Radiation and nitrogen use in wheat and oilseed rape crops

Raising yield potential of crops with an efficient use of nutrients is imperative, given the prospects of increase in world population and the need to reduce environmental problems. Yield potential is proportional to the total biomass of a crop, which is highly responsive to nitrogen supply. In this thesis, the response of biomass formation to nitrogen availability and the possibilities to manipulate it to increase yield potential were investigated.The study was focused on wheat ( Triticum aestivum L.) and oilseed rape ( Brassica napus L.), the most important winter-spring components of cereal-oilseed rotations of temperate regions. Experiments were combined with models of explanatory nature. It was demonstrated that in oilseed rape there is scope for raising biomass and yields by prolonging the duration of leaf area during reproductive stages. In wheat, the improvement in the capacity to produce biomass will have to rely on future breakthroughs of photosynthesis at the leaf level. In both crops, selecting genotypes with high capacity to form reproductive organs is essential for the expression of potential production in a high CO 2 -world. The chances of application of these findings by crop breeding and nitrogen management are discussed.