Biomass yield development of early, medium and late Maize varieties under a future climate in Lower Saxony, Germany

Abstract. Lower Saxony, with a total land area of about 46 500 km², constitutes one of the most important agricultural areas in Germany and thus within Europe. Roughly one third of its agricultural area is used for maize cultivation and as of today only few information exist on how a future changing climate will affect its local growing conditions. Thus the newly developed carbon-based crop model BioSTAR and a high-resolution regional climate data-set (Wettreg) were used to evaluate the change in biomass yields of an early, medium and late maize variety. The climate input data is based on the SRES A1B scenario, with a potential fertilization effect or better still, an increased water use efficiency due to rising CO₂ levels, taken into account. The biomass yield for all varieties was calculated for each year from 2001 until 2099 on a total of 91 014 sites. The results suggest clearly differentiated development paths of all varieties. All three show a significant positive trend until the end of the century. However the medium variety shows a statistical significant decline of 5% during the first 30 years and only a slight recovery towards +5% around the century's end. The late variety has the clearest and strongest positive trend, with partially more than 30% increase of biomass yields around the end of the century or +25% mean increase in the last three decades. The early variety can be seen as in-between, with no negative but also not an as strong positive development path. All varieties have their strongest increase in yields after the mid of the 21st century. Statistical evaluation of these results suggests that the shift from a summer rain to a winter rain climate in Germany will be the main limiting factor for all varieties. In addition summer temperatures will become less optimal for all maize crops. Only if the plants can supply themselves sufficiently with water outside of the increasingly dry summer months, when also temperatures are much more favorable, an increase in biomass yields is feasible. As the data suggests the increasing atmospheric CO₂ concentrations will play a critical role in reducing the crops water uptake, thus enabling yield increases in the first place.