From California Agriculture
Since 2016, California’s Healthy Soils Program (HSP) has allocated more than $162 million from cap-and-trade proceeds through California Climate Investments to improve soil health and sequester carbon (C). Program funding has supported both grower adoption of practices such as compost application, reduced tillage, and cover cropping, and demonstration projects evaluating these practices in California cropping systems.
By minimizing soil organic carbon (SOC) loss associated with tillage and adding organic C from external inputs and plant biomass grown in situ, HSP practices increase soil C storage and help mitigate climate change (Kӧgel-Knabner et al. 2023). However, soil microorganisms also produce the potent greenhouse gas (GHG) nitrous oxide (N2O) (Butterbach-Bahl et al. 2013). For practices that affect nitrogen (N) cycling, such as fertilization, tillage, and irrigation, the balance between changes in SOC and N2O emissions needs to be considered (Verhoeven et al. 2017).
California agriculture faces increasing challenges from climate change, including more frequent and severe drought and rising input costs. In addition to mitigating climate change, HSP practices can improve soil structure, fertility, and microbial activity (Lazcano et al. 2020). Soil health, defined as the soil’s ability to provide these services, can help manage extreme weather, drought, fertilizer costs, and disease, all of which are expected to increase with climate change. Therefore, soil health management is a key strategy for both climate change mitigation and adaptation.
While many studies on HSP practices focus on cereal cropping systems in temperate climates (Karlen et al. 2019), California’s Mediterranean climate and diverse cropping systems require tailored solutions. To address this, we conducted seven field trials in California’s Central Coast region. Here, we highlight lessons learned from these efforts. Note, it is not our intent to provide a comprehensive review of HSP practices or their global impacts, but rather to share region-specific experiences, outcomes, and take-home messages from field trials conducted in California’s Central Coast.
