Progress 07/01/20 to 06/30/22
Outputs
Target Audience:The target audiences that have been focus of my effort for the duration of this project are: Farmers, master gardeners and agricultural stakeholders in Solano, Yolo, Salinas and Amador counties interested in soil carbon, sustainable agriculture and soil microbial communities. I did this via presentations as part of the Solano RCD Farmer Workshops in Winter 2021 and Spring 2022, the Amador County Master Gardener program, and the June 2021 Healthy Soils Program workshop at Russell Ranch. I also participated in consultations on how to measure healthy soils with agricultural extension agents and researchers in the Salinas valley. Agricultural stakeholders in California and the wider USA interested in soil metagenomics and belowground biodiversity. I did this by speaking at the California Farm Demonstration Network's "Nitty Gritty on California Soils" speaker series, and as a participant in the Belowground Biodiversity Action Committee, a joint effort between the California Department of Food and Agriculture, and the California 30x30 initiative. Mayan farmers, Belizean NGOs and Belizean researchers in the Maya Wildlife Corridor and the Golden Stream regions of Central and Southern Belize, and the Environmental Research Institute hosted at the University of Belize. I did this by organizing a 1-week training program for Mayan extension officers on soil sampling and soil biology, culminating in a 1-day workshop on the soils of Belize. I also assisted researchers from the University of Belize in conducting farmer surveys and farm visits in the Maya Wildlife Corridor and have continued to work with researchers at the University of Belize on developing a digital Belizean soil map. Undergraduate students in Soil Microbiology and Hydrology, undergraduate students of color, and graduate students in the UC Davis Soil and Biogeochemistry graduate group. I did this by organizing a remote Soil Microbiology lab in Winter 2021, mentoring an undergraduate in their thesis project on alpine meadow soils of the Sierra Nevada, participating in the MANRRs (Minorities in Agriculture and Natural Resources Research) program as a student mentor, organizing a graduate seminar on diversity in academia and teaching in Fall 2020, and helping to organize the Spring 2022 graduate student orientation on equity and diversity at UC Davis. Members of the scientific community working in soil science and soil microbiology. I did this by presenting my research results via posters at the SSSA/CSA/ASA 2020 conference and the AGU 2020 and 2021 conferences, and a research presentation at the SSSA/CSA/ASA 2021 conference. I also presented my research results as part of the Washington State University SoilCon virtual conference in Dec 2020. Members of the NGO, policy and agribusiness communities interested in soil science outreach and policy. I did this through consultations on the analysis and sampling of soil microbiology with researchers and policymakers at the Environmental Defense Fund, Nature Conservancy, General Mills, Natural Resources Defense Council and Soil Health Institute during the 2021-2022 year. Members of the general public. I did this through outreach via Youtube, Twitter and my personal website. During the project period this outreach has generated over 200 likes, retweets and views both on videos uploaded to Youtube and soil science related tweets. Changes/Problems:Due to the unprecedented global disruption caused by the global COVID-19 pandemic, and the prominence of the national conversation about race and racism in American society in 2020, there were some changes to the action plan for this fellowship. 1) To better fit with the needs of the graduate students in the department, the planned seminar on carbon storage was changed to a seminar on Justice, Equity, Diversity and Inclusion that focused on career development by helping students compose their own diversity statements. 2) Additionally, the PI's plan to help teach the Soil Microbiology laboratory section was disrupted by the switch to online instruction. The PI accommodated this by performing the up-front work of planning and organizing the remote lab, and helping put together portable lab kits that were delivered to students on several different continents. 3) The disruption to lab and fieldwork meant that the PI was unable to access his primary research site, Russell Ranch, for nearly a year to obtain new soil samples for metagenomic sequencing. In order to stay on schedule for graduation, the PI obtained sequence data for frozen samples from the same plots taken in 2012 and has used that to address goal #2. 4) Due to contracting COVID-19 at the end of 2021, the PI was unable to attend the AGU 2021 conference. 