•Intercropping systems promote complementarity between plants, legumes in particular and facilitation processes in soil.•Complementarity/facilitation processes lead to better exploitation of soil ...resources.•Plant production is positively correlated with soil microbial abundance and diversity.•Increased attention should be paid to innovative perennial systems with intercropping for facilitative root interactions.
Intercropping is a powerful way to promote a more diversified plant community in the field, thereby enabling complementary and facilitative relationships. In these systems, legumes are a key functional group, and are highly valued for the agroecological services they provide. This review identifies the different complementarity and facilitation processes in soils in intercropped legume/cereal systems and the key role of soil microorganisms in these processes.
The intercropped legumes/cereal systems reduce inter-specific competition by enhancing complementarity/facilitation processes thereby improving the exploitation of resources, which is, in turn, reflected in the increase in plant production corresponding to greater efficiency of the agroecosystem as a whole.
Plant production, including above- and belowground biomass, is positively correlated with microbial abundance and diversity. This microbial life is assumed to play a significant role in the availability and transfer of soil nutrients to plants as well as in plant health and soil fertility. Although we are currently unable to identify a reliable and exhaustive pattern of plant-microbe interactions, perhaps simply because no universal relationship exists between plants and microorganisms, reliable scenarios reveal strong trends and define the conditions required for successful intercropping systems and microbial interactions.
Given our incomplete knowledge of facilitation processes and belowground interactions, intercropping systems must learn from and apply the experience gained in successful experiments. Intercropping dynamics play a critical role in explaining the establishment of facilitative root interactions and finally suggest perennial plant associations may be more effective than annual ones.
The forecasted 9.1 billion population in 2050 will require an increase in food production for an additional two billion people. There is thus an active debate on new farming practices that could ...produce more food in a sustainable way. Here, we list agroecological cropping practices in temperate areas. We classify practices according to efficiency, substitution, and redesign. We analyse their advantages and drawbacks with emphasis on diversification. We evaluate the potential use of the practices for future agriculture. Our major findings are: (1) we distinguish 15 categories of agroecological practices (7 practices involve increasing efficiency or substitution, and 8 practices need a redesign often based on diversification). (2) The following agroecological practices are so far poorly integrated in actual agriculture: biofertilisers; natural pesticides; crop choice and rotations; intercropping and relay intercropping; agroforestry with timber, fruit, or nut trees; allelopathic plants; direct seeding into living cover crops or mulch; and integration of semi-natural landscape elements at field and farm or their management at landscape scale. These agroecological practices have only a moderate potential to be broadly implemented in the next decade. (3) By contrast, the following practices are already well integrated: organic fertilisation, split fertilisation, reduced tillage, drip irrigation, biological pest control, and cultivar choice.
•Conservation tillage in organic farming increase soil compaction.•Earthworm population doesnt increase after 10 years of conservation tillage.•Conservation tillage stratifies soil organic matter and ...nutrients in the topsoil.•Roots frequency is limited by soil compaction with conservation tillage.
