Switchgrass (Panicum virgatum L.) is considered as an important biofuel crop but further studies on factors that may have an effect on agronomic performance and energy attributes are needed to help elucidate managemen...Switchgrass (Panicum virgatum L.) is considered as an important biofuel crop but further studies on factors that may have an effect on agronomic performance and energy attributes are needed to help elucidate management strategies for the crop. A 2-yr field study at the Brown Loam Branch Experiment Station, Raymond, Mississippi, USA, quantified the effects of four N application rates and four genotypes on biomass yield, ethanol yield, and nutrient removal of switchgrass. Biomass yield response to N rate was linear in 2008 and quadratic in 2009. Among genotypes, biomass yield averaged across N rate and years, ranked lowland NF/GA992 (13.9 Mg·ha<sup>-1</sup>) = lowland NF/GA001 (13.4 Mg·ha<sup>-1</sup>) > lowland Alamo (11.5 Mg·ha<sup>-1</sup>) > upland Cave-in-Rock (6.1 Mg·ha<sup>-1</sup>). There was no effect of N rate on tissue mineral concentrations but there was an N rate effect on Ca and Mg removal. Also, N use (biomass yield produced per unit N applied) and recovery (N removed in biomass) declined as N rate increased. Total ethanol yield was the greatest in Alamo (165.8 L·Mg<sup>-1</sup>) and averaged 162.0 L·Mg<sup>-1</sup> for the other three genotypes. Total ethanol production was related more to biomass yield than chemical composition differences and was similar among lowland genotypes but different from Cave-in-Rock in 2008 (1.7 vs. 0.9 kL·ha<sup>-1</sup>) and 2009 (2.6 vs. 1.1 kL·ha<sup>-1</sup>). Feedstock grown from lowland Alamo, NF/GA001 or NF/GA992 produced greater biomass yield and ethanol as well as greater N use efficiency and recovery. These results indicate that there is opportunity to increase switchgrass biomass production through genotype selection and N management.展开更多
Cardinal temperatures for plant processes have been used for thermotolerance screening of geNotypes, geoclimatic adaptability determination and pheNological prediction. Current simulation models for switchgrass (Panic...Cardinal temperatures for plant processes have been used for thermotolerance screening of geNotypes, geoclimatic adaptability determination and pheNological prediction. Current simulation models for switchgrass (Panicum virga-tum L.) utilize single cardinal temperatures across geNotypes for both vegetative and reproductive processes although intra-specific variation exists among geNotypes. An experiment was conducted to estimate the cardinal temperatures for seed germination of 14 diverse switchgrass geNotypes and to classify geNotypes for temperature tolerance. Strati-fied seeds of each geNotype were germinated at eight constant temperatures from 10oC to 45oC under a constant light intensity of 35 μmol m-2 s-1 for 12 h d-1. Germination was recorded at 6-h intervals in all treatments. Maximum seed germination (MSG) and germination rate (GR), estimated by fitting Sigmoidal function to germination-time series data, varied among geNotypes. Quadratic and bilinear models best described the MSG and GR responses to temperature, respectively. The mean cardinal temperatures, Tmin, Topt and Tmax, were 8.1, 26.6, and 45.1oC for MSG and 11.1, 33.1, and 46.0oC for GR, respectively. Cardinal temperatures for MSG and GR;however, varied significantly among geNotypes. GeNotypes were classified as sensitive (‘Cave-in-rock’, ‘Dacotah’, ‘Expresso’, ‘Forestburg’, ‘Kanlow’, ‘Sunburst’, ‘Trailblazer’, and ‘Warrior’), intermediate (‘Alamo’, ‘Blackwell’, ‘Carthage’, ‘Shawnee’, and ‘Shelter’) and tolerant (‘Summer’) to high temperature based on cumulative temperature response index (CTRI) estimated by summing individual response indices estimated from the MSG and GR cardinal temperatures. Similarly, geNotypes were also classified as sensitive (Alamo, Blackwell, Carthage, Dacotah, Shawnee, Shelter, and Summer), moderately sensitive (Cave-in-rock, Forestburg, Kanlow, Sunburst, and Warrior), moderately tolerant (Trailblazer), and tolerant (Expresso) to low temperatures. The cardinal temperature estimates would be useful to improve switchgrass models for field applications. Additionally, the identified cold- and heat-tolerant geNotypes can be selected for niche environments and in switchgrass breeding programs to develop new geNotypes for low and high temperature environments.展开更多
