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Doktorsavhandling, 2021

Growth and nitrogen economy of cereal-legume sole- and intercrops, and their effects on weed suppression

Ajal, James


Crop production currently faces the dilemma of using methods that increase crop yield but with adverse environmental effects, or attaining lower yields with less environmental impacts. Applying ecological principles has shown potential in finding a middle-ground of maintaining crop yield with less inputs. In this thesis, I evaluated the role of intra– and interspecific functional diversity of cereal–legume intercrops in increasing nitrogen accumulation efficiency, competition against weeds, and improving the productivity of the mixture compared to sole crops. Peabarley and faba bean-wheat species combinations were grown in the field in Uppsala, Sweden and Taastrup, Denmark as sole crops and two-species mixtures. In addition, a pot experiment with various combinations of faba bean, wheat, and a common weed was set up under semi-controlled conditions in Sweden. Both crops and weeds were evaluated for nitrogen economy, biomass accumulation, and grain yields. Using trait space analysis, I demonstrated that intercropping, cultivar identity, and environmental differences influence trait space through phenotypic plasticity. Furthermore, intercropping facilitated more N acquisition in the cereals compared to when grown in sole crop. For crop-weed interaction, pea-barley intercrop reduced weed biomass compared to the sole-cropped pea, and the weed species’ competitiveness and dominance was influenced by nitrogen availability in the soil. Based on the results presented in this thesis, there is need to pay more attention to the functional traits of species components when designing mixtures. The weed species composition should be taken into account before nitrogen addition, otherwise, the additional nitrogen may favour mostly weed growth, at the expense of the crops. This study is timely considering the current emphasis on crop production methods that use ecological principles to address challenges in arable farming.


cereal-legume; intercropping; nitrogen use efficiency; functional traits; weed suppression; crop mixtures; trait space; hypervolumes

Publicerad i

Acta Universitatis Agriculturae Sueciae
2021, nummer: 2021:54
ISBN: 978-91-7760-786-1, eISBN: 978-91-7760-787-8
Utgivare: Department of Crop Production Ecology, Swedish University of Agricultural Sciences