It has become commonplace to consider ploughing as an agricultural practice that destroys soil fertility. Organic farmers have traditionally used the plough to till their soil and control weeds. However, there is a growing interest in adopting tillage practices without ploughing to preserve long-term soil fertility and in the hope, subsequently, of increasing crop yields. The aim of this paper is to assess if conservation tillage treatments in organic farming did in fact improve long-term soil fertility, wheat rooting and yield in a long term field experiment (2004–2015). We compared the effects of conservation tillage treatments (superficial tillage – ST- with chisel at 15cm depth and very superficial tillage – VST- at 5–7cm depth) and conventional tillage treatments (traditional mouldboard ploughing- MP at 30cm depth and shallow mouldboard ploughing – SMP- at 18cm depth without skim coulter) during 10 years on a sandy loam soil in France. To assess soil fertility, physical (soil penetration resistance, visual soil profile observation), chemical (organic carbon – Corg, total nitrogen – Ntot and available phosphorus – OlsenP) and biotic (earthworms biomass, density and diversity) soil properties were measured in 2004-5 and 2015. The effect of soil fertility on wheat roots and crop growth was also measured in 2015. VST, and to a lesser extent ST, increased Corg, Ntot and OlsenP in the upper soil layer (from 0 to 15cm) compared to ploughing treatments. On the contrary, soil compaction increased using conservation tillage treatments (VST and ST) during the 10 years of experiment, especially in the layers between 15 and 30cm depth in comparison with ploughing treatments. This effect is not offset by an increase in earthworm abundance and activities in conservation treatments. Earthworm biomass and endogeic abundance were even higher in SMP compared to ST. Soil compaction limits roots, with less roots in depth with VST (from 12 to 30cm and 48 to 70cm) and ST (from 24 to 30cm) compared to ploughing treatments. Conservation tillage treatments had positive effects on soil chemical components in the upper soil layer and contributed to the increase of wheat biomass until tillering stage. However, no wheat yield difference was found between treatments. Physical and biotic soil properties had not significantly improved after 10 years of conservation tillage. This could be due either to the insufficient duration of the experiment to foster a positive earthworm effect on soil porosity, or to the sandy soil, too sensitive to soil compaction in this organic cropping system (intensive mechanical weeding) and unfavourable for the development of the earthworm population.
Background and Aims: Organic farmers are showing increasing interest in using conservation tillage to improve the biological activities of soils. Here, we assessed whether conservation tillage in ...organic farming improves earthworm populations, root growth and soil physical quality in a sandy loam after 16 years of experiment. Methods: We compared the effect of a tillage gradient, with of two non-ploughed treatments (superficial tillage ST at 15 cm; very superficial tillage VST at 5–7 cm) and two ploughed treatments (moldboard ploughing MP at 30 cm; shallow moldboard ploughing SMP at 20 cm). Soil clod types, penetration resistance, abundance and activity of earthworms, root traits and biomass were assessed. Results: VST decreased soil compaction in topsoil (0 to 10 cm) compared to ploughed treatments (MP and SMP), but led to more compacted soil at 15 to 30 cm. Earthworm biomass (especially anecic) was higher under VST compared to MP and SMP and their galleries were better connected to the soil surface. However, there was no significant difference in the total volume of pores or diameter of galleries between 0 and 30 cm. Soil compaction in the non-ploughed treatments affected root traits, especially under VST, with lower specific root length, higher root diameter, and lower root tip elongation compared to MP and SMP. Conclusion: Biological activity did not compensate for the compaction of a sandy soil after 16 years without ploughing in organic farming. A more integrated approach (i.e. considering all 5 soil health principles) is needed to sustain soil health and functions, and meet current expectations about “ecological intensification”.
► Profil cultural method is a visual soil profile observation method to assess topsoil and subsoil structure. ► Assessment of the transition layer between top and subsoil is necessary to better ...understand subsoil rooting. ► Cracking and biological activity are closely related to root density in subsoil.
In France, agronomists have studied the effects of cropping systems on soil structure using a field method based on a morphological description of soil structure. In this method, called “profil cultural” or soil profile in English, the soil structure of the tilled layer is observed on a vertical face of a pit. Subsoil and more especially the transition layer between topsoil and subsoil have not always been given specific consideration. However, these layers undergo the effect of cropping systems through soil compaction or smoothing/smearing. A more accurate quantification of earthworm macropores and cracks in the transition layer would enable a more precise evaluation of the agronomical potential of the soil, manifest in root development or water retention. Thus, the aim of this paper is to present the profil cultural method in detail, along with the improvements we have made to quantify the ability of roots to penetrate compacted zones in the transition layer. We propose two indicators: (i) number of earthworm burrows per m2 counted on a horizontal surface at the bottom of the transition layer in the soil pit (ii) cracking quantified by taking a 50-mm×50-mm×100-mm sample of soil from the transition layer and examining the number of cracks. Results from experiments on different tillage treatments are used to demonstrate why it is worthwhile to take into account cracks and earthworm activity. Soil profiles were examined in mouldboard ploughed and no tillage fields, and described using the profil cultural method and the new indicators. Root maps were also traced to observe the effect of soil structure on root growth. Preliminary results show that the classification of cracking and the quantification of the number of earthworm burrows per m2 can explain observed root development in subsoil. This first approach towards a better observation of subsoil structure and the effect it has on roots needs to be confirmed through further research, and especially via quantification and scoring of soil structure impact on roots.
