Search

A two-year nutrient omission trial was conducted on semiarid wasteland to determine the effects of nitrogen (N), phosphorus (P), and potassium (K) on the chemical composition and theoretical ethanol yield (TEY) of switchgrass (Panicum virgatum L.). The fertilizer treatments were the following: NPK, PK, NK, NP, and no nutrient inputs (CK). Results indicated that the crude protein (CP) content and protein yield of switchgrass aboveground biomass decreased significantly in the PK treatment (N omission) and the CK, compared with the NPK treatment. The omission of N, P, or K did not significantly affect the other feed and energy quality indicators. When averaged across the two years, the neutral- and acid-detergent fiber contents were lower in the NPK and NP treatments, but the CP, dry matter digestibility, dry matter intake, total digestible nutrients, net energy for lactation, and relative feed value were higher, indicating that the suitable application with combination of N and P was helpful to improve the forage quality of switchgrass. In PK and CK treatments, the contents of soluble sugar, cellulose, and hemicellulose were higher but that of ash was lower than that in other three treatments, indicating that no N application meant better quality of switchgrass aboveground biomass for bioethanol production. The TEY at NPK was 2532 L ha−1 in 2015 and 2797 L ha−1 in 2016; in particular, the TEY decreased significantly by 15.1% in PK, 14.7% in NK, 10.5% in NP, and 29.9% in CK in 2016. To conclude, N was the most limiting factor in switchgrass productivity and the combined N, P, and K nutrient supply management strategy is recommended based on the consideration of quality and quantity of switchgrass as forage and bioenergy feedstock on semiarid marginal land. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) is a C4, warm season, perennial native grass that has been strongly recommended as an ideal biofuel feedstock. Accurate forecasting of switchgrass yield across a geographically diverse region and under future climate conditions is essential for determining realistic future ethanol production from switchgrass. This study compiled a switchgrass database through reviewing the existing literature from field trials across the U.S. Using observed switchgrass data, a process-based model (ALMANAC) was developed. The ALMANAC simulation results showed that crop management had more effect on yield than location. The ALMANAC model consists of functional relationships that provide a better understanding of interactions among plant physiological processes and environmental factors (water, soil, climate, and nutrients) giving realistic predictions in different climate conditions. This model was used to quantify the impacts of climate change on switchgrass yields. Simulated lowland switchgrass would have more yield increases between Illinois and Ohio in future (2021–2050) under both Representative Concentration Pathway (RCP) 4.5 and 8.5 pathways with low N fertilizer inputs than high N fertilizer inputs. There was no significant effect of climate variability on upland simulated yields, which means that N fertilization is a key factor in controlling upland switchgrass yields under future climate conditions. [ABSTRACT FROM AUTHOR]