GLBRC Switchgrass Nitrogen-rate Experiment
The GLBRC Switchgrass Nitrogen Rate Experiment was established in 2008 at the KBS GLBRC Intensive Field Site to examine the effects of nitrogen fertilization levels and harvest frequencies (once versus twice per year) on switchgrass productivity and greenhouse gas emissions. The experiment was established as a randomized split block design with harvest frequency comprising the split. The harvest frequency treatment was terminated after the 2012 harvest; since 2013 all split plots are harvested once in the fall, with yields recorded separately 2013-2022 and combined starting in 2023. Eight N applications levels range from 0 to 196 kg N/ha and began in 2009. Split plots are 4.5 x 7.6 m (15 x 25′) arranged in each of 4 replicate blocks, for a total of 8 x 4 = 32 plots for each original harvest frequency treatment. A 0.5 m deep aluminum barrier now separates plots within the discontinued double harvest treatment plots (only), installed for a mycorrhizal experiment. 

Lysimeters (soil water samplers) are installed in various plots.