Improving Carbon Sequestration through Bale Grazing and Keyline Cultivation

It is important to review climate conditions because variables like temperature and precipitation can influence a number of the parameters measured within this project. Hayfields and pastures were moderately productive in 2022; however, drought conditions returned in early July. The winter started seemingly mild, but a series of blizzards occurred in December/January and April. 

Hayfields and pastures were quite productive in 2023. The winter was mild with minimal snowfall and above normal temperatures in December. However, a prolonged cold spell occurred in January.

Baseline soil samples were collected during the spring of 2022 to assess soil nutrient and microbial activity (Haney Soil Test) prior to bale grazing and Keyline cultivation, see tables below. Soil samples were also collected in the spring of 2023 and 2024 to monitor changes over time. Samples were collected at varying depths to monitor the scale of impact. We were particularly interested to see if we could influence subsoil nutrient and microbial activity through the use of Keyline cultivation and bale grazing.

Data associated with soluble salts was variable across replicates. Excess lime at 0-6” was minimal during all years of the study. At 6-24”, excess lime was high during 2022 but changed to none or low by 2024. % OM had a neutral or positive response to Keyline cultivation and bale grazing from 2022 to 2023, but reduced from 2023 to 2024. While we expected to see this number continue to increase in 2024, added residue may need additional time to be broken down by soil microbes.

 Soil respiration is a test aimed at measuring the amount of CO2-C a soil can produce over a 24 hour incubation period following a significant drying and rewetting event. Most microbes produce CO2 through aerobic respiration and the more CO2 a soil produces the more life it contains or the higher the microbial biomass. Soil respiration readings can fall anywhere from near zero to 1000 ppm of CO2-C.  However, most agricultural soils are currently degraded and do not read above 200 ppm.  In general, the higher the number the better.  Soil respiration was variable across replicates in 2022 and 2023, but ranged from slightly below average to above average at 0-6" and low to below average at 6-24". Soil respiration was classified as above average or high at 0-6" and slightly below or above average at 6-24" in 2024. It is important to note that climate conditions at the time of sampling are likely to influence these results. 

Below is a table created by Ward Laboratories used to interpret CO2-C measurements. 

N, C, P, K, and Zn positively responded to Keyline cultivation and bale grazing at 0-6” and 6-24”.

% microbially active C is how much of the C pool was acted upon by the microbes. If this value is below 25%, carbon is probably not the factor limiting your soil respiration. Ward Laboratories suggests that perhaps it is the soil’s overall fertility, prolonged cold temps or drought that is limiting microbial biomass. If the value is above 80% this suggests that C could become limiting to microbial respiration soon and your management focus should be on introducing more carbon into the system. The values from 2022 to 2023 declined and is likely due to prolonged cold temps during the spring of 2023. However, the values from 2023 to 2024 increased or were similar to baseline levels.

The soil health score is a summary of the soil respiration, C, and N and represents the current health level of your soil.  The score can range anywhere from 0 to 50, but most soils do not score higher than 30.  In general, the higher the score the better. Ward Laboratories likes to see the score above 7, though this is just a starting point. All samples were above 7 at 0-6”, but dropped below 7 at 6-24”. The general trend is an increase in overall soil health at both 0-6" and 6-24". 

We also collected samples in the fall of 2023 to monitor soil nutrient and microbial response to the direct and indirect impact of bale grazing alone, see table below. The direct impact samples were collected underneath a bale that had been bale grazed, whereas the indirect samples were taken from the bale graze area but not directly underneath a bale that had been grazed.

The data shows that parameters respond more to the direct impact of bale grazing. The use of more bales or the rotation of bale grazing locations could spread the direct impact of bale grazing.

Additionally, samples were collected from a location that continues to be managed as a hayed perennial, with no Keyline cultivation or bale grazing (see table below).  The site is near the project area and has a similar soil type. It has a history of cover cropping (2016-2018) and was planted to a perennial in 2019. Soil samples were collected in the fall of 2019 and 2023.

Overall, the soil nutrient and microbial response to traditional management was very limited. Doing nothing created no results in terms of improving soil nutrients or creating an environment to that promotes soil health. 

