Date of Award:

12-2021

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Plants, Soils, and Climate

Department name when degree awarded

Plant, Soils and Climate

Committee Chair(s)

Matt A. Yost

Committee

Matt A. Yost

Committee

Jeanette Norton

Committee

Grant Cardon

Committee

John Stevens

Committee

Kristen Veum

Abstract

Soil health is a concept and condition of the soil where measurable soil properties represent the capacity of a soil fulfilling its intended use, such as producing crops, without constraint to its agro-ecological quality. Soil health assessments are used to estimate the health of a soil by assessing soil biological, chemical, and physical attributes, called soil health indicators, and scoring them on a scale, usually 0 to 100, to guide soil and crop management. However, there are few large-scale analyses of soil health assessment scores and their relationships with crop yield. Understanding how soil health assessments relate to crop yield can support soil health practitioners and growers in making decisions that can direct efforts to improve soil health monitoring and management.

The Soil Health Partnership (SHP) was a sizeable farmer-led network of on-farm trials assessing soil health throughout the Midwestern US. The on-farm data was used to explore the relationship between soil health and crop yield in three ways. First, how variability in soil health affects variability in yield. Second, the strength of the relationships between soil health assessment scores and crop yield. And third, the effects of conservation management on soil health indicators, scores, and yield.

These analyses found that soil health indicator variation in time accounted for relatively little variability in corn and soybean yield over a two-to-four-year timespan at the SHP sites. Second, soil health scores of individual indicators or composite scores were not often correlated with crop yield on a site-to-site basis. This might suggest to soil health researchers and growers that other soil health outcomes, such as field runoff water quality, be measured to determine how soil health is improving additional soil ecosystem services. Third, the on-farm soil health trials revealed that few soil health indicators were affected by cover crops within a short one to four years of treatment timespan. Overall, these results suggest to growers that a whole-of-ecosystem approach be taken to monitoring soil health and that soil health measurements be taken before beginning a new conservation management plan, then every two to four years to allow time for soil health improvement.

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