Optimizing type, date, and dose of compost fertilization of organic cotton under climate change in Mali: A modeling study.

Adapting organic farming to climate change is a major issue. Cotton yields in Mali are declining due to deteriorating climatic conditions, soil fertility, and poor management. This study aimed to improve organic cotton yield in Mali in the future climate with the optimal choice of compost type, date, and dose of application. Experimental data collected in 2021 from the Sotuba research station in Mali was used for calibration and evaluation of the crop model DSSAT CSM-CROPGRO-Cotton model using phenology, leaf area index, and seed cotton yield. Climate data from the RCP4.5 and RCP8.5 scenarios of the GFDL-ESM2M model were used for future weather datasets for 2020-2039, 2040-2059, and 2060-2079. The model was able to simulate anthesis and maturity with excellent results, with nRMSE < 4%, and seed cotton yields moderately well, an nRMSE of 26% during calibration and 20.3% in evaluation. The scenario RCP8.5 from 2060 to 2079 gave the best seed cotton yields. Seed cotton yields with RCP4.5 and RCP8.5 were all better with the mid-May application period of small ruminant silo compost at 7.5 t/ha. In such conditions, more than 75% of the cases would produce more than 2000 kg/ha of seed cotton.

Soil fertility and plant nutrition in an organic olive orchard after 5 years of amendment with compost, biochar or their blend.

The agronomic use of compost and biochar as soil amendments may exhibit contrasting results in terms of soil fertility and plant nutrition. The effects of the biennial application of biochar, compost and a blend of compost:biochar (90:10; % dw:dw) on the agronomical performance of an organically managed and well established 25-year-old olive orchard was assessed 5 years after the initial application. The agronomical evaluation was based on the assessment of the soil physical, chemical, and biological characteristics, and the assessment of the soil fertility by both crop production and nutritional status of the orchard, and the bioassay with olive plantlets. Biochar mainly benefited the physical properties (bulk density, total porosity, aeration, water retention capacity) of soil, especially in the top 0-5 cm. Compost and its blend with biochar improved microbial activity, soil nutritional status (increasing the content of soluble organic C, N, and P) and favoured the formation of aggregates in soil. The bioassay conducted with young plantlets confirmed the enhanced soil fertility status in the three amended treatments, particularly in the case of biochar and its blend with compost. However, this effect was not significantly observed in the adult plants after 5 years of application, reflecting the slow response of adult olive trees to changes in fertilization. Based on these results, alongside the desirable long-residence time of biochar in soil and the ready availability of compost, the blend of biochar with compost assayed in this study is defined as a valid strategy for preparing high quality soil organic amendments.

Joint analysis of land, carbon and nitrogen reveals diverging trends in the sustainability of organic crops in Spain.

The world's top ten Organic Farming (OF) countries by converted area include several Mediterranean countries, including Spain. Despite this, little is known about the consequences of OF on crop production and environmental sustainability in this country. In this article, we conduct an agronomic analysis of Spanish considerable conversion rate to OF, which tends to concentrate in certain provinces and crops. Indeed, in the case of various crops and in several provinces, the organic share of total agricultural land exceeds 20-30 %. This concentration makes it possible to compare information obtained from farmers through interviews and provincial statistical information. The study data consisted of information collected from interviews of a representative sample of organic farmers conducted in 2004 and 2020 as well as official statistical information. The results showed that no yield gap between OF and conventional farming was found for vegetables and fruit trees, while it showed an increasing trend in arable crops. Presumably, the reason is that fruit trees and vegetables generate and incorporate high levels of carbon (C) flows into the soil and have a low land cost per unit of incorporated nitrogen (N) (or can be paid for), allowing to meet crop needs and to increase soil organic matter (SOM). Conversely, in the case of rainfed arable crops, the soil C and N inputs are deficient due to the low crop residues and the high land cost of N. Consequently, SOM destruction and N deficit progressively broaden the yield gap, undermining the agroecosystem sustainability. To reverse the situation, among other measures, it is necessary to implement agricultural policies designed to make rotations with high legume ratios viable and to plant varieties presenting higher production of residues and roots, such as traditional varieties.

