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Production technology of the Swedish energy willow varieties


1. Permission process and grant of the plantations

2. Basic issues in the planting and maintenance of a successful plantation

3. Choosing and preparation of the field

4. Quality requirements of the propagation material

5. Time and implementation of the planting

6. Weed-control

7. Nutrient-supply

8. Plant protection

9. Yields

10. Harvesting work

11. Life expectancy of the plantations

12. Deforestation of the plantations

 Permission process and grant of the plantations

Character of the grant:

For the establishment and the maintenance until the first yield a support can be applied that is not to be refunded.

Extent of the grant:

a, 40% of the total eligible costs of the investment;

b, 50% of the total eligible costs in case of a young agricultural producer or of an area with disadvantageous parameters;

c, 60% of the total eligible costs in case of a young agricultural producer and of an area with disadvantageous parameters;

The size limit of the supported field is at least 1 ha (the plantation has to be permitted in case of a field size above 0.15 ha).

Condition of the grant:

a, a valid planting permission. The application has to be addressed to the authorized regional Central Agricultural Office. The application can be submitted continuously.

Following have to be attached to the application:

- the approval of the owner (in case the field of plantation is not owned by the planter itself)

- plantation plan, that contains the definition of the applied variety and species, a declaration on the source of the used propagation material, a description of the technology (prepared by the nursery) and a copy of the maps;

b, the size of the undertaking exceeds 4 ESU (in case of starting enterprises it has to be undertaken that this limit will be achieved at least at the end of the first calendar year after finishing the investment);

c, the plantation has to be finished within 12 months after the reception of the grant decision;

d, the planter is obligated to maintain the plantation at least 5 years after the plantation;

e, The yield of the plantation has to be harvested within five years after plantation;

f, the planter disposes of a pre-agreement or agreement on the sales of at least 50% of the produced material and at least for 5 years, or in case of own use of the produce material he declares about this utilization;

g, before the last payment request the planter has to take part in a training.

Submission of a grant application:

According to the valid regulations (2011) grant applications have to be submitted between the 1st October and the 15th November.

Following documents has to be attached to the application:

- planting permission,

- a notified copy of the primary producer card or individual undertaking card,

- a custom block-map on which the boundary of the energetic plantation is marked,

- the agreement on the sales of the wood chips,

- in case of grant applications exceeding 15 M HUF a business plan.

Payment request:

Payment requests have to be submitted together with the standard field based subvention application until the 15th May. Further pay-off requests related to the established and in May registered plantations can be submitted between the 1st and 31st August. The map with the borders of the established plantation and a confirmation about the participation on the training has to be attached to the payment request.

 Basic issues of the successful establishment and maintenance of the plantations

Rentable and well operated plantations can only be established by highly observing production technology.

Parallel to the appearance of energy willows in the market there has been a trend that overemphasized the extensiveness and frugality of these plantations and suggested that in case the propagation material is planted – no matter how the soil is – the plantations do not need any concerning and they only have to be harvested. This approach is proper at all. The tokens of the successful willow plantations are the right choice of the plantations field, the soil preparation, the adequate time and method of the planting with quality-propagation material and the correct weed-control technique. Following chapters will clear these issues.

Willow plantations have to be cultivated carefully and with due foresight from the soil preparation works through the planting until the middle of the first vegetation season! The key-issue of the success of our plantation is that it has to be free of weeds until the end of June in the year of the establishment. And this issue needs intensive care and cultivation.

After the first harvest plantations need to be fertilized, because a high amount of the macro- and micro-element content of the soil is extracted with the high biomass yields. Mineral fertilizers can be used for this purpose, but it is far cheaper, effective and useful to bring out sewage sludge to the fields as fertilizer material. It is only possible to bring out the fertilizing material in a few months after harvest. In case this movement is default, we cannot count on high yields in the next season. We will clear the fertilizer dosages in the chapter about nutrient supply.

