Our research addresses the relationships among land management, biogeochemical and water cycles, and global environmental change. More specifically, we assess the sustainability of food production systems by examining their effects on interactions among plants, soils, carbon, nutrient, and water cycles. The primary questions that motivate our research are:
- How can the dual objectives of increasing food production and food security be met in a way that minimizes environmental costs?
- What is the effect of agriculture on local ecosystem services including: nutrient cycling, carbon storage, food provisioning, and climate regulation?
agroecological systems in the mid-atlantic region:
farming systems can be productive and promote ecosystem services
Heavy N fertilizer application in agriculture leads to nitrate loading in both surface and ground waters, and local rivers and the Chesapeake Bay are undergoing eutrophication. In many cases, conventional best management practices have reached their potential for mitigating N losses, and still, further reductions are needed. Unconventional and innovative nutrient management strategies should be employed to further reduce N losses from intensively farmed systems, but these strategies must be developed along with practitioners. I will work with farmers to direct research initiatives that will integrate field measurements with modeling approaches to examine the effects of nutrient management on soil fertility, yields, and pathways for N loss from agroecosystems and the landscapes that contain them.
effects of sea-level rise and saltwater intrusion on nutrient dynamics in coastal farmlands
This research project will examine the effects of tidal marsh migration, in response to sea level rise, on plant community and nutrient dynamics. This project is inherently interdisciplinary as our research questions are built on principles from the fields of biogeochemistry, wetland biology, and agroecology. As tidal marshes migrate upland, they consume natural forest and in some cases, encroach on farmland, taking it out of production. Specifically, we propose to quantify the rate of marsh migration into coastal farmland and forest, compare nutrient releases across these ecotones, and investigate downstream effects on marsh plant species diversity, which is known to be affected by nutrient loading. Specifically, we are examining the response of phosphorus (P), which is applied at high concentrations to many lower eastern shore fields associated with poultry operations. P is relatively insoluble when bound to soil, but may be freed by saltwater intrusion. Our findings will be used to inform salt marsh conservation practices, including the management of problem species, Phragmites australis, prioritize protected land acquisition, and probe the capacity of migrating wetlands and transitioning forest to buffer water quality, which could provide the basis for a best management practice for coastal farms.
environmental impacts of the african green revolution
This work examines tradeoffs between productivity and other ecosystem services in subsistence agricultural systems in sub-Saharan Africa. Current proposals and policy associated with the call for an African Green Revolution aim to improve food production and soil fertility by increasing nutrient application rates six-fold on smallholder farms. While crop yields are anticipated to rise significantly in response to increased N application, a scarcity of biophysical data makes it nearly impossible to predict the environmental impacts of this widespread change in nutrient management.
mechanisms for nitrogen retention in cultivated soils
Unlike the Green Revolution of the 1970s to the 1990s in Asia and Latin America, which occurred predominantly on relatively fertile, young soils (Entisols and Inceptisols), the agricultural transition in sub-Saharan Africa is occurring on more highly weathered soils that range from low fertility high clay Ultisols, and Oxisols to very sandy Alfisols. We are examining how available N varies throughout the growing season and at depth in the soil profile (down to 4 meters!) to determine how and where nitrogen is stored in these agricultural soils and how this differs with soil texture and subsoil mineralogy.
using drones to measure cover crop nitrogen
Nutrient loss from agriculture can have significant consequences for both environmental and human health. Cover crops may provide a mechanism for reducing nitrogen (N) losses from agriculture by taking up N during the fall and making it available to crops in the spring. However, large spatial heterogeneity within and among farm fields makes spring N-release difficult to predict, thus farmers may apply excess fertilizer to ensure profitable yields. We are developing a high-resolution method for mapping N status in cover and cash crops using an unmanned aerial system (UAS) mounted with a multispectral camera. We will take multispectral images of (1) radish, rape, or rye fields in the late fall 2015, (2) unfertilized, immature corn in the spring 2016, and (3) mature corn in the fall. We will combine flight data with field measurements to develop the best models for predicting (1) N held in cover crop biomass, (2) N released during the spring to the corn crop and (3) N held in corn at the end of the growing season. These data will be used to produce field-specific variable rate N fertilizer maps.
co-benefits of agroforestry in smallholder farming systems
The term agroforestry usually calls to mind the wooded coffee plantations of Latin America, where coffee bushes are cultivated under the broad canopy of fruit and timber trees. Agroforestry in sub-Saharan Africa can take many forms, from hedgerows and windbreaks bordering farm fields, to short-term maize-legume rotation, where the "agroforest" is a shrubby covercrop that is grown on the field for a few months during the "short rainy" season. We are examining the effects of growing trees or short-term legume crops on a variety of ecosystem services - nitrogen and carbon cycling, water retention, and microbial diversity and functioning.