Optimizing crop rotations for soil health and plant disease management in California processing tomatoes

Project Overview

Project Type: Graduate Student
Funds awarded in 2023: $29,999.00
Projected End Date: 10/01/2024
Grant Recipient: UC Davis
Region: Western
State: California
Graduate Student:
Principal Investigator:


  • Agronomic: mustard, other, wheat
  • Vegetables: broccoli, carrots, garlic, greens (leafy), greens (lettuces), onions, other, tomatoes


  • Crop Production: cover crops, crop rotation, cropping systems, fallow, multiple cropping, nutrient cycling, nutrient management
  • Education and Training: decision support system, demonstration, display, extension, on-farm/ranch research, workshop
  • Pest Management: biofumigation, field monitoring/scouting, weed ecology
  • Production Systems: agroecosystems
  • Soil Management: green manures, organic matter, soil analysis, soil chemistry, soil physics, soil quality/health

    Proposal abstract:

    Problem and question: Valued at $1.2 billion and ranking the second most valuable vegetable crop, processing tomatoes are a vital component of California's agricultural industry (CDFA, 2020).  A new Fusarium disease (F. falciforme) is driving severe yield loss and the only management practices are chemical-based and harmful for the environment (PMSP- Processing Tomato, 2021). This pathogen appears to affect other warm season rotation crops—however, effects on cool season crops are unknown.  In addition, several weeds appear to be hosts but, weed studies have not included winter species, which are the primary weed management targets due to winter rains.

    Research and outreach: The goal of this project is to assess California cool season cash/cover crops and weeds to determine the host status to F. falciforme, and the effect on disease development in processing tomato and soil health and nutrition. This information will be used to develop avoidance and crop rotation guidelines in an effort to improve overall sustainability of the processing tomato industry.

    Dissemination: We propose to disseminate our findings to growers across the state through outreach meetings and newsletter articles. Our lab will host a Vegetable Disease Field Day in 2024 with our research trial as a demonstration plot for effects of cool season crop rotations on tomato disease development.

     Projected outcomes: (1) Avoidance recommendations for 10 cash/cover crops, (2) cool season crop rotation recommendations for one key annual rotation crop-tomato, (3) weed management guidelines for host weeds, (4) outreach publications (two) and presentations (three) summarizing above, to facilitate adoption.

    Project objectives from proposal:

    Research Objectives: 

    1. Developing avoidance, rotation crop and weed management strategies which minimize losses from soil borne Fusarium falciforme in annual crops, particularly the highly susceptible keystone annual, processing tomatoes.
      1. Assess disease development of Fusarium falciforme in common California winter cash crops to determine highly susceptible crops to avoid planting in infested fields
      2. Evaluate common California winter cash and cover crops for their ability to reduce disease incidence in tomato when compared to chemical fallow.
      3. Assess cool season weed hosts, to determine weed management targets.
    2. Assessing the effect of common California rotation and cover crops on soil physiochemistry, carbon cycling, and associated decomposition of pathogen-infested litter.
      1. Characterize soil nutrition, structure and compaction, and organic matter under different winter cash and cover crops.
      2. Measure the decomposition rates of different pathogen-infested crop residues in order to compare the level of organic matter addition, rates of carbon cycling, as well as effects on persistence of infested tissue residing in the soil.
    3. Work with producers to quantify the benefits of rotation and cover crops for crop health and disease control in annual crops, with an emphasis on tomatoes. 
      1. Work with growers who are currently utilizing a rotation plan to assess the effects on soil health and disease losses

    Education Objectives :

    1. Provide crop recommendations in publications distributed via  Cooperative Extension blogs, updates to the UC IPM F. falciforme pest note (in prep), tomato crop rotation recommendation webpage, newsletters, a hard copy trifold pamphlet, and a more detailed hard copy spiral bound booklet.
    2. Present a summary of outcomes and recommendations at the winter cooperative extension outreach meeting.
    3. Present at the Vegetable Crop Disease field day so that stakeholders can see the research in progress, using our research trial as a demonstration plot.
    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.