Use of waste water sludge and wood ash as fertiliser for Salix cultivation in acid peat soils
‘Silava’ Latvian State Forest Research Institute, Riga iela 111, Salaspils, LV–2169, Latvia; e-mail: email@example.com
Two problems have become more topical in recent years – production of solid biofuel from wood and the utilisation of ash and organic waste, including waste water sludge. The purpose of this research is to model simultaneous solutions for both of these problems through their use as fertilizer and to identify useful indications for the use of waste water sludge and wood ash as fertilisers. Opportunities to boost the efficiency of the applications of waste water sludge by combined spreading with wood ash are addressed in this study. An experiment is carried out in vegetation pots with different proportions of peat, sludge and ash to determine the impact of stem and root system development related to chemical and nutrient availability. Due to these studies, it is determined that waste water sludge has a comparably small liming effect. The fertilising effect of sludge can be increased by the admixture of wood ash and dolomite. These materials reduce the acidity of the soil and provide additional nutrients. Using dolomite as a liming material in the amount of 10 t ha-1 secures a change in pH of 0.6–1.2 units in peat soil. Significant changes in pH were found just a few centimetres into the upper layer of the soil. The application of an equal amount of wood ash produces a faster effect in terms of neutralisation. The limiting element is phosphorus. However, the mineralisation of peat increases the percentile proportion of all mineral elements in substrates as well as heavy metals.