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Organized Oral Session

Career Track

Public-Private Sector

Session: : Natural Climate Solutions from Concepts to Practice – Bridging the Gap Between Science and Action

OOS 2-5 - Climate mitigation in agroecosystems across California's Central Coast Region

Monday, August 7, 2023
2:30 PM – 2:45 PM PDT
Location: 256
In 2016, the California legislature passed Senate Bill 859, which established the Healthy Soils Program (HSP). The program is funded from the State’s cap and trade proceeds, also known as California Climate Investments (CCI). The program includes two components, the HSP Incentives Program and the HSP Demonstration Projects. The HSP Incentives Program provides farmers and ranchers with financial assistance for implementation of conservation management that improve soil health, sequester carbon (C) and reduce greenhouse gas (GHG) emissions. The HSP Demonstration Projects are meant to assess and showcase the impact of implementation of HSP practices, including but not limited to reduced tillage intensity, compost application, and cover cropping. Here, we summarize findings from seven controlled field trials across various agroecosystems assessing the potential of HSP practices to improve soil health and mitigate climate change in California’s Central Coast region. Across all trials, we found no evidence of a tradeoff in terms of increased emissions of the potent GHG N2O with the adoption of conservation practices. The effect of compost application on soil health and C sequestration varied between trials and was impacted by application rate, compost source, and soil properties. Effects of tillage intensity were assessed in a vineyard and a dryland forage field. Reducing tillage intensity had limited effects on soil health and C sequestration in the short term, but fuel and labor savings of reducing tractor passes should be considered in the context of HSP practice adoption. Cover crops planted in two lemon orchards showed very few effects on soil health indicators assessed during the 3 year project period, likely due to the low biomass production of rainfed cover crops during drought years. Both lemon orchards had a history of mulching in the drive rows, which was reflected in higher soil C content in the drive rows compared to under the tree canopies. Likewise, soil C content was greater in drive rows compared to under the vine in vineyards that had a long history of cover cropping. This highlights the importance of longer-term assessments to quantify effects of HSP practices on soil health and C sequestration, and to evaluate potential returns on investment. In general, adoption of many conservation practices has been relatively low in California’s specialty cropping systems. We recommend that incentives programs go beyond C sequestration and consider the delivery of ecosystem services as a whole.