Biofungicides Based on Plant Extracts: On the Road to Organic Farming.

Phytopathogenic fungi are responsible for diseases in commercially important crops and cause major supply problems in the global food chain. Plants were able to protect themselves from disease before humans played an active role in protecting plants. They are known to synthesize a variety of secondary metabolites (SMs), such as terpenes, alkaloids, and phenolic compounds, which can be extracted using conventional and unconventional techniques to formulate biofungicides; plant extracts have antifungal activity and various mechanisms of action against these organisms. In addition, they are considered non-phytotoxic and potentially effective in disease control. They are a sustainable and economically viable alternative for use in agriculture, which is why biofungicides are increasingly recognized as an attractive option to solve the problems caused by synthetic fungicides. Currently, organic farming continues to grow, highlighting the importance of developing environmentally friendly alternatives for crop production. This review provides a compilation of the literature on biosynthesis, mechanisms of action of secondary metabolites against phytopathogens, extraction techniques and formulation of biofungicides, biological activity of plant extracts on phytopathogenic fungi, regulation, advantages, disadvantages and an overview of the current use of biofungicides in agriculture.

Effects of 3-year organic farming management on soil antibiotic resistant genes and virulence factors in a double rice cropping system.

Investigating the antibiotic resistance genes (ARGs) and virulence factors (VFs) within soil microbial communities is crucial for understanding microbial ecology and the evolution of antibiotic resistance. However, the study of ARGs, VFs, and their predominant microbial hosts in soils under varying rice production management practices remains largely underexplored. To this end, a three-year field experiment was conducted under organic management within a double rice cropping system in South China. The study revealed that, in contrast to conventional management (CK), organic farming practices did not significantly alter the total reads of ARGs and VFs. However, there was a notable alteration in the ARGs abundance at the antibiotic class level, such as an increase (P < 0.05) in the abundance of Multidrug ARGs (by 1.7 %) and a decrease (P < 0.05) in Rifamycin (by 17.5 %) and Fosfomycin ARGs (by 15.3 %). Furthermore, a significant shift in VFs was observed under organic farming compared to CK, characterized by an increase (P < 0.05) in offensive VFs and a decrease (P < 0.05) in nonspecific VFs and the regulation of virulence-associated genes. Key microbial taxa identified as influencing ARGs and VFs in the tested soil samples, e.g., Proteobacteria. The findings highlight the need for more detailed attention to soil ecology within organic rice production systems in South China, particularly concerning the significant alterations observed in ARGs and VFs.

Feeding strategy in organic pig farming as a lever to improve various quality dimensions of pork.

Since 2022, European specifications for organic pig farming have evolved to distribute 100 % organic feed and to reinforce the link to the soil with feed resources that should primarily be obtained from the farm or the same region. Feeding strategy acts as a lever to improve various quality dimensions of organic (as well as conventional) pork, including intrinsic dimensions (carcass composition, nutritional, organoleptic, technological, sanitary qualities) and extrinsic dimensions related to animal farming (image). Diet may also influence the risk of undesirable odours or flavours that may be found in pork from non-castrated male pigs. This study aimed at evaluating the effects of a specific feeding strategy on several quality dimensions of organic meat from non-castrated male pigs. The experiment was conducted with 77 organic non-castrated male pigs (Piétrain NN × Large White) reared according to organic specifications and distributed in two batches. Within litters, male littermates were allocated at around 33 kg of live weight to either a Control group which received a Control feed (C) corresponding to the organic specifications or in a Bio+ group which received an organic test feed based mainly on French raw materials and which contained more fibres (faba bean and access to forages) and omega-3 fatty acids (linseed, camelina). All pigs were reared in the same building on deep straw bedding (1.3 m2/pig) with free outdoor access (1.0 m2/pig) using one pen per experimental group. Pigs were fed ad libitum until slaughter at about 125 kg live weight. Average daily gain, carcass weight and lean meat content did not differ significantly between C and Bio+ pigs. Compared to C, Bio+ pigs had higher (P < 0.05) ultimate pH in the loin (Longissimus muscle) and ham (Gluteus medius, and Semimembranosus) muscles, associated with a lower Longissimus muscle glycolytic potential (P < 0.001). Loin and ham meat from Bio+ vs. C pigs was lighter (P < 0.05) and had a more intense red colour (P < 0.10). The Bio+ strategy led to a lower Longissimus muscle n-6:n-3 fatty acid ratio (P < 0.001), indicating an improvement in pork nutritional value. Backfat skatole concentration was lower in Bio+ than in C pigs whereas backfat androstenone was higher in Bio+ than in C pigs (P < 0.05). Altogether, we demonstrated that the Bio+ strategy had positive impacts on several qualities of organic pork from non-castrated male pigs.

