Publications

Soil organic matter drives cropland biogeochemistry in a myriad of ways. Here we asked if SOM fractions, like POM and MAOM, could help us to understand why areas of a field are stable in their yields from year to year. We identified a complex feedback loop, with high productivity areas accumulating POM due to interactions between weather, topography, and management.

In areas with complex topography, landscape position can be a major driver of cropping system performance. Here we review the literature to understand how that relationship is mediated by annual weather, finding that for corn, correlations between yield and elevation or slope became more positive as precipitation increased, however, the opposite was true for soybeans.

Understanding where water is sourced from is critical to creating robust management strategies for future climates. In this work, we used geochemcial isotopic tracers to understand how water made it into the stream. The results show distinct contributions of different groundwater sources to stream flow, and indicate seasonal variability in stream flow generation sources.

Cover crops provide a number of benefits, one of which is decreasing the evaporative loss of water from the soil surface. Here we use cropping system models to investigate the impact of this increased water on yield stability over a 30 year period. We found that cover crops increased the amount of water available to crops during critical time, increasing yields and decreasing overall variability.

We isolate physical SOM fractions through a variety of methods. While the resulting fractions often share a conceptual definition, here, using a combination of chemical, isotopic, and spectral evidence, we show that there are important distinctions among the various procedural definitions, and that nuance is needed to understand what we’re isolating.

Establishing robust methods of separating soil organic matter into physical fractions (e.g., particulate and mineral associated organic matter) is critical to fostering useful syntheses and collaborations. Here we discuss methods of physical soil organic matter fractionation, dispersion, and analysis, and offer examples of protocols employed in both our lab and across the field.

Rolling hill landscapes engender increased variability in soil ecosystems, with differences in everything from soil temperature to crop productivity. Here we examined whether landscape position affects the decomposition rate of cover crop residue in two fields. We found significant differences in soil water status and temperature, but limited influence on decomposition.

The first work I ever published. Here we used stable water isotopes to understand the seasonal differences in stream flow generation in a mountain watershed. We found complex patterns of intermittent connection between stream and soils during winter months, pushing back on the assumption that winter stream flow is synonymous with base flow.

The diversity-stability relationship is a deeply entrenched paradigm in ecological sciences. Previous work has shown that at the national level, this pattern extends to crop production. Here we ask, “At the sub-national level, does this relationship hold?” and find that responses diverge depending on whether you’re looking at the production of dollars or of calories.

Nitrous oxide is a potent greenhouse gas, often associated with agricultural systems. In this work, we used stable N, H, and O isotopes combined with mass balance analysis to show that a substantial amount of denitrification occurs from soils during fallow periods. This flux represents a significant loss of soil N, but up till now has been under-counted, with important implications for climate change.

In order to maximize the benefits of cover crops, science-based management recommendations are required. In this work, we examined the effects of fungicide, fertilizer, and termination timing on corn yields following a rye cover crop. We found that earlier termination improved corn yields, and that increasing inputs likely cannot alleviate stand loss in late-terminated systems.