In the context of climate change, French Polynesia is committed to increasing qualitatively and quantitatively local food production. In this regard, agroecology is perceived as a sustainable pathway ...to improve farming practices. This article proposes first a theoretical framework to analyze the proximity of farmers' management to agroecological principles. Second, it describes the current use of agroecological pest and soil management practices by French Polynesian farmers. And third, it explains which agronomic and socio-economic factors drive the implementation of agroecological practices. For this, qualitative interviews were conducted with 32 farmers on three islands, and statistical analyses were carried for correlation between the use of practices and socio-economic variables. Results show that French Polynesian farmers implement different soil and pest management practices that are in line with agroecological principles. Farmers scored better in terms of pest management with high plant diversity, implementation of crop rotations, and mechanical weed management. There is a significant influence of the “cropping system” and the “production system” (organic, integrated, and conventional) on the use of practices as well as proximity to agroecological principles. Identified pathways for an agroecological transition are implementing farmer to farmer knowledge exchange, farmer networks, and farm demonstrations as well as training of extension services staff.
In the past few years, polychlorinated biphenyls (PCBs), a class of environmental pollutants, have been associated with metabolism dysregulation. Muscle is one of the key regulators of metabolism ...because of its mass and its important role in terms of glucose consumption and glucose storage. It has been shown that muscle alterations, such as oxidative stress and mitochondrial dysfunction, contribute significantly to the development of metabolic diseases. No study has yet investigated the toxicological effect of PCBs on muscle mitochondrial function and oxidative stress in vivo. The aim of this study was to assess the effect of PCB126 in vivo exposure (single dose of 1.05 μmol/kg) on muscle mitochondrial function and oxidative stress in rats. PCB126-treated rats showed a marked increase in
Cyp1a1
mRNA levels in skeletal muscles in association with a 40% reduction in state 3 oxygen consumption rate measured with complex I substrates in permeabilized muscle fibers. Furthermore, PCB126 exposure altered the expression of some enzymes involved in ROS detoxification such as catalase and glutaredoxin 2. Our results highlight for the first time a toxic effect of coplanar PCBs on skeletal muscle mitochondrial function and oxidative stress. This suggests that acute PCB exposure, by affecting muscle metabolism, could contribute to the development of metabolic disorders. Studies are needed to determine if lower-level but longer-term PCB exposure exhibits the same effect.
Organic agriculture is a production system which relies on ecosystem management and ecological processes rather than on the external flow of agricultural inputs. The development of the organic sector ...has induced a spatial decoupling of livestock and crop production. This has increased the flow of nutrients that occurs between farms compared to what happens within individual farms. Organic systems have replaced synthetic inputs with site-specific management practices to balance input and output nutrients to ensure short-term productivity and long-term sustainability. This paper addresses the nutrient management of mixed and specialized farming systems, with a special emphasis on the reliance on livestock production for the nutrient management of arable farmland. We assessed the nutrient budgets of nitrogen (N), phosphorus (P), and potassium (K) of 28 organic farms selected according to livestock density from three French counties. The farms were classified as stockless, mixed, and cattle farming systems. A soil surface nutrient budget was calculated for each farm based on inputs (N fixation, excreta, and manure) and outputs (grazing offtake, harvests) on annual crops and grasslands. Inputs due to N atmospheric deposition and seeds and losses due to leaching and volatilization were not considered in this study. Nutrient budgets of the 28 farms revealed N, P, and K deficits, although disparities between farming systems and their geographical location were also observed. Stockless farms presented high N deficit whereas mixed and livestock farming systems presented lower deficits (close to equilibrium) or even surpluses in a county with a high density of livestock farms. Differences between farming systems in terms of P and K budgets followed the same trend, but regional specificities appeared significant in stockless and livestock systems (related to the size of farms and the stocking rate). None of the farms purchased off-farm organic fertilizers when exchanges of manures and straw were observed at the regional scale. When livestock is present on the farm, the nutrient resources came mainly from recycling internal resources (manures, excreta, and N fixation), whereas stockless farming systems purchased organic manure from neighboring farms (14 to 58 % of total N inputs, 10 to 100 % of total P and K inputs). The sustainability of stockless organic farming systems is questioned, noticeably those that were located in regions where resources of organic matter are scarce. Only farming systems producing large quantities of manure or which purchased feed showed balanced nutrient budgets.
