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Phytotechnology with Biomass Production
herbicides with several energy crops. They noted that M. × giganteus from
rhizomes was more tolerant than seedlings of hybrid Miscanthus.
Careful field preparation and use of a broad spectrum, short-lived herbicide such as glyphosate has been found to be important for obtaining good
vigorous M. × giganteus stands in the US and UK (Caslin et al., 2011; USDA/
NRCS, 2011). For regulatory reasons we cannot make specific recommendations for U.S. registered herbicides in Europe or Asia, and vice versa.
Song et al. (2016) confirm the essential need for strong weed control and
provide a useful example of the range of herbicides that are effective with
M. sacchariflorus in Korea. Similar results are described for M. × giganteus
(Roik et al., 2019).
Management of weeds after M. × giganteus has begun growing requires
special care to not damage the plants. Tillage methods can only be used
between rows, carefully avoiding close approach to the plants themselves.
Herbicide application must be under strictly defined conditions of temperature, soil moisture, and wind speed to meet regulatory requirements and
avoid damaging stressed plants. Because M. × giganteus is a single clone;
no genetically modified (GM) form of the plant is available to make use of
resistance to specific herbicides, unlike maize resistant to glyphosate and
dicamba.
A comparison study in Kentucky and Virginia by Smith et al. (2015b)
showed that weed competition in those two locations, on ground previously
in no-till rotations with winter cover-cropping, was not a significant obstacle
for several energy crops including M. × giganteus CVs Illinois, Nagara, and
(tetraploid fertile) PowerCane. The main difference between this study and
the earlier work in Illinois was that the soils of Illinois are richer in N, having
been in crop rotations requiring high N levels, mainly maize. They may also
have larger seed banks of weedy species.
Our first effort to grow Miscanthus in the field began May 1, 2015,
at Ft. Riley, KS (~39 N latitude). It made use of large propagules of the
M. × giganteus Bluemel strain kept 1 month or 13 months at 4°C, and smaller
plantlets grown under lights during the previous summer, autumn, and
winter. Those were grown under several conditions including soil from the
planting site, with or without fertilizer; perlite, or perlite plus vermiculite
both with 1/2 strength Hoagland’s solution. Rhizomes (60–90 g) harvested
from larger potted (~12 L) plants stored cold 6 or 18 months, and freshly harvested (from a field site) actively growing rhizomes were also tested. Some
plantlets were grown up and then stored 5 months in cold.
The site was grassland, with alfalfa, normally mowed several times per
year. All vegetation was cut to ~1–2 cm with a “weedeater” and propagules
were planted at 45 cm intervals in 11 rows, spaced 45 cm apart. Including border edges, the plot was 6 × 6 m. Fertilizer, tillage, and herbicide treatments
were avoided. Every Miscanthus plant was marked with a bamboo stick. Rain
was abundant, with three intervals of >10 cm rain, after 3 days, during the
following 3 weeks and again during 2 weeks. Weeds were trimmed down to