文摘Switchgrass (Panicum virgatum L.) is considered as an important biofuel crop but further studies on factors that may have an effect on agronomic performance and energy attributes are needed to help elucidate management strategies for the crop. A 2-yr field study at the Brown Loam Branch Experiment Station, Raymond, Mississippi, USA, quantified the effects of four N application rates and four genotypes on biomass yield, ethanol yield, and nutrient removal of switchgrass. Biomass yield response to N rate was linear in 2008 and quadratic in 2009. Among genotypes, biomass yield averaged across N rate and years, ranked lowland NF/GA992 (13.9 Mg·ha<sup>-1</sup>) = lowland NF/GA001 (13.4 Mg·ha<sup>-1</sup>) > lowland Alamo (11.5 Mg·ha<sup>-1</sup>) > upland Cave-in-Rock (6.1 Mg·ha<sup>-1</sup>). There was no effect of N rate on tissue mineral concentrations but there was an N rate effect on Ca and Mg removal. Also, N use (biomass yield produced per unit N applied) and recovery (N removed in biomass) declined as N rate increased. Total ethanol yield was the greatest in Alamo (165.8 L·Mg<sup>-1</sup>) and averaged 162.0 L·Mg<sup>-1</sup> for the other three genotypes. Total ethanol production was related more to biomass yield than chemical composition differences and was similar among lowland genotypes but different from Cave-in-Rock in 2008 (1.7 vs. 0.9 kL·ha<sup>-1</sup>) and 2009 (2.6 vs. 1.1 kL·ha<sup>-1</sup>). Feedstock grown from lowland Alamo, NF/GA001 or NF/GA992 produced greater biomass yield and ethanol as well as greater N use efficiency and recovery. These results indicate that there is opportunity to increase switchgrass biomass production through genotype selection and N management.
文摘Cardinal temperatures for plant processes have been used for thermotolerance screening of geNotypes, geoclimatic adaptability determination and pheNological prediction. Current simulation models for switchgrass (Panicum virga-tum L.) utilize single cardinal temperatures across geNotypes for both vegetative and reproductive processes although intra-specific variation exists among geNotypes. An experiment was conducted to estimate the cardinal temperatures for seed germination of 14 diverse switchgrass geNotypes and to classify geNotypes for temperature tolerance. Strati-fied seeds of each geNotype were germinated at eight constant temperatures from 10oC to 45oC under a constant light intensity of 35 μmol m-2 s-1 for 12 h d-1. Germination was recorded at 6-h intervals in all treatments. Maximum seed germination (MSG) and germination rate (GR), estimated by fitting Sigmoidal function to germination-time series data, varied among geNotypes. Quadratic and bilinear models best described the MSG and GR responses to temperature, respectively. The mean cardinal temperatures, Tmin, Topt and Tmax, were 8.1, 26.6, and 45.1oC for MSG and 11.1, 33.1, and 46.0oC for GR, respectively. Cardinal temperatures for MSG and GR;however, varied significantly among geNotypes. GeNotypes were classified as sensitive (‘Cave-in-rock’, ‘Dacotah’, ‘Expresso’, ‘Forestburg’, ‘Kanlow’, ‘Sunburst’, ‘Trailblazer’, and ‘Warrior’), intermediate (‘Alamo’, ‘Blackwell’, ‘Carthage’, ‘Shawnee’, and ‘Shelter’) and tolerant (‘Summer’) to high temperature based on cumulative temperature response index (CTRI) estimated by summing individual response indices estimated from the MSG and GR cardinal temperatures. Similarly, geNotypes were also classified as sensitive (Alamo, Blackwell, Carthage, Dacotah, Shawnee, Shelter, and Summer), moderately sensitive (Cave-in-rock, Forestburg, Kanlow, Sunburst, and Warrior), moderately tolerant (Trailblazer), and tolerant (Expresso) to low temperatures. The cardinal temperature estimates would be useful to improve switchgrass models for field applications. Additionally, the identified cold- and heat-tolerant geNotypes can be selected for niche environments and in switchgrass breeding programs to develop new geNotypes for low and high temperature environments.
