Abstract
Application of nitrogen (N) fertilizer plus biochar may increase crop yield, but how biochar will interact with N fertilization to affect bioenergy crop switchgrass physiology, biomass, and soil CO2 emission (i.e., soil respiration) from switchgrass fields remains unclear. Here, we assessed this issue by conducting a field experiment near Nashville TN with two levels of biochar treatment (a control without biochar addition and biochar addition of 9 Mg ha−1), and four N fertilization levels (0 kg N ha−1, 17 kg N ha−1, 34 kg N ha−1, and 67 kg N ha−1, labeled as ON, LN, MN, and HN, respectively). Results showed that both biochar addition and N fertilization did not influence switchgrass leaf photosynthesis and biomass, but biochar addition enhanced leaf transpiration, and reduced water use efficiency. Soil respiration was reduced by biochar addition, but significantly enhanced by N fertilization. Biochar and N fertilization interactively influenced soil respiration and seasonal variation of soil respiration was mostly controlled by soil temperature. Our results indicated that switchgrass can maintain high productivity without much N input, at least for several years. The findings from this study are useful to optimize N fertilization and biochar addition in the switchgrass fields for maintaining relatively high productive switchgrass biomass while reducing soil CO2 emission.
Highlights
With an increasing world population and improvements in living standards, the demand for energy and food has continued to increase over the past decades [1,2]
Results of analysis of variance (ANOVA) showed that biochar and N fertilization did not influence leaf photosynthesis rate (Table 1)
No significant interaction of biochar and N fertilization was found for leaf photosynthesis, transpiration, and Water use efficiency (WUE)
Summary
With an increasing world population and improvements in living standards, the demand for energy and food has continued to increase over the past decades [1,2]. To reduce fossil fuel dependence and greenhouse gas emissions, and to meet the mandate of the US Energy Independence and Security. Act (EISA) of 2007, the generation of biofuels from bioenergy crop biomass has been promoted [3,4,5]. One of the most promising bioenergy crops is switchgrass (Panicum virgatum L.) [5,6]. Switchgrass can grow in less productive soils under a broad range of environmental conditions, and requires minimal soil preparation and a relatively small amount of nitrogen (N) [8,9]. Numerous approaches have been proposed to improve switchgrass productivity while reducing environmental impacts [10,11,12,13,14]
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