SummaryDespite increased concerns regarding the heavy reliance of many cropping systems on chemical weed control, adoption of ecological weed management practices is only steadily progressing. For this reason, this paper reflects on both the possibilities and limitations of cultural weed control practices. Cultural weed control utilises a number of principles, predominantly: (i) a reduced recruitment of weed seedlings from the soil seedbank, (ii) an alteration of crop-weed competitive relations to the benefit of the crop and (iii) a gradual reduction of the size of the weed seedbank. Compared with chemical control, the general applicability, reliability and efficacy of most measures is only moderate, and consequently, cultural control strategies need to consist of a combination of measures, resulting in increased systems complexity. Combined with the trade-offs connected to some of the measures, this hampers large-scale implementation. It is argued that tailoring cultural weed management strategies to the needs and skills of individual farmers would be an important step forward. Research can aid in improving the utilisation of cultural weed control strategies by focussing on a broadening of the range of available measures and by providing clear quantitative insight in efficacy, variability in outcome and trade-offs of these measures.

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In an intercropping system with leek (Allium porrum L.) and celery (Apium graveolens L. var. dulce (Mill.) Pers.), weed suppression is improved through increased canopy light interception. Intra‐ and interspecific competition in the system, however, affects the performance of the crops with respect to yield and quality. The objective of the study was to quantify intra‐ and interspecific competition by leek and celeriac [Apium graveolens L. var. rapaceum (Mill.) Gaud.‐Beaup] or celery in an intercropping system. A 3 yr study was carried out to investigate the effects of plant density, relative proportion of component crop, spatial arrangement, and N input on biomass production, crop quality, and N use in an intercropping system with leek and celeriac or celery. Land equivalent ratios exceeding unity were found, indicating an improved resource use by the crop mixture. Relative yield totals around one showed that with respect to biomass production, no yield advantage was found in the crop mixture. Analyses using a hyperbolic yield density response model showed that the competitive ability of celeriac and celery was significantly higher than that of leek. Effects of intra‐ and interspecific competition resulted for both crops in a reduction of the quality. Nitrogen utilization efficiency (EU) was generally poor in all crop stands, particularly at a high N application rate. The intercropping system needs improvement with respect to crop quality, and it is suggested to apply ecophysiological crop growth models to maximize crop complementarity and competitive ability against weeds.

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