5) Due to an emergency medical procedure in May/June 2022, the PI was unable to submit the final two manuscripts prepared as part of this fellowship for publication before the fellowship period ended. The manuscripts are planned for submission before the end of the 2022 year. What opportunities for training and professional development has the project provided?Professional Development Activities In response to the events of May 25th, 2020, and the ongoing national discussion around race and racism in American society, the PI co-organized a seminar for graduate students in the Land, Air and Water Resources Department at UC Davis around the themes of Justice, Equity, Diversity and Inclusion in the geosciences. The PI worked with a fellow graduate student and faculty mentors to provide a space for discussions led by graduate students, early career faculty, and representatives from the UC Davis Office of Diversity, Equity and Inclusion. At the end of the seminar, attendees had the chance to submit diversity statements that were reviewed by faculty for comment. Based on weekly feedback polls, 66% of attendees rated the seminar 5/5, with the other 33% rating it 4/5. Attendees stated that the seminar "greatly enhanced their understanding of justice, equity, diversity and inclusion in the geosciences", and "provided a much-needed forum for conversations around race in our department". Additionally, the PI served as a graduate student mentor in the MANRRS (Minorities in Agriculture, Natural Resources and Related Sciences) program for the second year, advising an undergraduate student on research, pursuing careers in academia, and sharing their experiences in navigating college as a minority student. The PI also coordinated student feedback for the 2020 faculty interviews for the position of "Assistant Professor of Soil Biophysics". The PI organized student attendance at virtual interview sessions, collected student feedback and submitted student rankings to the search committee. This opportunity provided an inside look at the faculty search process and gave valuable insight into what a search committee is looking for in a successful academic candidate. As part of their commitment to teaching during this fellowship, the PI also planned and organized a remote lab session for Soil Microbiology during the pandemic. The PI worked with a lab manager to plan experiments that demonstrated concepts in soil microbiology such as the electron tower and decomposition, and could be conducted using household materials and a small, low-cost lab kit that was mailed to students. As part of this fellowship, the PI reached out to and consulted with several soil scientists in the public and private arenas to get a better idea of gaps in research and communication when translating scientific advances in soil science into actionable policies. After consultation with scientists from the Environmental Defense Fund, Nature Conservancy, General Mills, Natural Resources Defense Council and Soil Health Institute during the 2021-2022 year, the PI was able to successfully secure a position as an Agricultural Soil Carbon Scientist with the NRDC immediately after graduation. Training Activities The PI organized a 3-day training session and workshop on soil carbon, microbes and soil sampling for extension officers working for the Ya'axche Conservation Group in southern Belize; as well as presenting at 3 conferences during the 2020-2021 year. The PI also attended 2 virtual workshops on metagenomics and metabolomics hosted by the Lawrence Berkeley National Lab. These workshops focused on teaching attendees how to use Kbase, an open-source online platform funded by the DOE that helps process and archive metagenomic data. The skills acquired from these workshops have allowed the PI to analyze large metagenomic datasets as part of their project. The Brodie lab has also provided support by assigning a mentor to work with the PI on bioinformatics and functional gene analysis, providing invaluable support. How have the results been disseminated to communities of interest?We have disseminated results via workshops, presentations and scientific conferences and farmer field days. A large portion of efforts have been focused on the historically underserved Mayan communities of Southern Belize, in order to provide them, and the organizations that serve them, with soil-based knowledge and resources. It is the PI's goal to share knowledge and expertise based on the communities' stated needs and desires, while respecting their traditional knowledge and stewardship of their communally owned lands. The PI has also expanded their online presence, engaging with scientists and the public on social media (Twitter, Facebook), and through their personal website (danrath.github.io). These