CAFF’s Biointensive No-Till Project is an on-farm demonstration project partnering with small, diversified vegetable farms in Northern California who are committed to minimizing tillage and interested in learning about how it affects soil health. In our last project update linked here, we shared the underlying principles that guide no-till farming systems and discussed some of the results of our soil testing such as total carbon concentrations. Since then, we’ve partnered with additional no-till farms, learned about other soil health metrics like active carbon quantities and microbial populations, and distilled farmer insights along the way.
WHAT WE'VE BEEN UP TO
While CAFF’s preliminary on-farm research trials have wrapped up, we’ve continued to visit no-till farms in Northern California in partnership with UC Berkeley’s Agroecology Lab. Together, last spring we visited both rural and urban farms like Kern Family Farm in the Sierra Foothills, and Red H Farm and Singing Frogs Farm in the North Bay. Guided by the hypotheses and general interests of these farmers, we helped UC Berkeley researchers sample and process soils to look at how farming practices of minimizing tillage, applying compost and intercropping affect soil health at different partner farms.
Digging into the Data
Recall that in our latest blog post, we reported on the soil health metric of total carbon: a measurement of all the carbon in the soil including its organic and inorganic forms. We report on total soil carbon because of its ability to positively affect a myriad of soil properties and functions as well as for its potential to be sequestered.
In addition to quantifying total carbon concentrations, the project looked at just a fraction of organic carbon in the soil known as active or labile carbon. Active carbon, scientifically referred to as permanganate-oxidizable carbon (POX-C), is a fraction of organic carbon that has a much faster turnover rate compared to the long-term storage carbon or even organic carbon. POX-C is more readily available for microbial decomposition and more sensitive to management practices. As a result, it is often viewed as a good indicator of soil health. Similar to the results for total carbon, active carbon concentrations were higher in no-till plots at each of CAFF’s partner farms for each depth measured. These results show that the soils within the no-till farming systems had more active carbon that was readily available for microbial use.
In addition to assessing the chemical composition of healthy soils, the project also quantified the biological composition by looking at the soil health indicator of total microbial biomass. Total microbial biomass quantifies the mass of living bacteria and fungi in the soil. Microbial biomass is considered a soil health indicator given the beneficial role microbes play in the soil. They decompose plant and animal residue, and cycle nutrients into forms available for plant uptake. The project found higher quantities of microbial biomass in the no-till plots than the control plots. These results align well with the POX-C data, suggesting an active and abundant microbial community in the no-till farming system.
What our partner farmers have to say
While soil sampling and laboratory analyses can tell us a lot about what goes on in the soil, the observations and insights of farmers and land stewards bring depth and context to conversations around soil health. After all, farmers often spend sun-up to sun-down farming the same plot of land for months, years and even decades. During CAFF’s partnership with Hillview Farms (2017-2022), farmer Michael Whamond shared his experience observing changes in the soil over time.