3. Field-selection and soil preparation


It is worth to establish a willow plantation on fields with rather high soil water level or where the amount of the precipitation in the vegetation period is square high in the average of several years. Field with periodical water cover – due to floods or polder are also suitable. Different meadow and moorlands, humus-sandy soils, sandy loam soils are also considered to be suitable. But the alkaline soils, soils with high CaCO3-content or too low organic matter content can be a reason for the exclusion from the plantation.

As a general practical rule it can be stated that willows are suitable for fields on which maize is mostly yellow, backward and cannot yield rentable because of the high soil water content. Due to the high soil water level or polders the iron-uptake of the plants, therefore their photosynthetic activity stays back. In case this is related to a high calcium-content, this effect is much more intensive. But willows are not sensitive to iron-deficiency that is caused by anaerobe soil conditions and they grow better under higher soil water-content. Therefore it is expedient to replace uneconomic crop production with filed wood chips production on such fields.

The field condition is of great importance as well! After pre-crops like cereals or maize the field can be brought to a state that is suitable for planting in a lower cost-level and there is enough time until the next spring – the time of the planting – to execute these tasks. In case of grasslands, reeds, bushy fields it is almost impossible to prepare a suitable soil for planting within some months.

Grasslands are also turned to plantations. The cultivation of these grasslands has to be started already in the middle of the summer in order to establish suitable soil conditions for the planting. As a first step to this a total weed control and after 2-3 weeks soil cultivation with disk harrow (from more directions and several times) have to be executed. Plough the soil in September-October. By the application of nitrogen-fertilizers and bacteria preparations before the ploughing we can accelerate the degradation of the grassland-residues.

What shall we do if we have a plough-land quality field? In this case it’s easy. After the harvest we have to prepare the soil with a disc harrow. Sometimes it is useful to smash the plant residues or apply the disc harrow several times, or even at right angles. After this movement only minimal plant residues can remain on the soil surface. The soil of the field has to be ploughed later (in October-November) in order to have a perfect soil rotation. The length of the cutting is about 17-18 cm. The basic soil cultivation has to be two-times deeper. Therefore there is no need for a real deep plough, bet the digging the soil in a 20-25 cm depth is not allowed either.

It’s recommended to make the plough already in the autumn – in adequate soil moisture level state – even by using disc harrow or cultivator. It is important not to work either by too high or too low soil moisture content! Mounds prepared by the plough have to break up and a loose earth has to remain. No plant residue shall be turn up on the soil surface at this time at all. Making the soil even already before winter is important because the planting will be implemented early (in March-April of the following year) and the soil moisture level will possibly not allow a quality preparation operation at that time.

In the springtime we can plant into the even, in the winter well-prepared soil, but in case the soil properties allow we may refresh the soil in the springtime by a disc harrow or cultivator.

It’s not necessary to use germicides either before planting or later. The fertilizer amount – based on the soil science professional advice or our subjective opinion – shall not be applied before plough, but before making the soil surface even after plough, because willows have their root system in the upper soil level (80% of the roots are placed in the upper 40 cm level) and the nutrients that would become deeper would be only later –after the half of the vegetation period – available.

Before starting the planting it is recommended to make a test planting by hand. The 18 cm long cuttings shall easily placed down into the soil. In case it’s not the situation a cultivation of this layer is necessary.

4. Quality requirements of the propagation material

Willows are planted with cuttings (without any roots). The cuttings of the licensed varieties are produced according to the – by us – elaborated technology at our mother plantations.

The EU regulation that is applicable to the willow cuttings is the following:

- cuttings shall be at least 17 cm long

- the size of the diameter of each cutting at the basic end has to be at least 8 mm

- the size of the diameter of each cutting at the basic end shall not exceed 23 mm

- the number of the traces of the pruning of secondary shoots shall not exceed 3

- cuttings shall be of the same variety, clean and free of pathogens

- cuttings shall be in hormonal dormancy stage at the time of the planting

- the origin of the cuttings shall in every case authentically confirmed with a certification

The increased thickness parameter cuttings of the Holland Alma Ltd: The Holland Alma Ltd. provides its own-produced propagation material to be of higher quality than any other inland or foreign propagation material. Therefore our partners get greater technological freedom, better growth and greater yield.