conversations have sparked potential collaborations with Belizean and American scientists and generated numerous likes and retweets. The PI has also been interviewed for a student-led podcast by students from the University of Belize and given a presentation on soil science to elementary school students at the Peninsula International Academy in Belize. While pursuing fieldwork in Belize, the PI was able to meet with several of the largest farming operations in Belize, such as Silk Grass Farms and Valley of Peace Farms, to discuss the potential for sustainable agricultural practices such as cover cropping, compost application, and no-till farming. These conversations revealed that many of these large operations were open to sustainable farming practices and were mostly hindered by a lack of agronomic and soil science expertise. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
In the 2020-2022 period, this project accomplished the following: 1) Quantify how organic carbon and nitrogen inputs via compost and cover crops affect distribution, dynamics and retention of carbon and nitrogen in the top 1m of the soil profile. During the fellowship period, we published a manuscript comparing subsoil C dynamics in tomato-corn rotations after 25 years of differing C and nutrient management in the California Central Valley: CONV (mineral fertilizer), CONV+WCC (mineralfertilizer + cover crops) and ORG (composted poultry manure + cover crops). We did this by analyzing 189 samples for dissolved carbon, available nutrients (N,P,S, Ca, Mg), hydraulic indicators (saturated hydraulic conductivity, moisture content), microbial community via PLFA, and soil carbon chemistry via FTIR. Our results showed a ~19 Mg/ha increase in SOC stocks down to 1m under ORG systems, and no significant SOC increases under CONV+WCC or CONV systems. We identified a potential interaction between cover crops and compost that may be behind this SOC increase, where increased soil porosity from cover crop roots facilitated the transport of soluble C from compost into the subsurface, where it can be stored for longer periods of time. We also noted an increase in the proportion of aromatic carbon, which may be more resistant to microbial decomposition, under ORG systems. This manuscript was published in the open-source SOIL journal organized by the European Geophysical Union. We also disseminated this information to the scientific community via a poster presentation at the SSSA 2021 annual meeting, as well as a flash talk presentation at the Washington SoilCon 2021 conference where the PI was awarded the "Best Flash Talk" award. 2) Quantify and characterize microbial taxa associated with carbon gains and losses in 1m soil profiles by using a novel lifestyle grouping strategy. During the fellowship period we prepared a manuscript outlining how 25 years of cropping systems at the Russell Ranch Agricultural Experiment had affected genes related to microbial carbon and nutrient cycling, drought resistance and lifestyle strategy. We obtained metagenome sequence data from 16 soil samples in the Russell Ranch experimental systems (CONV, CONV+WCC, ORG) at depths of 0-15, 15-30, 30-60 and 60-100cm. We used a custom HMM (microtrait) developed by the Brodie Lab to identify entire functional pathways associated with carbon and nutrient transformations in the overall microbial community. We then filtered, dereplicated and curated this metagenome data to reconstruct 230 MAGS (metagenome assembled genomes) representing a variety of microbial taxa from 0-100 cm. This data was used to test hypotheses generated from the synthesis of soil health indicators and large body of existing research from Russell Ranch. Our results showed increased functional potential for C breakdown and N transformation under compost and cover crop amendment, but no significant changes in overall microbial community structure in any of the three systems. These changes in functional potential supported our hypotheses based on soil health measurements and may indicate the potential impact of soil health practices on soil microbial communities. We disseminated this information to the scientific community via a poster presentation at the AGU 2021 annual meeting and a conference presentation at the SSSA 2021 annual meeting. This project also fostered numerous collaborations between the Brodie and Scow labs, with multiple guest presentations and group discussions. 