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Impact of barley cultivar (including unsown controls and mixtures as cultivars) and sowing density (120, 220 or 320 seeds m −2 ) on (a) cover (mid-June) and (b) biomass at final harvest for barley and common weeds, respectively. Data shown are mean values for the treatment combinations, with error bars showing standard errors for the means.
Source publication
Background: Intensive farming affects farmland biodiversity, and some arable plants in particular. Increasing crop genetic diversity can increase crop productivity or resilience and could also benefit rare arable plants.
Aims: We examined whether barley presence, sowing density and genetic diversity impacted the rare plant Valerianella rimosa and e...
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... sub-plot contained seven 0.7 m × 0.7 m sub-sub- plots. The first and the last sub-sub-plot were positioned 2 m away from the sub-plot ends, and the other five sub-sub-plots were regularly interspersed between them (i.e. with 1.3 m gaps between sub-sub-plots; full details of the experimental sowing layout are shown in Figure S1). The sub-sub-plots within each sub-plot were assigned randomly to one of seven treatments. Five rare arable plant species were sown sepa- rately into sub-sub-plots at the start of the experiment ( Figure S1) but of these only V. rimosa germinated in suffi- cient quantities to permit statistical analysis. Consequently, here we focus only on a subset of the full experimental design: the control (crop-free) sub-sub-plots and barley sub-sub-plots, which also had V. rimosa sown into them or had no rare weeds sown in. Although an annual commonly associated with autumn-sown crops, often germinating in the autumn and over-wintering in rosette form before flowering the following summer, V. rimosa also germinates in spring, albeit to a lesser extent. In addition, whilst sometimes strug- gling to produce seed prior to the harvest of winter-sown crops, V. rimosa is more likely to successfully produce seed in spring sown crops which are harvested later ( Preston et al. 2002). Consequently, although not mimicking the most com- mon growth patterns of V. rimosa, our use of it in a spring- sown experiment was still ...
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... sub-plot contained seven 0.7 m × 0.7 m sub-sub- plots. The first and the last sub-sub-plot were positioned 2 m away from the sub-plot ends, and the other five sub-sub-plots were regularly interspersed between them (i.e. with 1.3 m gaps between sub-sub-plots; full details of the experimental sowing layout are shown in Figure S1). The sub-sub-plots within each sub-plot were assigned randomly to one of seven treatments. Five rare arable plant species were sown sepa- rately into sub-sub-plots at the start of the experiment ( Figure S1) but of these only V. rimosa germinated in suffi- cient quantities to permit statistical analysis. Consequently, here we focus only on a subset of the full experimental design: the control (crop-free) sub-sub-plots and barley sub-sub-plots, which also had V. rimosa sown into them or had no rare weeds sown in. Although an annual commonly associated with autumn-sown crops, often germinating in the autumn and over-wintering in rosette form before flowering the following summer, V. rimosa also germinates in spring, albeit to a lesser extent. In addition, whilst sometimes strug- gling to produce seed prior to the harvest of winter-sown crops, V. rimosa is more likely to successfully produce seed in spring sown crops which are harvested later ( Preston et al. 2002). Consequently, although not mimicking the most com- mon growth patterns of V. rimosa, our use of it in a spring- sown experiment was still ...
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... season cover of the weeds was significantly affected by the barley cultivar treatment (Table 1), being always higher in unsown sub-plots compared to those sown with barley (P < 0.001 for all barley varieties; Figure 1a). This negative effect of barley cover on weed cover was also demonstrated by a significant negative relationship between weed cover and barley cover (F 1,35 = 41.39, P < ...
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... harvest, there was a strong trend towards a significant relationship between barley biomass and the presence/ absence of V. rimosa (Table 1) There were trends towards sowing density and barley cultivar effects on barley biomass (Table 1), but with post-hoc contrasts showing the only significant differences being higher barley biomass at the highest compared to the lowest sowing density (P = 0.024) and a similar tendency between the intermediate and the lowest sowing density (P = 0.058). These results indicate a relatively weak effect of the sowing density and barley cultivar treatments on harvested barley biomass, with no evidence of an effect of the multiple cultivar treatment (values for which tend to be an average of those for the five components; Figure ...
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... was a highly significant effect of barley cultivar treatment on early season barley cover, and a trend towards a significant interaction effect of sowing density and barley cultivar treatment (Table 1). The significant cultivar effect resulted from higher cover of Tipple and Westminster compared to Optic (Figure ...
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... biomass at harvest was not significantly affected by the presence or absence of V. rimosa (Table 1). Despite the weak effect of the barley cultivar treatment on barley biomass, there was a highly significant effect of the barley cultivar treatment on weed biomass (Table 1). This resulted from a strong effect of simply the presence of barley on weeds: post hoc contrasts indicated that, irre- spective of sowing density, total weed biomass was sig- nificantly higher in the unsown (i.e. barley-free) sub-plots than in all sown sub-plots (P < 0.001; Figure ...
