What is SRC willow?

Short Rotation Coppice willow is a perennial agricultural crop that is cultivated for the production of wood chips used for heat and power generation. SRC willow can be planted close to its users, thus contributing towards a local energy supply that is sustainable in the long term.

Can I grow any willow?

A SRC willow plantation consists of densely planted, quick-growing species of willow. There are a large number of species of naturally growing willow (related to SRC willow) in the northern hemisphere, around 300 in all, but only a few have a growing pattern that is suited to fast-growing SRC willow plantations. Different species of SRC willow have been cross-cultivated since the 1970s in order to produce fast-growing hybrids that are suitable for this kind of cultivation.

What harvesting result can I expect?

The production of wood chips in a well-managed, pest-free plantation can reach 8-12 oven dried tonnes of wood chips per hectare, corresponding to an equivalent energy value of 4-5 m3 oil. The energy ratio in a SRC willow plantation is high compared to other crops. The energy input in establishing, maintaining and harvesting a SRC plantation represents no more than 5% of the total energy value of the crop.

When do I plant?

Planting takes place in the spring and early summer (March-June). Harvesting takes place in the winter (November-May) The crop is harvested at intervals of 2-3 years. New shoots grow from the coppiced stools after harvesting, which means that there is no need for re-planting.

How often do I have to replant?

The life span of a well-managed SRC plantation is estimated to be more than 25 years, which means that an SRC plantation can be harvested at least 7-12 times during its life. When a SRC willow plantation is to be removed, the stools can be broken up and mulched using conventional agricultural equipment and the land can be returned to arable cropping regimes.

How do I make the willow plantation a success?

Like other agricultural crops, SRC willow needs good management if it is to grow well. The most important element of achieving a high yield in the long term is a successful establishment; any weeds must therefore be controlled effectively. Once the SRC willow plantation is established, it must also be fertilised in order to grow well. Apart from planting and harvesting, most management measures can be performed using standard agricultural equipment.

How do I determine where to grow the willow?

The site of the plantation should be selected so that the distance to end-user of wood chips is as short as possible. The fields should not be too small with a minimum recommendation of 4-10 hectares.

As with all other plants, land with good production conditions creates higher yields. The soil’s pH level should be between 5.5 and 7.5. Light or medium clays and even heavy clays are suitable for SRC willow cultivation. Sandy soils may also be suitable if the plants have access to water or organic nutrients can be applied to provide moisture retention.

SRC willow grows well in organic soil, although such soil is often difficult to manage in terms of controlling weeds. Organic soils are often also at low altitude, e.g. frost hollows, river flood plains and valley bottoms. If there is a high risk of frost, varieties that are more resistant to frost must be used.

Small parcels of land in areas surrounded by forest should be avoided, as there is a high risk of damage by game. Fields with pronounced undulations and steep inclines can make harvesting difficult and should therefore also be avoided. (Slopes Max 25%)

Archaeological and nature conservation interests must be taken into consideration before you create plantations. As SRC willow will probably be growing on the same site for more than 20 years and the shoots can reach a height of 7-8 metres, it is important to consider how the plantation affects the profile of the landscape.

The local authorities and relevant environmental agencies may have views on this matter. It is therefore a good idea to get  an understanding of the suitability of a plantation before submitting an application for planting grant and support to the relevant government body. In the right location, SRC willow can make a positive contribution to the profile of the landscape.

In an open landscape, dominated by annual agricultural crops, a SRC willow plantation provides a new environment, where a wide biodiversity of plants, birds and mammals can become established.

How do I prepare the land?

Land preparation in the year before planting is very important in terms of eradicating ‘couch grass’ in the first instance, as well as other perennial weeds. You control the couch grass  with a glyphosate preparation during the summer. If the area is covered by an arable crop the year before planting, the weed can be controlled after harvesting using the same

glyphosate preparation and suitable ground cultivation. The field must be ploughed during the autumn. If there is any couch grass remaining in the spring, an additional spraying with glyphosate may be undertaken, as late as possible before planting. The couch grass must have grown 3-4 leaves for spraying to take effect. It is important here that the ground is not worked before spraying, if at all possible.

Before planting the land must be harrowed as before normal arable seeding, a well-prepared seed bed means that the earth closes firmly around the willow cutting and counteracts drying out of the cuttings. The depth reached by the harrowing process must be 6-10 cm, this is particularly important in heavy clays. Large stones must be removed from the field, as the harvesting machines cut the SRC willow stems using saw blades, and any stones present make the harvesting process extremely difficult.

 How do I plant?