3) Analyze microbial and nutrient data using linear models, ANOVA and linear modelling to determine significant drivers of carbon storage. Results will provide a platform for improved soil carbon monitoring, predictions of global C fluxes, and increased resilience and sustainability of crop yields. During the fellowship period we analyzed data from 300+ samples taken from Russell Ranch in 1993 and 2018 using statistical models to determine the environmental factors most closely correlated with carbon loss and gain under the treatments stated above (CONV, CONV+WCC, ORG). We collected outputs from a range of linear and partial least squares path models looking at how nutrient (N, P, S) content, moisture content, microbial biomass, and PLFA indicators explain variation over 25 years in easily decomposed carbon as well as total carbon stocks. Our results showed that available soil phosphorus and moisture content explained most of the variation in total carbon stocks (0-100 cm) between 1993-2018. Variation in 0-15cm carbon stocks was also best explained by changes in microbial biomass and PLFA stress ratios. Changes in soil phosphorus, microbial biomass and PLFA stress ratios were closely correlated with compost input, indicating that the phosphorus added in compost may play an important role in increasing C stocks throughout the 1m soil profile. These model outputs were used to inform further sampling at Russell Ranch, and an additional 120 soil samples comparing subsurface drip vs furrow irrigation were collected and analyzed for carbon, nutrient and microbial community indicators. Our results showed that furrow irrigated plots were associated with 10% lower organic matter content in the top 30 cm from 2012-2019 compared to drip irrigated plots. We identified differences in the spatial variation of water distribution under drip vs furrow irrigated plots as a potential driver of this decreased organic matter content but noted that these differences in applied water did not significantly reduce the amount of carbon and nutrients stored in subsoils over 5 years. 4) Communicate research results to farmers, students, policy makers and the general public in order to increase awareness of the importance of soil microbes, carbon storage and deeper soil layers for agricultural sustainability. During this reporting period we were able to communicate our research results to farmers, students, environmental NGOs and the general public both in the US and Belize via a series of workshops on soil microbes and carbon storage. We were also able to compile a database of surveys that identified farmer concerns, questions and attitudes towards conservation issues in the Golden Stream and Central Wildlife Corridor regions of Belize. The PI was able to deliver four talks on soil microbes and carbon storage to California farmers in the Solano (70 attendees, 42 attendees), Amador (~30 attendees) and Yolo (35 attendees) counties via virtual webinars. The PI also delivered a seminar as part of the "Nitty Gritty on California Soils" webinar series (63 attendees) on "Using genetic testing of soil organisms to understand biological diversity in the soil: soil health, pest management, nutrient cycling and more" The PI also delivered a 4-day training workshop on soil sampling, texturing and the role of soil microbes and carbon in agriculture. Based on post-workshop surveys of Belizean extension officers, 80% of workshop attendants (n=5) stated that the workshop was extremely helpful (5/5 ranking) in helping them understand the role of soil and soil microbes in agriculture in the Toledo district. Attendants cited the chance to gain hands-on experience in texturing and recognizing different soil types as the biggest benefit of the workshop and had several follow-up questions about how microbes impact nutrient and carbon cycling in tropical soils. This research partnership has sparked further collaborations between the University of Belize, Ya'axche Conservation Group, the NRCS and UC Davis with the goal of making Belizean soil survey data more available to the public.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2022
Citation:
Rath, D., Bogle, N., Deiss, L., Parikh, S. J., Wang, D., Ying, S., Tautges, N., Berhe, A. A., Ghezzehei, T. A., and Scow, K. M.: Synergy between compost and cover crops in a Mediterranean row crop system leads to increased subsoil carbon storage, SOIL, 8, 5983, https://doi.org/10.5194/soil-8-59-2022, 2022.
- Type:
Theses/Dissertations
Status:
Other
Year Published:
2022
Citation:
Rath, D., Long Term Impacts of Farming Practices on Carbon, Water and Microbes in a Mediterranean Ecosystem. [Unpublished Dissertation]. University of California at Davis, California.
- Type:
Theses/Dissertations
Status:
Other
Year Published:
2022
Citation:
Rath, D., Karaoz, U., Dubinsky, E., Bill, M., Gelardi, D., Samaddar, S., Schmidt, R., Brodie, E.L., and Scow, K.M.: Changes in microbial functional potential but not overall community structure after 20 years of practices intended to improve soil health. [Unpublished Thesis Chapter]. University of California at Davis, California.
