Epsilon Archive for Student Projects

Abstract

There is a growing interest in diversifying agricultural systems both in Sweden and globally, particularly through the use of intercropping systems with legumes and cereals. These types of systems provide potential benefits such as increased biodiversity, reduced dependency on nitrogen fertilizer, and increased resource-use efficiency. Legumes, such as faba bean, are particularly promising due to the plant’s ability to form symbiotic relationships with nitrogen-fixating bacteria, thereby reducing input needs and improving soil fertility. However, the success of these intercropping systems are dependent on functional compatibility and complex inter- and intraspecific plant-plant interactions, which in turn are strongly influenced by the phenotypic plasticity of the crop components of the intercrop.

The aim of this thesis was to examine whether or not trait plasticity of faba bean is different when it is grown in pure and mixed cultures, and whether different neighbouring crops affect the faba bean differently. Finally, to determine whether or not it is possible to predict traits and phenotypes of faba bean grown in mixed cultures from their corresponding phenotypes found when grown in pure culture. The study was conducted based on data from a field trial in Uppsala 2024 (Sweden), where two varieties of faba bean (‘Stella’ and ‘Vertigo’) were grown as pure cultures and as mixed cultures with spring oat and spring wheat, with two different fertilizer treatments (no N and +N).

Grain yield showed significant differences both between pure and mixed cultures, and with different neighbours, with faba bean overall having higher yields compared to cereals. The land equivalent ratio showed a significant difference between the no N and +N treatments, with mixture grown with no N being able to utilize a smaller land area to produce the same yield of aboveground dry biomass. Trait plasticity analysis, especially for later stages, showed significant differences for faba bean in trait plasticity of aboveground dry biomass under different fertilizer treatments for different neighbours (faba bean, spring oat and spring wheat) as well as mixtures grown with no N tending to exhibit an increased trait responsiveness to intercropping. In biomass traits for cereals, although no significant difference was seen between different neighbours or fertilizer treatments, mixed cultures tended to exhibit a decrease or suppression in trait responsiveness to intercropping.

This thesis concluded that significant effects on trait plasticity were more frequently observed later into the growing season, especially under no N treatments. This suggests a stronger contribution due to environmental factors increasing over time.