From the desk of Marc Suderman…
February 2022
The last three issues of SoilMatters have dealt with some key details to be aware of when soil samples are collected and sent to the lab for analysis. First, the lab extraction methods are important for accurate nutrient and pH measurement. Second, the extraction methods should be standardized in order to limit the variables being measured. Next, the Base Saturation Cation Percentage and the Cation Exchange Capacity are critical calculations for achieving cation balance, a stable pH resulting in improved water and nutrient use efficiency.
The final analytical measurement tool is the Denele Soil Health Report (DSHR). It is useful for getting an accurate soil health assessment, in terms of the soil microbial population and the activity levels. The Soil Respiration test starts by irrigating the sample with neutralized water and bringing it up to field saturation capacity based on the soil cation exchange capacity (CEC). Once field saturation is reached, it is held at 68°F for seven days, in order to allow time for the microbiology to reproduce and nutrient compounds to react.
Once field saturation is reached, it is held at 68°F for seven days, in order to allow time for the microbiology to reproduce and nutrient compounds to react.
The first microbial calculation is done at the beginning of the process to establish the total starting population of the soil. The second microbial calculation is made at the end of the seven day analysis period. The second value reveals how much microbial “food” is available and releasing from the soil.
If the population value increases, that means the microbes are reproducing because there is available “food” to sustain microbial life. Soils that are imbalanced hold cations tightly with limited release and therefore provide only limited amounts of “food” to support microbial activity. When there is limited microbial activity, there is limited nutrient release and availability to plant roots for uptake to support crops.
Figure 1, shows a DSHR where the microbial population declined from 0.8 to 0.6, over seven days. This verifies that the soil needs better cation balance, it also needs soil inoculation with organic acids to supply a microbial energy source which in turn will stimulate increased beneficial microbial activity.
Consider that alkaline and calcareous soils can often have large volumes of bicarbonates. These could be calcium bicarbonate, potassium bicarbonate, sodium bicarbonate, etc. Regardless, each of these compounds will react and release carbon dioxide.
These could be calcium bicarbonate, potassium bicarbonate, sodium bicarbonate, etc. Regardless, each of these compounds will react and release carbon dioxide.
This is a chemical reaction that produces carbon dioxide. If the analysis being performed counts total carbon dioxide release as microbial respiration activity, the bicarbonate chemical reactions will skew the true microbial results. For a Soil Health assessment to be most accurate it must separate the chemical reactions from the microbial reactions.
One way to do this effectively is by allowing time for chemical reactions to occur and equalize so that in time, the microbial respiration activity can be differentiated and accurately measured.
Finally, the DSHR also accurately measures soil nitrogen release. Soil microbial nitrogen release activities can contribute significantly to nitrogen availability. Nitrogen that has been microbially processed is a “bio-available” form of nitrogen that is non-fixing and non-leaching.
Every soil on every farm is different, but regardless of soil variability, microbial nitrogen release can significantly improve nitrogen use efficiency and plant productivity.
This test calculates available nitrogen and nitrogen release over the growing season. In figures 1, 2 and 3 the Total Available Nitrogen is quite low which confirms microbial release activity is low. This is valuable information for planning a Nutrient Management Plan to ensure nitrogen is supplied when needed and over-applications are reduced if not eliminated.
When fertilizer prices are at expensive levels, it is important to be precise, efficient and effective. The best way to be sure sure you are maximizing your fertilizer investment and benefit, is by annual soil sampling and in season plant tissue sampling. Remember, rebuilding soil health is good stewardship, but quite doable with the right tools and guidance. One final note, In figures 1 and 2 the Microbial Counts (Red Boxes) declined, but in the third year of soil inoculations and monitoring, the populations increased significantly. When undertaking the task of rebuilding soil health, it is good to have reasonable expectations as to how quickly you can expect to see your soil turn around.
Visit me at www.soilmatters.net or email me directly at marcs@soilmatters.net. I have some information to share with you and help you start improving your soil health.
Here’s to your crops’ success!