**5.3. Reed canarygrass**

*5.2.4. Biomass yields and characteristics*

10 Advances in Biofuels and Bioenergy

*5.2.5. Switchgrass as a bioenergy crop*

when the soil pH is between 6 and 8 [72].

The highest biomass yields per hectare can be obtained when switchgrass is harvested once or twice per year. In fact, one- or two-cut systems often provide similar average yields [65]. Wullschleger et al. [66] compiled 1190 biomass yield observations for both lowland and upland types of switchgrass grown on 39 sites across the USA, from field trials in 17 states, from Texas to North Dakota to Pennsylvania. In this study, it was found that much of the differences in biomass yields could be explained by the variation in the growing season, precipitation, annual temperature, nitrogen fertilization, and the type of switchgrass grown in a specific region. Annual yields averaged 12.9 t DM ha−1 for lowland and 8.7 t DM ha−1 for upland ecotypes. Some field sites in Texas, Oklahoma, and Alabama reported biomass yields

The main characteristics of switchgrass biomass are listed in **Table 1**. Sladden et al. [67] compared eight switchgrass genotypes that were cut at the same maturity and found the six upland types did not vary much in their biomass composition. However, "Alamo" and "Kanlow" showed significantly lower N contents and higher fiber contents in their biomass which is explained by the later harvest date at maturity instead of differences in nutrient partitioning.

Switchgrass is established mainly by seeding. Successful stand establishment during the seeding year is essential for economically viable switchgrass as a bioenergy crop [68]. Stand failure as a result of poor seed quality or seedling physiology will have important implications on the cost of switchgrass biomass. However, weed competition is the major reason for switchgrass stand failure. Acceptable switchgrass production can be delayed by one or more years due to poor weed management and deficient stand establishment [69]. Switchgrass is readily established when high-quality seed of an adapted cultivar is used with the appropriate planting date, seeding rate, seeding method, and proper weed control. Switchgrass can be drilled in a conventional seedbed or by direct seeding methods. According to Sladden et al. [67], a row spacing of 80 cm is recommended because this led to higher yields in the second and third years than row spacing of 20 cm. Before planting, soil tests are recommended. N fertilizer is not recommended during the planting year since it will promote weed growth, increase competition for establishing seedlings, and increase economic risk and cost associated with establishment if stands should fail [70]. Economically viable yields will require N fertilization rates between 50 and 100 kg ha−1 yr.−1 [71]. N fertilizer should be given in late spring. P and K can be applied before seeding to promote root growth and encourage rapid establishment. Switchgrass can tolerate moderately acid soils, but optimum germination of the seed occurs

Weeds can be an important obstacle for switchgrass establishment, especially summer annuals. Spraying herbicides to control broadleaf weeds is usually needed only once or twice every 10 years in established and well-managed switchgrass stands. One year before planting, the field must be plowed or chiseled [63]. A reduction of weed competition can also be achieved by cutting infrequently at 10 cm. In order to control grasshoppers, crickets, and other insects

which may affect the new seedlings of switchgrass an insecticide may be needed [63].

greater than 28 t DM ha−1 using the lowland cultivars "Kanlow" and "Alamo."
