1. Soil Respiration
The first part of the Haney Soil Health Test is soil respiration test or CO2 24 hr. burst test is an indicator of soil microbial biomass. When we receive the sample we dry the soil over night at 110 F and then crush the soil and collect soil that passes through a 2 mm sieve (opening is the size of a window screen). We measure out 40 grams (about 1 ½ ounces) of soil and add water at the bottom of the beaker so the water moves up into the soil by capillary action. Because we “killed” the microbes by drying and grinding, we wet the soil to activate some of the microbes and they feed on the readily available carbon, which is the “killed” microbes in the soil. The more microbial life the more CO2 produced, indicating more microbial biomass. A good CO2 respiration is 60 to 120.
2. Water Extract
A water extract is another part of the Haney Soil Health Test. We measure total organic carbon (TOC) and total nitrogen (TN). The microbes live in the water films that adhere to surfaces of soil particles. The TOC in the water is the food (energy) for the microbes. The TN includes nitrate and ammonium (inorganic N) and organic N. Organic N (TON) is inorganic N subtracted from TN. This organic N is the protein source for the microbes. Ideally the water extractable C:N ratio (TOC:TON) 10:1. A good range is 8:1 to 15:1.
3. H3A Organic Acid Extract
The organic acid extract mimics plant root exudates. The H3A extracts nitrate, ammonium, orthophosphate, and ICAP phosphorus (total P), potassium, calcium, magnesium, sulfur, zinc, iron, manganese, copper, and aluminum. This extract is a good measure of nutrient supply. It is interesting to me to compare the H3A extract to our standard soil tests. The test values are related. In other words, a low value in our standard tests are low in the H3A tests.
The three organic acids used to extract the nutrients are malic, oxalic and citric acid. Nitrate and ammonium are very similar to standard soil tests. Other H3A tests that are similar to the standard soil tests are total P, sulfate, sodium, manganese and copper. The other H3A tests; potassium, calcium, magnesium, and zinc are lower than the standard soil tests. We cannot estimate cation exchange capacity (CEC) from the H3A extract.
Nitrogen fertilizer recommendations are lower for the Haney test because we are able to measure mineralizable organic N and ammonium that we normally do not analyze in a standard soil test. The Haney test lets us know how active our soil is then how much better we can manage our N fertilizer application.