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... experiment was set up as a split-split plot design ( Figure S1). The experiment consisted of four blocks, each containing three 16 m × 13.85 m plots. Within each block, the three plots were allocated one to each of three barley planting densities: 120, 220 or 320 seeds/m 2 . The plots were themselves divided into seven 16 m × 1.55 m sub-plots separated by an unsown 0.5 m gap (for access). The sub- plots within each plot were assigned randomly to one of seven spring barley cultivar treatments: unsown control (i.e. crop-free sub-plot), sowing with one of five spring barley cultivars (Optic, Oxbridge, Sebastian, Tipple, Westminster), or sowing with an equal mixture of all five barley cultivars. All sub-plots within a plot were sown at the allocated plant- ing density. All barley seeds were obtained from seed stocks held at the James Hutton ...
Citations
... Thus, belowground temporal niche separation could have developed into aboveground competition during later growth stages. Such a shift from a positive, belowground effect early in the season to a negative, late-season aboveground effect has been observed in a study of the interactions between barley and the rare arable weed Valerianella rimosa (Brooker et al., 2018): early in the season barley had a positive, soil-driven effect on V. rimosa abundance but with time this shifted to growth suppression by barley, most likely due to light competition (Brooker et al., 2018). Besides belowground partitioning, exudation of organic acids could have played an additional role in the oat-camelina mixture. ...
... Thus, belowground temporal niche separation could have developed into aboveground competition during later growth stages. Such a shift from a positive, belowground effect early in the season to a negative, late-season aboveground effect has been observed in a study of the interactions between barley and the rare arable weed Valerianella rimosa (Brooker et al., 2018): early in the season barley had a positive, soil-driven effect on V. rimosa abundance but with time this shifted to growth suppression by barley, most likely due to light competition (Brooker et al., 2018). Besides belowground partitioning, exudation of organic acids could have played an additional role in the oat-camelina mixture. ...
Intercropping, i.e., the simultaneous cultivation of different crops on the same field, has demonstrated yield advantages compared to monoculture cropping. These yield advantages have often been attributed to complementary resource use, but few studies quantified the temporal complementarity of nutrient acquisition and biomass production. Our understanding of how nutrient uptake rates of nitrogen (N) and phosphorous (P) and biomass accumulation change throughout the growing season and between different neighbors is limited. We conducted weekly destructive harvests to measure temporal trajectories of N and P uptake and biomass production in three crop species (oat, lupin, and camelina) growing either as isolated single plants, in monocultures or as intercrops. Additionally, we quantified organic acid exudation in the rhizosphere and biological N2-fixation of lupin throughout the growing season. Logistic models were fitted to characterize nutrient acquisition and biomass accumulation trajectories. Nutrient uptake and biomass accumulation trajectories were curtailed by competitive interactions, resulting in earlier peak rates and lower total accumulated nutrients and biomass compared to cultivation as isolated single plants. Different pathways led to overyielding in the two mixtures. The oat–camelina mixture was characterized by a shift from belowground temporal niche partitioning of resource uptake to aboveground competition for light during the growing season. The oat–lupin mixture showed strong competitive interactions, where lupin eventually overyielded due to reliance on atmospheric N and stronger competitiveness for soil P compared to oat. Synthesis: This study demonstrates temporal shifts to earlier peak rates of plants growing with neighbors compared to those growing alone, with changes in uptake patterns suggesting that observed temporal shifts in our experiment were driven by competitive interactions rather than active plant behavior to reduce competition. The two differing pathways to overyielding in the two mixtures highlight the importance of examining temporal dynamics in intercropping systems to understand the underlying mechanisms of overyielding.
... The positive effects of barley on S. pecten-veneris germination could be due to favourable changes in microclimate caused by barley growth. In a previous study, Brooker et al. (2018) have found positive effects of barley on the number of seeds germinated for the rare arable plant Valerianella rimosa Bastard and that this co-occurred with a decrease in soil moisture levels. ...
Background
As agriculture has intensified, many once-common wildflowers have declined in arable landscapes, which has wide-spread implications for associated ecosystem services. Incorporation of sustainable practices, for example, growing living mulches (in-field, non-crop plant ground cover, maintained during the target crop growing season), can boost arable biodiversity, but few wildflower species have been utilised in this context.
Aims
Our aim was to determine the suitability of arable wildflower species, once considered weeds, for use as living mulches.
Methods
We first screened a number of arable wildflower species for germination when growing with a common cereal, barley (Hordeum vulgare). We then grew two (Centaurea cyanus and Scandix pecten-veneris) in pots in a glasshouse with and without barley, and grew barley alone to test the impact of the wildflowers on barley growth and biomass.
Results
Neither of the wildflowers significantly negatively impacted barley biomass. Barley initially facilitated germination in S. pecten-veneris, but ultimately suppressed the above-ground biomass of both wildflowers. However, both wildflower species were able to coexist alongside barley.
