Switchgrass and Giant Miscanthus Agronomy - Engineering and Science of Biomass Feedstock Production and Provision - page 50

Nitrogen has been the primary mineral nutrient examined in fertilization studies
of M . × giganteus in both Europe and the USA, usually without showing a response
[ 71 , 88 , 89 , 90 ]. The lack of N response in most cases was attributed to adequate
natural soil fertility. Clifton-Brown et al. [ 91 ] showed an inconsistent N response
over several years and attributed this to climatic effects. In Italy, Ecroli et al. [ 92 ]
reported a yield response to N in an irrigated fourth-year planting of giant miscan-
thus. Finally, Arundale [ 93 ] saw an N response in mature (after growing season 6)
M . × giganteus in Illinois. It is likely that M . × giganteus will respond to fertilization
in some locations or after a period of productive growth. In these situations, fertilizer
applications will need to be adjusted based on local testing and future experiences.

3.3.4 Harvesting Giant Miscanthus

In the Midwestern USA, M . × giganteus is usually harvested during the winter and
early spring (mid-December through late March) following full senescence and
prior to the onset of spring emergence. European researchers have recommended
harvesting in spring immediately prior to emergence because the biomass is drier,
an advantage when it is combusted [ 89 ]. Harvest yields will typically be less in
March than in December due to leaf loss and stem drying [ 94 ], and moisture in giant
miscanthus biomass in Illinois dropped from approximately 50 % in October to less
than 10 % in February [ 73 ]. Finally, in another Illinois study, Parrish [ 95 ] reported
that over three growing seasons, harvesting established giant miscanthus before
December resulted in stand decline, even when the grass was supplemented with
variable rates of nitrogen fertilizer.
Giant miscanthus can be harvested using modern agricultural equipment used for
harvesting hay, although the operation is usually slower due to crop density and
stem toughness [ 63 , 76 ]. Either a combination of mower/conditioners plus balers or
forage choppers can be used [ 74 , 76 ]. Both rectangular and round bales are used.
Rectangular bales can be easier to stack and move, while round bales may shed
moisture better. Regardless of the shape, bales should be packed tightly to reduce
the number of bales transported and maximize loads, ease stacking, and reduce the
storage area required [ 75 ]. If kept dry, bales of giant miscanthus can be stored for at
least 3 years without deterioration (authors' observation).
A benefi t of harvesting giant miscanthus with forage choppers is that for nearly
all applications, the biomass will need to be chopped prior to use. Harvesting with
forage choppers thus eliminates a step at the processing plant. Conversely, chopped
biomass can be very expensive to transport for even relatively short distances due to
a lack of density. Moisture levels for both baled and chopped giant miscanthus
should be 20 % or less to avoid heating and ensure safe storage [ 75 ].
Chapters 5 and 6 discuss the harvesting and transportation issues in detail. The
reader can fi nd detailed comparisons of different harvesting options, machinery
requirement, and machinery performance in those chapters.