Note: This is part of a Research Update series that highlights projects funded by the California Department of Food and Agriculture’s (CDFA) Fertilizer Research and Education Program (FREP) annual grant program.
Project Title: Achieving Efficient Nitrogen Fertilizer Management in California Wheat
Project Leader: Mark Lundy, Assistant Cooperative Extension Specialist, University of California, Davis
Project Status: Completed 2023
Project Locations: The project team conducted on-farm demonstrations in the Sacramento Valley, the San Joaquin Valley, the Delta region, and the Intermountain region of Northern California.
Caption: Photos from a project field day demonstrating the benefits of using nitrogen rich reference zones and plant and soil measurements to guide nitrogen management decisions.
Overview
Wheat and other small grains are grown in diverse agricultural environments throughout California. Approximately 90% of the wheat, triticale, and barley in California is fall-sown and relies to some degree on precipitation that varies dramatically across the state. These conditions make efficient nitrogen (N) fertilizer management difficult because the right rate varies from field-to-field and year-to-year. Therefore, the goal of this project was to demonstrate and enable new ways of achieving best N management practices in California wheat and related winter cereals.
Key Takeaways
This project demonstrated that California wheat growers can effectively increase crop productivity and save N fertilizer by using:
- N-Rich Reference Zones
- Plant and Soil Measurements
- UC Nitrogen Fertilizer Management Tool for California Wheat
N-Rich Reference Zones
The N-rich reference zone is a relatively small area within a field where extra N fertilizer is added at the beginning of the season. This extra fertilizer ensures that the reference zone is not N limited between planting and the time when an in-season fertilizer decision is made. When a grower is determining whether and how much N fertilizer to add in-season, plant measurements from both the reference zone and the broader field are compared and combined with soil nitrate measurements to understand whether the broader field is sufficient in available N.
For more information about establishing a N rich reference zones visit: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=42576
Plant and Soil Measurements: Canopy and Leaf Reflectance
Reflectance measurements help determine plant vigor by measuring light reflected from the whole plant canopy or absorbed by a single leaf. Comparing measurements made in and immediately outside of N-rich zones in representative areas of the field helps determine if the crop is likely to respond to more N fertilizer.
For more information about taking reflectance measurements visit: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=42903
Plant and Soil Measurements: Soil Nitrate Quick Test
The soil nitrate quick test is a simple and low-cost DIY test. It provides a ballpark estimate of the soil nitrate-N concentration in the crop rootzone. Nitrate is a highly plant-available form of nitrogen. Using the soil nitrate quick test when N fertilizer decisions are being made will help narrow the range of fertilizer rates appropriate for a field.
For more information on how to conduct a soil nitrate quick test visit: http://smallgrains.ucanr.edu/Nutrient_Management/snqt/
UC Nitrogen Fertilizer Management Tool for California Wheat
The University of California (UC) Nitrogen Fertilizer Management Tool for California Wheat estimates grain yield and protein responses to in-season applications of N fertilizer. The tool combines site-specific weather and soil data with user-supplied, field-specific measurements and management information to produce real-time estimates of crop responses to added N fertilizer.
The online tool provides crop monitoring information to produce a targeted in-season N fertilizer recommendation. Recommendations produced for commercial fields throughout the project resulted in an average yield increase of 28% when N deficiency was detected. In addition, when monitoring confirmed that crops were sufficient in N supply, growers saved an average of 50 lb./ac N compared to their typical N fertilizer rates. Overall, crops in the demonstration activities removed more N from the soil than was applied as fertilizer, indicating efficient N fertilizer management.
To view the UC Nitrogen Fertilizer Management Tool for California Wheat (Beta) visit:
https://smallgrain-n-management.plantsciences.ucdavis.edu/?page=landing_page
Project Impact
The N fertilizer management practices demonstrated over the course of this project can help California wheat farmers manage their N fertilizer more efficiently. Eight California small grain producers were directly engaged with this project covering over 1,800 acres. Further adoption will improve economic outcomes and reduce N pollution in the state. Case studies detailing site specific management practices and outcomes by region can be found on the project website along with links to other project resources: https://smallgrains.ucdavis.edu/Nutrient_Management/N-rich_reference_zones To learn more about this project and other current and completed FREP projects please visit: https://www.cdfa.ca.gov/is/ffldrs/frep/Research.html