- Type:
Theses/Dissertations
Status:
Other
Year Published:
2022
Citation:
Rath, D., Gelardi, D., and Scow, K.M.: Furrow irrigation is associated with higher surface organic matter losses compared to subsurface drip irrigation in a Mediterranean row cropped soil. [Unpublished Thesis Chapter]. University of California at Davis, California.
- Type:
Journal Articles
Status:
Other
Year Published:
2022
Citation:
Bogie, N.A, Berhe, A.A, Rojas, Y.P, Schaefer, M.V., Brodie, E.L., Scow, K.M., Nico, P.S., Ying, S.C., Rath, D.A, Ghezzehei, T.A. High efficiency irrigation and cover cropping leads to the presence of new organic matter across water stable soil aggregate size classes with minimal effect on C storage and aggregate size distribution. [In Prep].
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Progress 07/01/20 to 06/30/21
Outputs
Target Audience:During this reporting period I reached: 1) California farmers in the Solano and Yolo RCDs interested in soil carbon, sustainable agriculture and soil microbial communities. I did this via research presentations as part of the Winter 2021 Solano RCD Farmer Workshop, and the June 2021 Healthy Soils Program workshop at Russell Ranch. 2) Mayan farmers, Belizean NGOs and Belizean researchers in the Maya Wildlife Corridor and the Golden Stream regions of Central and Southern Belize. I did this by organizing a 1-week training program for Mayan extension officers on soil sampling and soil biology, culminating in a 1-day workshop on the soils of Belize. I also assisted researchers from the University of Belize in conducting farmer surveys and farm visits in the Maya Wildlife Corridor. 3) Undergraduate students in Soil Microbiology and Hydrology, undergraduate students of color, and graduate Soil and Biogeochemistry students. I did this by organizing a remote Soil Microbiology lab in Winter 2021, mentoring an undergraduate in their thesis project on alpine meadow soils of the Sierra Nevada, participating in the MANRRs (Minorities in Agriculture and Natural Resources Research) program as a student mentor, and organizing a graduate seminar on diversity in academia and teaching in Fall 2020. Changes/Problems: Due to the unprecedented global disruption caused by the global COVID-19 pandemic, and the prominence of the national conversation about race and racism in American society in 2020, there were some changes to the action plan for this fellowship. 1) To better fit with the needs of the graduate students in the department, the planned seminar on carbon storage was changed to a seminar on Justice, Equity, Diversity and Inclusion that focused on career development by helping students compose their own diversity statements. 2) Additionally, the PI's plan to help teach the Soil Microbiology laboratory section was disrupted by the switch to online instruction. The PI accommodated this by performing the up-front work of planning and organizing the remote lab, and helping put together portable lab kits that were delivered to students on several different continents. 3) Finally, the disruption to lab and fieldwork meant that the PI was unable to access Russell Ranch for nearly a year to obtain new soil samples for metagenomic sequencing. In order to stay on schedule for graduation, the PI obtained sequence data for frozen samples from the same plots taken in 2012 and has used that to address goal #2. The difference in cost will be applied to sequencing soil samples taken in Southern Belize in order to compare functional potential for carbon storage and nutrient cycling in tropical and Mediterranean soils. What opportunities for training and professional development has the project provided? Professional Development Activities In response to the events of May 25th, 2020, and the ongoing national discussion around race and racism in American society, the PI co-organized a seminar for graduate students in the Land, Air and Water Resources Department at UC Davis around the themes of Justice, Equity, Diversity and Inclusion in the geosciences. The PI worked with a fellow graduate student and faculty mentors to provide a space for discussions led by graduate students, early career faculty, and representatives from the UC Davis Office of Diversity, Equity and Inclusion. At the end of the seminar, attendees had the chance to submit diversity statements that were reviewed by faculty for comment. Based on weekly feedback polls, 66% of attendees rated the seminar 5/5, with the other 33% rating it ?. Attendees stated that the seminar "greatly enhanced their understanding of justice, equity, diversity and inclusion in the geosciences", and "provided a much-needed forum for conversations around race in our department". Additionally, the PI served as a graduate student mentor in the MANRRS (Minorities in Agriculture, Natural Resources and Related Sciences) program for the second year, advising an undergraduate student on research, pursuing careers in academia, and sharing their experiences in navigating college as a minority student. The PI also coordinated student feedback for the 2020 faculty interviews for the position of "Assistant Professor of Soil Biophysics". The PI organized student attendance at virtual interview sessions, collected student feedback and submitted student rankings to the search committee. This opportunity provided an inside look at the faculty search process, and gave valuable insight into what a search committee is looking for in a successful academic candidate. As part of their commitment