Research

Research Philosophy and Goals

The Midwest is one of the world’s most productive agricultural systems. Yet, the ecological characteristics that make conditions in the region favorable to crop production (i.e., humid summers, highly fertile and loamy textured soils, and drainage of shallow water tables) also pose critical challenges to the efficient management of water and nutrients in summer annual cropping systems, leading to downstream and downwind negative impacts on environmental quality. My research seeks to increase our understanding of the biophysical controls on agroecosystem productivity, carbon (C) and nitrogen (N) cycling, and how these differ across cropping systems with varying degrees of biological diversification. While the scope of my scientific interest covers various aspects of spatial and temporal diversification, my primary focus is on understanding how crop sequences and carry-over effects influence resource-use efficiency, N losses, and resilience to environmental stress. I leverage field data from small plots, long-term experiments, publicly available databases, and process-based models to fully examine the soil-plant-atmosphere continuum and extrapolate the behavior of the system across a wide range of weather, soil, and management variables. As an agronomist, I strive to provide decision makers with relevant and rigorously tested information, packaged in easy-to-use tools to support the design and implementation of strategies to improve farm profitability and sustainability. Here, I briefly summarize the contributions of my prior and ongoing work and lay out a vision for a future research program that will seek to improve the design and implementation of diversified cropping systems in the region.

Corn emerging in rye cover crop stubble in Ames, Iowa, 2017. My research aims to quantify how carbon and nutrient cycles change with management and land-use decisions.

Previous and Ongoing Research

Despite the known soil and environmental quality benefits of extended crop rotations, their adoption in Iowa and other Midwestern states remains low, mainly because of potential tradeoffs with productivity and short-term economic returns. Throughout my graduate research, I have worked to characterize the extent and magnitude of these tradeoffs. My M.S. thesis focused on evaluating the inclusion of winter canola (Brassica napus) – a high-yielding oilseed crop used for edible vegetable oil – into summer annual crop rotations. Winter canola can be good candidate for this purpose as it provides soil cover throughout the winter and produces a marketable grain compatible with existing production and distribution infrastructure. By tracking canola growth and development throughout the fall, winter, and spring, the research published in *Crop, Forage and Turfgrass Management* showed that while canola can provide soil cover benefits, timely fall seeding is crucial. Because these seeding dates conflict with standing crops during most years, the economic profiles of various cropping pattern alternatives were examined. The enterprise budgets for winter canola developed as part of this work were published through Iowa State University Extension’s Ag Decision Maker. I have been recognized for my thesis work by the Iowa State University’s Research Excellence Award in 2015, and the Midwest Association of Graduate Schools/ProQuest Distinguished Master’s Thesis Award in 2018.

My Ph.D. research has focused on examining the underlying mechanisms by which crop sequences and management practices affect water and N cycling, and their link to crop productivity and environmental N losses. As an example, I focused on studying how rye cover crops affect the crop ecophysiology and nitrate losses in subsurface drainage tiles in continuous corn systems. I synthesized and analyzed experimental, literature, and simulated data to test the hypothesis that the effect of rye cover crop on corn yield, tile water flow, and nitrate losses is proportional to the amount of rye biomass produced at termination. Results of the study were published in Field Crops Research. This and similar analyses expose the difficulty of comparing the efficiency of N cycling across cropping systems with distinct crop types and sequences, mainly because available metrics are largely crop-specific and designed primarily for evaluating crop responses to inputs or management. In this context, the prevailing view is that lower nutrient losses in a variety of systems can be achieved by reducing the net surplus of applied N, but this largely ignores long-term changes in soil nutrient stocks. In a recent study published in Agriculture, Ecosystems and the Environment, I examined the case of corn-soybean rotations in the Midwest to show that this crop-based view generally underestimates N losses and that it is insensitive to improvements in soil N cycling (e.g., with cover crops). The paper laid out a conceptual framework to link the soil and crop components of N-use efficiency at the system level. It indicated that the majority (55%) of N losses in corn-soybean systems actually originate from the release of native soil N into the environment because of the asynchrony between soil mineralization and crop uptake.

My ongoing work examines and quantifies the impact of various genetic, environmental and management drivers of crop yield and N-loss trade-offs, and identifies potential management strategies to mitigate them. Using various quantitative methods, I am currently analyzing high-dimensional data sets of management, weather, and system state variables that were generated with well-calibrated simulation models using data from sites across a gradient of soil and climatic characteristics in the Midwest. In addition, I am leading research efforts to improve simulation models by developing and testing new algorithms (e.g., grain dry down in corn and soybeans), and collecting, curating, and managing multi-process data sets that can be used for model calibration and validation in future research projects.

Future Research Directions

The agroecosystems of the Midwest can be designed to optimally provide commodities, bioenergy, and regulation of water and nutrient cycles. This can be achieved by using knowledge of the spatial (subfield) and temporal (multi-year) variability to identify marginal field areas where grain yields are too low or variable because of low fertility or recurrent water stress (i.e., drought or flood). An important aspect to consider is that grain production in the region has already expanded into too many areas that are ecologically better suited to perennial vegetation uses (e.g., riparian zones, wetlands). Thus, strategic placement of biological diversity in the landscape may provide many opportunities to improve farm profitability, maintain soil resources, and enhance environmental quality in the region.

My current research explores potential spatial and temporal configurations of diversity as strategies to improve production and environmental quality.

Although these ideas have been gaining traction, few examples of successful implementation exist, and we lack knowledge of the potential performance of different spatial and temporal diversification schemes under current and future climate scenarios. I intend to pursue future research to develop spatially explicit, integrative approaches to link soil characteristics, topography, hydrology, weather patterns, and management to the yield potential and variability of various commodity, bioenergy, and emerging crops. These approaches will be employed to scale up field plot data to farm and regional levels, and evaluate the potentials and tradeoffs of various diversification strategies. Results from this research will be synthesized to develop data-driven tools relevant for monitoring, decision-support, and education.

I  seek to cultivate tight cross-disciplinary partnerships with researchers who are specialists in different components of the crop-soil-atmosphere continuum, identifying areas where my research can add value to the existing data sets, and filling data and knowledge gaps through my own experimentation, data mining, and modeling efforts. My ultimate aim is to provide realistic, robust representations of the potential and the limitations of diversified cropping systems in the Midwest, and the role these can play in helping feed and power a crowded and warming planet.