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Goal: Deliver Benefits to the Public Water Quality Effects of Switchgrass Intercropping on Pine Forests in Coastal North Carolina

Bales of switchgrass

Research site with loblolly pine and intercropped native switchgrass plants. Photo by Augustine Muwamba, College of Charleston.


Six recent years of data from site preparation to full growth of switchgrass, as a celluolosic bioenergy crop, suggested that planting switchgrass between loblolly pine tree beds improved downstream nutrient water quality when compared to traditional managed pine forest at a North Carolina Coastal Plain site. However, a switchgrass only treatment yielded higher nitrogen levels than the intercropped site.


A large amount of land is under pine production in the U.S., with loblolly pine (Pinus taeda L.) widely used for timber and other wood products. Intercropping switchgrass (Panicum virgatum L.), as a celluolosic bioenergy crop, in loblolly pine stands is hypothesized to provide bioenergy feedstock without competing for land currently in food production. Switchgrass is a native perennial grass that uses water efficiently and prevents soil erosion. However, in order to recommend this novel intercropping practice to forest managers and landowners, there is a critical need for information about its impacts on water quantity and quality. Accordingly, six recent years (2009-2014) of data from a watershed-scale field experiment conducted on Weyerhaeuser’s managed pine forest in coastal North Carolina suggested that fully grown switchgrass between pine tree beds improved downstream water quality by reducing nitrate and phosphate concentrations and loads compared to the traditional pine forest. However, the watershed planted with only switchgrass yielded higher nitrate concentration and loads than the intercropped site, possibly due to greater outflow from the former site. Pine-switchgrass intercropping may thus be a viable method of producing a sustainable bioenergy crop on pine forest lands while improving water quality, except for its site preparation period.

Principal Investigator
Devendra M. Amatya, Research Hydrologist
4353 - Center for Forest Watershed Research
Strategic Program Area
Water, Air, and Soil
Water quality effects of switchgrass intercropping on pine forest in Coastal North Carolina
Effects of site preparation for pine forest/switchgrass Intercropping on water quality
CompassLive Story
Switchgrass in Pine Plantations
External Partners
North Carolina State University
Weyerhaeuser Company
CatchLight Energy
University of Georgia