Therefore we have developed a production technology in our mother plantations and use a treatment technology for our cuttings that enables us to produce a cutting quality that is higher than the EU prescriptions.

What kind of plus values do we add?

In case of the ready-to-plant cuttings our cuttings are thicker than the EU norms. We have raised the prescript cutting diameter values of 8-23 mm to 10-30 mm level. What have enabled us to do so? It’s been the exact weed-control measurements of our mother plantations. These plantations are free of weeds, their state and condition is excellent. During the treatment of the cuttings we simply sort out the cuttings that are below the 10 mm limit. Why is it recommended to use thicker cuttings? The larger the diameter of the cutting is, the more nutrients and energy is contained in it to have a successful growth. The thicker a cutting is, the more shoots in the first year are produced. Cuttings with 8 mm diameter produce only one shoot in general, while those of 10-20 mm there are two, and in case of cutting above 20 mm there are 3-4 first-year shoots. In the first year willows produce almost only height growth and it is the second year where shoots build up the main part of the biomass. 80% of the biomass is incorporated one year later than the plantation is executed. Therefore it is not all the same for us whether one, two or three shoots are thickening.

The upper limit of the European standard has been determined, because automatic whole rod planting machines are able to cut exactly only rods with a maximum diameter of 23 mm. These machines are not so common in inland plantations, therefore we could raise the size and the upper limit of the cuttings.

The rows of the mother plantations of the Holland Alma Ltd. are densified. According to this a secondary shooting is only in the peripheral parts if the plantations (because of the early use of light potential). Therefore minimal wounds can be seen on our cuttings where the secondary shoots have been cut away.

The 18 cm size of the cuttings can be raised until 20 cm on the request of our partners free of charge. So the cutting can be placed deeper, into the wetter soil layer.

The upper end of the cuttings can be covered with paraffin upon request that minimizes the risk of drying out after planting.

50 cuttings are collected into a bundle with the same direction of the buds. The bundles are bound with a rubber tape. The easy management and the right orientation of the bundles is assured in case of both machinery and hand planting. The 50-pieces boundless are packed into units upon the partners’ request and stored in cold store with controlled air moisture content at 2-4 °C.

5. Time and execution of the planting

The optimum time for planting the cuttings is spring. The optimal time interval ranges from the 10th March to the 5th May. Even if there is possible to execute the planting before and later than this, we recommend the planting in the early springtime.

In case of fields affected by heavy polders it is possible to apply the vegetation planting technology that has been elaborated in 2010. This technology is based upon the fact that the cuttings stored frozen are viable until October. In case of fields where the spring planting is hindered by the too high moisture content of the soil we have to wait until the field will be ready and dry enough to be cultivated. The plantation can be executed only afterwards. The most extreme precedent for a planting was the 19th July at a temperature of 33 °C. The cuttings have been put into a wet soil and they started to grow perfectly. This field could not have been cultivated during any spring. We cannot count on a spectacular growth in case of planting in the middle of the vegetation period. These plantations can be harvested only after 3-4 years.

Willows start to grow early. The effective heat unit that is essential for the burst of the buds is rather low; therefore it is essential to keep the cuttings in dormant stage in a cold store. Willows are often flower early, already in February that is followed by the burst of the buds.

Cuttings start to grow very quickly after they come out from the cold store and are planted – in case of a warm spring it takes only a few days. The too early planting has the risk that the shooting is too early and a late frost can harm the shoots. The cutting is able to regenerate at this stage, but looses a lot of energy.

The late planting is also risky. For the plants start to grow so early, we may lose days from the vegetation period by postponing the whole planting. The cuttings without roots start to develop and differentiate root promotions and adventitious roots within a few days. Still, these roots are extended only in the upper soil level. The viable root system becomes fully developed in June. This already means a significant soil volume. But until this time the moisture content of the soil is of high importance. By postponing the planting we risk not only the duration of the possible vegetation period, but the decrease of the soil moisture content and therefore the good growth as well.

