As a follow up to our 2016 Conservation Field Trial of rangeland compost application, the soil crew from University of California Silver Lab returned with Jeff Borum, CA Soil Health Specialist for Resource Conservation District, to collect samples 6 months after the initial compost application in our Lone Tree Hill pasture. The application of just a ¼ inch of compost is predicted to help restore the health of this field that was conventionally farmed until 2011 by jump starting forage production and the soil’s microbiology and keeping them well-fueled with the carbon the compost supplies to the microbes to maintain a regenerative cycle in the soil.
We selected this site due to the land use history and the carbon content being one of the lower values on the ranch at 2.1%. This pasture is located at the top of a hill exposing it to ocean breezes throughout the year. While the ocean view is wonderful, the pasture is somewhat stunted and in need of some sort of stimulation to boost forage production and improve water holding capacity through increased soil carbon and protective continuous cover.
Joining Jeff were lab technician Sam Grubinger and PhD candidate Allegra Mayer to assist in the soil sampling from 0-40cm to gauge the active carbon levels in the top layer of the soil. Gisele Herren, nematologist, took microbial samples and Aaron Marubbi, botanist, took a vegetation survey to determine the different plant types we have in this pasture.
In order to calculate biomass production, Gisele laid out a 94” hoop to clip the vegetation contained within.
With the rainy season essentially winding down, you can see the pasture is starting to dry out and when Jeff used his penetrometer to get a compaction reading, the ground was not very accepting.
It will be interesting to compare the infiltration and bulk density values from the original sampling.
Jeff also used a double ring infiltrometer and compared to other locations on the ranch, infiltration was fairly slow. Hopefully, good management can reverse this result to generate more porosity and soil structure.
Overall, when scanning the site, it’s hard to say if the pasture looks a lot different from the exclosure. There are minor differences in growth in some places, but other spots look similar to what we see in the exclosure. However, it should be noted that the treatment was a 1/4″ layer of compost, which would not be much from a fertilization perspective to expect a particularly noticeable difference in growth right away. The goal of the compost application is to act as a stimulative approach that gets microbial activity moving again in the soil. Over time, through healthier soil, we should see an increase in biomass boosting our forage production. It all starts in the soil and that is why it is so important to have good monitoring. We’ll let you know when we get the results back from the lab.