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ŠUMARSKI LIST 1-2/2014 str. 56     <-- 56 -->        PDF

In plots 1, which are harvested every year at the end of vegetation, bioproductivity was found to vary. After the first vegetation in 2008, dry matter amounted to 12 t/ha (Krpan and Tomašić 2009), after the second (2009) it came to 7.87 t/ha (Krpan et al. 2011a,b), and after the third (2010) it was 9.79 t/ha. It can therefore be concluded that, in relation to the first vegetation, bioproduction manifests a downward trend. The average annual production of two-year-old indigobush is 8.19 t/ha, while that of three-year-old indigobush is 7.03 t/ha. Hence, a downward trend in bioproduction is present here as well.
A quantity of 2.68 kg seed or 1,073 kg/ha was collected in exp. plots 3. This result is tentative because a large amount of seed naturally falls off by the time of collection, as well as during collection due to shaking caused by bending the branches. According to our estimates, seed loss may amount to over 50 %. To avoid the possibility of incorrect evaluation, seed loss will not be analysed in more detail here. It is evident from the above that almost all the seed is lost during harvesting after vegetation, handling, chipping and transport and that it cannot be expected to accompany the leaves in the combustion process in energy plants.
The results of indigobush research in the third year of the project show that, despite the established downward trends in bioproductivity, the plant still retains its competitiveness in the field of renewable energy sources, particularly because it occurs and develops naturally. It does not require any agrotechnical measures, nor does it incur any costs (except for harvesting and handling costs), which are otherwise indispensable when establishing and managing energy cultures and short rotation orchards of well-known fast growing tree species.
Key words: indigobush bioproductivity, energy benefit, lowland forest ecosystems, Croatia