Participating in the Largest Field Scale Vermicompost Soil Health Study

Part of the field sampling team at a small organic farm in the Spring of 2025.

All the way back in late 2022 (feels like forever ago) Aggrego Data was asked to lead the microbiome collection and analysis on what will be the largest field scale vermicompost agricultural study to date. This project was proposed as a USDA Conservation and Innovation Grant (CIG) and being lead by Professor Cristina Lazcano and postdoc Dr. Halima Malal from UC Davis. They are partnering with local water treatment and vermicomposting (known as vermifiltration) company BioFiltro to understand the soil health and carbon sequestration of BioFiltro's finished vermicompost from their vermifilter treatment system. Two of BioFiltro's largest vermifilter systems produce about 23,000 cubic yards of vermicompost annually. BioFiltro is on track to hundreds of thousands of cubic yards of vermicompost from their rapid growing vermifilter operations which is making large scale agricultural application feasible.

BioFiltro's vermifilters in operation as of 2022.

Last year (2025) we completed the first baseline year of sampling and vermicompost was applied in the fall. I don't have any data to share yet - I mainly just want to introduce the project, give a sense of what's involved in a project like this, and share some pictures.

Background Info

This project is titled "Vermicompost Application to Improve Soil Health and Mitigate Climate Change." Vermicompost application ties soil and health and climate change together primarily through carbon sequestration in the soil. Vermicomposting has proven to be a viable method to treat organic waste which accounts for 46% of global solid waste making it potentially a scalable option to address current agriculture deficiencies.

Overview of how vermicompost adds to soil health and mitigates climate change.

Soil Health

Vermicompost is known to have many soil health benefits due to its rich organic matter and microbial communities. Increased organic matter in soils increases cation to change capacity (CEC) which helps retain positively charged nutrients like ammonia, potassium, calcium, and iron (basically everything but phosphate). Organic matter in the soil helps maintain soil structure through aggregation and increased water infiltration. For every 1% increase in soil organic carbon, soil water holding capacity increased by ~1-3% providing drought resilience. The increase in soil carbon also stimulates microbial growth leading to increased nutrient solubilization and reduction of soil borne diseases. Vermicompost itself has also been shown to contain a high amount of plant available nutrients and plant growth hormones from the high microbial activity during the composting process.

Climate Change

The rate of greenhouse gas (GHG) emissions from the agricultural sector is expected to

grow. Vermicompost is composed primarily of recalcitrant humified organic matter, making it more likely to sequester carbon in the soil for a longer period of time. Vermicomposting and vermifiltration is a viable alternative to treat liquid and solid manure produced by the livestock sector, one of the largest agricultural sources of environmental air and water pollution in the US. Additionally, vermicompost has shown to retain 75% of nitrogen from organic waste and, compared to traditional thermophilic composting releases 40% less methane (CH4) and 30% less nitrous oxide (N20).

Study design

This project includes 12 farms across Central California and Washington. Most of these farms are perennial crops like vineyards and orchards, but we have a couple of annual crop farmers as well. This study is taking place over 5 years with the first year being a baseline sampling. Vermicompost is being added in the fall of each year at a rate to replace 35% of the nitrogen requirements for each crop. An estimated 5,600 cubic yards will be applied in total over 4 years. In most cases vermicompost will be applied as a top dressing with a manure spreader.

Field sample collection in Spring 2025: Starting top left moving left to right, top to bottom: a) Multiple teams collecting samples and taking measurements; b) (left to right)Field specialist Charlie, Postdoc Halima, BioFiltro's Sabina, and Prof. Lazcano; c) soil moisture meter; d) field base camp; e) composite soil core sample; f) sample collection - each person has a job for each sampling point; g) microbiome collection kit; h) penetrometer for measuring compaction; i) Zack taking a microbiome sample.

Experimental Design

Each farm site is divided into an experimental plot (vermicompost application) and control plot (current practice, mostly conventional fertilization) that are in most cases multiple acres in size. Each of these control and experimental plots is sub-divided into 3 blocks for replication. Composite samples were taken from each block for nutrients from 5 different cores at 3 different depths: 0-15cm, 15-30cm, and 30-45cm. Each depth of the 5 cores was combined in a separate bucket and homogenized before samples were taken for nutrient and microbiome analysis. As you can see, pretty extreme measures were taken to reduce soil variability on each farm.

Data Collection

Soil Data

A host of soil physical, chemical, and biological characteristics are being collected on each study block. The physical soil properties we are monitoring include water infiltration, soil moisture, and compaction. The microbiome samples will be analyzed for bacteria and fungal diversity and abundance as well as community shifts over time including the quantification of beneficial organisms. The chemical properties are of course going to include plant nutrients but the major focus is going to be on carbon sequestration in the soils. In total about 220 samples were collected and tested and nutrient and microbiome analysis for the first baseline.

Farm Data

Each farmer participating in the study will be collecting crop yield data for each of the two plots on their farm. During the season, field workers will also have a log to write down any treatments other than vermicompost application and monitor any disturbance events. Farmers will also be interviewed to understand any barriers to vermicompost application and understand how the practice can be suited for their farm. An economic analysis is also being performed based on the yield data, vermicompost cost, labor in application, and reduction of other fertility inputs.

Project Goals

In conclusion, this project's goals are multifaceted including understanding improvements to soil health, water storage, nutrient fertility, and microbiome shifts from broadscale vermicompost application. The impacts on climate change through carbon sequestration and reduction of greenhouse gas emissions from soils is the other big "science" topic.

However, what I think is the most important is understanding the perspective of the farmer. None of the science matters much if the process isn't broadly adopted. Sure the scientific evidence might help convincing with adoption, but guidelines are needed for application and understanding barriers to implementation are critical. Many of these farmers are comparing organic vermicompost application to conventional fertilization and need both a practical and economically viable pathway forward. By interacting and listening with farmers over the 5 years study should yield valuable information and trust in the practice.

On a more personal note I am grateful to have Aggrego Data be selected to consult on the project. Participating and learning from Professor Lazcano's group of soil experts has been a wonderful experience I am grateful for. Hopefully I can share some of the data moving forward before peer reviewed publication...so stay tuned.