Competitive suppression of weeds in a leek-celery intercropping system : an exploration of functional biodiversity

<p>Late-emerging weeds, although not directly damaging the crop, may cause long-term weed management problems due to excessive seed production. Particularly in weak competitive crops with high quality requirements, such as leek, financial losses due to weed competition or weed management costs can be considerable.</p><p>Weed suppression by the crop is an important component of any weed management strategy. It is affected by crop characteristics and cropping systems design. Improving the weed suppression by increasing the canopy light interception is the basic concept underlying the research described in this thesis. To reduce growth and particularly the seed production of late-emerging weeds, an intercropping system was developed that combines leek with the more competitive celery.</p><p>The competitive relationships between leek and celery in the intercropping system and their interaction with <em>Senecio vulgaris</em> , which was chosen as target weed, was investigated in a series of field- and glasshouse experiments. Moreover, modelling studies, using an eco-physiological simulation model for interplant competition, were performed. Eventually, the design of the intercropping system was optimised through a combined mechanistic and descriptive modelling approach.</p><p>The competitive ability of celery was significantly higher than that of leek, owing to a more effective light interception. Therefore, the weed suppression of the intercropping system was considerably improved compared to the leek monoculture, resulting in a shorter critical period for weed control. The reproductive capacity of late-emerging <em>S. vulgaris</em> was strongly reduced in the intercropping system. Modelling studies confirmed the relatively greater competitive strength of celery compared to leek. Quantitative analysis showed that particularly differences in morphological characteristics, such as the early leaf area development, determined the differences in competitive ability between the crops. Further exploration and optimisation with a combined modelling approach allowed the design of a highly productive and profitable intercropping systems with improved weed suppressive ability.</p><p>The successful improvement of the weed suppressing ability through combination of morphological and physiological crop characteristics in a highly productive intercropping system demonstrates the functionality of enhanced biodiversity for weed management.</p><p><strong>Keywords:</strong> leek ( <em>Allium porrum</em> L.), celery ( <em>Apium graveolens</em> L.) <em>Senecio vulgaris</em> L., intercropping, weed suppression, modelling, functional biodiversity.</p&gt