Research Objectives

The overarching objectives of my research are to: 

  1. Understand the impact of soil health management on short-term carbon/nitrogen cycling and microbial physiology (i.e. carbon use efficiency, microbial growth rate), as well as the stabilization and stratification of soil organic matter; 
  2. Develop regional monitoring networks and engage in transdisciplinary collaborations to investigate long-term impacts of soil health management on productivity, profitability, and the provision of ecosystem services (i.e. carbon/water storage, pest/pathogen suppression, nutrient density); using data to calibrate novel tools/sensors and inform process-based models; 
  3. Facilitate the co-creation of regionally and contextually relevant soil health recommendations, assessments, and thresholds for interpreting them across the diversity of California soils, climates, and cropping systems; 
  4. Elucidate economic impacts of soil health management, as well as drivers and barriers to adoption (i.e. sociocultural, policy, market)

Specifically, I am interested in the influence of minimum disturbance, residue management and whole orchard recycling on nutrient immobilization; the influence of cover crop species, planting date and termination date/strategy on carbon and water dynamics; the impact of deficit irrigation on soil salinity and crop quality; and the impact of rates, frequencies, and forms of biological amendments on nutrient density and pest/pathogen suppression. Broadly, I am interested in the role of agroforestry and perennials in California’s future; how multi-functionality breeds resilience; and how novel equipment (i.e. robotics, drones, aerial harvesters) can support monitoring, management and harvesting in diverse systems.

Current Projects

The Almond Project

Treehouse Nuts, Pacific Agriculture, Simple Mills, Daily Harvest, Capello's, Cal Ag Solutions

Quantifying long-term impact of cover crops, compost + sheep grazing on soil health and ecosystem services using side-by-side comparisons in both organic and conventional systems (stratified random sampling). Analyses include soil carbon (C), texture, pH, EC, aggregate stability, water extractable C & nitrogen, mineralizable C, nitrate/ammonium, complete nutrient analysis, water holding capacity, water use, pest damage, yield, leaf tissue analysis, and almond nutrient density.

Soil Health in Almonds

Ben & Jerry's, Gonzales-Siemens Family Farm, White Buffalo Land Trust, Cal Ag Solutions

Investigating the long-term impact of stacking soil health practices (compost, cover crop, grazing, conservation tillage, and biological inocculum) on soil carbon (0-100 cm), pH, texture, nitrate/ammonium, complete nutrient analysis, POXc, mineralizable C, ACE protein, aggregate stability, water holding capacity, pest damage, invertebrate abundance/diversity, beehive health, yield, and GHG impact (life cycle assessment); randomized block design.

Hedgerows & Soil Health

UC Davis, UC Ag and Natural Resources

Quantified long-term impact of hedgerows on soil health (0-20 cm) and soil carbon (0-100 cm) at 21 sites (>600 samples), representing a range of soil texture (16 to 51% clay). Used multivariate statistics (PCA) to identify factors contributing to accrual of soil C and relationship between biological and physicochemical properties; evaluated soil health metrics most sensitive to management; estimated climate change mitigation potential of planting hedgerows on farm borders statewide (at 50 and 80% adoption).

Farmland Transition Program

General Mills

Developed monitoring program for 23 farms and ranches in California; 10 farms in Minnesota. Over 1000 samples analyzed for soil carbon and bulk density; ~500 data points on pH, EC, active carbon (POXc), ACE protein, respiration, microbial biomass/diversity (PLFA), complete nutrient analysis, and texture; ~300 for aggregate stability; and ~400 in-field assessments of infiltration rate and surface/subsurface hardness

Soil Health Risk Model

Land Core USA, University of California - Berkeley, Michigan State University, Compeer Financial

Building an actuarially-sound, predictive model to evaluate the risk mitigating benefits of soil health, as a tool to inform lenders and insurers. Specifically, using hierarchical modeling, causal inference, and Bayesian statistics to assess how adoption of crop rotations and reduction of tillage affects yield responses in extreme weather conditions and across edaphoclimatic contexts.

White Buffalo Science Plan

White Buffalo Land Trust

Developed and implemented monitoring plan at Summerland avocado orchard using three toposequences to assess impacts of soil health management systems on soil C, bulk density, texture, pH, EC, total nutrients, aggregate stability, PLFA, and in-field indicators: infiltration and (sub)surface hardness. Additionally conducting soil C monitoring for 2 CDFA Healthy Soils Projects.


Mitchell, J.P., Cappellazi, S.B., Schmidt, R., Chiartas, J.L., Shrestha, A., Reicosky, D., Ferris, H., Zhang, X., Ghezzehei, T., Araya, S. Kelly, C., Fonte, S., Light, S., Liles, G., Roy, R., Bottens, M., Horwath, W.R., Koch, G.M., Scow, K.M. 2022. Improved soil health with the long-term use of no-tillage, surface residue retention, and cover crops in the San Joaquin Valley. California Agriculture (in review)

Chiartas, J.L., Tiffany, S.E., Jackson, L.E. 2022. Understanding the Science of Climate-smart Agriculture in California. UCANR Publications (in review)

Stanley, P., Spertus, J., Chiartas, J., Stark, P. B., & Bowles, T. 2023. Valid Inferences About Soil Carbon in Heterogeneous Landscapes. Geoderma 430, 116323.

Chiartas, J. L., Jackson, L.E., Long, R.F., Margenot, A.J., O’Geen. 2022. Hedgerows on crop field edges increase soil carbon to a depth of 1mSustainability 14(19), 12901.

Chiartas, J. 2021. Long-Term Impact of Management on Deep Soil Carbon and Soil Health in Mediterranean Agroecosystem. Dissertation.

Climate Change Task Force. 2021. Advancing Resilient Agriculture: Recommendations to Address Climate Change. Crop and Soils.

Tautges, N. E.*, Chiartas, J. L*., Gaudin, A. C., O’Geen, A. T., Herrera, I., & Scow, K. M. 2019. Deep soil inventories reveal that impacts of cover crops and compost on soil carbon sequestration differ in surface and subsurface soilsGlobal Change Biology25(11), 3753-3766.
*Share joint first authorship