![]() ![]() Some carbon may also be stored in the soil, however the extent of this carbon storage is dependent on the carbon content of the soil to begin with. SRC has a low greenhouse gas impact as any carbon dioxide released in power generation will have been sequestered by the plantation over just a few years. Correctly managed, there is little need for pesticides or treatments.Įnvironmental impacts Greenhouse gases Small-scale production can be combined with the production of material for wicker work. This is not a relatively high-return crop, but it is low-maintenance and is a way of utilising difficult fields. The price of dry willow as a heating fuel is currently around 45 euro per tonne in most of Europe. Harvesting Poplar requires heavier machinery as it produces fewer and heavier stems. Direct chipping reduces costs as a separate chipping in the store will not be needed however, the wood chip needs to be well stored to avoid it composting. Some can be attached to a normal tractor and a hectare can be harvested in around three hours. These are heavy self-powered machines that cut and chip the shoots on a loading platform. Where wood chip is being produced it is most efficient to use direct-chip harvesters. The stems can be cut further into billets that may not need to be chipped depending on use. The stems can be dried for combustion in a pile outdoors the moisture content of the wood will decrease to about 30% on average until the next autumn. When willow or poplar shoots are harvested as whole stems they are easy to store. A plantation can be harvested for up to 20 years before needing to be replanted. A plantation will yield from 8 to 18 tonnes of dry woodchip per hectare per year. The established root system and the nutrients stored in the roots and stumps guarantee vigorous growth for the shoots. Harvests take place on a two- to five-year cycle, and are carried out in winter after leaf fall when the soil is frozen. However, in the UK grants are available to support establishment, and in Sweden an extensive scheme of subsidies was developed during 1991–1996, being reduced after that time. The primary barrier to establishing plantations is the cost as there is no financial reward for four years from a large initial investment. Saplings are left to grow for one or two years and then coppiced. The most efficient planting machines plant four rows at a time and can plant a hectare in around three hours. Planting takes place around March to take advantage of the high moisture of the soil in the spring and the amount of sunshine in the early summer. In other countries like Canada, a single row design ranging from 0.33 m between plants on a row and 1.5 m between rows (20,000 plants ha −1) to 0.30 m on the row and 1.80 m between rows (18,000 plants ha −1) is more common. In most North European countries (Sweden, UK, Denmark) and in the US, the most frequent planting scheme is the double row design with 0.75 m distance between the double rows and 1.5 m to the next double row, and a distance between plants ranging from 1 m to 0.4 m, corresponding to an initial planting density of 10,000–25,000 plants ha −1. Willow SRC can be established according to two different layouts. Saplings are planted at a high density, as much as 15,000 per hectare for willow and 12,000 per hectare for poplar. Water availability to the roots is a key determinant for the success of the SRC. Where used as a pioneer species the SRC yield may be smaller. SRC can be planted on a wide range of soil types from heavy clay to sand, including land reclaimed from gravel extraction and colliery spoil. The management of the plantations highly affects the productivity and its success. To combat pests such as brassy and blue willow beetles, as well as the fungal pathogen Melampsora (a rust), planting a carefully selected mix of varieties is recommended. Species are selected for their acceptance of varying climate and soil conditions, relative insusceptibility to pests and diseases, ease of propagation and speed of vegetative growth. ![]() Poplar is generally planted for visual variation rather than being a commercial crop, although some varieties can outperform willow on suitable sites. Typically willow species chosen are varieties of the common osier or basket willow, Salix viminalis. SRC uses said high yield varieties of poplar and willow. ![]()
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