Effect of permanent ground cover on agronomic properties and soil fertility in an organic peach orchard

In conventional orchards, weeds on the raw are mainly controlled with chemical herbicides because of their efficiency, their low cost and ease of use. The most common method in organic orchard to eliminate weeds on the raw consists of tillage operations. However, some drawbacks of these mechanical methods have been demonstrated: (1) the energetic cost (non-renewable energy) is high, (2) this method is time-consuming, (3) tillage interferes with the development of superficial roots and can hurt the trunk, (4) the physical, chemical and biological properties of the soil can be disturb and (5) erosion and runoff potentially increase. Cover crops are interesting alternatives to manage ground cover but the effect on the agronomic properties and the soil fertility of these methods should be assessed. This study is included in the national program “Casdar SolAB” supported by the French Ministry of Agriculture. The effect of a White Clover crop versus tillage practice on the tree raw was assessed in an irrigated organic Peach orchard. White Clover was sowed in 2004. Soil parameters (water and nutrients availability, soil porosity, root density, earthworms density, soil profile) and agronomic parameters (yield, fruit quality, pests and diseases damages) were recorded since 2004. A 50% decrease of the organic fertilizer supply in the White Clover treatment has not affected yield and fruit quality from 2005 to 2009. It suggests this cover crop is well adapted to our pedoclimatic conditions without exerting a significant competitive effect. Root density is higher in the superficial layers of the soil in the White Clover treatment. Simplified Beerkan test used to assess soil porosity has also shown that soil porosity is higher in this treatment. No vole damage was observed in the plot

Effect of White clover (Trifolium repens cv. Huia) cover crop on agronomic properties and soil biology in an organic peach orchard

In orchards, cover crops are interesting alternative strategies to tillage or chemical herbicides for managing weeds in the tree row. However, little is known about the effect of cover crops on agronomic properties and soil biology in organic orchards. To fill this gap, the effects of two weed managements, a White clover cover crop (CC) versus classical tillage practice (T) on the tree row, were assessed in an irrigated organic Peach orchard. White clover was sown in 2004, 2006 and 2009 in the tree row and ploughed in 2006 and 2008. Root density, earthworm density, water infiltration rate, nitrogen content and water availability were measured in the soil, in the tree row. In 2009, peach root density observed in the superficial layers was higher in CC treatment. Sampling dates and treatment have a significant effect on total earthworm density with higher abundance observed in CC. However, no difference was observed between CC and T anecic earthworm groups known to make large and vertical burrows. Infiltration rate measured with the simplified Beerkan method was higher in CC treatment. This could be explained by the thick superficial root mat which was associated to a significant higher epigeic earthworm density in CC. Whereas nitrogen supplies were twice lower in CC treatment since 2005, soil nitrogen availability was equivalent in both treatments. These results demonstrate the agronomic interest of nitrogen-fixing plants used as a cover crop in organic peach orchards

Evidence of the role of earthworms in the regeneration of compacted soils under field conditions

At the INRA Estrées-Mons experimental site, the possible role of earthworm in the regeneration of compacted soils was studied in a reduced tillage plot where a compaction event was done using a 8-tons tractor on a wet soil. Earthworm communities and earthworm burrow systems were then studied either 2 weeks after or 8 or 24 months after the compaction in the control or compacted zone. Earthworms were observed to recolonise the compacted zone in less than 8 months whereas the regeneration of earthworm burrows was a slower process under field conditions

Earthworm burrowing modes and rates depend on earthworm species and soil mechanical resistance