to teaching during this fellowship, the PI also planned and organized a remote lab session for Soil Microbiology during the pandemic. The PI worked with a lab manager to plan experiments that demonstrated concepts in soil microbiology such as the electron tower and decomposition, and could be conducted using household materials and a small, low-cost lab kit that was mailed to students. Training Activities As stated above, the PI organized a 3-day training session and workshop on soil carbon, microbes and soil sampling for extension officers working for the Ya'axche Conservation Group in southern Belize; as well as presenting at 3 conferences during the 2020-2021 year. The PI also attended 2 virtual workshops on metagenomics and metabolomics hosted by the Lawrence Berkeley National Lab. These workshops focused on teaching attendees how to use Kbase, an open-source online platform funded by the DOE that helps process and archive metagenomic data. The skills acquired from these workshops have allowed the PI to analyze large metagenomic datasets as part of their project. The Brodie lab has also provided support by assigning a mentor to work with the PI on bioinformatics and functional gene analysis, providing invaluable support. How have the results been disseminated to communities of interest?As stated above, we have disseminated results via workshops, presentations and scientific conferences and farmer field days. A large portion of efforts have been focused on the historically underserved Mayan communities of Southern Belize, in order to provide them, and the organizations that serve them, with soil-based knowledge and resources. It is the PI's goal to share knowledge and expertise based on the communities' stated needs and desires, while respecting their traditional knowledge and stewardship of their communally owned lands. The PI has also expanded their online presence, engaging with scientists and the public on social media (Twitter, Facebook), and through their personal website (danrath.github.io). These conversations have sparked potential collaborations with Belizean and American scientists and generated numerous likes and retweets. The PI has also been interviewed for a student-led podcast by students from the University of Belize and given a presentation on soil science to elementary school students at the Peninsula International Academy in Belize. While pursuing fieldwork in Belize, the PI was able to meet with several of the largest farming operations in Belize, such as Silk Grass Farms and Valley of Peace Farms, to discuss the potential for sustainable agricultural practices such as cover cropping, compost application, and no-till farming. These conversations revealed that many of these large operations were open to sustainable farming practices and were mostly hindered by a lack of agronomic and soil science expertise. What do you plan to do during the next reporting period to accomplish the goals?During the next reporting period, the PI will accomplish the following goals: 1) Quantify how organic carbon and nitrogen inputs via compost and cover crops affect distribution, dynamics and retention of carbon and nitrogen in the top 1m of the soil profile. The PI will follow up on the findings from their current manuscript by looking at the impact of drip vs furrow irrigation on microbial, carbon and nutrient stocks in agricultural systems at Russell Ranch. These results will demonstrate the impact of an increasingly popular farming practice (drip irrigation) on carbon storage in subsurface soils, as well as provide insight to the effect of drought on carbon stocks in Mediterranean farming systems. 2) Quantify and characterize microbial taxa associated with carbon gains and losses in 1m soil profiles by using a novel lifestyle grouping strategy. The PI will produce a manuscript describing the functional and taxonomic changes that take place in the soil microbial community after 25 years of compost, cover cropping and mineral fertilizer application. This research will highlight which combination of practices had the greatest positive effect on carbon storage and will provide insight into how microbial carbon and nutrient cycling differs between surface and subsurface soils. 3) Analyze microbial and nutrient data using linear models, ANOVA and linear modelling to determine significant drivers of carbon storage. Results will provide a platform for improved soil carbon monitoring, predictions of global C fluxes, and increased resilience and sustainability of crop yields. The PI will produce a manuscript incorporating results from these statistical models and their measurements of changes in soil microbial, carbon and nutrient stocks under drip and furrow irrigation. This will provide a greater understanding of the environmental factors that shape changes in surface and subsurface carbon stocks over decades. 4) Communicate research results to farmers, students, policy makers and the general public in order to increase awareness of the importance of soil microbes, carbon storage and deeper soil layers for agricultural sustainability. The PI will present their research results at the 2021 AGU and SSSA conferences, and continue to engage with American farmers and agricultural stakeholders by presenting at workshops and field days. The PI will also continue to engage with underserved communities in Belize, including Mayan, Garifuna and Mennonite farmers, to share knowledge and advocate for sustainable farming practices.
