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"Leys"
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Diversification improves the performance of cereals in European cropping systems
In the face of climate change, cropping systems need to achieve a high performance, providing food and feed and adapting to variable environmental conditions. Diversification of cropping systems can support ecosystem services and associated biodiversity, but there is little evidence on which temporal field arrangement affects the performance of crop yields (productivity and stability), partly due to a lack of long-term data and appropriate indicators. The objectives of this study were to quantify the effect of cropping system diversification on yield stability, environmental adaptability, and the probability of diversified systems to outperform less diverse cereal-based systems in Europe. Spring and winter cereal yields were analyzed from long-term field experiments from Sweden, Scotland, and France. We investigated diversification through (i) introduction of perennial leys, (ii) increasing the proportion of ley in the rotation, (iii) varying the order in which crops are positioned in the rotation, (iv) introduction of grain legumes, and (v) introduction of cover crops. The results showed that cereal crops within cropping systems incorporating perennial leys outperformed systems without leys in 60–94% of the comparisons with higher probabilities at low fertilizer intensities. The yield stability of oat did not differ, but mean yields were 33% higher, when grown directly after the ley compared to oat grown two years later in the crop sequence under similar management. Durum wheat grown in a cropping system with grain legumes had higher yields in lower-yielding environmental conditions compared to rotations without legumes. Diversification with cover crops did not significantly affect yield stability. We conclude that diverse cropping systems can increase cereal productivity and environmental adaptability and are more likely to outperform less diverse systems especially when introducing perennial forage legumes into arable systems. Effects of diversification on cereal yield stability were inconsistent indicating that higher productivity is achievable without reducing yield variability. These novel findings can support the design of more diverse and high-performing cropping systems.
Journal Article
LEY FRANCESA DE REFORMA UNIVERSITARIA
LEY FRANCESA DE REFORMA UNIVERSITARIA Ley Núm. 88 - 978 del 12 de noviembre de 1968
Journal Article
The biodiversity effect of reduced tillage on soil microbiota
The conversion of natural habitats into farmland has been a leading cause of species loss worldwide. Here, we investigated to what extent less intensive soil disturbance can mitigate this loss. Specifically, we examined whether reduced soil disturbance by tillage in agricultural fields could contribute to soil microbial biodiversity by providing a habitat for species that are limited by conventional tillage. To do so, we studied the diversity of soil biotas from three agricultural practices representing conventional tillage, reduced tillage and no tillage. Study fields were sampled by taking a bulk soil sample at the centre and edge of each field. The soil communities were recorded with environmental DNA metabarcoding using three molecular markers targeting bacteria, fungi and eukaryotes. While these three markers represent the vast majority of biotic variation in the soil, they will inevitably be dominated by the megadiverse microbiota of bacteria, microfungi and protists. We found a significant differentiation in community composition related to the intensity of tillage. Richness was weakly correlated to tillage, and more influenced by whether the sample was taken in the center or the edge of the field. Despite the significant effect of tillage on composition, comparisons with natural ecosystems revealed that all 30 study fields were much more similar in composition to other rotational fields than to more natural habitats, oldfields and leys. Despite a slightly higher similarity to oldfields and semi-natural grasslands, the contribution of no-till soil communities to biodiversity conservation is negligible, and our results indicate that restoration on set aside land may contribute more to conservation.
Journal Article
Flow and stability of natural pest control services depend on complexity and crop rotation at the landscape scale
Increasing landscape complexity can enhance biodiversity and ecosystem services in agroecosystems. However, policies based on conversion of arable land into semi-natural habitats to increase landscape complexity and ecosystem services can be difficult to implement. Although it appears to be a promising management option, nothing is known about the effect of increasing landscape diversity through crop rotations on the delivery of ecosystem services. In this study, we examined how landscape complexity and crop rotation intensity in the landscape at different spatial scales affect the flow and the stability of natural pest control services in barley fields using manipulative cage experiments. Exclusion experiments revealed that natural enemies can have a strong impact on aphid population growth and that the delivery of pest control services is strongly dependent on the landscape context. We found that the overall level of pest control increased with landscape complexity and that this effect was independent of crop rotation intensity. In addition, the within-field stability in pest control services increased with crop rotation intensity in the landscape, although stability in parasitism rates decreased. Multiple spatial scales analyses showed that the mean level of natural pest control was best predicted by landscape complexity at the 0 center dot 5-km and the 1-km spatial scales. The stability in overall pest control decreased with proportion of ley at the 2 center dot 5-km and the 3-km spatial scales. Synthesis and applications. Our study disentangled, for the first time, the relative effects of landscape complexity and crop rotation intensity on the delivery of an ecosystem service. We show that combined management of semi-natural habitat and crop rotation can stabilize and enhance natural pest control in agricultural landscapes. Our findings have important implications in terms of management options to maintain and enhance ecosystem services in agroecosystems. They suggest that conservation of heterogeneous landscapes, characterized by a higher proportion of semi-natural habitats such as pastures and relatively small fields, is essential for maintaining and enhancing effective biological control in agroecosystems.