Comparison of microbial diversity and metabolic activities in organic and conventional rice farms in Thailand.

Studies of the soil microbial community have revealed that several factors, both biotic and abiotic, can influence the community structure, diversity, and function. Human agricultural practice has been one of the key factors that affect microbial structure in soil. In this study, we examined the effect of two rice farming practices (i.e., conventional and organic) on soil microbial diversity and their metabolic activities. We proposed that the use of herbicides and chemical fertilizers in the conventional rice farming may decrease the soil microbial diversity and that it may lead to a decline in soil quality. However, our results show that there is no significant difference in the soil chemical properties, microbial diversity, and microbial metabolic activities between the two agricultural management systems. The wetland water cycling regime of rice agriculture in Thailand perhaps prevents the accumulation of chemicals in the soil, thus subdue the effect of these chemicals on soil microbes. Furthermore, our results showed that the key determinant of soil chemical properties as well as microbial community structure and diversity is the soil physical property, while the farming activity influences the microbial metabolic functions. These findings indicate the complex nature of the soil, microbes, and human farming interactions.IMPORTANCERice is a major export commodity in Thailand. As such, an understanding of the effect of conventional or organic farming approaches on soil microbial community could enable a suitable farming management. In this study, microbial communities were surveyed and compared between the two rice farming practices for their diversity and metabolic activities. Results showed no significant differences in microbial community structure and diversity between the two rice farming practices, but significant differences were observed due to the soil type, namely, clay, silty clay, silty clay loam, loam, and silty loam. Interestingly, significant differences in metabolic functions were also observed in different soil farming activities, such as land rest, period of growth, and post-burning, but not due to conventional or organic practices. These findings showed that the soil physical type and the farming activity impact the microbial community more than whether it is conventional or organically farmed.

Harnessing the Power of Traditional Organic Formulations for Crop Growth and Microbial Harmony.

The utilization of various agrochemicals in crop production technology leads to soil health and fertility depletion. Multiple measures have been taken to revitalize the health of polluted soil. In this context, organic agriculture has increased over the past few years to overcome the detrimental effects of extensive modern agricultural practices. Several traditional organic formulations, such as panchagavya, jeevamurtha, beejamurtha, bokashi, etc., are vital in converting polluted farmlands into organic. Various countries have their own organic formulations to improve crop growth and yield. These formulations are rich sources of many macro and micronutrients, growth-promoting phytohormones, and provide resistance against biotic and abiotic stresses. Apart from these benefits, these formulations consist of several groups of beneficial microorganisms that belong to the phyla Proteobacteria, Firmicutes, Bacteroides, and Actinobacteria, while some of the novel groups of microorganisms were also reported from the ingredients used in the preparation of these organic formulations. These microorganisms can solubilize nutrients such as phosphorous and zinc, oxidize sulfur, reduce nitrate, and are also involved in the production of indole acetic acid, ethylene reduction enzyme (1-aminocyclopropane-1-carboxylic acid deaminase), and organic acids that promote plant growth and induce resistance in the plant system. Hence, the utilization of traditional organic formulations helps in the reclamation of environmental health without compromising crop yields. This review describes the importance of organic farming, the preparation and application of different types of traditional organic formulations in different countries, and the microbial composition and mechanism of growth promotion of different traditional organic formulations.

