On the energy willow farming on the old peat industry areas

Pohjonen, Veli

In English

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Veli Pohjonen

Energiapajujen viljelystä vanhoilla turvetuotantoalueilla

Pohjonen V. Energiapajujen viljelystä vanhoilla turvetuotantoalueilla.

English title: On the energy willow farming on the old peat industry areas

Tiivistelmä

By the end of this century the peat industry in Finland will leave an area of approximately 50 000 hectares behind, an area where the peat mining is over and the problems of further utilization must be solved. There is still a thin bottom peat layer left above the mineral soil. This layer of 30—50 cm bottom peat is a fertile growing media for different cultivated plants. First, as an environment it is exceptionally sterile. There are no weeds, no diseases, no insects. Secondly, the bottom peat is rich, much richer than the surface peat in nitrogen and in calcium. Moreover, the drainage is still in sufficient order after the last peat mining machines. As such, these old peat industry areas are suitable for energy production at a new level: using energy willows for energy farming. Fast growing energy willows have been studied in Finland since 1973. The energy yields have been promising, from 200 GJ to 400 GJ per hectare in a year (10—20 tn/ha dry matter). The main lines of the energy willow husbandry have been established. The most important part in it is fertilization. The fertilization of energy willow growing on old bottom peats is based on the use of ash and booster nitrogen. The yearly removal in a moderate (12 tn/ha dry matter) yield is 500—600 kg/ha ash and about 150 kg/ha nitrogen. The ash is circulated again and again between the energy plantation and the burning plant (for instance district heating unit). One part of the nitrogen is released from the peat resources through mobilization. The other part of nitrogen is given as booster for the early summer growth when the mobilization rate is low. When regarding the nutrient utilization efficiency, the yearly fertilizer need for the old peat industry area is estimated to be 100—150 kg/ha nitrogen and 1000—2000 kg/ha willow ash.

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