Willows are planted at a row distance of 1.5 + 0.75 m and a plant spacing of 0.65 m. This means a twin-row spacing planting system in which a row distance of 150 cm is followed by a 75 cm one. The 150 cm wide rows do not mean a cultivating row, but this distance has to be used for the better utilization of the light potential in the plantation. The light demand of willow is rather high. On the other hand the gauges of the harvesting machines require this planting spacing. In case we use any other planting system, we risk the effectiveness of the machinery harvesting. In case of this planting system 14 500 to 14 800 cuttings per hectare are needed.

Steeping the cuttings from the cold store can contribute to the better start of the growth, but in case of adequate wet weather and soil conditions this treatment can be skipped. Still it is highly recommended to watch out protect the cuttings from drying out.

There are several methods for the technological implementation of the planting work. The simplest, most exact way for the planting that results in the highest growth is marking the rows by a machine followed by planting by hand. In case of careful implementation this method results in the best and the most intensive growth. It is a disadvantage that this method has a high hand work demand and the cheap, but qualified workforce is not always and everywhere available. We can calculate that a group of 10 workers plant an area of 2.5-3 hectares a day.

Among the available machines there are forestry machines that are suitable for planting the cuttings. These consist of a coulter that opens the rows, followed by a compressing roll. Some types are equipped with a filling cultivator hoe and a compressing roll as well. The area performance of these machines is 2-3 ha per day, depending on the degree of practise and the soil properties. There are two- and four-row machines. The higher performance rate is given for the four-row machines. For the operation of the machine an all-wheel drive engine is needed. The staff for the operation consists of the driver and four people, just as one person who serves the planting.

A fully automatic Danish model of a whole rod planting machine is – already in Hungary – available. The batch units of this machine cut the whole rods into exactly 17 cm long pieces and the plant distance can be adjusted exactly as well. The performance of the machine is extreme high. In case the size of the field is large enough and we don’t have to waist the time with turning the machine is able to plant 2 hectares per hour. Within an extended of in two shifts an area of 20-30 hectares can be planted a day. The machine that is available and for rent in Hungary as well is able to plant four rows parallel, but there are 6-row versions too.

For the operation of the heavy machine a front weight loaded and double wheeled engine with at least 200 HP performance. The machine has to be adjusted separately on each soil type; therefore it can be only operated by a practised stuff.

Independent from the chosen technology we have to own the criteria of the exact and good planting. The upper end of a well-planted cutting has to be placed to the soil surface level, or even better one or two centimetres below. More than one cm of the cutting can no way be seen above the soil surface level. Above this limit the planting is not acceptable. This criterion is independent from the planting method, but is depending on the basic soil cultivation and the quality of the soil preparation work!

The bed for the cuttings cannot be lumpy, for this soil cannot be compressed enough. The planted cuttings cannot be placed too loose in the soil. The soil shall be compressed enough around the cutting. It is often a mistake that the soil is compressed from above besides the cutting, but if we have a look at the side, the cutting can be seen.

Cuttings shall be placed upwards or nearly upwards in the soil. In our experiments we have revealed that the cutting placed horizontal and 10 cm below the soil surface will reach the surface level, but its latter growth and the root-development will not be adequate. The cuttings, that have been placed upside down into the soil, are also start growing, but lose a lot of energy. Therefore we pay attention during the preparation and packing of the cuttings that the buds of the cuttings face the same directions. If we have a look at the triangle-shaped buds we can easily decide which side is the upper and which one is the lower. In case we use lease-work we have to control this consequently and continuously. Please consider that for the workers the only important thing is that the cuttings are planted, but for us it is also a main point how they are placed into the soil. Planting is a work phase where the owner has to be present or at least practise continuous control.