Pomegranate Rhizosphere Microbial Diversity Revealed by Metagenomics: Toward Organic Farming, Plant Growth Promotion and Biocontrol?

Food production must undergo systems change to meet the sustainable development goals (SDGs). For example, organic farming can be empowered by soil microorganisms with plant growth promotion (PGP) and biocontrol features. In this context, there have been limited studies on pomegranate. We investigated microbial diversity in rhizosphere of the pomegranate "Bhagwa" variety and its potential role in PGP and biocontrol. Both bulk and rhizosphere soil samples were analyzed for their physicochemical properties. Whole metagenome sequencing was conducted using the Illumina NovaSeq6000 platform. Surprisingly, we found that bulk and rhizosphere soil samples had comparable microbial diversity. Metagenome sequencing revealed the abundance of Streptomyces indicus, Bradyrhizobium kalamazoonesis, and Pseudomonas cellulosum in the rhizosphere that are reported here for the first time in agricultural literature. Pathway prediction analysis using KEGG (Kyoto Encyclopedia for Genes and Genomes) and COG (clusters of orthologous genes) databases identified metabolic pathways associated with biocontrol properties against pathogens. We confirmed the metagenome data in vitro, which demonstrated their PGP potential and antimicrobial properties. For instance, S. indicus produced high concentration of indole-3-acetic acid, a PGP phytohormone, that can stimulate plant growth. In addition, an antimicrobial susceptibility assay suggested that bacterial extracts displayed activity against Xanthomonas, a primary pathogen causing the pomegranate wilt disease. In conclusion, this study suggests that S. indicus, B. kalamazoonesis, and P. cellulosum can potentially be PGP and biocontrol agents that may contribute to increased crop productivity in pomegranate cultivation. These agents and their combinations warrant future research with an eye on SDGs and so as to enable and innovate organic farming and pomegranate agricultural practices.

Organic farming reduces pesticide load in a bird of prey.

Human activities have led to the contamination of all environmental compartments worldwide, including bird species. In birds, both the environment and maternal transfer lead to high inter-brood variability in contamination levels of pollutants, whereas intra-brood variability is generally low. However, most existing studies focused on heavy metals or persistent compounds and none, to our knowledge, addressed the variability in contamination levels of multiple pesticides and the factors influencing it. In this study, the number of pesticides detected (of 104 compounds searched) and the sum of their concentrations in the blood of 55 Montagu's harrier (Circus pygargus) nestlings from 22 nests sampled in 2021 were used as metrics of contamination levels. We investigated the effect of organic farming at the size of male's home range (i.e., 14 km2) and chicks' sex and hatching order on contamination levels. We did not find a difference between inter-brood and intra-brood variability in pesticide contamination levels, suggesting a different exposure of siblings through food items. While chicks' sex or rank did not affect their contamination level, we found that the percentage of organic farming around the nests significantly decreased the number of pesticides detected, although it did not decrease the total concentrations. This finding highlights the potential role of organic farming in reducing the exposure of birds to a pesticide cocktail.

The fruit quality and nutrient content of kiwifruit produced by organic versus chemical fertilizers.

