Soil carbon is not mainly leftover residue, and that changes everything you think you know about building healthier fields. Dr. Jennifer Pett-Ridge reveals why the real engine of soil organic matter is the life and death of microbes—and why managing the whole underground food web may matter more than chasing a bucket of bugs.
What happens beneath your feet is far more dynamic than most farmers have been told. Jennifer, a soil ecologist whose work spans Yale, Berkeley, and Lawrence Livermore, breaks down why dead microbes, or necromass, make up a massive share of soil carbon, how roots feed the system through exudates, and why diversity above ground creates diversity below ground. If you want to understand how cover crops, reduced tillage, and perennial strips can change water cycling, nutrient availability, and resilience, this conversation connects the dots.
Subscribe to AgEmerge Podcast for bi-weekly episodes on soil health, regenerative practices, innovative technology, grower stories, and the future of agriculture. New episodes drop every other Tuesday.
Hosted by Monte Bottens
Produced by Ag Solutions Network & Power2Gro
Watch more: https://www.youtube.com/@AgSolutionsNetwork
Listen on your favorite podcast platform: Search "AgEmerge Podcast"
Ag Solutions Network Socials:
https://www.agsolutionsnetwork.com/agemergepodcast
https://www.facebook.com/ASN.farm
https://www.linkedin.com/company/agsolutionsnetwork
https://twitter.com/POWER2GRO
https://www.instagram.com/agsolutionsnetwork/
Ag Solutions Network website:
https://www.agsolutionsnetwork.com/
Click to watch or listen and as always, let us know if you have any questions or guest ideas by emailing
[email protected].
Timestamps
04:14 — Why dead microbes matter as much as living microbes
06:32 — Why many commercial inoculants may be ineffective or dead
07:21 — Necromass and why dead microbial material is a major carbon pool
09:21 — Root exudates as the starting point for soil carbon
10:35 — Plants and microbes as a trading system for nutrients and water
11:50 — Why crop diversity creates microbial diversity and more necromass
14:40 — Biomass turnover as the path toward stable carbon
16:35 — Why low-disturbance tillage still raises tradeoffs
18:37 — Fungal networks, drought resilience, and the cost of cutting biological highways
22:54 — DNA sequencing, what it reveals, and why it can become “stamp collecting”
24:12 — Only a small fraction of microbes are active at any one time
33:37 — Why “species” is a messy concept in the microbial world
34:57 — Managing soil as a system, not as individual microbes
37:22 — A real-world example of alternating corn, cover crops, and grazing
38:32 — Complexity in soil often means complexity in labor and logistics, too
39:31 — Practical farmer routines for establishing and terminating cover crops
46:48 — Carbon intensity, lower nitrogen use, and water resilience
48:22 — Soil organic matter as a sponge for both drought and flood
51:39 — Nitrogen losses, nitrous oxide, and why fertilizer efficiency matters
52:14 — Carbon intensity credits and the economics of lower-input systems
53:09 — Gene editing, photosynthetic efficiency, and root improvements
56:11 — Seed endophytes as a way to improve function without changing plant DNA
58:46 — Risks of stacked engineering and unintended input increases
About our Guest:
Dr. Jennifer Pett-Ridge is a Distinguished Member of Technical Staff at LLNL, Adjunct Professor at UC Merced and a principal investigator at the UC Berkeley Innovative Genomics Institute. She uses the tools of systems biology and biogeochemistry (stable isotope probing, NanoSIMS imaging, molecular microbial ecology, computational modeling) to study how earth system changes affect microbiome interactions and ecosystem processes. Much of her current work focuses on soil carbon persistence and sustainable agriculture. She leads the Carbon Initiative at LLNL.