Our recommendations for sustainable agricultural production and future research:

1. 1.  Only half of participating growers understand their test results and which actions are indicated. They are more interested in what actions they need to take than their actual test results.  It is hard for some of them to make the jump from a lab test result to a recommended action.  Many of them need someone to help them interpret their soil testing results and  recommend actions. However, soil health testing is relatively new and many local Ag advisors are not familiar with the tests and don’t have experience interpreting them.  We need a program to teach local Ag advisors how to interpret soil health tests and how to advise growers based on those results.
   2. 53% of growers want more individualized consults with soil health experts.   51% of our growers said that they would like to receive a list of recommended actions to consider, in conjunction with their soil health lab reports.  However, when we ran this idea by local conservation district staff and other Ag professionals, they said that they were already overtaxed with their current workload, and they could not take on any additional work.  They also expressed reservations regarding the wisdom of making recommendations without a site visit to really understand the issues on a site, and without developing a more formal conservation plan for the site. 
   3. Although our entire CSSHP data set identifies broad soil health group trends, individual grower’s data is erratic, without clear trend lines for most growers.  We are seeing a great deal of variability (big swings up AND down) in individual soil health test results, which makes it very difficult to assess individual grower’s progress.   More grazing days and greater organic matter inputs seems to correlate with more variability in soil health test results.  The variability we are seeing makes me question the worth of spending a lot of money on soil testing (which is what we are doing at the CSSHP).  For us, it turns out that the tests and their results are just the excuse folks need to get together and share information.  It is the information sharing through annual meetings, Farm field days, short videos of CSSHP growers discussing their solutions, photos of others’ fields, and more where the change happens.  Trust building is key, and trust-building takes many years of persistent human contact.  So, it is really good that our project is 10 years long.  A 3-year-long project (which is all most grants fund) is just too short.
      
   4. Much of Western Ag is supplied with Colorado River water, including our area, the Colorado Front Range.  We all know that water travels uphill to money, so as Colorado River water becomes more scarce, Ag-water will be gobbled up by urban areas, leaving Ag with less and less supplemental irrigation water.  Western research should be focused on how to maximize water yield for Ag in a time of dwindling supplies.

2024 Findings

PLFA PROBLEMS: This year, we saw illogical and precipitous drops in PLFA scores, but only on the soil samples our growers collected in the fall.  The 3 graphs below illustrate this.  The first 2 graphs show the 2019 and 2021 PLFA results for total microbial biomass for all our sites, with each dot representing one site’s score and the date it was collected.  You can see a wide range of scores in both spring and fall for all our sites in both 2019 and 2021.

This third graph shows our sites’ total microbial biomass in 2023.  This graph shows the same wide range of scores in the spring, but suddenly in the fall, all sites start having very low scores.

When we brought this to our lab’s attention, they initially suggested that the cause could be a very wet May-June-July followed by a very hot dry August-September-October, as we experienced in 2023.  When soil microbial populations expand rapidly under favorable conditions like we experienced last May-June, they can sometimes use up all their available resources, and then suddenly crash.  If this were the cause of our problem, we would expect to see a difference in the drops in PLFA scores of dryland fields, compared to fields which continued to receive supplemental irrigation water throughout the growing season.  However, we did NOT see any difference between the total microbial biomass scores of our dryland fields and our irrigated fields, as the next graph shows.

We also checked to see if the amount of time samples were stored in freezers, or if the type of crops grown in the field were correlated with the drop in scores.  They were not.  We checked the Haney test scores which were pulled from the same soil samples.  Haney test results were all within normal ranges.   Our sampling and shipping protocols have stayed exactly the same for the last 5 years.  All this means that the problem is most likely something that happened while the soil samples were in route to the lab, or at the lab itself.

Our lab has bent over backwards to ascertain the cause of this problem.  They reran samples and re-calibrated their machinery multiple times, tore apart then cleaned and reassembled their machines, substituted all new reagents, switched lab techs performing the test, sent samples to other labs, re-checked other clients’ samples and results, called other researchers for advice, and bought several new parts for their machines.   I have sent them new samples from now-frozen fields and am investigating whether our shipper might have done something to our packages in route.  Our lab has finally isolated the problem to a combination of slight leakage within the gas chromatography machine, and an oven with variable inconsistent heat.  The re-run results we have recently received seem more in line with previous years' results.