BACKGROUND: Currently, organic farming has become a feasible approach for the production of high-quality fruits. To evaluate the response of fruit quality and mineral nutrition contents of Hayward Kiwifruit affected by different organic and inorganic fertilizers, the present study was conducted in Citrus and Subtropical Fruits Research Center, Iran, in 2017-2021, as a randomized block design with three replications. The studied treatments were organic fertilizers (cow, vermicompost and Azolla) and chemical fertilizers. After 4 years of fertilization, the fruit's nutritional elements content and some fruit bioactive compounds were evaluated after 3 months of cold storage and then analyzed by the principal component analysis (PCA) method. RESULTS: The use of organic amendments boosted the calcium, phosphorus, potassium and iron content of the kiwifruits compared to chemical fertilizers. The highest fruit potassium and phosphorus content were recorded in the cow manure treatment. The lowest amount of nitrate and the highest calcium, zinc, copper and manganese accumulation were recorded in the fruits treated with vermicompost. In addition to mineral nutrients, the dry matter, total soluble solids, total phenolic and antioxidant capacity of kiwifruit were improved by the application of vermicompost amendment compared to the other fertilizer sources. However, the highest fruit vitamin C and total soluble carbohydrates were measured in the cow manure treatment. The PCA results of the fruit quality indices indicated that fertilization treatments were ranked as vermicompost (1.88) > cow manure (1.63) = chemical (1.60) > Azolla (1.54). CONCLUSION: It is concluded that the application of 40 kg of vermicompost or 40 kg of cow manure in the next rank in Hayward kiwifruit orchards in March (growth stage beginning of bud swelling) may be a more suitable approach for improving the nutritional quality of the fruit. © 2024 Society of Chemical Industry.

Fruit quality in organic and conventional farming: advantages and limitations.

Fruit quality is essential for nutrition and human health and needs urgent attention in current agricultural practices. Organic farming is not as productive as conventional agriculture, but it can provide higher quality in some fruit crops, thanks to the absence of synthetic fertilizers and pesticides, enhanced pollination, and the reduction of protection treatments, hence boosting antioxidant compound production. Although organic farming does not always provide healthier food than conventional farming, some lessons from organic farming can be extrapolated to new sustainable production models. Exploiting natural resources and an adequate knowledge transfer will undoubtedly help improve the quality of climacteric and nonclimacteric fruits in new agricultural systems.

Anaerobic Soil Disinfestation and Vermicompost to Manage Bottom Rot in Organic Lettuce.

Rhizoctonia solani Kühn (teleomorph: Thanatephorus cucumeris [Frank] Donk) is an aggressive soilborne pathogen with a wide host range that survives saprophytically between crops, presenting a challenge for organic vegetable farmers who lack effective management tools. A 2-year field experiment was conducted at two organic farms to compare anaerobic soil disinfestation (ASD) and worm-cured compost (vermicompost) to manage bottom rot caused by R. solani subspecies AG1-IB in field-grown organic lettuce (Lactuca sativa). At each farm, four replicate plots of seven treatments were arranged in a randomized complete block design. Randomization was restricted by grouping treatments to evaluate ASD, and treatments to evaluate vermicompost in starter plugs. ASD experiment treatments were three different ASD carbon sources that are commonly used and widely available to local farmers in Vermont: compost, cover crop residues, and poultry manure fertilizer, as well as a tarped control. Vermicompost experimental treatments were vermicompost compared with two types of controls: a commercial biocontrol product (RootShield PLUS + G), and unamended (untarped control). This study demonstrated that the ASD method is achievable in a field setting on Vermont farms. However, neither ASD nor vermicompost produced significant disease suppression or resulted in higher marketable yields than standard growing practices. Given the laborious nature of ASD, it is likely more appropriate in a greenhouse setting with high-value crops that could especially benefit from being grown in plastic tarped beds (e.g., tomatoes and strawberries). This study is the first known attempt of field-implemented ASD for soil pathogen control in the northeastern United States.

Exploring membrane vesicles in citrus fruits: a comparative analysis of conventional and organic farming approaches.