6. Weed control

The basic issue after an exactly implemented planting is the chemical weed control of the plantations. The weed control of willows can be perfectly executed using S-metolachlor + linuron compounds. These agents ensure the first 6-8 weeks free from any weeds, but for the sake of this we have to pay attention to the following:

energia, fűz, gyommentes, tiszta, Inger, ültetvény
Such clean and weed free plantations are to be achieved. 6th week of the vegetation (variety: Inger, 2008)

- timing

- dosage/amount of the liquid/area

- perfect coverage and spraying pattern

- demand on precipitation

The exploiting growth start of the cuttings requires a chemical weed control measurement possibly on the day of planting, or maximum within three days. In case of larger fields the planting and weed control measurements are executed parallel to each other. Timing means on the one hand this, on the other hand it is related to the water demand. The substances S-metolachlor and linuron are effective only if there is an at least 10 mm precipitation within1-14 day after planting. It’s therefore worth watching the weather forecasts, as well. Compounds that inhibit the germination build a film on the soil surface, that’s why the precipitation is essential.

Compounds of these weed control chemicals may be adsorbed on the surface of the large-molecule soil organic matter and their effectiveness can decrease! Therefore it is recommended to raise the dosage to one and a half, or even two-time as high on soils with a high organic matter content. This measurement has no harmful effect on the cuttings! In case a weed control step is not properly executed in the early stage, our plantation can kept free of weeds later only by expensive and less effective mechanical weed-control practices.

A chemical agent dosage shall be applied with 300-350 litres of water per hectare. In case we apply the adequate dosage with double water amount (6-700 litre/ha) the chemicals will be less sensitive to the amount of precipitation after the application. (The film will be developed without any precipitation.) The chemicals can be applied using a field sprayer frame. We have to take care of the state of the spreader and the appropriate spraying pattern, just as the overlap of the rows next to each other.

As the future of a plantation lies in the hands of the planting team, the machine operator is the key person during the weed-control. Fancy, what happen if the operator switches to one speed higher. The amount of the chemicals, just as the liquid amount applied to an area unit will change as well. Therefore a continuous control is essential! There in no successful chemical weed control in willows without an adequate dosage in 300 litres of liquid per area unit. 

In case the chemical weed control is not appropriate – because of an objective reason, e.g. we have spared/someone has stolen the chemical, the operator drove faster than he supposed to, the amount of liquid was too low, the overlap was not appropriate, the spreader is clogged, the pressure decreased, there has not fallen enough precipitation etc. – the field has to be cultivated by a cultivator machine used in maize production. (The weed control of this plantation established in 2008 was not successful because of the lack of precipitation, so we kept the field free of weeds with a cultivator in filling position.) In case weeds are small (2-3 cm high) or even in cotyledon stage they can be easily, quickly and effectively controlled. Each delayed and late control measurement will be more expensive and less effective. Let’s imagine a totally clean plantation that is free of weeds, and strengthen efforts to achieve this state in practise.

In case we adjust the cultivator to a filling position – as the weeds are in cotyledon stage – we can achieve a 2-3 weeks weed free period. It is possible to use the cultivator until the willows bend down below the machine and the cultivator without breaking. This means until the plantation is 6-8 weeks old and a height growth of 60-100 cm. At this time the plantation itself is strong enough to fight the weeds back. Later there will be no need to apply either mechanical or chemical weed control.

Due to the early start of growth in the next years willows grow much more intensive than one or two-year, or even perennial weeds. It is a common symptom that elder plantations are often grassy, but this does not lead to serious yield problems.

The monocotyledonous weeds that possibly appear in the plantations can be controlled any time chemically in all periods of the vegetation period.

7. Nutrient supply

It is highly recommended to have a simplified soil sample analysis
on the macro element-content, plasticity, humus-content, Ca-content and pH before the establishment of the plantation. Based upon the results of this analysis the extent of the basic fertilization can easily be determined. It is recommended to use mineral fertilizers for this fertilization in the method described by the soil preparation.

In case cheap organic fertilizer is available, it is recommended to apply that before the cultivation not after ploughing, but before the basic soil cultivation in order to avoid its possible weeding effect. It is not always possible to apply sewage sludge because we do not always have enough time for the permission process of the application.

In case we do not have soil analysis data, we can only rely on our subjective opinion and decide whether we apply filling up fertilization and in case yes, with which dosages. Taking the specific nutrient demand of the willows into account it is recommended to use a nutrient rate of 3:1:2 N:P:K.

