California Institute for Water Resources
California Institute for Water Resources
California Institute for Water Resources
University of California
California Institute for Water Resources

Online irrigation and nitrogen management tools for vegetables

Summary:

Cool season vegetable production requires significant inputs of water and nitrogen fertilizer to maximize yield and quality. Proposed changes in water quality regulations on the Central Coast of California, along with higher fertilizer prices in recent years, have prompted grower interest in increasing efficiency of nitrogen fertilizer use in lettuce and other cool season vegetables. By improving water management and matching nitrogen applications to the uptake pattern of the crop, growers could potentially reduce fertilizer use and address water quality concerns. The results of this project will increase the capacity of CropManage, an online resource that uses weather, soil, and crop data to assist growers in using water and nitrogen fertilizer efficiently for producing cool season vegetables.

Investigator:

Michael Cahn
Advisor
UC Agriculture and Natural Resources

Project description:

Cool season vegetable production requires significant inputs of water and nitrogen fertilizer to maximize yield and quality. Proposed changes in water quality regulations on California's Central Coast, coupled with higher fertilizer prices in recent years, have prompted grower interest in increasing efficiency of nitrogen fertilizer use in lettuce and other cool season vegetables. By improving water management and matching nitrogen applications to the uptake pattern of the crop, growers could potentially reduce fertilizer use and address water quality concerns.

Two tools available, the quick soil nitrate test and weather-based irrigation scheduling, have been shown to help lettuce producers better manage water and fertilizer nitrogen. Trials we conducted in commercial fields have demonstrated that soil nitrate concentrations greater than 20ppm NO3-N are sufficient to maximize crop production. In addition, we have shown that evapotranspiration data available from the California Irrigation Management and Information system (CIMIS) can be used to accurately estimate the appropriate volume of water to apply to meet crop needs and minimize potential leaching losses. 

Both the quick nitrate soil test and weather based irrigation scheduling require increase management time for growers to implement these practices in their farming operations. The quick nitrate soil test entails collecting a representative soil sample in the field, extracting the sample, and estimating the concentration of soil nitrate. Weather based irrigation scheduling requires calculating crop evapotranspiration from CIMIS reference data and a crop coefficient corresponding to the developmental stage of the crop. In addition, information on the soil type and irrigation system is needed to determine the optimal irrigation interval and run-time. With multiple fields and ranches to track throughout the season, customizing water and fertilizer for individual fields could become a significant cost for growers.

CropManage, an online database-driven tool, was developed by UC Cooperative Extension to assist growers and farm managers in determining water and nitrogen fertilizer applications on a field-by-field basis. The software automates steps required to calculate crop water needs from CIMIS ET data, and estimates fertilizer N needs for lettuce using quick N test data and models of crop N uptake. The web application also helps growers track irrigation schedules and nitrogen fertilizer applications on multiple fields and allows users from the same farming operations to view and share data. This project will increase the capabilities of CropManage. We will expand for additional vegetables including broccoli and cauliflower, and automating importation and display of soil moisture data.

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CIMIS station near Watsonville, CA
(Mike Cahn)

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Drip irrigated lettuce (Mike Cahn)

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Tensiometers that automatically record soil moisture for CropManage (Mike Cahn)

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