BACKGROUND: Recently, vesicles derived from plant cell membranes have received attention for their potential use as active biomolecules and nanocarriers, and obtaining them from organic crops may be an interesting option because different farming systems can affect production, plant secondary metabolism and biochemistry of cell membranes. The present study aimed to determine how organic and conventional farming affects the mineral nutrition, gas exchange, CO2 fixation and biochemical composition of lemon fruits, which could have an impact on the different fractions of cell membranes in pulp and juice. RESULTS: Organic trees had higher intrinsic water use efficiency (WUEi) but conventional trees had higher stomatal conductance (gs) and nitrogen use efficiency (NUtE). Also, organic lemons had significantly higher levels of some micronutrients (Ca, Cu, Fe and Zn). Second, the main differences in the membrane vesicles showed that organic pulp vesicles had a higher antioxidant activity and more oleic acid, whereas both types of vesicles from conventional lemons had more linoleic acid. CONCLUSION: In conclusion, organic farming did not alter carbon fixation parameters but impacted nitrogen fixation and water uptake, and resulted in higher micronutrient levels in lemons. These mineral nutritional changes could be related to the higher production of membranes that showed suitable morphological traits and a high antioxidant activity, positively correlated with a high amount of oleic acid, which could have stronger cell protection characteristics. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Role of Fungi in Imparting General Disease Suppressiveness in Soil from Organic Field.

Soil microbial communities are key players responsible for imparting suppressive potential to the soil against soil-borne phytopathogens. Fungi have an immense potential to inhibit soil-borne phytopathogens, but the fungal counterpart has been less explored in this context. We assessed the composition of fungal communities in soil under long-term organic and conventional farming practice, and control soil. The disease-suppressive potential of organic field was already established. A comparative analysis of the disease suppressiveness contributed by the fungal component of soil from conventional and organic farms was assessed using dual culture assays. The quantification of biocontrol markers and total fungi was done; the characterization of fungal community was carried out using ITS-based amplicon sequencing. Soil from organic field exhibited higher disease-suppressive potential than that from conventional farming, against the pathogens selected for the study. Higher levels of hydrolytic enzymes such as chitinase and cellulase, and siderophore production were observed in soil from the organic field compared to the conventional field. Differences in community composition were observed under conventional and organic farming, with soil from organic field exhibiting specific enrichment of key biocontrol fungal genera. The fungal alpha diversity was lower in soil from the organic field compared to the conventional field. Our results highlight the role of fungi in contributing to general disease-suppressive ability of the soil against phytopathogens. The identification of fungal taxa specifically associated with organic farming can aid in understanding the mechanism of disease suppression under such a practice, and can be exploited to induce general disease suppressiveness in otherwise conducive soil.

The spatial influences of organic farming and environmental heterogeneity on biodiversity in South Australian landscapes.

The potential link between certified organic farming and biodiversity and conservation remains unexplored in Australia, despite the country having the world's largest amount of certified organic farmland and unprecedented biodiversity loss. This study modelled the spatial effects of organic farming (intensity of local farming systems), environmental heterogeneity, and urbanisation on two widely studied environmental taxa - vascular plant and bird species richness (surrogate measures of biodiversity) - in South Australia, using a unique certified organic farming postcode level dataset from 2001 to 2016 (N = 5440). The spatial Durbin error model results confirmed the positive spatial congruence of organic farming with greater vascular plant species richness, whereas only weak to no significant evidence was found for bird species richness. Landscape features (habitat heterogeneity) and green vegetation (a proxy indicator of resource availability) - rather than organic farming - appeared to be most associated with bird species richness. Both plant and bird species richness were positively associated with habitat heterogeneity (land cover diversity and elevation range), plant productivity and proportion of conservation land and water bodies. Whereas, increased anthropogenic land use for cropping and horticultural farming, soil type diversity and proximity to the coast significantly reduced species richness of both taxa. The results suggest that a multi-scale spatially refined biodiversity conservation strategy, with spatial targeting that promotes low intensive farming systems and increases landscape heterogeneity to provide quality habitat (a whole of landscape approach by incorporating private agricultural landholders), could be beneficial for biodiversity conservation.

Soil microbial diversity and community composition during conversion from conventional to organic agriculture.