► New methodology to identify metal transfer from soil to snails. ► Internal concentration of reference (CIRef) for snails are identified for six trace elements. ► The soil parameters influence the ...bioavailability and transfer of metals to snails. ► The sum of excess of transfer (SET) allows the ranking of site priority management.
Current soil quality evaluation does not include an assessment of metal bioavailability to organisms. However, sentinel soil-dwelling invertebrates can be used for such an assessment. This study aims to establish the modulating soil parameter of metal bioavailability to snails and a procedure for ranking field sites (n=9; 43 plots) based on the evaluation of the transfer of metals to the land snails used as indicators of metal zooavailability. Multivariate regressions identify soil pH, organic carbon and iron oxides influence cadmium, chromium, copper, lead and zinc zooavailability to snails underlining the need to consider other parameter than total soil concentration during bioavailability assessment. However, for As, no influence of soil parameter on it bioavailability to snails was identified. Internal Concentrations of Reference (CIRef) of Cd, Pb, As, Cr, Cu and Zn were determined in Cantareus aspersus that were caged on unpolluted plots. CIRef allow for the identification of contaminated sites. CIRef have revealed unexpected metal transfer on some “unpolluted” sites and a lack of transfer on some contaminated sites, thus confirming the necessity for biological measures to evaluate metal mobility. The Sum of Excess of Transfers (SET) index ranked the industrially impacted sites as the top priorities for management.
We recommend that the SET methodology be used for future environmental risk assessment. By highlighting real metal transfers and considering the numerous parameters influencing environmental bioavailability, the snails watch provides information on environmental quality.
Microbial indicators exhibit a high spatial heterogeneity which often masks comparison of the effects of different soil management treatments. It is therefore desirable to use a proper sampling ...design which integrates spatial heterogeneity at field level. Thus, the objectives were: (1) to study the spatial heterogeneity of biological and chemical soil variables, and (2) with obtained maps of spatial variability to test different sampling strategies to assess the usefulness of this ‘new’ soil map unit. 63 soil samples were collected according to a 10 m × 10 m grid on a 0.48 ha plot. On each of these samples, 10 variables were measured: soil water content, cation exchange capacity (CEC), organic carbon (OC) and total nitrogen (N), C/N, soil microbial biomass (SMB), labile soil organic matter (LOM), mineralisable C (C
min) and N (N
min), inverse of specific respiratory activity (1/SRA = SBM/C
min). The spatial heterogeneity of each variable was charted with geostatistics. The biological variables exhibited spatial variability of the same order of magnitude as physicochemical parameters. From the maps, zones with different levels of organic matter, microbial biomass and specific respiratory activity were identified. The spatial patterns of SMB and SRA were related to CEC (positively for SMB and negatively for SRA), pointing out the effects of soil protection on microbial biomass and availability of organic substrates. The definition of these zones for a pool of variables (OC, N, SMB, LOM, CEC) is useful at 3 levels: (1) to record the initial values of the measured variables for each plot, (2) to integrate these zones as blocks in experimental design for future experiments, and (3) to focus analysis of specific biological mechanisms such as activity of micro-organisms.
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