PS 20-26 - Ten years of regenerative practices improved soil properties and altered soil biota on an organic farm in coastal California.

Abstract: Topsoil loss is one of the most pressing environmental concerns faced by humanity today. Conventional agriculture often contributes to impoverished soils through heavy reliance on fertilizers and pesticides. Alternatively, regenerative practices including cover cropping, compost addition, and grazing rotations can improve soil structure, biosequestration, and biodiversity. These practices promote agroecosystem inherent fertility and resilience, lessening the need for synthetic inputs. However, little is known about the rate and extent by which soil properties respond to regenerative practices, and how these practices might affect soil microbial community composition and putative function.



Here we sampled soil from a lemon orchard, avocado orchard, pasture, and vegetable garden one, five, and nine years after conversion from conventional to regenerative practices. To determine changes in soil abiotic and biotic properties through time, we analyzed water stable aggregates, soil organic matter, microbial biomass, and microbial community composition. We wanted to know (1) if and at what timescale changes to soil properties might occur? (2) If regenerative practices affected the composition of microbial community including fungal functional guilds?



Across crop types we found increases in soil organic matter (88%), water stable aggregates (87%), and a doubling of microbial biomass. Contrary to expectation, fungal:bacterial ratios did not change. In terms of community composition, bacteria responded more to organic inputs than fungi that showed higher fidelity to crop type. Focusing on fungal guilds, we found that the relative abundance and richness of putative saprotrophs increased whereas relative abundance and richness of putative pathogens decreased. Arbuscular mycorrhizal fungi showed little change over time.



We show that regenerative practices improved soil properties over nine years with the most dramatic changes occurring in the first five years. Our results suggest responses to regenerative practices can be both fast and substantial with potentially far-reaching consequences for soil function.