Soil Health Key Findings

 

  • Winter cover crops increased soil organic matter content in the top foot of soil without decreasing tomato yields over 24 years of analysis

  • Annual inputs of poultry manure compost along with winter cover cropping significantly increased mycorrhizal fungi and microbial biomass, compared to conventional management with synthetic fertilizers and no winter cover crops

  • Organic management with compost inputs increased the large macro-aggregate fraction (a type of soil particle association that is beneficial for healthy soil structure) of soils compared to conventional management

We are exploring how different farming techniques impact soil health, and how soil health in turn affects crop productivity and the environmental impact of farming

Soil Health in Context

  • Soil that is healthy can sustain its ecosystem of plants, animals, and microbes over long time frames
  • Healthy soil provides benefits on the farm, like better water-holding capacity and nutrient cycling, reduced nutrient runoff and soil erosion, and improved crop yields
  • Farmers and researchers are exploring how different farm management systems can be used to improve soil health and help ensure the sustainability of California agriculture

How we look at soil health

For over 20 years we have been exploring how different management practices affect soil health. Practices we are investigating include:

  • Winter cover crops: Legume cover crops take nitrogen from the atmosphere and add it to the soil. Cover crops planted in the wintertime when fields may otherwise lay fallow can also help reduce runoff and the associated losses of sediment, nutrients, and pesticides.

  • Applying compost or other organic wastes: Using wastes such as manure, compost, and biochar as alternatives to fossil-fuel-based mineral fertilizers may improve soil health by enhancing the soil’s water-holding capacity.

Side by side of plants and soil

Key research questions we are exploring at the Ranch include:

  • How do soil amendments—like cover crops, biochar, manure, and biodigestate—affect soil chemistry, soil biology, and crop productivity?
  • How do organic, conventional, and mixed crop management systems affect soil health?
  • How does the long-term use of a soil management practice (over 20+ years) affect soil microbial diversity?
  • How does soil microbial diversity, in turn, affect greenhouse gas production and soil structure?
  • How does the long-term use of a soil management practice (over 20+ years) affect the amount of atmospheric carbon sequestered in the soil?

 

Featured Research Projects

  • California Tomato Farm Soil Health Survey
  • Goal: A survey on 34 fields (11 farms) was conducted throughout the Sacramento and San Joaquin Valleys. The goal of this survey was to identify and characterize soil chemical, physical, and biological parameters on northern and central CA tomato farms, and assess how these parameters impact tomato crop management, health, and yields. Different irrigation and fertility management strategies in processing tomato systems were also evaluated using a Land Use System (LUS) economic model to quantify and evaluate tradeoffs associate with those strategies. 

    Objectives:
    - Identify relationships between soil health properties, irrigation history, agricultural management practices and inputs, and tomato yields/quality.
    - Identify relationships between particular management practices (e.g., SSDI management, compost inputs, cover cropping, crop rotation, etc.) and how these impact soil health indicators and soil fertility, ultimately impacting productivity.
    - Evaluate impacts of irrigation management and potential strategies to improve soil health (e.g. cover crops, compost) on farm economics by quantifying tradeoffs related to water use, labor inputs, and crop performance.

    Read more about the project in the full report.
  • Management systems and soil quality
  • Manure and winter cover crops are used by organic farmers as sources of nitrogen and other nutrients. Research at Russell Ranch is exploring how combining these fertilizers with conventional farming methods impacts crop yields, soil chemistry, and soil health.

    Explore organic, conventional, and mixed system impacts on inputs and soil chemistry in the interactive graphic.
  • Soil health assessment
  • This section is still under development. See some Russell Ranch research results below, and stay tuned for updates.
    The use of cover crops increases active carbon, soil organic matter, soil respiration, and aggregate stability, which are all indicators of soil health. Figure adapted from NRCS Soil Health Assessment at Russell Ranch.

    The use of cover crops increases active carbon, soil organic matter, soil respiration, and aggregate stability, which are all indicators of soil health. Figure adapted from NRCS Soil Health Assessment at Russell Ranch.
    Aggregate size fractions in organic furrow- and drip-irrigated systems with poultry manure compost inputs, compared to a conventional drip-irrigated system with synthetic inputs.

    Aggregate size fractions in organic furrow- and drip-irrigated systems with poultry manure compost inputs, compared to a conventional drip-irrigated system with synthetic inputs.