It is generally assumed that the dependence of conventional agriculture on artificial fertilizers and pesticides strongly impacts the environment, while organic agriculture relying more on microbial functioning may mitigate these impacts. However, it is not well known how microbial diversity and community composition change in conventionally managed farmers' fields that are converted to organic management. Here, we sequenced bacterial and fungal communities of 34 organic fields on sand and marine clay soils in a time series (chronosequence) covering 25 years of conversion. Nearby conventional fields were used as references. We found that community composition of bacteria and fungi differed between organic and conventionally managed fields. In the organic fields, fungal diversity increased with time since conversion. However, this effect disappeared when the conventional paired fields were included. There was a relationship between pH and soil organic matter content and the diversity and community composition of bacteria and fungi. In marine clay soils, when time since organic management increased, fungal communities in organic fields became more dissimilar to those in conventional fields. We conclude that conversion to organic management in these Dutch farmers' fields did not increase microbial community diversity. Instead, we observed that in organic fields in marine clay when time since conversion increased soil fungal community composition became progressively dissimilar from that in conventional fields. Our results also showed that the paired sampling approach of organic and conventional fields was essential in order to control for environmental variation that was otherwise unaccounted for.

Biodiversity and yield trade-offs for organic farming.

Organic farming supports higher biodiversity than conventional farming, but at the cost of lower yields. We conducted a meta-analysis quantifying the trade-off between biodiversity and yield, comparing conventional and organic farming. We developed a compatibility index to assess whether biodiversity gains from organic farming exceed yield losses, and a substitution index to assess whether organic farming would increase biodiversity in an area if maintaining total production under organic farming would require cultivating more land at the expense of nature. Overall, organic farming had 23% gain in biodiversity with a similar cost of yield decline. Biodiversity gain is negatively correlated to yield loss for microbes and plants, but no correlation was found for other taxa. The biodiversity and yield trade-off varies under different contexts of organic farming. The overall compatibility index value was close to zero, with negative values for cereal crops, positive for non-cereal crops, and varies across taxa. Our results indicate that, on average, the proportion of biodiversity gain is similar to the proportion of yield loss for paired field studies. For some taxa in non-cereal crops, switching to organic farming can lead to a biodiversity gain without yield loss. We calculated the overall value of substitution index and further discussed the application of this index to evaluate when the biodiversity of less intensified farming system is advantageous.

Turnover and nestedness drive plant diversity benefits of organic farming from local to landscape scales.

Biodiversity-benefits of organic farming have mostly been documented at the field scale. However, these benefits from organic farming to species diversity may not propagate to larger scales because variation in the management of different crop types and seminatural habitats in conventional farms might allow species to cope with intensive crop management. We studied flowering plant communities using a spatially replicated design in different habitats (cereal, ley and seminatural grasslands) in organic and conventional farms, distributed along a gradient in proportion of seminatural grasslands. We developed a novel method to compare the rates of species turnover within and between habitats, and between the total species pools in the two farming systems. We found that the intrahabitat species turnover did not differ between organic and conventional farms, but that organic farms had a significantly higher interhabitat turnover of flowering plant species compared with conventional ones. This was mainly driven by herbicide-sensitive species in cereal fields in organic farms, as these contained 2.5 times more species exclusive to cereal fields compared with conventional farms. The farm-scale species richness of flowering plants was higher in organic compared with conventional farms, but only in simple landscapes. At the interfarm level, we found that 36% of species were shared between the two farming systems, 37% were specific to organic farms whereas 27% were specific to conventional ones. Therefore, our results suggest that that both community nestedness and species turnover drive changes in species composition between the two farming systems. These large-scale shifts in species composition were driven by both species-specific herbicide and nitrogen sensitivity of plants. Our study demonstrates that organic farming should foster a diversity of flowering plant species from local to landscape scales, by promoting unique sets of arable-adapted species that are scarce in conventional systems. In terms of biodiversity conservation, our results call for promoting organic farming over large spatial extents, especially in simple landscapes, where such transitions would benefit plant diversity most.