Earthworms drive multiple soil processes, but their specific impact on soil functions differs between earthworm species and ecological categories. A key challenge in modern agriculture is soil compaction due to heavy ma-chinery, but we have limited quantitative knowledge about how the burrowing activity of different earthworm species is affected by compaction. Here, we address this question in a laboratory experiment with 2-D terraria, where we used Aporrectodea caliginosa (Savigny, 1826) and Aporrectodea longa (Ude, 1885) as representatives of two different ecological categories. We exposed both species to four different soil mechanical resistance levels and monitored their burrowing activity for three days. We quantified burrowing rates and cast production, assessed the burrowing mode, and estimated energy requirements as a function of soil mechanical resistance. The results showed that the burrowing rates of both earthworm species significantly decreased with increasing soil mechanical resistance, but that the impact was species-dependent and lower for A. longa. Earthworms changed their burrowing mode towards ingestion when soil mechanical resistance increased, and this shift was more prominent for A. caliginosa that primarily burrowed via cavity expansion (i.e. by pushing soil aside) at low soil mechanical resistance. We further show that energy requirement and cast produced per unit burrow length increased with soil mechanical resistance. Our study revealed significant and species-dependent adverse effects of soil mechanical resistance on earthworm burrowing, which in turn has consequences for many soil processes mediated by earthworms, such as water infiltration, soil aeration, nutrient cycling and soil organic matter turnover

Earthworm’s influence on phytoavailability and Human gastric bioaccessibility of metals

►Introduction : Le développement d’entreprises de recyclage des métaux comme la Société de Traitement Chimique des Métaux (STCM) participe à l’économie circulaire. Cependant, ces activités de recyclage ont durant plusieurs décennies également engendré des émissions de polluants dans l’environnement induisant une augmentation de sites pollués par les retombées atmosphériques de particules fines enrichies en métaux et métalloïdes. Par ailleurs, le ver de terre, organisme clé de l’écosystème sol, apparait comme un ingénieur physique et mécanique des sols, et fait désormais l’objet de nombreuses études environnementales. Pour cette étude, notre objectif était d’évaluer l’influence de la bioturbation des vers de terre sur la phytodisponibilité des métaux et les mécanismes en jeu en lien avec leur compartimentation, leur spéciation et leur écotoxicité. ►Mise en œuvre : Dans ce contexte, une expérience de 25 jours a été menée en microcosmes, avec ou sans vers de terre dans le sol et avec un gradient d’Eléments Traces Inorganiques (ETI) dû aux retombées des particules atmosphériques. L’influence de l’activité des vers de terre sur les transferts sol-plante des métaux a été étudiée au moyen de microcultures de laitues (dispositif RHIZOtests®) réalisées sur 3 conditions différentes de sols : sols non bioturbés (SNB), sols bioturbés (SB) et turricules (T, déjections des vers). Les concentrations en ETI dans les sols, les vers et les salades ont été mesurées et la bioaccessibilité gastrique humaine a été déterminée à partir du test in vitro BARGE. Par ailleurs, des analyses de spéciation chimique du plomb dans divers compartiments abiotiques (sols et turricules) et biotiques (divers organes du vers de terre) ont été réalisées par spectroscopie EXAFS au synchrotron de l’ESRF à Grenoble. ►Résultats & Discussions : L’activité des vers de terre n’est pas significativement impactée par les concentrations en ETI appliquées dans les sols. Mais, la bioturbation des vers augmente la concentration en ETI présents dans les feuilles de laitues (parties consommées par l’homme). La concentration en ETI dans les feuilles de salades peut augmenter avec l’activité des vers de terre, de plus de 45% et 36 % pour le Pb et le Zn respectivement. Généralement, dans les sols et les plantes, les concentrations mesurées en ETI pour les différentes conditions sont classées ainsi : SNB < SB et T. La bioaccessibilité gastrique humaine est fonction de la nature des ETI et augmente pour SB et T, dans le cas du Zn et du Cu notamment. Des changements de spéciation du plomb mettant en évidence l’effet des vers de terre sur le sol ont été observés par spectroscopie EXAFS, en comparant les sols SNB et T, et les tissus des vers de terre. La figure 1 présente les voies d’exposition des ETI pour les vers, et les mécanismes proposés pour expliquer l’augmentation de phytodisponibilité induite par la bioturbation. Figure 1. Voies d’exposition des vers de terre aux ETI et mécanismes potentiellement impliqués dans l’augmentation de phytodisponibilité du fait de la bioturbation. ►Conclusion : La bioturbation des vers de terre modifie le devenir des ETI dans les sols par des changements de spéciation pouvant augmenter la mobilité des métaux, et certainement aussi en raison de modifications de la distribution des matières organiques présentes dans le sol

