Agroecosystem resilience and multifuctionality
Soil-health management practices that maximize crop yields while improve yield resilience are need in the face of resource variability and climate change. Using yield, weather, and soil data of a 25-year cropping systems trial (Russell Ranch Sustainable Agricultural Facility at UC Davis), I found that ecological intensification approaches, such as organic management and cover cropping, could help maintain comparable yields as conventional systems and increased yield stability under extreme environmental conditions. Such management practices could also maximize soil multi-functionality by simultaneously improving soil structure, soil-water relations, and nutrient cycling.
Related papers: Li et al. (2019) Yields and resilience outcomes of organic, cover crop, and conventional practices in a Mediterranean climate. Scientific Reports
Harnessing plant-soil-microbe interactions for agroecosystem sustainability
Root exploitation of soil heterogeneity and microbially mediated rhizosphere processes play critical roles in plant resource uptake and stress resistance. Using the Russell Ranch long-term field trial, I discovered that organically managed systems harbored more diverse, stable rhizosphere communities and resulted in better crop performance relative to conventional systems under drought. However, water-saving irrigation strategies, such as subsurface drip irrigation (SDI), could lead to trade-offs by limiting root development and rhizosphere microbial activities, and reduce crop yields in organic systems. My study highlights the importance of assessing root-soil-microbe interactions to build up agricultural resilience and maximize resource-mining potential for organic management systems.
Related papers: Li et al. (2020) Impact of irrigation strategies on tomato root distribution and rhizosphere processes in an organic system. Frontiers in Plant Science
Integrated weed management and arbuscular mycorrhizal fungi
I have been involved in several projects to integrate arbuscular mycorrhizal fungi (AMF), an essential soil microbial group, in agricultural systems for crop production and ecosystem services. My Ph.D. research identified AMF taxa that improved crop competitiveness against weeds, and also assessed soil management strategies that enhanced this relationship. Some identified AMF taxa were highly beneficial to crops but negatively affect weed growth. I also demonstrated that tillage and cover cropping could promote the abundance of these AMF taxa by altering the AMF community. As a follow-up, I am currently working on projects using maize mutants to advance our understandings of AMF genetic architecture and mechanisms for maize production.
Related papers: Li et al. (2019) Interspecific variation in crop and weed responses to arbuscular mycorrhizal fungal community highlights opportunities for weed biocontrol. Applied Soil Ecology
Outreach: Deficit irrigation to optimize tomato quality and yield
Outreach has been an important part of my long-term career goal. I have been involved in developing guidelines for processing tomato growers to implement late-season water-saving deficit irrigation strategies in California. We used a simple field measurement, the normalized difference vegetation index (NDVI), to determine the onset of deficit irrigation. Using this method, I discovered that water cut-back to 75% of the crop evapotranspiration one week after the NDVI peak could successfully increase fruit total soluble solids without negatively affecting tomato yields. This result has been disseminated extensively through the Russell Ranch Field Day and growers meeting in the field.
Related stories: Russell Ranch Field Day, UC Davis