OUR GROWERS HAVE MADE PROGRESS!!: Reaching the halfway mark of a 10-year project is a good time to look back and assess the progress made in improving our soil’s health.  The variability we continue to see in our lab results has thrown a great big monkey wrench into our ability to assess progress using only our lab results.  (More on that in the next section of this report.)  However, we can still assess the progress our growers have made in increasing their use of tried-and-true soil health practices, including:

• Increasing their Days of Living Cover
• Increasing their use of Cover Crops
• Decreasing their Tillage Intensity
• Increasing their Organic Matter Inputs

We have 5 years of data on the 51 sites which have been in the project since the very beginning, with data on both their management practices as well as their soil testing results.  The following graph shows that the average Days of Living Cover of these 51 sites has increased by 20 days since 2019. 

Our growers have increased their Days of Living Cover by increasing their use of cover crops, converting annual crops to perennial systems, and incorporating more fall-planted small grains into their rotations.

We examined the 200 sites for which we have cover crop data, and found that our growers’ Cover Crop Use has increased for almost all our crop categories including Commercial Veg/Flower/Fruit, Commodity Row Crops, and Home Gardens.  Only when a rancher inter-seeds a cover into an existing pasture, or reseeds an annual field into a perennial crop do we credit a cover crop to that site, so we expect that cover crop use would be low for many of our established Perennial Hay/Alfalfa/Pasture sites.  Dryland grain sites, which depend on 420 days of fallow soil to store enough soil moisture for a biennial small grain crop, avoid cover crops because cover crops can deplete soil moisture.  Our growers have increased their days of cover crops on average by 25 days/site since 2019.

When we examine the Tillage Intensity of the 191 sites for which we have tillage data and group them into their 5 crop categories, we see that 4 crop groups have made very good progress in reducing their Tillage Intensity, with Commercial Veg/Flower/Fruit sites and Dryland Grains making the most progress.  Perennial Hay/Alfalfa/Pastures have held steady with quite low Tillage Intensity scores.

When we examine just the 51 sites for which we have 5 years of data, we see the same trend of Tillage Intensity decreasing by 17 points over the last 5 years.

However, our news on Organic Matter Inputs is more mixed.  The good news is that a majority of all our growers have used organic matter inputs on their sites in the last 5 years, with home gardeners leading the way.  We only count the organic matter inputs which are acquired off-site in this analysis.  Manure deposited by grazing animals on-site, or clippings from on-site cover crops, are not counted as organic matter inputs here.  Thus, perennial fields with aftermath grazing often show as having no organic matter inputs, even though they may have many days of grazing animals depositing manure and urine in their fields.

However, the bad news is that when we examine our successive years of data and divide our sites into their different crop categories, we see that only home gardeners have increased their Organic Matter Inputs in 2023.  All other crop categories have seen a sharp decrease in Organic Matter Inputs.  Commercial Veg/Flower/Fruit growers have seen the biggest decrease.  (See graph below.)  Organic Matter Inputs have decreased by 13T/acre on average since 2019.

There are several possible causes of this decrease. 

• We experienced an exceptionally wet May-June-July in 2023. Growers had a hard time planting, cultivating and harvesting between storms.  They may not have wanted to or been able to get additional machinery into soggy fields to spread amendments.
• Our very tight labor market meant growers struggled all season to fill vacant positions. They may not have had enough workers to do things like spread amendments. Additionally, our tight labor market has increased labor costs sharply.  This has affected Commercial Veg-Flower/Fruit growers the most as their crop category is the most labor intensive.  Recent high labor costs may have consumed any profit that formerly paid for purchased amendments. 
• Some growers with excessively high phosphorus levels may have decided to forego organic matter inputs and use cover crops instead, to avoid increasing their soil phosphorus to dangerous levels.