The high amount of produced – and each two or three years harvested – biomass means a high rate of nutrient uptake. We can count only on the mineralization of the organic matter of the foliage as a natural nutrient source. The high rate of produced wood chips is only sustainable in case we apply nutrient supply with mineral or organic fertilizers during the post-harvest period – when there is no plant coverage.

In Sweden nitrogen and wood ash is commonly used as mineral fertilizer. Research results from Hungary and abroad, just as the producers’ experiences confirm that willow have a low reaction degree to phosphorous and potassium fertilization. In contrast they react to the 70-140 kg ha-1 active substance plus bacteria fertilization with a spectacular yield increment in the next two years.

According to our experiences so far, the most effective and the cheapest fertilization method is the sewage sludge application. Sewage sludge is available in all regions of the country and sewage works often undertake to bear the transport costs in order to save the costs of the mitigation. The sewage sludge application is an activity for that a written permit is necessary. For this process a soil analysis is essential. The applicable dosage is determined by the soil science specialists based on the results of this analysis. According to our experiences the specialists sometimes permit the application of too high dosages. The dosages of 20-25 t ha-1 resulted in favourable conditions of our plantations. Too high – above 50 t ha-1 – dosages can cause toxic symptoms or even yield decrement.

The application of sewage sludge can be executed after each harvest from November until April. The material transported to the field shall be applied within 48 hours. In case of soils with low nutrient level the first fertilization has to be executed already after the first harvest (in two or three year old state). In case of soils with better nutrient state this measurement can be postponed until the second or even the third harvesting period (4-6years old state).

The dry matter content of sewage sludge is quite low; therefore it is difficult to manipulate the material. It is recommended to ask the sewage plants for a sludge that has already mixed with straw or mix the straw by us. The commonly used organic manure spreader machines are not suitable for sludge application. (The material is of too fluid consistency.) The composted sludge that can already be manipulated easily is not available for free at the plants, but it is still competitive with mineral fertilizers, cheap and can be easily manipulated – spread.

8. Plant protection

Both autochthonous Hungarian and imported European willow varieties and clones are damaged by several polyphag and wide-spread agents.

Among insects willows are damaged by several louse species, weevils, leaf-rolling weevils etc. Among fungal diseases rust diseases are considered to be common in willow plantations.

In countries, where willows are commonly produced no chemical measurement is applied against diseases and pests. Plant protection is not an essential part of the production technology. The chemical protection is also hindered by the fact, that there are no cultivating paths in the plantations where the machines could be performed.

As the whole biomass of the plantation is harvested every two or three years, most of the pests and diseases will also be removed from the field, so the infection centres are done away as well. Harvest can be considered as disinfection plant protection measurement.

Plant protection experts and nature conservation activists have previously considered these Swedish willow varieties as potential infection centres and as a spoiler of the ecosystems. This attitude at the beginning has already been eliminated since then.

It’s worth considering: what has changed in our home country since these Swedish willows have appeared? The breeders abroad use the same white and basket willow species as basis for the breeding program, that are autochthonous in Hungary as well. Why would that be a potential risk for the forests? No genetic modification has been applied during the breeding process.

The Hungarian plant protection specialists have come to a uniform opinion, that pests and diseases cause not so significant loss is caused that it would be worth to apply any chemical plant protection measurement against them. In order to avoid the fears and habits we often suggest our planting partners executing a plant protection spraying measurements only on the peripheral parts of their plantations.

9. Yields

After a temporary stagnation period plants start growing intensively. In case of appropriate water supply new plantations can reach a height growth of 120 centimetres until the end of May. The really intensive growth phase is between the beginning of June and the middle of September. In extreme situations willows can produce a height growth of 5-7 centimetres. This is not so surprising, since under favourable conditions an acacia seedling is able to produce such a growing intensity in August for example. At the end of the first vegetation period plants can reach a height between 3 and 5 metres. The diameter of the above-ground shoots is 10 to 30 mm, but we have measured a diameter of 40 mm at the end of the first year. Still the height growth is typical in the first year. If we take the yield of the second year as 100%, it can be stated that only 20-30% of the biomass is built up in the first year.

