Wood ash and wastewater sludge recycling success in fast-growing deciduous tree - Birch and alder plantations

Due to the increasing of wood as energy renewable resource in power and heat plants the amount of wood ash as waste will increase. Wood ash contains plant macronutrient elements P, K and different elements as micronutrients, only organic and nitrogen are missing. Wastewater sludge from small municipalities is usually clean, first-class material and contains a lot of nitrogen and phosphorus. Wood ash can be a good fertiliser and a liming material not only for acid organic soils, but also for mineral soils, but with a less significant effect on the tree growth in first seasons than a nitrogen rich fertiliser wastewater sludge. The effects that wood ash and wastewater sludge have on the increment and survival of trees were tested during the years 2011 and 2012 on loam and loamy soils at plantations of black alder, birch and grey alder, and they were compared with the results collected in the previous research started in 2005. It was observed that wood ash in the first two seasons did not significantly increase the growth of silver birch, as wastewater sludge did, but it had a positive effect on the annual increment of grey alder. Fertilisation of the whole field decreased the survival of trees because of weed competition and different injuries. The aim of the study was to evaluate the growth of fast-growing deciduous trees seedlings as short rotation crop under fertilisation of wood ash, and wastewater sludge on former agricultural land.