Author
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Springer, Timothy |
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Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/22/2017 Publication Date: 4/3/2017 Publication URL: http://handle.nal.usda.gov/10113/5763403 Citation: Springer, T.L. 2017. Effect of nitrogen fertilization and residual nitrogen on biomass yield of switchgrass. BioEnergy Research. 10(3): 648-656. Interpretive Summary: A scientist at the USDA-ARS Southern Plains Range Research Station, Woodward, Oklahoma found that switchgrass biomass yields in excess of 10 Mg ha-1 are possible in areas with 600 mm of annual precipitation, and where the climate varies from dry-subhumid to semiarid. Annual N fertilization of switchgrass at 80 kg ha-1 provided for sustainable biomass yields that averaged 11.7 Mg ha-1. This level of N fertilization was least affected by environmental conditions (such as drought in 2011) as indicated by the overlapping of annual biomass yields from 2008 to 2011. After four years of nitrogen fertilization, the biomass yield of switchgrass the first year after N fertilization ceased (2012) averaged 12.2 Mg ha-1 for the 80 kg ha-1 nitrogen rate. The year 2012 was also a drought year. Residual N effects failed to sustain high forage biomass yields the second through fourth years after fertilization ceased. The data suggest that producers could occasionally skip a year of N fertilization without detrimentally impacting the production of switchgrass biomass. Additional research is needed to determine the rate of C accumulation in the soil profile for well managed switchgrass grown in dry-subhumid to semiarid environments. Technical Abstract: Switchgrass, Panicum virgatum L., grown for biomass has been extensively researched where the mean annual precipitation exceeds 760 mm, and the climate varies from humid to moist-subhumid. Research is lacking for areas that receive less than 700 mm of precipitation, and where the climate varies from dry-subhumid to semiarid. The objectives of this study were to determine: 1) the effect of N fertilization on biomass production; 2) the effect of residual N on biomass production; and 3) the concentration of soil organic carbon of fertilized and non-fertilized switchgrass. Plots were fertilized annually with N at the rates of 0, 40, 80, and 120 kg ha-1 from 2008–2011 and plots were not fertilized from 2012–2015. When fertilized, the biomass yield averaged 4.4, 9.4, 11.6, and 13.2 ± 0.4 Mg ha-1 for the 0, 40, 80, and 120 kg ha-1 N rates, respectively. When unfertilized, the biomass yield averaged 2.6, 5.3, 7.3, and 7.3 ± 0.3 Mg ha-1 for the 0, 40, 80, and 120 kg ha-1 N rates, respectively. Plots that received N did not differ in the concentration of soil organic carbon (SOC), but the concentration of SOC of fertilized plots was greater than that of unfertilized plots (P < 0.05, 56.4 ± 2.9 g kg-1 versus 50.1 ± 2.9 g kg-1). Also plots that were fertilized with N maintained the concentration of SOC once N fertilization ceased. Annual N fertilization at 80 kg ha-1 provided sustainable biomass yields that were least affected by variations due to the environment. |
