Date of this Version
Dissertation presented to the faculty of the Graduate College at the University of Nebraska-Lincoln in partial fulfillment of requirements for the degree of Doctor of Philosophy
Major: Agronomy and Horticulture (Crop Physiology and Production)
Under the supervision of Professors Andrea Basche and Daren Redfearn
Lincoln, Nebraska, United States, April 2023
Soil health management practices have increasingly been promoted across US agroecosystems to address many interrelated environmental and economic food system challenges. Sustaining conservation behavior – through farmer’s adoption and continued use of practices – is key for achieving many soil health-related intended social-ecological benefits. Using a range of scientific methods, from lab-based experiments to on-farm research to farmer interviews, the overall objective of this dissertation research was to explore soil and human dimension considerations to design farming and knowledge transfer systems for sustaining soil health management in the US Midwest. In a multivariate analysis of ten on-farm research sites, we found that ecological intensification of cropping systems via cover crop use had the greatest impact on changes in properties related to soil organic matter (SOM), carbon (C) and nitrogen (N) dynamics. The study also highlighted the potential of synthetic fertilizer reductions and economic savings from improved soil biological activity via longer cover crop use. Analyses comparing four on-farm sites with annual crop rotations with and without cover crops (i.e., cropland soils) with perennial grassland sites (i.e., reference soil) found that framing soil metrics relative to reference soils and ensuring appropriate sampling intensity were important to quantify cover crop impacts on farms. Analysis of C and N distribution at the same four sites using SOM fractions of distinct ecological relevance found less pronounced cover crop effects but highlighted the potential of perenniality as an approach to agroecosystem design for improved SOM C and N dynamics and related soil functions. Through analysis of in-depth interviews, interactive activities, and annual on-farm reports, we identified five distinct factors supporting farmer’s social networks influences on sustained use of soil health practices: land tenure, perceived acceptance, family farming traditions, co-learning, as well as on-farm experimentation and adaptive management. By linking learnings from on-farm experimentation and factors related to farmers’ social and informational networks, this research advances important lessons for conservation efforts with respect to soil health assessment, sampling approach, and knowledge transfer.