takes into account the soils biological activity, physical structure, and chemistry. You can do comparisons of this with dried clods in the field or you can send them into certain labs and they can do a WAS test.
 

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