Valdez, Z., W. C. Hockaday, C. M. Masiello, M. E. Gallagher, and G. P. Robertson. 2017. Soil carbon and nitrogen responses to nitrogen fertilizer and harvesting rates in switchgrass cropping systems. BioEnergy Research doi: 10.1007/s12155-016-9810-7.

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The environmental sustainability of bioenergy cropping systems depends upon multiple factors such as crop selection, agricultural practices, and the management of carbon ©, nitrogen (N), and water resources. Perennial grasses, such as switchgrass (Panicum virgatum L.), show potential as a sustainable bioenergy source due to high yields on marginal lands with low fertilizer inputs and an extensive root system that may increase sequestration of C and N in subsurface soil horizons. We quantified the C and N stocks in roots, free particulate, and mineral-associated soil organic matter pools in a 4-year-old switchgrass system following conversion from row crop agriculture at the W.K. Kellogg Biological Station in southwest Michigan. Crops were fertilized with nitrogen at either 0, 84, or 196 kg N ha−1 and harvested either once or twice annually. Twice-annual harvesting caused a reduction of C and N stocks in the relatively labile roots and free-particulate organic matter pools. Nitrogen fertilizer significantly reduced total soil organic C and N stocks, particularly in the stable, mineral-associated C and N pools at depths greater than 15 cm. The largest total belowground C stocks in biomass and soil occurred in unfertilized plots with annual harvesting. These findings suggest that fertilization in switchgrass agriculture moderates the sequestration potential of the soil C pool.

DOI: 10.1007/s12155-016-9810-7

Associated Treatment Areas:

Switchgrass Nitrogen/Harvest Experiment - GLBRC

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