Impacts
What was accomplished under these goals?
In the face of increasing levels of drought, flooding, and severe weather patterns across the world, we need to shift to more resilient, productive, and sustainable agricultural systems to meet the global demand for food, energy and climate change mitigation. Building soil organic carbon (SOC) can power that sustainable shift, trapping carbon from the atmosphere in the soil where it simultaneously alleviates climate change and improves soil structure, water infiltration, and nutrient cycling. Since soil microbial communities are the drivers of SOC formation, and up to 60% of global SOC stocks are stored deeper than 30 cm, increasing SOC stocks requires a better understanding of microbial-carbon interactions in both surface (0-30 cm) and subsoils (>30cm). Increasing SOC stocks worldwide also requires education and outreach on soil carbon management to farmers and agricultural workers to enable them to make effective management decisions for long term sustainability. In the 2020-2021 year, this project accomplished the following: 1) Quantify how organic carbon and nitrogen inputs via compost and cover crops affect distribution, dynamics and retention of carbon and nitrogen in the top 1m of the soil profile. During this reporting period, we submitted a manuscript comparing subsoil C dynamics in tomato-corn rotations after 25 years of differing C and nutrient management in the California Central Valley: CONV (mineral fertilizer), CONV+WCC (mineral fertilizer + cover crops) and ORG (composted poultry manure + cover crops). We did this by analyzing 189 samples for dissolved carbon, available nutrients (N,P,S, Ca, Mg), hydraulic indicators (saturated hydraulic conductivity, moisture content), microbial community via PLFA, and soil carbon chemistry via FTIR. Our results showed a ~19 Mg/ha increase in SOC stocks down to 1m under ORG systems, and no significant SOC increases under CONV+WCC or CONV systems. We identified a potential interaction between cover crops and compost that may be behind this SOC increase, where increased soil porosity from cover crop roots facilitated the transport of soluble C from compost into the subsurface, where it can be stored for longer periods of time. We also noted an increase in the proportion of aromatic carbon, which may be more resistant to microbial decomposition, under ORG systems. We submitted a manuscript based on these results to the open-source SOIL journal, where it is currently under review. We also disseminated this information to the scientific community via a poster presentation at the SSSA 2021 annual meeting, as well as a flash talk presentation at the Washington SoilCon 2021 conference where the PI was awarded the "Best Flash Talk" award. 2) Quantify and characterize microbial taxa associated with carbon gains and losses in 1m soil profiles by using a novel lifestyle grouping strategy. During this reporting period we obtained metagenome sequence data from 16 soil samples in the Russell Ranch experimental systems noted above (CONV, CONV+WCC, ORG) and analyzed this data to determine how 25 years of cropping systems had affected genes related to microbial carbon and nutrient cycling, drought resistance and lifestyle strategy. This sequence data we collected represents the 3 farming systems mentioned above (CONV, CONV+WCC, ORG) at depths of 0-15 , 15-30, 30-60 and 60-100cm. We filtered, dereplicated and curated this metagenome data to reconstruct 230 MAGS (metagenome assembled genomes) representing a variety of microbial taxa from 0-100 cm. We then used a custom HMM (hidden markov model) developed by the Brodie Lab to identify entire functional pathways associated with carbon and nutrient transformations. Data analysis is still ongoing, but we found a significantly higher number of genes associated with the conversion of nitrate -> nitrous oxide, and nitrate ->nitric oxide in CONV systems. This may indicate that long-term mineral fertilizer use can be associated with increased potential for incomplete denitrification, where nitrate is converted to NOx instead of N2 gas. We disseminated this information to the scientific community via a poster presentation at the AGU 2021 annual meeting. This project has also fostered further collaboration between the Brodie and Scow labs, with multiple guest presentations and group discussions. 