Root dynamics and nitrogen interactions in wheat/faba bean mixtures: The effect of nutrient availability, light signaling and relative emergence time

Research output: Thesisinternal PhD, WU

Abstract

Intercropping, the practice of growing multiple crop species together, is a promising strategy for enhancing resource-use efficiency and promoting sustainable agriculture. However, it remains unclear whether spatial niche differentiation in mixed cropping systems is primarily driven by inherent root architecture differences or by plastic responses to the environment. Moreover, the specific environmental factors that trigger these changes are yet to be fully understood. This dissertation addressed this knowledge gap by exploring the potential role of environmental cues, such as nutrient availability, aboveground signaling, and the relative timing of species emergence in cereal/legume intercropping systems. It used wheat (Triticum aestivum L.) and faba bean (Vicia faba L.) as a model system, employing mesocosms of varying sizes to focus specifically on root distribution in plant mixtures.
The spatial dynamics of root distribution were examined in wheat/faba bean inter-row mixtures under varying nitrogen (N) levels in the vegetative stage. Wheat’s roots exhibited earlier and more extensive horizontal and vertical foraging compared to faba bean, positioning wheat as the dominant competitor in the vegetative growth. These results highlight the role of inherent root architecture in shaping competitive dynamics, with nitrogen availability influencing wheat’s root/shoot ratio but not faba bean’s root behavior. I further investigated this root dynamic for nitrogen uptake. Wheat showed significant phenotypic plasticity, reallocating roots to deeper soil layers in mixtures and demonstrating higher nitrogen uptake per unit root length compared to monocultures. Faba bean displayed limited plasticity, maintaining consistent nitrogen uptake across systems. Together, these findings reveal a complementary mechanism in which wheat effectively utilizes nitrogen that faba bean does not access, enhancing overall nitrogen uptake in mixtures.
The extent of root response to low R/FR conditions (via far-red light enrichment) in mixed-species environments was quantified. Specifically, wheat responded to low R/FR by producing more adventitious roots, increasing both their number and mass in shallower soil depths, leading to a decrease in D75 (the depth at which 75% of root biomass is located) regardless of the cropping system. Faba bean, on the other hand, reduced biomass allocation to roots under low R/FR only in mixture, driven by a decrease in adventitious root growth. Low R/FR counteracted the niche differentiation in root depth within the wheat/faba bean mixtures, reducing D75 in wheat while increasing it in faba bean.
Using an aboveground separator, I explored the belowground priority effect, examining how the relative emergence timing of wheat and faba bean influences root competition and resource acquisition. Early-emerging wheat suppressed faba bean’s root growth, nitrogen uptake, and biomass production, while late-emerging wheat promoted these aspects. Wheat’s root system, however, was largely unaffected by faba bean’s emergence timing, highlighting cereals' competitive dominance in mixed systems.
The final chapter synthesizes these findings, discussing their implications for root ecology, ecophysiology, and agronomy. I also reflected on the indices and methodologies, discussing their strengths and limitations in capturing the complexity of root interactions in mixed cropping systems
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Anten, Niels, Promotor
  • Evers, Jochem, Promotor
  • Schneider, Hannah, Promotor
Award date24 Jan 2025
Place of PublicationWageningen
Publisher
Print ISBNs9789465103808
DOIs
Publication statusPublished - 24 Jan 2025

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