The rest 70-80% of the biomass growth comes from the thickness growth in the second vegetation period. In contrast to the first year, willows grow only 1-2 metres in the second year. But the average shoot diameters will be three times higher and reach values between 30 and 90 mm. Please consider that it is not unimportant whether one, two, three or even four shoots are developed in the first year, because in the second year this one or these two or three or four shoots will be thicker and that means once, twice or even three times so high yields. That’s why we have increased the thickness parameters of our propagation material. A thicker cutting = more nutrients = greater reserves = more energy = more shoots = higher yields at the beginning.

The well-developed plantations shall be harvested in the second year. This is the result of the earlier closing of the well-developed plantations and therefore the light potential becomes limited from the second year. In case a well-developed plantation is left uncut for the third vegetation period, the biomass growth will be marginal, because the photosynthetic activity will be decreased through the earlier closing.

After the first harvest each stock produces more than ten shoots. Still, this does not mean a ten times higher yield in the next vegetation period in contrast to the first harvest. Why? More shoots mean more growing points as well. The water, nutrients and energy that is transmitted by the same root-system is divided between more points. The plantation reaches the maximum light utilization rate; the photosynthetic activity starts to decrease earlier. Beside this we have to count on the concurrence between the roots. It is usually typical that in contrast to the first yields we can count on a yield increment of 30-40% from the second harvest.

Our economic calculations are based upon a quite moderate dry-matter yield (20t ha-1 a-1). The return of the plantation investments is ensured at the first harvest even in case of such low yield level. (Taking the financial planting grant and the area-based financial grant into account, as well.)

Significantly higher yields have been reported in practice. The average yields are between 20 and 30 t ha-1 a-1, that means a return even without the grants within two years. At our harvesting demonstration event on the 12th February 2010 we have measured the yield of our plantation that consists of several varieties and was of different development state. The yield was 25.2 tons of absolute dry matter per year. In our repeated experimental measurements in January 2011 the lowest yield was measured in case of the variety Gudrun (12.6 ta ha-1 a-1), while the highest was in case of the variety Inger (32.1 ta ha-1 a-1). (In its publications the Holland Alma Ltd. uses always the form ta ha-1 a-1, that means the absolutely dry biomass yield (0% water content) that was produced in one year on one hectare.)

Our measurements and experiences are confirmed by the data of the College of Nyíregyháza, the Slovakia State Forestry and the Agricultural University of Nitra.

10. Harvest

As described in the chapter ‘Yield’, energy willows are harvested each 2-3 years. Adequate developed plantations shall be harvested each two years. It is recommended to use a harvesting rotation of three years only in case the growth is poor.

As energy willows appeared there have been some people who emphasized that it is necessary to harvest the plantations each year. This is not correct because of the reasons described before. Beside this the rate of bulk and husk is also inappropriate in case of one-year-old plantations, and therefore the chips quality is low.

The harvest is executed with forage harvesters. A well-known model of this kind of machine is the Claas Jaguar that is or was available near to the larger animal farms. The factory cutting and chopping part of the Jaguar is not suitable for the harvest of woody crops. That’s why a special continuity desk and chopping part has been developed. The same construction changes have been made by other manufacturers as well. The harvest can be solved by using a smaller, one or two row, strengthened maize ensiling adapters. Harvesting machines that have been developed in Hungary are already available as well.

The row distance of the plantations ensures the optimal utilization of the available light and beside this it is adapted to the gauge of the harvesting machine. Forage harvesters are able to cut and chop plant material with 10 cm diameter. At the edge of the plantations even larger diameters may be produced – due to the better utilization of the light potential. These trees have to be cut away from the beginning and the end of the rows by a chainsaw. It can be a solution as well, if the rows at the edge and the first and last plants in each row are a variety with a less intensive growth that will not be so thick.

