08.08.2015   Fertilization

Cultural Practices

4.3.1 Establishment

Successful establishment is critical for Miscanthus because it ensures biomass production in the year of planting [63-65], which in turn improves its frost tolerance in areas such as northern Europe [24]. In addition, a well established crop ensures rapid growth in the second year, with more nutrients translocated to the rhizome upon which winter survival and re-growth depend [24, 66, 67].

The sterile hybrid Miscanthus x giganteus, which must be vegetatively propagated, makes up the majority of Miscanthus currently cultivated in Europe [65]. Miscant — hus x giganteus is propagated using either macro or micropropagation methods. In macro­propagation, small rhizome sections are obtained through mechanical division and planted out. In micropropagation, plantlets are generated via tissue culture and then established in the field. Other genotypes, such as M. sinensis, can be propagated either vegetatively or by seed [68,69].

Table 4.2 Summary of optimal conditions to ensure good establishment of Miscanthus by rhizome (based on Miscanthus x giganteus) or by seeds (based on Miscanthus sinensis).

Seed of M. sinensisa

Rhizome of Miscanthus x giganteus

Soil temperature

Base temperature: 8.3-11.6°C [65, 68]

Recommended temperature >16°C [65, 68] but optimum temperature 25°C [68, 70]

Light and fluctuating diurnal temperatures enhance germination [71,72]

Base temperature: 8.5°C [73]

Optimum temperature: 25°C [74] Recommended date in Northern Europe from March until May [24, 75, 76]

Soil moisture

Base water potential: -1.46 Mpa [68] Cultural practices to keep soil moisture: Irrigation [65, 77], fine seedbed [77], rolling seedbed [77], mulch [77]

Soil moisture recommended >40%

[78, 79]

Cultural practices to keep soil moisture: Irrigation [39, 66, 74], fine seedbed [78], rolling seedbed [78], mulch [74]

Planting depth

Sowing depth proposed [77]: 10 mm

Planting depth: at 100 mm [67, 80]

and density

Sowing density proposed [77]:

500 seeds m-2

There is no study on the optimal depth and density; the values proposed are order of magnitude from Christian et al. [58]

Planting depth if high risk of frost: 200 mm [75, 81]

Planting density 1 -4 plants m-2

[6, 24, 39, 68, 69]

ph

4 < pH < 8.5 [70]

5.5 < pH < 7.5 [76]

Plant material

Seed characteristics:

Rhizome characteristics:

quality

Seeds are very small (250-1000 mg for 1000 seeds) [39] and have low nutrient reserves

Large seeds have faster germination [70] Heavy seeds produce larger seedlings [19] Breaking dormancy:

1-10 ppm giberrellic acid [70]

Chilling seed [19, 68]

At least 100 mm and optimum 200 mm

[75]

At least 20-40 g [67, 79] optimum 60-75 g [67]

Minimum 2-3 buds [76]

5-yr old [69]

Storage

Cold storage 4°C [19, 68]

<4°C until 4 mo [74, 79]

Weed control

Chemically [39, 82, 83] or manually [74, 75]

Chemically [39, 82, 83] or manually [74, 75]

Machine

Seed drill [77, 84]

(modified) potato planter, bespoke planter [76, 78, 79]

aCombination of several studies on different genotypes ofM. sinensis.

Successful establishment depends on many factors acting individually or in combination [63,64] (Table 4.2).

Rhizome or macropropagation appears to be the best propagation method because:

• Seed production is limited in northerly latitudes where the growing period is too short to ensure sufficient flowering and fertile seed production. Soil temperatures in spring in some areas such as northern Europe (Denmark, UK, etc.) are not high enough for seed germination [64,65, 75].

• Micropropagation results in a lower survival rate during winter of the first year [66, 75, 84-86] and is more expensive [64, 69, 75] than macropropagation. It is more suited to areas such as southern Europe with mild winters and low frost risk.

• Stem segment propagation requires high temperatures (about 25-30°C) to be successful [64,87]. Such conditions are not achieved in temperate climates. This method also results in lower emergence rates than rhizome propagation [87] and is impractical as the best time to cut stems is in late summer while planting occurs in spring, making it necessary to store the stem-propagated plants over winter [75].

Much of the research on establishment of has been done in Europe, where Miscanthus is being investigated as a bioenergy feedstock [88, 89]. However, the findings can be transferred to other environments, such as North America [39].