Energy and wood production in alley cropping agroforestry systems

PosterBioenergy was the second most important source of renewable energy - after wind-energy - in Germany to provide electricity during 2012. As the German government fixed an objective of 35 % of renewable resources in the final energy consumption by 2020, biomass production will continue to increase (Böhme and Musiol, 2013). Wood, as a source of renewable bioenergy can contribute to combined or separate heat and/or power production. It can be produced on farm land in short rotation coppices (SRC), mostly with poplars and willows. Such plantations have a high tree number and short harvest cycles (3 to 6 years), reaching a total of 6000 ha in Germany. Agroforestry systems combine tree and crop exploitation on one field, offering the possibility to simultaneously produce energy wood and food products. Many authors report of the benefits of such combination, especially of the increase in productivity of both, the annual and perennial plants compared to a conventional cropping system with only trees or annual crops (Dupraz and Liagre, 2011). Other positive effects of such a system can be the prevention of wind erosion, the introduction of valuable landscape structures and raising biodiversity (Nair, 1993). However, little information can be found on the productivity of short rotation coppice in alley cropping systems. In 2008, such a system has been established with poplars near Brunswick in Lower Saxony. The border rows among the six rows of the SRC-strips are showing a faster growth than the middle rows, profiting possibly from a higher light availability. They have bigger stem diameters and after coppicing more shoots resprouting from the stool. Leeward rows can produce even more biomass than the windward rows, while no increase in ash content could be observed. Thus, short rotation coppice in agroforestry can be more productive than extensive plantations of SRC, especially due to the higher proportion of side rows contributing to sustainable energy wood production