Norton: Producers can evaluate soil health using simple steps
Casper – When it comes to soil health, Jay Norton believes checking the health of the soil is similar to going to the doctor for an annual checkup.
“How are current management practices affecting future sustainability?” asks Jay Norton, University of Wyoming (UW) associate professor for ecosystem science and management. “Some soil properties are excellent indicators for sustainable land management practices.”
To help producers look at soil health indicators, Norton developed a stepwise approach that includes identifying monitoring and reference locations, observing soil features, obtaining field measurements and collecting samples for lab testing.
The first step, according to Norton, is to break up the rangeland into soil vegetation zones with similar management and soil types.
“For smaller pieces of property, producers can split the rangeland, or for bigger properties, they can lump the zones together,” Norton states, adding aerial photos, maps and soil survey tools can help producers form monitoring zones.
“Soil map units from a soil survey might work as initial soil management zones,” Norton adds, noting soil formation defines the soil map units for producers to assess soil health.
“Soil formation is a combination of climate, organisms, topography, parent material and time, which results in soil types with unique potential for productivity and resilience,” he states.
A reference location is also a necessary component for monitoring soil health, says Norton, adding the reference location should be placed where the soil performs best.
“The reference location is the benchmark for a zone,” he explains. “After setting up soil vegetation management zones and reference areas, producers need to establish and mark permanent transects in every zone’s reference area.”
Producers should take 10 or more samples per transect to attain average values for soil health indicators, Norton explains.
According to Norton, the indicators for soil health are surface horizon thickness, soil structure and texture, resistance to penetration, signs of sheet or rill erosion, salt accumulation, soil moisture and soil content.
“Dig a hole and then take a slice out of the side to determine the surface horizon thickness. Look for changes in color, structure, texture, firmness and root density,” he says. “The surface horizon responds rapidly to changes in vegetation, traffic and surface flow and is crucial for water infiltration and seedling establishment.”
Norton notes compaction and wind and water erosion decrease surface horizon, but the thickness is an important soil health indicator.
Structure and texture
Soil structure is formed by organic decomposition and microbial activity that creates glues to hold soil particles together.
“The soil structure should be blocky or granular in the surface horizon,” states Norton, adding this structure provides increased infiltration, water holding capacity, water and air movement and root exploration.
“The loss of structure from compaction, reduced organic matter or surface horizon results in single-grained soil that falls through our fingers,” he adds.
Good blocky soil structure is crumbly but has aggregates or clumps of soil, Norton explains.
As for soil texture, he mentioned texture is an inherent property that allows for comparison between soil types.
“Soil texture can also indicate the loss of surface horizon if there is a loamy texture in one area and clay texture in another where the loam has eroded,” he states.
Resistance and erosion
A very popular soil health tool is measuring the resistance to penetration, which requires a penetrometer with a gauge, says Norton.
“Another way to test resistance is to use a knife and jab it into the ground,” he mentions. “Even with a knife, a sensitivity can be developed for how hard it is to push the knife into the ground.”
Resistance to penetration correlates with root elongation, porosity, density and water properties like infiltration.
“The U.S. Forest Service developed severity classes for resistance where a zero is considered a natural reference area condition and one through three indicated increased resistance,” notes Norton.
Erosion is another soil health indicator producers should look for on a micro-scale, he adds.
“Producers should look for little canyons and plateaus, which indicate soil movement, lack of water infiltration and movement across soil that could be the beginning of a problem,” Norton says. “On a micro-scale, look for water starting to pool and move, which creates micro-cracks.”
Pedestaling, which happens when coarse rocks sit on top of little pedestals due to fine soil particles being washed away, should also be monitored.
The next step is to send soil samples to the lab, but it is important to carefully take the samples, according to Norton.
“Soil samples need to represent the area producers are interested in. Take multiple samples in one area, mix them all in a bucket, pour the mixture in a bag and send it off,” he explains.
Norton recommends taking samples during dry conditions because some soils are more moist than others, which can have an impact on soil analysis.
“Sample depth depends on management. We should sample the surface horizon,” adds Norton. “Don’t leave the soil samples in moist conditions on the dash of the truck, either, because that changes the soil. Dump the soil onto a paper plate and let it dry out.”
He notes most labs offer a routine analysis for soil samples, but when it comes to rangelands, Norton says, “I think producers can get just as much information from going out with a knife to determine what their management actions should be.”
In conclusion, Norton states, “Simple observations of soil and surface conditions, combined with vegetation monitoring, can provide a great deal of information about the sustainability of producers’ management practices.”
At the 2017 Natural Resources Rendezvous in Casper on Nov. 28, Jay Norton presented “Rangeland soil health indicators: A stepwise guide to assessing management effects on rangeland sustainability.”
Heather Loraas is assistant editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.