Adjusting Ley Grassland Duration in Crop Rotations to Reconcile Food Production and Soil Carbon Stocks

Introduction of grasslands into cropping systems represents a strategy to ensure food production while reducing soil carbon losses. Yet, mixed crop and grassland management systems need to be evaluated in terms of achieving balanced food production and soil carbon (C) sustainability. The objectives of the study are: 1) to explore the impact of grassland duration on C input and soil C changes in agricultural systems; and 2) to test the variation in C input and soil C changes between rotations using grassland fertilized at high or low Nitrogen (N) application rates and their impacts on productivity. Field data regarding C input, soil C and crop production were collected during 2005–2016 from a longterm experimental site in Lusignan, France. Root biomass C was sampled annually, and the stable C isotope signature (δ13C) was determined to quantify the amount of C input from the root biomass. The results showed that integrating ley grassland in crop rotations increased the C input in the 0–30 and 0–60 cm soil layers (P \u3c 0.05) but showed limited improvements in shoot biomass C and grain yield of these crops. In addition, C stocks also increased in the 0-30 cm but not always in the 0-60 cm layer. Compared with cropland, permanent grassland did not show a greater C input, whereas the latter showed a C stock increase of 0.6–1.4 Mg C ha−1 yr−1. In addition, in crop rotations integrated with ley grassland together with high-N or low-N fertilization did not impact C input, changes in soil C at either 0-30 cm or 0-60 cm soil layers, or even the crop production, while the grass production decreased by 22.2%-66.6% for low-N fertilization. In conclusion, integrating ley grassland in crop rotations increases the C input and soil C stocks in top soil, while reducing the time and production of crops

Modelling nitrous oxide emissions from mown-grass and grain-cropping systems : Testing and sensitivity analysis of DailyDayCent using high frequency measurements

The lead author, Nimai Senapati (Post doc), was funded by the European community’s Seventh Framework programme (FP2012-2015) under grant agreement no. 262060 (ExpeER). The research leading to these results has received funding principally from the ANR (ANR-11-INBS-0001), AllEnvi, CNRS-INSU. We would like to thank the National Research Infrastructure ‘Agro-écosystèmes, Cycles Biogéochimique et Biodiversité (SOERE-ACBB http://www.soere-acbb.com/fr/) for their support in field experiment. We are deeply indebted to Christophe deBerranger, Xavier Charrier for their substantial technical assistance and Patricia Laville for her valuables suggestion regarding N2O flux estimation.Peer reviewedPostprin

Refining Soil Conservation and Regenerative Practices to Enhance Carbon Sequestration and Reduce Greenhouse Gas Emissions

Modern agricultural technology, in all its aspects, has enabled increased agricultural production to meet the growing demand for food and fulfill the Sustainable Development Goals of the UN Agenda 2030. Yet the impact of these achievements on soil degradation and greenhouse gas (GHG) emissions is considerable. Agricultural practices that increase soil carbon stocks and reduce greenhouse gas emissions, as outlined under the international 4per1000 initiative, constitute valuable strategies for mitigating global warming while increasing soil carbon stocks and ensuring soil health. The objective of this proposal is to evaluate the influence of conservationist and regenerative agricultural practices on carbon (C), nitrogen (N) and phosphorus (P) cycling, soil biodiversity and GHG emissions with a particular emphasis on long-term SOC stocks, and processes governing C persistence. This project represents an exploratory effort to couple the stoichiometric drivers to microbial populations related to C, N, and P cycling and stocks, and GHG emission under diverse agricultural practices. To this end, we set up a long-term consortium of field experiments that assess the impact of different cropping systems and agricultural practices on soil properties. The participants from twelve different countries represent a total of 37 field sites with different time sequences and/or contrasting agricultural management. Twenty-six sites have been established for at least ten years. At each site, estimates and modelling scenarios of possible N2O, CO2 and CH4 emissions from crop/pasture/forestry systems will be carried out using best available IPCC or local emission factors and GHG emissions will be measured at a subset of sites. To compare the impact of different climatic and edaphic conditions among sites, we propose a standard soil organic matter (OM) physical fractionation procedure resulting in two contrasting soil fractions including particulate organic matter (POM), which consists mainly of partially decomposed plant residues, and the mineral-associated OM (MAOM), principally of microbial origin. This project will build a worldwide database of C and N stocks, bulk density, soil fertility and GHG emissions across different ecosystems and under differential agricultural management. Moreover, the project will determine the extent to which climatic conditions, net primary production of cropping systems and soil type affect carbon and nitrogen stocks, nutrient dynamics and greenhouse gas emissions. The final product of the project will be to recommend best management practices for production of food crops which would promote soil C accumulation, especially MAOM, without increasing GHG emissions thus contributing to the sustainability and resilience of agriculture

Land-use intensification differentially affects bacterial, fungal and protist communities and decreases microbiome network complexity

Background: Soil microbial communities are major drivers of cycling of soil nutrients that sustain plant growth and productivity. Yet, a holistic understanding of the impact of land-use intensification on the soil microbiome is still poorly understood. Here, we used a field experiment to investigate the long-term consequences of changes in land-use intensity based on cropping frequency (continuous cropping, alternating cropping with a temporary grassland, perennial grassland) on bacterial, protist and fungal communities as well as on their co-occurrence networks. Results: We showed that land use has a major impact on the structure and composition of bacterial, protist and fungal communities. Grassland and arable cropping differed markedly with many taxa differentiating between both land use types. The smallest differences in the microbiome were observed between temporary grassland and continuous cropping, which suggests lasting effects of the cropping system preceding the temporary grasslands. Land-use intensity also affected the bacterial co-occurrence networks with increased complexity in the perennial grassland comparing to the other land-use systems. Similarly, co-occurrence networks within microbial groups showed a higher connectivity in the perennial grasslands. Protists, particularly Rhizaria, dominated in soil microbial associations, as they showed a higher number of connections than bacteria and fungi in all land uses. Conclusions: Our findings provide evidence of legacy effects of prior land use on the composition of the soil microbiome. Whatever the land use, network analyses highlighted the importance of protists as a key element of the soil microbiome that should be considered in future work. Altogether, this work provides a holistic perspective of the differential responses of various microbial groups and of their associations to agricultural intensification

