Alternative Soil Testing Gives Insight
Published: Friday, March 18, 2022
Farmers chase the promise of improved soil health and fertility through use of cover crops. Increased organic matter and water holding capacity, accelerating the carbon cycle and greater soil fertility are among the goals.
Measuring the results towards the goals of a cover cropping program sometimes gets overlooked, replacing hard data with general estimates found in outdated tables and charts in old textbooks.
During Van Buren Conservation District's Farming for the Future Conference, Lance Gunderson, president and owner of Regen Ag Lab in Pleasanton, Neb., discussed different tests designed to extract specific information on individual components of the soil beyond NPK, pH and organic matter.
Several types of tests can help determine the potential for a soil, provide accurate nutrient credits from a cover crop and determine progress on goals.
Determining goals and working them through a cover cropping program is a good starting point such as compaction break up, weed control, or increased organic matter. Once a cover crop plan is in place, tailor the testing system around the plan.
Gunderson said that tests conducted in Regen laboratories more closely mimic processes found in nature, designed to save farmers money by reducing fertilizer inputs, especially nitrogen (N). On an average of 100,000 samples performed through the lab, he says that farmers save and average of 20 pounds N per acre by utilizing their trademark Haney Test results.
The total nutrient digest report measures carbon, nitrogen phosphorus, potassium, calcium, and the micronutrients to determine how much is really in the soil and how much fertilizer is needed for the next crop. It's comparable to a bank checking account that shows amounts available. The key is not spending the account down to zero, but strategically adding back into the account to support the life and nutrient cycling of plants and soil life.
"I am talking about getting the best bang for your buck from fertilizer," Gunderson said.
Sampling procedures must be precise and targeted, skipping the large field samples where a hundred acres or more are dumped into one composite sample. If a sample is targeting compaction at 6 inches, then samples must reflect that depth to get accurate information.
Samples should never be left lying in heat and sunlight or left to mix with contaminants like the diesel fuel or grease residues frequently found in most farm pickup truck beds.
The fertilizer value of a cover crop can be determined through Regen's Cover Crop test. The method requires clipping all the cover crop at ground level from a small area such as one, two- or three-square feet, carefully excluding any roots or soil. The plant material is placed in a tightly sealed plastic bag and shipped to the lab for analysis. Plant matter is weighed, dried, then weighed again to determine dry matter tonnage per acre. The process is comparable to a feed sample analysis.
Total carbon and nitrogen contents are evaluated next, providing a second component of understanding which is the carbon decomposition (CDM) ratio of the crop. The higher the carbon content the slower the crop breaks down.
A plant tissue analysis next determines the macro and micronutrients held in the plant material. A simple example would be the plant sample shows 10 percent nitrogen—4,000 pounds per acre results in 400 pounds nitrogen in the above ground biomass of the cover. The same process is used to determine other nutrients.
The test provides an idea of what nutrients are being tied up in the cover crop. The nutrients came from the soil, are being held by the plant to prevent leaching or runoff and will be returned to the soil through decomposition for a future crop.
"As farmers transition down the regenerative path, tools like the Haney Test become more valuable over time and the more conventional testing methods become less impactful on the farm," Gunderson said.
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