Fertilisation efficiency of wastewater sludge and the changes in soil chemical composition in energy plantations | Notekūdeņu dūņu mēslojuma efektivitāte un augsnes ķīmiskā sastāva izmaiņas enerģētiskās koksnes plantācijās
2006
Lazdina, D., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Lazdins, A., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Zarins, Z., Latvian State Forest Research Inst. Silava, Salaspils (Latvia) | Kaposts, V., Latvian State Forest Research Inst. Silava, Salaspils (Latvia)
Based on the data of 2004-2006 project supported by the Forestry Development Fund, the objective of the given study is to assess the economic efficiency of sludge fertiliser and its environmental impact with a view to developing in the future as practicable fertilisation model (including fertilisation by sludge and wood ash) to raise the efficiency of energy crop cultivation, increase the yield, and improve the quality of energy wood. Because of high nutrient content of sludge fertiliser, weed control was the major problem in the first growing season, after harvesting the shoots of the first year an abundant re-growth of annual shoots was observed with the amount of biomass 4.6-5.5 t dry mass/ha. Increased amount of biomass was observed for both the fertilised plots and the control; in the fertilised plots the average increase was 5.5 t dry mass/ha/yr. The content of heavy metals in willow wood harvested on fertilised plots was on the average by 4-8% higher than on the control sampling plots. The fertilisation by wastewater sludge increased also the content of heavy metals in the topsoil layer (0-20 cm deep), which was still below the maximum values as provided the respective regulatory acts. Proceeding from the current price level the establishment and management costs of willow plantations in the first three years are estimated at 760 LVL/ha. With the harvesting operating all the year round and the transportation distances in one direction below 40 km, the harvesting, chipping, and delivering costs are about 3.4 LVL/cu. m loose volumes.
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