Conclusions
Our experiment provides evidence that wildflowers that were considered weeds in traditional agriculture have the potential to be grown alongside barley and could be incorporated as part of a living mulch.
... Cover crops are planted for benefits that do not arise from a final harvest of the crop itself, but arise instead from having some kind of 'cover' on the land, including preventing soil erosion and improving soil health, soil nutrient status and drainage (Bergtold et al., 2017;Snapp et al., 2005). benefits (Brooker et al., 2017) and-specific to IPM-mitigating selection for fungicide resistance by enhancing disruptive selection in the pathogen population, thereby enhancing crop protection and yield (Kristoffersen et al., 2020). ...
We review the need for increasing agricultural sustainability, how this can in part be delivered by positive biodiversity–ecosystem function (BEF) effects, the role within these of plant–plant facilitation, and how a better understanding of this role may help to deliver sustainable crop (particularly arable) production systems.
Major challenges facing intensive arable production include overall declines in biodiversity, poor soil structure and health, nutrient and soil particle run‐off, high greenhouse gas emissions, and increasing costs of synthetic inputs including herbicides, pesticides and fertilisers.
Biodiversity–ecosystem function effects have the potential to deliver win–wins for arable food production, whereby enhanced biodiversity is associated with ‘good outcomes’ for farming sustainability, albeit sometimes through negative BEF effects for some components of the system. Although it can be difficult to separate explicitly from niche differentiation, evidence indicates facilitation can be a key component of these BEF effects.
Explicit recognition of facilitation's role brings benefits to developing sustainable crop systems. First, it allows us to link fundamental ecological studies on the evolution of facilitation to the selection of traits that can enhance functioning in crop mixtures. Second, it provides us with analytical frameworks which can be used to bring structure and testable hypotheses to data derived from multiple (often independent) crop trials.
Before concrete guidance can be provided to the agricultural sector as to how facilitation might be enhanced in crop systems, challenges exist with respect to quantifying facilitation, understanding the traits that maximise facilitation and integrating these traits into breeding programmes, components of an approach we suggest could be termed ‘Functional Ecological Selection’.
Synthesis. Ultimately, better integration between ecologists and crop scientists will be essential in harnessing the benefits of ecological knowledge for developing more sustainable agriculture. We need to focus on understanding the mechanistic basis of strong facilitative interactions in crop systems and using this information to select and breed for improved combinations of genotypes and species as part of the Functional Ecological Selection approach.
The intensification of agriculture over the last century has significantly increased agricultural production per unit area, while at the same time depleting natural resources and degrading the agro-ecosystem. A new approach is needed to restore the environment to pre-industrial levels and return to nature. There is a growing awareness among scientists from different disciplines that innovations in cropping system design can be effective in promoting agri-environmental changes. Eco-engineers see the need for a renewed focus on biodiversity in the agri-environment, which is visible through the inclusion of flowers and herbs in cropping system design. Flower strips and herb/flower mulches have been shown to provide a wider range of ecosystem services through increased interactions between plant species, spatio-temporal niche diversity and greater diversity of field habitats. The Green Revolution model has helped us meet the increasing demand for food over the past half century. Achieving stable crop productivity in the future will depend heavily on our ability to design of novel farming systems that bring farming practices closer to nature.
Enhancing diversity within crop systems can have benefits including increased resource use efficiency and productivity, and increased control of weeds, pests and diseases. Some benefits are expected to operate through biodiversity-driven insurance effects, whereby enhanced diversity increases the chance that a system component can compensate for the impacts of adverse environmental conditions. Studies of insurance effects in natural and agricultural systems have provided equivocal results. As insurance effects are expected to play a key role in helping to maintain crop production in more variable future climates (for example under periodic drought), it is essential to know when and how they operate and interact with other potentially beneficial biodiversity-function effects. Using barley as a model crop, and pot-based plant communities, we studied the interactive effects of barley cultivar diversity and drought stress on plant productivity and the response of agricultural weeds, fungal disease, and aphids. Drought reduced barley and weed biomass, but there were no interactive effects of drought and cultivar diversity on plant productivity. Increased cultivar diversity enhanced weed suppression, potentially as a result of reduced functional space availability, and reduced disease severity on a susceptible cultivar; these effects were consistent irrespective of drought. Aphid responses were more complex, with idiosyncratic response patterns on individual cultivars. Overall, we found no evidence of an insurance effect of enhanced cultivar diversity for the negative impact of drought on crop productivity, but our results indicate that other positive biodiversity effects (weed and disease suppression) are maintained under drought. However, it is clear that not all potentially-beneficial biodiversity effects respond in the same manner. Field trials are now needed to explore whether a range of responses also occur in crop field settings, whether these can be expected to occur predictably under a range of environmental conditions, and how these then impact on crop production.
