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In the top graph above, 71 sites with both grazing animals and organic matter inputs (OMI) are each represented by a quadruplet of data points connected by a vertical black line (a blue square for 2019, red circle for 2020, green triangle for 2021, and yellow diamond for 2022). Each square-circle-triangle-diamond-black-line combo represents the Soil Organic Matter (SOM) values for one site for 4 years. According to the literature, SOM is supposed to be quite stable and very difficult to change, and yet we are seeing large swings in individual sites’ SOM data, especially when grazing animals are present or organic matter is imported to the site, as is the case in the top graph above.
We only have 12 sites in our study which have no grazing animals or imported organic matter for 3 or more years. The second lower graph shows that the variability in SOM values for these 12 sites is much less than for sites with grazing animals or organic matter inputs.
We examined our 28 sites which have the most variability in their soil health scores. We call these sites our “Swingers”, and they are evenly split between organic and conventional growing methods.
Over half the “Swinger” sites are pastures with the rest split evenly between home gardens and commercial vegetable sites. Their most common crop is grass hay with mixed vegetables coming in second. Their average water season is 127 days long. “Swinger” sites have an average soil health score of 27.6, which is very high, especially for Colorado. The growers of these “Swinger” sites are all Soiley Award winners or nominees. They have adopted many soil health practices, as you can see in the following graph.
The lesson here seems to be that no good deed goes unpunished. It seems that one result of adopting good soil health practices may be a great deal of variability in soil health lab results. If you see your Haney test results bouncing around a lot, year-to-year, it does not necessarily mean that you are doing anything wrong. It may mean that you are doing many things right! We will explore this hypothesis further in coming years as we gather more data.
We sorted our sites into 3 groups and calculated the average variability for each group. This bar graph shows that the groups which grazed animals or added organic matter to their sites for 2 consecutive years have approximately three times as much variability in their lab results as the group with NO grazing animals and NO organic matter inputs.
Elizabeth Black is the producer of the Citizen Science Soil Health Project