The table below summarizes our growers’ excellent progress incorporating soil health practices in 5 years:

VARIABILITY:  We continue to see a great deal of variability in our lab results when we compare sites with themselves year-to-year.  This year we divided our sites into 4 crop categories (Commercial Veg/Flower/Fruit; Commodity Row Crops and Dryland Grains; Home Gardens; and Perennial Hay/Alfalfa/Pastures) and examined each category’s variability.  The 4 graphs below show that an examination of past practices can often explain some of the exceptionally big jumps in variability which we see in every crop group.

In the 4 previous graphs, each site’s 3-5 years of soil health scores are represented by a column of 3-5 colored data points connected by a vertical black line (a blue square for 2019, red circle for 2020, green triangle for 2021, yellow diamond for 2022 and aqua diamond for 2023). Each square-circle-triangle-diamond-Blackline combo represents the Soil Health Scores for one site for 3-5 years. 

These 4 graphs show that Home Gardens and Perennial Hay/Alfalfa/Pastures have the most variable soil health scores year-to-year.  Last year we showed that large amounts of organic matter inputs and more days of grazing animals increased variability.  This year we have shown that home gardeners apply the highest rates of organic matter to their sites, and we know that grazing animals are usually found in pastures.  It makes sense then that Home Gardens and Perennial Hay/Alfalfa/Pastures would experience the greatest variability in Soil Health Scores.

SWINGING SITES VS PARKED SITES:  This year, we decided to compare our sites with the most variable soil health scores (our Swingers) with our sites with the least variable scores (our Parked sites).  We calculated the Percent Relative Range ((maximum score minus minimum score) divided by average score) of scores for each site, and compared the 28 sites with the largest Percent Relative Range (our Swingers) with the 28 sites with the smallest Percent Relative Range (our Parked sites).  Several significant differences became apparent, as shown in this graph.

2/3rds of Swinging sites are pastures, and the majority of Swinging sites use conventional growing methods.  Swinging sites also apply an average of 7.5 T/acre of organic matter inputs, almost half again as much as Parked Sites at 5.6 T/ac.  Almost half of the Parked sites grow mixed vegetables and use reduced tillage.  The most significant difference between the 2 groups is that Swinging sites have 3 times the number of average grazing days as Parked sites. While Swinging and Parked sites have the same numbers of sites with grazing animals, Swinging sites have animals grazing on-site for a much longer period of time.  These findings support our 2022 findings that more grazing animals and organic matter inputs increase variability.

Many thanks for reading all the way to the end!  I hope you have found it interesting and informative.

2023 Findings

SOIL PH AND LOCATION: In previous years, we have found that as pH increases and becomes more alkaline, soil health decreases.  We wondered if geographical location could have anything to do with pH, and indeed it does.  We compared our sites’ soil pH with longitude (east-west location).  We found that sites further east out on the plains tend to have higher pH than sites closer to the Front Range foothills and up in the mountains.  This could be due to several things. 

Precipitation is higher in the mountains and foothills than further out on the plains.  Higher rainfall is associated with more acidic soils.  Also, a site’s original parent soil material is more acidic in the mountains and foothills than on the plains.  Furthermore, the pH of irrigation water can change soil pH with repeated applications.  Irrigation water becomes more alkaline as it travels further east, picking up tail-water, salts and minerals.  All this means that the location of a field might determine its soil pH as well as its soil health, since soil pH has a significant effect on soil health.

We wondered if certain kinds of sites might be located further east or west, thus influencing their soil pH.  We sorted our sites into 7 groups. Most groups include both organic and conventional fields.

• Dryland Grains : Dryland wheat and millet, no irrigation, using a crop-fallow system.
• Commodity Row Crops: Irrigated crops like corn, triticale, wheat, hemp, beans, sugar beets, barley, millet, silage.
• Commercial Vegetable/Flower/Fruit : Irrigated vegetables, flowers and fruit, sold commercially.
• Perennial Hay/Alfalfa/Pasture: Irrigated perennial pasture systems of grass, hay and alfalfa.
• Home Gardens: Vegetables, flowers and fruit trees for home consumption.
• Non-farm Grasslands : Dryland grasslands with no recent tillage or farming practices.
• Trees : Forests and tree farms. 