Following moisture events, observations were made both above and below the Keyline cultivated areas to note changes in sheet or rill erosion, as well as water runoff. The Keylines were very successful at capturing runoff and slowing down or disrupting sheet and rill erosion. After bale grazing occurred, it was observed that organic matter and manure was deposited into the Keyline slits. Following a winter of record snowfall, it was observed during the spring of 2023 that no runoff occurred below the Keylines. 

It was intended to use a soil probe to monitor moisture at a depth up to 24" from the base of the Keyline to determine contribution to subsoil moisture. When conditions allowed for the soil probe to be used, soil was at saturated levels. However, when soil was not saturated the probe was not able to penetrate the soil. Therefore, soil moisture levels are not reported. 

Soil compaction was measured at varying depths and distances from the Keyline to monitor the scale of impact following bale grazing in spring of 2023. Measurements will be repeated in spring of 2024. 

Below is an example of penetrometer test results from three different locations on June 4, 2023, which show a typical response observed throughout the testing period. As demonstrated, measurements above the Keyline tend to have greater levels of compaction as compared to in the rip. It should be noted that biological life is greatly reduced at 300 pounds per square inch and above. The measurements obtained within the rip indicate that there is an opportunity for biological life to flourish. This, coupled with observations of improved water infiltration fosters an environment that is necessary for soil biology.

Baseline forage production within the project area was determined by clipping. The baseline forage production in 2022 was approximately 2,700 lbs/acre. The direct impact of Keyline cultivation and bale grazing resulted in twice the amount of forage production as compared to areas that were indirectly impacted in 2023, see table below. When compared to the traditionally managed system, forage production was 64% and 28% greater in the direct and indirect areas, respectively.

Prior to bale grazing during the winter of 2022, cows had an average body condition score of 5.5 which means they had a good overall appearance. On palpation, fat cover over ribs feels spongy and areas on either side of tail head have palpable fat cover. Sheep body condition was scored at 3 which means that vertical processes are smooth and rounded. The bone is only felt with pressure. The horizontal processes are also smooth and well covered; hard pressure is required with the fingers to find the ends. The loin muscle is full and with a moderate fat cover. Multi-species bale grazing began on December 12, 2022 and ended on May 30, 2022. The cows actually calved in the project area, while continuing to bale graze. Prior to calving, the average body condition score was 4.5 which means that some cows appeared thin, with ribs somewhat visible and backbone showing. Muscle tissue was not depleted through the shoulders or hindquarters. Other cows were described as moderate to thin. The decline in body condition is attributed to the record breaking snowfall received during the winter. 

The sheep were actually pulled from bale grazing halfway through the winter. Although supplementation was provided to help them maintain their condition, the sheep preferred to stay with the cows in the project area during winter storms. They would not come in on their own, even when additional windbreak and supplementation was provided. As a result, they crowded together with the cows and some ended up with broken legs. To prevent any further injury or loss of condition, it was decided to pull them from bale grazing and feed them in the corral until the weather conditions improved. 

Prior to bale grazing during the winter of 2023, cows had an average body condition score of 5 which means that most were able to rebound from the harsh winter. Again, sheep body condition was scored at a 3. Body condition will continue to be monitored and a final report will be made upon removal from bale grazing. Currently, the winter has been very mild with little to no snowfall. The livestock have been able to graze forage regrowth while bale grazing. It has been observed that both the cows and sheep prefer to graze what they can before eating hay. 

For more information on body condition scores of beef cattle:<https://beef.unl.edu/learning/condition1a.shtml>

For more information on body condition scores of sheep: <https://extension.sdstate.edu/sites/default/files/2021-07/MC-02221.pdf>

While these initial results are interesting, we look forward to collecting soil samples in the spring of 2024 to better evaluate change over time. We also plan to make more observations regarding runoff and will continue to track time and money spent to implement bale grazing and Keyline cultivation versus other management strategies. As we work through the final stages of the project, a self assessment will be performed to evaluate one's own satisfaction with the project.