Switchgrass and Giant Miscanthus Agronomy - Engineering and Science of Biomass Feedstock Production and Provision - page 46

3.3.1 Giant Miscanthus Growth and Planting Sites

In central Illinois (approximately 40° N latitude), shoots typically emerge in April
[ 62 ]. Giant miscanthus is able to commence growth and photosynthesize at cool
temperatures; thus, it is able to take advantage of snowmelt and spring rainfall.
Most years, it reaches 2 m by early June and continues to grow vegetatively through
summer [ 62 ]. Peak biomass is produced in September, and the plants routinely
fl ower in late September or early October, having grown to 3-4 m. At the onset of
freezing temperatures, the plants senesce and begin dropping foliage. Harvest of the
bamboo-like stems occurs in mid-December through late March following full
senescence [ 62 ].
Several environmental criteria, especially water, soil, and temperature, need to
be considered when selecting a site for giant miscanthus production. First,
M . × giganteus responds to water. Annual precipitation and soil water retention need
to be ample enough to support the growth of this large, herbaceous plant, and
according to Richter et al. [ 64 ], available water may be the most limiting factor for
giant miscanthus growth. In European fi eld studies, it was shown that giant miscan-
thus required between 80 and 300 L of water to produce 1 kg of dry biomass. Beal
et al. [ 65 ], Dressler [ 66 ], and McIsaac et al. [ 67 ] wrote that there was more soil
moisture beneath switchgrass and maize-soybeans than beneath giant miscanthus,
indicating a higher water-use rate. Furthermore, Beale and Long [ 68 ] and Mediavilla
et al. [ 69 ] wrote that while giant miscanthus has a higher water-use effi ciency than
most C3 crops, the growth of giant miscanthus is often limited by water availability,
even though roots can extend to approximately 2 m in the soil. This is supported in
a report by Maughan et al. [ 71 ] in which the biomass yield of M . × giganteus pro-
duced in New Jersey was less in the third growing season than in the second grow-
ing season due to below-average precipitation, sandy soils, and a shallow root zone.
Moreover, not all precipitation reaches the ground; Finch and Riche [ 72 ] found that
approximately 20 % of the precipitation that fell between September and harvest
evaporated from leaves and stems. Once established, drought can negatively impact
biomass production, but the grass is normally able to survive dry periods and regrow
acceptably the following season [ 70 ], as has occurred in portions of the eastern USA
during portions of the 2010, 2011, and 2012 growing seasons. Without supplemen-
tal irrigation, the authors recommend planting “Illinois” type of giant miscanthus in
sites that receive at least 75 cm of precipitation annually.
Miscanthus × giganteus is tolerant of soils ranging from organic soils to sandy
soils [ 70 ]. Soils with pH ranging from 5.5 to 7.5 are recommended, and poor growth
has occurred on soils having an alkaline pH of 8 and above [ 70 ]. Heaton et al. [ 73 ]
recommend planting the grass on well-drained sites of medium to high fertility.
Williams and Douglas [ 74 ] recommend planting giant miscanthus on USDA NRCS
capability class I and II soils for best production with fewest inputs. While giant
miscanthus can grow on heavy, clay soils, it is important to consider the typical soil
conditions during winter harvest when wet, unfrozen sites may limit access [ 75 ].
Following planting, it commonly takes at least 3 years to reach full establishment