3) Analyze microbial and nutrient data using linear models, ANOVA and linear modelling to determine significant drivers of carbon storage. Results will provide a platform for improved soil carbon monitoring, predictions of global C fluxes, and increased resilience and sustainability of crop yields. During this reporting period we analyzed data from 300+ samples taken from Russell Ranch in 1993 and 2018 using statistical models to determine the environmental factors most closely correlated with carbon loss and gain under the treatments stated above (CONV, CONV+WCC, ORG). We collected outputs from a range of linear and partial least squares path models looking at how nutrient (N, P, S) content, moisture content, microbial biomass, and PLFA indicators explain variation over 25 years in easily decomposed carbon as well as total carbon stocks. Our results showed that available soil phosphorus content explained most of the variation in total carbon stocks (0-100 cm) between 1993-2018. Variation in 0-15cm carbon stocks was also best explained by changes in microbial biomass and PLFA stress ratios. Changes in soil phosphorus, microbial biomass and PLFA stress ratios were closely correlated with compost input, indicating that the phosphorus added in compost may play an important role in increasing C stocks throughout the 1m soil profile. These model outputs were used to inform further sampling at Russell Ranch, and an additional 120 soil samples were collected in order to investigate the effect of drip vs. furrow irrigation on changes in carbon stocks. The analysis of these samples will be combined with the output from these statistical models to further explore the drivers of carbon gains and losses in Mediterranean row crop system in a future manuscript. 4) Communicate research results to farmers, students, policy makers and the general public in order to increase awareness of the importance of soil microbes, carbon storage and deeper soil layers for agricultural sustainability. During this reporting period we were able to communicate our research results to farmers, students, environmental NGOs and the general public both in the US and Belize via a series of workshops on soil microbes and carbon storage. We were also able to compile a database of surveys that identified farmer concerns, questions and attitudes towards conservation issues in the Golden Stream and Central Wildlife Corridor regions of Belize. The PI was able to deliver two talks on soil microbes and carbon storage to Californian farmers in the Solano (70 attendees) and Yolo counties via virtual webinars. The PI also delivered a 4-day training workshop on soil sampling, texturing and the role of soil microbes and carbon in agriculture. Based on post-workshop surveys of Belizean extension officers, 80% of workshop attendants (n=5) stated that the workshop was extremely helpful (5/5 ranking) in helping them understand the role of soil and soil microbes in agriculture in the Toledo district. Attendants cited the chance to gain hands-on experience in texturing and recognizing different soil types as the biggest benefit of the workshop and had several follow-up questions about how microbes impact nutrient and carbon cycling in tropical soils. This research partnership has sparked further collaborations between the University of Belize, Ya'axche Conservation Group and UC Davis with the goal of making Belizean soil survey data more available to the public.
Publications
- Type:
Journal Articles
Status:
Under Review
Year Published:
2021
Citation:
Rath, D., Bogie, N., Deiss, L., Parikh, S., Wang, D., Ying, S., Tautges, N., Berhe, A. A., and Scow, K.: Synergy between compost and cover crops leads to increased subsurface soil carbon storage, SOIL Discuss. [preprint], https://doi.org/10.5194/soil-2021-19, in review, 2021.
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