What is Miscanthus?

The Miscanthus Giganteus (MG) crop has a straightforward growth pattern. Every year, fresh shoots are created from the underground rhizomes. By late August of the first year after planting, these shoots grow into upright, strong stems that have a diameter of up to 10 mm and reach heights of 0.5 to 1 m. The stems, which resemble bamboo canes in appearance, are often unbranched and have a spongy pith. From the third season on, the crop can grow as tall as 2.5 to 3.5 meters.

Senescence of the lower leaves and canopy closure starting in late July hinder enough light penetration. Senescence quickens after the first air frost of the fall, and the rhizome receives nutrients again. Then the leaves drop, creating a substantial layer of leaf litter. During the winter, any remaining leaf dies and the stems become relatively dry (moisture content: 30–50%). Free-standing, nearly leafless canes are still present by March, and the biomass' moisture content has dropped to under 20%, making it suitable for mechanical harvesting. Once the springtime temperatures rise once more, this growth cycle is repeated.

First-year MG grows to approximately waist height producing 2-5 canes. It grows to around head height in year two with probably 15-25 canes. It grows to about 2.4-meter height in year three with about 50+ canes. MG is in a yield-building phase over the first three years. Growth potential is dependent on temperature, the sun, the water capacity within the soil, and rainfall levels. Therefore sunlight and moisture are essential.

Yields will vary according to the age of the crop and environmental factors specific to any particular site. The crop will take three to four years to reach a mature yield (up to five years in marginal areas). After this initial yield-building phase, MG will continue for at least 15 years. The yield from the first season's growth, at 2-5 t/ha, is not worth harvesting; the stems do not need to be cut and may be left in the field until the following season. 

However, if springtime applications of translocated herbicides are planned, then the MG stems should be flailed to avoid any risk of crop uptake. From year two onwards, the crop is harvested annually. The second-year harvestable yields may range from 8-15 t/ha, and those in the third year may achieve between 16-25 t/ha or more at 20% moisture content. Harvestable yields reach a plateau after 3-4 years. The reasons for the variation in the yield building phase duration and yield in the plateau phase depend on planting material, planting density, soil type, and climate. Where moisture supply or exposure limits yield, there may be a longer 'yield-building' phase.

As a sterile hybrid, Miscanthus x giganteus (MG) cannot be planted from seeds; instead, it must be grown via vegetative materials like seedlings, plantlets, or rhizomes. Genuine MG should always be chosen over other types of Miscanthus because some of them can be invasive. It's crucial to use strong, healthy planting material. For phytosanitary concerns, only European or Mediterranean nations should be used as sources for MG rhizomes. 

The pH level of the soil should be between 5.5-7.5, and MG can be tailored to a variety of soil types. Fields need well-drained soils. The amount of lime needed to achieve the necessary pH can be determined by a soil test conducted the year before to the development of MG stands. At least six months must pass after lime application before planting MG.

In a well-established GM plantation, a plant population of 13,000–15,000 plants per hectare is ideal. Since it's advised to overplant in the first year due to the possibility that 20–30% of the seeds won't take, it's assumed that planting 17,800 rhizomes per ha (0.75 x 075 m) will result in an emergence of 13–15,000 plants per ha. This rate nevertheless provides the plant density necessary to reach optimal yields starting in year three and effectively suppresses weeds through competition while allowing for some establishment losses.

For good soil contact, rhizomes should be planted at eight -twelve  centimeters deep. Planting is typically done in late spring after the last frost. April – May is the recommended planting time (depending on geographic and climatic zone), and a longer growing season in the first year promotes rhizome growth. Early planting takes advantage of springtime soil moisture, allows an extended first season of growth, and enables larger rhizome systems to develop.

Three nutrients—nitrogen, phosphorus, and potassium—can be added at any time before or after planting and are crucial for MG's growth. Irrigation is strongly advised in dry places as it is necessary for rhizome growth and is hence essential. Controlling weeds is essential for MG, particularly in the early establishment phase. Weed competition could reduce the establishment rate or perhaps result in a complete failure of the MG stand to develop.

The year before rhizome planting, herbicide-tolerant crops should be pre-planted, followed by a winter cover crop, in order to begin weed management on the land that will be converted from fallow or grazing. To assist control weeds in the spring of the planting season, tillage, burndown, and the use of a pre-emergence herbicide are all advised.

Once properly established, the MG stand can outperform weeds and should not require any herbicide application after establishment (year two and beyond). Fertilizer amounts in the first year are recommended at the same level as growing corn. From the second-year forward, fertilizer application is linked to the removal of nutrients through harvesting, and there is a recommended rate by USDA (2011) accounting for the removal of each dry ton of MG biomass during harvest.

MG dry-matter yields can range from 15 to 25 t/he depending on the growing environment, with lower results in northern latitudes because of harsher winters. Before the field needs to be replanted, harvest can start in the second year and last for about 20 years. MG ceases to grow in the autumn after prospering in the summer. As the winter goes on, the crop's leaves fall off, and the stems begin to dry up, reaching a moisture content of about 30% the following spring.

When the moisture content is under 20%, harvesting is ideal and MG storage is simpler. Additionally, when the moisture content of biomass decreases, so does its calorific value. Early harvesting may result in a product with a high leaf content and moisture content that is inappropriate for many uses. Harvesting that is put off can harm the crop's fresh growth

So, between these two extremes is when to harvest the most effectively. MG can be harvested by cutting and chipping or by mowing and baling. If biomass is being baled, harvesting can be done with a silage harvester or a mower-conditioner. By minimizing contact with the soil and picking up leaf litter during harvest, 5 to 10 cm of stubble should be left in the field to reduce moisture and soil content in the biomass bales. In general, care must be taken when harvesting to generate clean bales that can be delivered to the energy plant for processing or combustion.