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Fertilizer Application Innovation at California Dairies

Two men leaning on either side of,  an arm on the thank of an SDI.

Dairies across the country use flush manure management systems and flood irrigation to fertilize their feed crops with liquid manure. However, these methods make it difficult for dairy producers to apply water and nutrients at the right rates for crop uptake, which can lead to nutrients leaching into groundwater or run-off into streams and rivers.

In 2017, Sustainable Conservation was awarded a national Conservation Innovation Grant (CIG)  to deliver liquid manure—an abundant fertilizer source found on dairies— in a more efficient and effective way. The project involved an innovative method of delivering manure nutrients through subsurface drip irrigation (SDI). With SDI, drip tape is buried underground close to the roots allowing diary producers to deliver water and fertilizer to a crop’s rootzone more precisely, which increases irrigation efficiency and conserves water.

By modifying a SDI system to apply liquid manure, the hypothesis was that this “manure SDI” system would save water, protect groundwater quality through precision nutrient application and reduce irrigation-related greenhouse gas emissions. If successful, manure SDI would provide dairies with a new tool to help improve water resiliency and water quality in their communities.

After years of research and experiments, the project results are in. Compared to flood-irrigated fields, the manure SDI fields showed increased crop yields, improved water and nutrient use efficiency and no additional salinity build-up. With these positive results, the manure SDI system was certified by California NRCS as an acceptable technology under the micro-irrigation conservation practice standard (CPS 441).
“We are always open to projects that add to our existing toolbox of practices and that add conservation opportunities for California farmers and the environment, said Carlos Suarez, NRCS State Conservationist in California. “We are grateful to the dairymen and partners who went out on a limb to test this new approach.”

Financial assistance for the system is available based on local priorities as decided by NRCS and its stakeholders. In 2020, dairy farmers in California could receive $2,872 per acre to install manure SDI through the Environmental Quality Incentives Program (EQIP) to help offset the costs of switching from flood irrigation to manure SDI. NRCS is exploring expanding the financial assistance to other states with large numbers of dairy producers.


Because of their successful CIG project, Sustainable Conservation received the 2020 U.S. Dairy Sustainability Award. “Sustainable Conservation crafts practical technology and solutions in lockstep with farmers and industry partners that lead to enduring environmental solutions,” said Karen Ross, Secretary of Agriculture in California. “This new drip system helps California dairies produce healthy milk while reducing their water and greenhouse gas impacts, and serves as a model for dairy producers across the U.S."

Many partners came together to work on the project including Netafim USA, Western United Dairies, UC Cooperative Extension and three California dairies. The three dairies represented a range of farm management practices, infrastructure, herd sizes and total acreages, helping the project partners evaluate how the manure SDI system could be integrated into different types of operations.

To learn more about the manure SDI system, please visit Sustainable Conservation's Technical Resources page.

For more information about the CIG program, visit the CIG website.