Harvesting machines are quite expensive and the above mentioned adapter is not cheap either. One of the main characters of these forage harvester machines is the low operation rate – especially in case of the decreasing number of animals. These machines are operated only some days a year and in the winter period – in the harvest period of the willows – they stay unused. We provide our partners assistance to find a harvesting machine and to organize the harvesting works.

The harvesting work can be executed in the dormant stage of the plants, from November until the middle of March. The water content of the plants is the lowest at this time (44-52%). During the harvest it has to be taken into account that fields with soggy soil shall be harvested on frozen days, rather than fields with drier soil. The harvester machine blows the wood chips to a plateau of a vehicle. The wood chips can be stored at the edge of the fields in prisms. The chips do not have to be store in a roofed place. This prism warms up inside but this is far from the temperature where it could catch on fire. (The size of the chips is too big, and so the prism is aired enough for that.) This warming up contributes to the natural loss of the water content of the chips. It is already economically profitable to transport wood chips with 35% water content. The drying phase to a water content of 30-35% takes approximately 4-10 weeks depending on the air temperature and humidity.

The natural precipitation enters the prism – due to the ramp angle and the chips characteristics – not deeper than 10-15 cm. This amount of water can be easily evaporated in a short time. The transport of the chips is possible when it dries to a water content of at least 35%. The transported material is loaded to self-emptying vehicles by mechanical loaders.

In 2010 wood chips was bought at a price niveau of 16 500 HUF ta-1; this price has increased to 17 200 HUF/ta-1 in 2011. The even more common heating plants, briquetting and pelletting manufactures, just as the automatic chips boilers – that are even more present beside the huge power plants may result an even higher price-increment.

11. Life span of the plantations

Among energy crops it is the willow that has the longest life span due to its extreme strong growth, resistance against shoot diseases and tolerance to cutting. The eldest plantations in Hungary are only six years old, therefore unfortunately don’t have enough own experience in this issue.

The eldest plantation that we have visited in Sweden was 48 years old. This plantation has been regularly (each 2 or 3 years) cut. The originally planted shoots and rows could be revealed even in this plantation. Rows could be seen, but the shoots have developed in a several ten centimetres circle.

Taking the Hungarian basket willow plantations as a basis, these experiences confirm the Swedish example.

It is worth to cultivate a plantation until yields do not show any significant decreasing tendency. The yield of the first harvest (in the 2nd or 3rd year) is usually lower than that of the second harvest (4th or 5th year). Yields can remain constantly high for a long time in case we apply appropriate mineral fertilization or sewage sludge. Of course an elder plantation cannot be completely homogenous. Due to the heterogeneity, yields will decrease after a while. In case this decreasing symptom cannot be stopped with reasonable expenditures, it is high time to wind up the plantation.

The gaps and empty spots in the elder plantation cannot be compensated by planting new cuttings. It is possible to fill in the gaps only in young plantations, because new cuttings do not grow so intensive as elder ones and fall back in growth.

12. Winding up a plantation

The windup of a plantation is related to the physiologic characteristics of willows. Willows do not have root offshoots, they are able to renew with shoots. Therefore it is easy to terminate the plantation with an appropriate technology. (We don’t have to count on the roots to bring offshoots, as it is common in case of acacia). It is the first step of the winding up of a plantation.

After the last harvest the plantation shall be left until it starts to grow. As shoots reach the size of 20-25 cm, the whole plantation shall be sprayed with 5-6 l ha-1 dosage of glyfosate active substance (total effect herbicide). Shoots dry within two weeks totally. At this time the field has to be cultivated by a vertical axle crusher machine. This measurement shall be followed by 2-3 heavy disc cultivation within the vegetation. Until autumn the area will be easy to be cultivated by a plough. Because of the high amount of root and shoot residues it is worth to bring out a middle large dosage of nitrogen fertilizer before ploughing. The degradation of these residues can be accelerated so. The field becomes suitable for crop production as well. The roots of the willows are easy to break that is placed mostly in the upper 40 cm soil level. The ploughing will not be hard therefore.

The other possible method is the application of a root rake after herbicides. The plant residues can also be chipped with the available mobile chippers and the material can be sold afterwards.

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