Evaluation of switchgrass, M. x giganteus, and sorghum as biomass crops: effects of environment and field management practices

摘要

Switchgrass (Panicum virgatum L.), Miscanthus x giganteus (M. x giganteus), and sorghum (Sorghum bicolor L.) have been proposed as potential bioenergy feedstock crops. This study evaluates how these crops performs in different environments under different crop management practices, particularly nitrogen (N) fertilizer rates. Chapter 1 provides the rationale of this research and a general discussion of the unique characteristics of these three crops. In Chapter 2, an extensive database of switchgrass biomass yields from 106 sites and 45 field studies in eastern two thirds of the USA and southeastern Canada is evaluated using descriptive statistics, and using a random coefficients model. Switchgrass has been researched extensively in North America as a biomass crop and data reported since the 1990???s reveal large variability in dry biomass yields which are related to multiple environment and field management practices. This analysis describes switchgrass biomass N response, and shows that in addition to N fertilizer rate the most important factors affecting switchgrass dry biomass yields are growing region, spring precipitation, growing season, ecotype, and harvest timing. Chapter 3 remarks that studies reporting M. x giganteus dry biomass yields to date in the USA are few in number and little information is available to suggest a suitable growing region. This study investigates M. x giganteus in four Midwest and Atlantic Coast environments under three N rates. Establishment success, plant growth, morphology, and dry biomass yields were evaluated and results reveal no response to N rate during the establishment years, large biomass yield differences among environments, and decreased yield when the crop experienced a combination of high heat and dry conditions. Chapter 4 introduces two types of sorghum, forage sorghum and biomass sorghum (referred to as energy sorghum) which have been proposed as crops with high biomass production potential although prior to this study no research had evaluated these sorghum types grown for biomass in IL. This field study evaluated two forage sorghum and two energy sorghum hybrids in four IL environments under different N rates. Measurements of morphology and crop growth were measured throughout the growing season, and dry biomass yields revealed significant differences between the two sorghum types. The energy sorghum hybrids achieved the greatest biomass yields in each environment with the effects of environment and N rate affecting the biomass yields. The results of these studies provide valuable information for stakeholders, producers, and scientists regarding the impact of environment and management practices on biomass yields of switchgrass, M. x giganteus, and sorghum. It is necessary that these factors be evaluated prior to making decisions as to which crop species and which cultivar or hybrid to plant in a given location. In most cases, no regional recommendations for species selection and N fertility rates are adequate and most field management practices must be made on a site-by-site basis.