Land-use intensification differentially affects bacterial, fungal and protist communities and decreases microbiome network complexity

Background Soil microbial communities are major drivers of cycling of soil nutrients that sustain plant growth and productivity. Yet, a holistic understanding of the impact of land-use intensification on the soil microbiome is still poorly understood. Here, we used a field experiment to investigate the long-term consequences of changes in land-use intensity based on cropping frequency (continuous cropping, alternating cropping with a temporary grassland, perennial grassland) on bacterial, protist and fungal communities as well as on their co-occurrence networks. Results We showed that land use has a major impact on the structure and composition of bacterial, protist and fungal communities. Grassland and arable cropping differed markedly with many taxa differentiating between both land use types. The smallest differences in the microbiome were observed between temporary grassland and continuous cropping, which suggests lasting effects of the cropping system preceding the temporary grasslands. Land-use intensity also affected the bacterial co-occurrence networks with increased complexity in the perennial grassland comparing to the other land-use systems. Similarly, co-occurrence networks within microbial groups showed a higher connectivity in the perennial grasslands. Protists, particularly Rhizaria, dominated in soil microbial associations, as they showed a higher number of connections than bacteria and fungi in all land uses. Conclusions Our findings provide evidence of legacy effects of prior land use on the composition of the soil microbiome. Whatever the land use, network analyses highlighted the importance of protists as a key element of the soil microbiome that should be considered in future work. Altogether, this work provides a holistic perspective of the differential responses of various microbial groups and of their associations to agricultural intensification

Organic matter composition and the protist and nematode communities around anecic earthworm burrows

By living in permanent burrows and incorporating organic detritus from the soil surface, anecic earthworms contribute to soil heterogeneity, but their impact is still under-studied in natural field conditions. We investigated the effects of the anecic earthworm Lumbricus centralis on fresh carbon (C) incorporation, soil organic matter composition, protists, and nematodes of a Cambisol under grassland. We used plant material labelled with stable isotope tracers to detect fresh C input around earthworm-occupied burrows or around burrows from which the earthworm had been removed. After 50 days, we sampled soil (0–10 cm depth) in concentric layers around the burrows, distinguishing between drilosphere (0–8 mm) and bulk soil (50–75 mm). L. centralis effectively incorporated fresh C into the drilosphere, and this shifted soil organic matter amount and chemistry: total soil sugar content was increased compared to unoccupied drilosphere and bulk soil, and the contribution of plant-derived sugars to soil organic matter was enhanced. Earthworms also shifted the spatial distribution of soil C towards the drilosphere. The total abundance of protists and nematodes was only slightly higher in earthworm-occupied drilosphere, but strong positive effects were found for some protist clades (e.g. Stenamoeba spp.). Additional data for the co-occurring anecic earthworm species Aporrectodea longa showed that it incorporated fresh C less than L. centralis, suggesting that the two species may have different effects on soil C distribution and organic matter quality

Soybean yield does not rely on mineral fertilizer in rotation with flooded rice under a no-till integrated crop-livestock system

In subtropical lowlands, the introduction of soybean and livestock in rotation are an alternative to rice monoculture. Due to the nutrient cycling process improved by animal grazing in winter fertilized pastures, soybean may not respond to mineral fertilization under a no-till integrated crop–livestock system (ICLS). Thus, the objectives of this study were to evaluate (i) the soybean yield response to different fertilization levels of phosphorus (P) and potassium (K) and (ii) the relationship between soybean yield and soil chemical properties sampled in different soil layers, in a no-till ICLS in subtropical lowlands. Two field studies were conducted in a system that included a soybean-flooded rice rotation integrated with cattle grazing during the winter season. During the 2015/2016 cropping season, five levels of P and K fertilization were applied to the soil. During the 2017/2018 cropping season, the relationships between soybean yield and soil chemical properties were evaluated under no fertilization treatment. Soybean yield under an ICLS did not respond to P and K fertilization, even when the soil P level was below the critical threshold. The associations between soybean yield and soil chemical properties were greatest in the 10–20 cm soil layer as compared with the 0–10 cm soil layer, especially for available P, followed by pH and soil organic matter (SOM). The crop rotation and ICLS adoption under no-till reduced the soybean reliance for mineral fertilization prior to cropping. Results of this study inform producers of possible fertilization adjustments, in which supplementing mineral fertilizer for soybean may not be necessary

Earthworm functioning in soil ecosystem services in relation to land use intensity

The FP7 EcoFINDERS project aimed to assess the relationship between soil biodiversity and ecosystem service provision. We studied functional responses for earthworms and fungi on soil formation and water regulation under different agricultural land uses representing a range in land use intensity. The aim was to establish and quantify these functional relationships by literature and field studies

Emergent large-scale integrated research infrastructure - the new role of scientists

Emergent large-scale integrated research infrastructure - the new role of scientists. International workshop on the design of an ecological observatory system for Colombi

Conditions écologiques et dynamique de la végétation : basses montagnes du Rif occidental au Maroc

Chabbi Abad. Conditions écologiques et dynamique de la végétation : basses montagnes du Rif occidental au Maroc. In: Travaux du Laboratoire de Géographie Physique Appliquée, n°13, Février 1995 1994. pp. 71-73