The planting material consists of one-year-old SRC willow rods. These are prepared in the winter and stored until planting at -4°C in a cold storage room, before being delivered in boxes a few days before planting. It is important that the boxes are kept in shaded, cool conditions during planting. Maps should be produced of the areas to be planted so that growers and contractors can easily plan the planting program. Reference to access routes and the direction of rows, boundary zones and storage must be included on the map.

Planting takes place from mid March until mid-June and should ideally start as early in the spring as ground conditions and the weather permit. Weather permitting, the planting season may be extended to the end of June. Early planting means better prospects of good establishment and healthy growth during the first year.

SRC willow is planted in a twin row formation. The distance between the rows alternates at 75 and 150 cm respectively. The distance between the rows is adapted to allow the harvesting machines to harvest two rows at a time, while at the same time allowing space for harvesters to move through the plantation. The distance between the plants in the rows is approx. 59–65 cm.

Planting takes place using a machine that, in one process, cuts the willow rods (1.8 – 2.4metres long) into cuttings and then plants them. The cuttings are around 18 cm long, and when planted the cutting is pressed down into the prepared ground so that only 1-2 cm protrudes above ground level. This provides the cutting with good soil contact and minimizes the risk of drying out. The total number of cuttings planted per hectare is around 15,000.

It is important to plan the planting process with care, so that management and harvesting can be performed

as rationally as possible, and also to achieve the best possible utilisation of the space in the field. The rows should therefore be laid out so that they are as long as possible, and ideally the end of the row should be at a track or similar access route. At the end of the row there must be a turning area of 8-10 m, as the harvesting machines need space to be able to turn. If facing deep ditches, the turning area must be 10 m, otherwise 8 m is sufficient. A boundary zone of around 3 m is left around other parts of the plantation.

How do I control the weeds after planting?

Controlling weeds during the establishment phase of SRC willow is extremely important. Weeds have a negative effect on the SRC willow plants as they compete for light, water and nutrition. In a plantation with a lot of weeds the SRC willow plants will be weaker and will grow more slowly. Controlling of weeds during the planting year takes place in both chemical and mechanical methods.

Directly after planting, before the cuttings have started to produce shoots (ideally within one week), the field should be sprayed with a suitable soil herbicide to prevent weeds spread by seed from developing. Later in the season, once the effect of the herbicide has worn off, mechanical measures may be required to keep the weeds under control.

If weed control is performed solely with a cultivator or similar weeder, the recommendation is to perform three cultivations during the season. If a weed harrow is used, however, 6-8 cultivations are recommended. The type of tool used is less important, the main thing is that control is performed and that weeds are kept in check. Whichever tool is used, it is important that the first round (and subsequent ones) is (are) undertaken in good time in order to be effective.

To decide whether it is time to deal with weeds, the following rule of thumb may be of help: control the weeds mechanically if there are 2-3 weeds higher than 2 cm under the palm of your hand. In the UK, this method of weed control is not standard  procedure.

How do I perform weed control?

If the weeds are not fully in check after the planting year, it is important that you also perform mechanical control the following year. As the SRC will be better established by then, as a rule it will be sufficient to perform two rounds at the beginning of the season using a cultivator or similar weeder in order to allow the plants to outgrow the weeds. If required, it is also possible to use chemical control in a growing crop, for example against

thistle and or against grass weed. The chemical weed preparations that can be used in SRC willow plantations will, however, often have a relatively minor impact and successful weed control prior to planting is highly recommended.

If weed control has been effective during the establishment year, no additional measures are required subsequently. In this phase the SRC will have developed a larger root system and will form a lot of new shoots, which together provide effective shade over the weeds. If weed control has been less successful, it may be necessary to perform some additional mechanical control, e.g. after a harvest.

Do I need to fertilize?

Once the SRC willow plantation is established fertilization may be required. If so it is  usually nitrogen that may need to be added. Nutrition can be added in the form of either commercial fertilizer or sludge from local waste treatment plants. However, sludge must be supplemented with extra nitrogen fertilizer. The need for nitrogen varies, depending on the age of the stock and the development of shoots. In older plantations nitrogen will

be released from the layer of fallen leaves that is formed, which means that the need for fertilization is reduced. In principle, it is the amount of nitrogen contained in the shoots that is removed during harvesting, that must be replaced by fertilization. In the UK, however, this application is extremely rare.

 What about harvesting?

Iggesund will supply a harvester that works efficiently and also provide transport for the harvest to the bio mass boiler in the mill.

If I’m interested in growing willow and selling it to Iggesund, whom do I contact?
Send an email to energycrops@iggesund.com or phone our specialists at 01900600122 and set up an appointment.