Journal Article
Marginal increase in nitrate leaching under grass–clover leys by slurry and mineral fertilizer
On dairy farms, fertilization of grass-clover swards ensures stable grass yields but may increase the potential for nitrate leaching on light-textured soils. The aim of this study was to quantify the N use efficiency and nitrate leaching under fertilized grass-clover leys. The study was conducted over 2 years at two sites, with increasing applications of mineral fertilizer (0–480 kg available N ha
−1
) alone or in combination with a basic application of cattle slurry. For plots fertilized with mineral N, the N soil surface balance was independent of the application rate and in the same range as for unfertilized plots (− 11 to 51 kg N ha
−1
). However, when plots were fertilized with slurry N (+ mineral N), the surplus was substantially increased owing to the fraction of organic N applied in slurry (95–100 kg N ha
−1
) and higher biological N
2
fixation inputs (55–228 kg N ha
−1
). The type of fertilizer had no effect on nitrate leaching across the full range of application rates. Nitrate leaching increased quadratically as a function of application rate, with a range of 3–117 kg N ha
−1
(0.33–17 mg l
−1
in soil solution sampled with suction cups) in the first year and less in the second year, when clover proportion was lower due to the self-regulatory nature of grass-clover mixtures. Importantly, the rate of marginal leaching increased with fertilization level: below 150 kg N ha
−1
there was no additional leaching from fertilization and at 200 kg N ha
−1
around 5% of additional fertilizer-N was leached. This is less than generally found for arable crops and thus even in intensive dairy systems, grass-clover leys are an environmentally favorable crop.
Journal Article
Field-scale monitoring of nitrate leaching in agriculture: assessment of three methods
Deterioration of groundwater quality due to nitrate loss from intensive agricultural systems can only be mitigated if methods for in-situ monitoring of nitrate leaching under active farmers’ fields are available. In this study, three methods were used in parallel to evaluate their spatial and temporal differences, namely ion-exchange resin-based Self-Integrating Accumulators (SIA), soil coring for extraction of mineral N (Nmin) from 0 to 90 cm in Mid-October (pre-winter) and Mid-February (post-winter), and Suction Cups (SCs) complemented by a HYDRUS 1D model. The monitoring, conducted from 2017 to 2020 in the Gäu Valley in the Swiss Central Plateau, covered four agricultural fields. The crop rotations included grass-clover leys, canola, silage maize and winter cereals. The monthly resolution of SC samples allowed identifying a seasonal pattern, with a nitrate concentration build-up during autumn and peaks in winter, caused by elevated water percolation to deeper soil layers in this period. Using simulated water percolation values, SC concentrations were converted into fluxes. SCs sampled 30% less N-losses on average compared to SIA, which collect also the wide macropore and preferential flows. The difference between Nmin content in autumn and spring was greater than nitrate leaching measured with either SIA or SCs. This observation indicates that autumn Nmin was depleted not only by leaching but also by plant and microbial N uptake and gaseous losses. The positive correlation between autumn Nmin content and leaching fluxes determined by either SCs or SIA suggests autumn Nmin as a useful relative but not absolute indicator for nitrate leaching. In conclusion, all three monitoring techniques are suited to indicate N leaching but represent different transport and cycling processes and vary in spatio-temporal resolution. The choice of monitoring method mainly depends (1) on the project’s goals and financial budget and (2) on the soil conditions. Long-term data, and especially the combination of methods, increase process understanding and generate knowledge beyond a pure methodological comparison.
Journal Article
Universal mechanism for Anderson and weak localization
Localization of stationary waves occurs in a large variety of vibrating systems, whether mechanical, acoustical, optical, or quantum. It is induced by the presence of an inhomogeneous medium, a complex geometry, or a quenched disorder. One of its most striking and famous manifestations is Anderson localization, responsible for instance for the metal-insulator transition in disordered alloys. Yet, despite an enormous body of related literature, a clear and unified picture of localization is still to be found, as well as the exact relationship between its many manifestations. In this paper, we demonstrate that both Anderson and weak localizations originate from the same universal mechanism, acting on any type of vibration, in any dimension, and for any domain shape. This mechanism partitions the system into weakly coupled subregions. The boundaries of these subregions correspond to the valleys of a hidden landscape that emerges from the interplay between the wave operator and the system geometry. The height of the landscape along its valleys determines the strength of the coupling between the subregions. The landscape and its impact on localization can be determined rigorously by solving one special boundary problem. This theory allows one to predict the localization properties, the confining regions, and to estimate the energy of the vibrational eigenmodes through the properties of one geometrical object. In particular, Anderson localization can be understood as a special case of weak localization in a very rough landscape.
Journal Article
Relative effects of arable land-use, farming system and agri-environment schemes on landscape-scale farmland bird assemblages
Context
Farmland biodiversity has been declining because of agricultural intensification and landscape simplification. Many farmland birds breeding in non-crop habitats use arable land as their feeding habitat (and vice versa) and understanding habitat composition and configuration at the landscape scale is important for their conservation.
Objectives
We explored the relationship between farmland bird densities and land-use characteristics at a landscape-scale (mean size 235 ha) to reveal the most important land-use elements driving avian farmland abundance.
Methods
We used bird territory mapping from 36 study landscapes across Finland to study relationships between densities of total farmland birds, open field species, edge species, farmyard species, and Farmland Bird Indicator (FBI) species, and multiple descriptors of the composition and configuration of the study landscape mosaics, reflecting the full range of available crop types, farmland structures, non-crop habitat types, and soil type.
Results
Densities of farmland birds increased with greater areas of leys and pastures, subsidized grasslands, habitat diversity, and farmyards with animals, and those effects were consistently stronger compared to effects of non-crop habitats. Positive effects of the relative area of leys and pastures in the landscape was most often consistent in the species-specific models, whereas species-level responses to other landscape characteristics were idiosyncratic, reflecting the variety of the species’ ecologies and habitat requirements.
Conclusions
We demonstrate that overall habitat diversity, and habitat elements like subsidized grasslands, pastures, and farmsteads with animal production support higher bird diversity at the level of landscape mosaics. Our results suggest that studies based on field-scale study units need to be complemented with landscape-scale studies to reveal a holistic understanding of land-use intervention impacts on farmland birds.
Journal Article