LONG TERM YIELDS AND GAS EMISSIONS FROM POPLAR AND WILLOW GROWN ON AGRICULTURAL LAND IN DEPENDENCE TO NITROGEN FERTILIZATION

Abstract

The production of biomass for energy has been intensified worldwide during the last
years. However, its potential to face climate change is far away to be fully used yet. Agricultural
energy crop cultivation removes CO2 from atmosphere and thermal conversion of
these crops can replace fossil fuels. This form of CO2-neutral energy supply however might
be constrained by other greenhouse gases, which are released during the production and
consumption of energy crops. Poplar and willow are very promising energy crops for farmers
due to their high productivity and low demand on inputs such as of fertilizer and labour.
To evaluate the whole process chain of field wood cropping, different plantations have been
established on a loamy sand soil in Northeast of Germany in 1994 and 2008. The measuring
program of the long-term practical oriented field experiment started in 1994 includes yields,
energy gain, N2O emissions as well as ecologically relevant plant and soil constituents.
Three different fertilization rates (0, 75, and 150 kg N ha-1 yr-1) have been investigated for
poplar (P. maximovizcii x P. nigra) and willow (Salix viminalis). Based on the results of
this experiment a second experiment with reduced fertilization rates with poplar and willow
arranged in a random block design has been started in 2008. The focus of this experiment is
on nitrogen flux. Nitrogen fertilization led to leaching of nitrogen in all tests. The application
of 75 kg N ha-1 yr-1 caused an average increase of N leaching in the willow and poplar
plots of 25 kg N ha-1 yr-1 and 40 kg N ha-1 yr-1, respectively. Furthermore, all results indicate
a more effective and environmentally sound field wood production without the use of
mineral nitrogen fertilizer and a low influence of fertilization on yields.