Notes from the Field: Waste Not Projects in Action

Sustainable Conservation’s Waste Not team has spent years developing and testing practical, science-based solutions that help farmers protect water quality, improve nutrient management, and build healthier soils. By collaborating with producers, researchers, agencies, and industry partners, we are advancing on-farm solutions that improve water quality and support the environmental and economic sustainability of California agriculture.

What started in 2014 as a pilot to recycle and filter surplus manure through subsurface drip irrigation is expanding across the San Joaquin Valley—now adopted by producers on 2.7% of dairy forage crops (4,432 acres) in California. Each year, MSDI saves over 2.3 billion gallons of water, 6.5 million pounds of CO2 equivalents, and 2.4 million pounds of nitrogen.

Powered by partnerships with dairy producers, scientists, policymakers, and the private sector, we’re building a circular model that transforms surplus manure into a solution for soil health, sustainable agriculture, and water security across the state.

Here’s a look at the science, the systems, and the people behind the work.

Corn harvest in MSDI sample field

Nitrous Oxide Study

Goal

Measure how much MSDI affects greenhouse gas emissions (N2O) compared to flood irrigation on dairy forage crops

Partners

A 2016 study showed the promise of MSDI to decrease nitrous oxide (N2O) emissions on forage crop fields. As the system expanded across dairies, we’re taking a closer look to quantify how it impacts greenhouse gas emissions and groundwater quality.

Over the past year, the team has conducted regular, intensive field measurements to track N2O gas emissions, soil nitrogen, and plant nitrogen from both flood and MSDI fields. We measure N2O directly from the field several times each week to capture how emissions change over time, especially during high emission events like right after irrigation, fertilizer applications, or tillage.

We also collect soil, water, and plant tissue samples to better understand how nitrogen moves through the system—whether it’s taken up by plants, remains in the soil, or escapes as gas. With all this data, we’re building a full nitrogen balance for the field and gaining a clearer picture of MSDI’s potential to reduce greenhouse gases and nitrate losses to groundwater.

Stay tuned as we analyze the results and share what we learn!

Preparing the chipper for the MSDI sample corn harvest (top), sampling soil in fall 2024 (left), processed corn sample (right), MSDI fertigated corn field (left), MSDI system (right)

Food Safety: MSDI and Almonds

Goal

Test whether manure subsurface drip irrigation (MSDI) can viably fertilize human-consumed crops, while reducing the need for imported synthetic fertilizers

Partners

Bonneville Environmental Fund, California Dairy Research Foundation (CDRF), Dellavalle Labs, DeJager Farms Inc., Google, Netafim, Natural Resources Conservation Service (NRCS), UC Davis

Sustainable Conservation collaborated with Netafim USA to develop the MSDI system and help farmers precisely irrigate and fertilize crops at the root zone to protect water quality, reduce methane emissions, and advance dairies’ environmental sustainability.

Until now, MSDI has only been used on feed crops for dairy cows. But there’s a missed opportunity. California imports 100s of thousands of tons of nitrogen fertilizers annually, while dairies here produce a growing surplus of manure, the original fertilizer. MSDI has successfully decreased nitrate contamination on dairies, but because fertilizing these crops with manure is already standard practice, there is still a surplus of on-farm nitrogen that could be repurposed as a fertilizer on neighbor farms. We’re testing whether MSDI can viably fertigate a human-consumed crop, almonds, to recycle surplus local manure and reduce reliance on synthetic fertilizers. In compliance with the USDA rule for manure amendments in organic agriculture, we apply manure at least 120 days before harvest.

Through a Conservation Innovation Grant through the Natural Resources Conservation Service, we’re testing MSDI on almonds. Each month, we sample orchard soil and blended manure water for pathogens. Then, we test the nuts themselves at harvest: meats, hulls, shells, along with the soil they fall on.

If these trials show promise, we hope to expand almond acreage and even to other crops, opening new ways to recycle manure safely while reducing synthetic fertilizer use. Stay tuned for results!

This work is supported by the USDA’s Natural Resources Conservation Service (NRCS) through its Conservation Innovation Grants (CIG) funding.

Goal

Test whether pairing whole orchard recycling (WOR) with surplus manure can improve soil health and reduce reliance on imported synthetic fertilizer

Partners

A client of AgIS, General Mills, Christine Gemperle (farmer)

We’re a farming outfit always looking to better our practices. Partnering with Sustainable Conservation is an exciting opportunity to test how old orchards and local manure can be recycled to rebuild healthier, more productive soil for the next crop. Homer Garza Jr., Ranch Foreman

When orchards reach the end of their productive life, farmers often grind up the trees and work the wood chips back into the soil before planting anew. This practice, called whole orchard recycling (WOR), boosts soil carbon. But soil microbes need nitrogen to break the woody material down, and without enough, they can tie up nitrogen that would otherwise be available to crops during the following season.

To mitigate the risk of low nitrogen availability for the next growing season, some farmers apply synthetic nitrogen fertilizers to help break down the high-carbon wood chips. Our team is testing whether surplus dairy manure can work just as well. Using manure would not only recycle a local surplus but also reduce the need for imported fertilizer, helping balance the soil’s carbon-to-nitrogen ratio. Manure provides co-benefits by adding organic matter and nutrients to improve soil’s function as a healthy, complex system.

When wood chips are applied, we measure the weight of a small portion applied to the field to estimate the total carbon added. Regular soil sampling is being conducted to understand the carbon-to-nitrogen balance in WOR fields.

Measuring a wood chip sample for weighing (top), barley field planted in last season’s WOR sample field with Homer Garza Jr. and Sustainable Conservation’s Sarah Castle and Emily Waring (left), soil core sampling with Dr. Sarah Castle (right)

Supporting Partners, Lending Expertise

Not all our field visits are for our own projects. Sometimes, we show up to listen, learn, or lend a hand.

This spring, the California Climate and Agriculture Network (CalCAN) invited us to join a field day with California Senator Jerry McNerny to see how the Alternative Manure Management Program funds work. We believe connecting policymakers to practices on the ground is one of the best ways to turn good science into better policy.

We’ve also continued supporting longtime partners like Trinkler Dairy. John Cardoza, our Waste Not Project Director, has been working with the Trinkler team to research and refine MSDI. Installed in 2022, their MSDI system now serves as a test site for Dairy Management Inc. (DMI), which leads industry-supported research into practices that protect water, conserve resources, and reduce greenhouse gases. DMI’s work is funded directly by the dairy community, with 10 cents from every 100 pounds of milk sold going toward research, education, and outreach.

This material is based upon work supported by the Natural Resources Conservation Service, U.S. Department of Agriculture, under agreement number NR243A750011G015. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the U.S. Department of Agriculture.