We then calculated each group’s average longitude, and calculated the average pH for each of the 7 groups, as shown in the next 2 graphs. No surprise, trees are located to the west in our forests, with dryland gains and commodity crops located to the east, where large sections of undeveloped agricultural lands remain. The order of the average pH of the 7 groups closely corresponds to their relative longitude.  These 2 graphs suggest that some crop groups face more of a disadvantage than others when it comes to soil health, since their location can determine their soil pH, which in turn can make improving their soil’s health more difficult.

SOIL HEALTH OF 3 DIFFERENT CROP GROUPS: In previous years, we learned that more supplemental irrigation water, more days of living cover, more organic matter inputs, more grazing days and more use of cover crops can all improve a site’s soil health.  We have also learned that lower tillage intensity and a lower soil pH improves a site’s soil health as well.  We decided to calculate the average use of each soil health practice for the 3 crop groups which most of our growers are in: 1) Hay/Pastures/Alfalfa, 2) Vegetables/Fruit/Flowers, and 3) Commodity Row Crops.  We wondered if each crop groups' average soil health practices could predict which crop groups would have the lowest and highest soil health scores.  See if you can predict which crop groups with have the best and worst soil health scores, just by looking at their relative rankings on soil health practices.  Remember that you are looking for HIGH water days, HIGH days of living cover, HIGH organic matter inputs and HIGH grazing days, but LOW tillage intensity and LOW soil pH to predict the highest soil health scores.

The following table has the average soil health scores of each of the 3 groups, for Soil Organic Matter, Soil Respiration, Organic Nitrogen, Organic Carbon, Soil Health Score, Total Microbial Biomass, and Number of Fungi, using the Haney and PLFA soil health tests. 

Perennial Hay/Alfalfa/Pastures : The Pasture group has the highest average soil health scores of these three crop groups. Although the Pasture group has lower supplemental water days and lower organic matter added, their very high days of living cover and very high grazing days, along with their very low tillage intensity and lower soil pH seem to more than make up for their water challenges, in terms of soil health.
Commodity Row Crops : The Commodity crop group has the lowest average scores of these three groups. Although they have done an excellent job of reducing their tillage intensity, that fact alone cannot make up for their high soil pH, lowest days of living cover and lowest organic matter added. They have only 2/3rds of the water availability as the Commercial Veg/Flower/Fruit group, which explains their lower days of cover crops that often require fall seeding and fall water. Inter-seeding cover crops aerially or when the main crop is still small are work-arounds but not always practical. Low commodity prices mean the cost of additional organic matter inputs like compost and manure are hard to justify.
Commercial Veg/Flower/Fruit: The Commercial Veg group has the highest tillage intensity by far, but also triple the organic matter inputs of the other 2 groups. These huge organic matter inputs, along with their longer water season, greater use of cover crops, and lower pH overpowers their intense tillage and boosts their average soil health scores above the commodity crops’ averages. Their longer water season means they can plant more fall cover crops and string together succession plantings for a longer growing season. Their high value vegetables mean that they can afford organic matter input costs and hauling fees.

VARIABILITY: We continue to be plagued with a great deal of variability in our lab results when we compare sites with themselves year-to-year. Last year we determined that grazing animals contribute to variability in lab results. This year we asked, “Does adding organic matter like compost, manure and mulches to a site also make lab results more variable year-to-year?” The answer: It seems to.
In the first graph below, 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. 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 first graph below.  We only have 12 sites in our study which have no grazing animals or imported organic matter for 3 or more years. The second graph shows that the variability in SOM values for these 12 sites is much less than for sites in the previous graph.

We then sorted our sites into 3 groups and calculated the average variability for each group.  The bar graph below 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.

Finally, we examined the 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.

GRANTS AND COLLABORATORS: We secured a generous partnership grant from St. Vrain and Lefthand Water Conservancy District, and a small grant from the Boulder County Sustainability Food and Agriculture Fund, which we have used to expand our educational outreach.  We receive an annual stipend from City of Boulder Open Space and Mountain Parks for our research with their lessees.   We have also received 4 very generous anonymous private donations.  We added 6 growers to our 47 growers and lost 3.  We now have 50 growers participating in the project and will not accept any more growers unless others drop out.