Impact of a Wastewater Treatment Plant Upgrade on Amphipods and Other Macroinvertebrates: Individual and Community Responses

In the present study, we investigated the efficiency of additional wastewater treatment based on powdered activated carbon and its benefit for the ecosystem of a connected river system in the catchment area of Lake Constance, Southern Germany. We focused on the overall health status of gammarids and the integrity of the macrozoobenthic community. Samples were taken up- and down-stream of a wastewater treatment plant (WWTP), as well as before and after its upgrading. The investigations showed that both sex ratio and fecundity of gammarids, as well as the macrozoobenthic community were affected by the effluent prior to the WWTP upgrade. After the upgrade, gammarids from the downstream site did not differ any longer from those collected upstream of the WWTP with respect to the investigated health parameters. Furthermore, the overall number of taxa and, particularly, the number of sensitive taxa within the macrozoobenthic community downstream of the WWTP increased considerably. Therefore, we conclude that the additional treatment with powdered activated carbon was highly efficient to improve invertebrate health and community integrity

Community‐specific impacts of exotic earthworm invasions on soil carbon dynamics in a sandy temperate forest

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116978/1/ecy201394122827.pd

Environmental assessment of the behavior of a BOF steel slag used in road construction : the PRECODD-ECLAIR research program

International audienceSteel production generate great amounts of by-products as steel slags. The use of Basic Oxygen Furnace slags (BOF slags) has been restrained due to insufficient volume stability, and due to the lack of environmental regulations. The purpose of the PRECODD-ECLAIR research program is to develop a behavior model based on a multi-scale physico-chemical, mechanical, hydrodynamic and ecotoxicological characterizations of a BOF slag used in a public works scenario. This paper aims at presenting the overall ECLAIR research program, the equipped experimental platform constructed using a BOF steel slag, and the first results of the slag characterization

Experimental simulation of environmental warming selects against pigmented morphs of land snails

H-R.K. and R.T. were gratefully hosted by INRA-PACA, Avignon, France, during the time of fieldwork in 2017. We gratefully acknowledge assistance in the field and with the open-top chamber experiments by Nik Triebskorn and Tim Triebskorn. The 35 field sites were sampled within the 2018 European Theba survey initiated by H-R.K and Thomas Knigge, Le Havre University, France. We also thank Menno Schilthuizen, Leiden University, the Netherlands, and another anonymous reviewer for constructive remarks on a previous manuscript version. Open access funding enabled and organized by ProjektDEAL.In terrestrial snails, thermal selection acts on shell coloration. However, the biological relevance of small differences in the intensity of shell pigmentation and the associated thermodynamic, physiological, and evolutionary consequences for snail diversity within the course of environmental warming are still insufficiently understood. To relate temperature‐driven internal heating, protein and membrane integrity impairment, escape behavior, place of residence selection, water loss, and mortality, we used experimentally warmed open‐top chambers and field observations with a total of >11,000 naturally or experimentally colored individuals of the highly polymorphic species Theba pisana (O.F. MÜLLER, 1774). We show that solar radiation in their natural Mediterranean habitat in Southern France poses intensifying thermal stress on increasingly pigmented snails that cannot be compensated for by behavioral responses. Individuals of all morphs acted neither jointly nor actively competed in climbing behavior, but acted similarly regardless of neighbor pigmentation intensity. Consequently, dark morphs progressively suffered from high internal temperatures, oxidative stress, and a breakdown of the chaperone system. Concomitant with increasing water loss, mortality increased with more intense pigmentation under simulated global warming conditions. In parallel with an increase in mean ambient temperature of 1.34°C over the past 30 years, the mortality rate of pigmented individuals in the field is, currently, about 50% higher than that of white morphs. A further increase of 1.12°C, as experimentally simulated in our study, would elevate this rate by another 26%. For 34 T. pisana populations from locations that are up to 2.7°C warmer than our experimental site, we show that both the frequency of pigmented morphs and overall pigmentation intensity decrease with an increase in average summer temperatures. We therefore predict a continuing strong decline in the frequency of pigmented morphs and a decrease in overall pigmentation intensity with ongoing global change in areas with strong solar radiation.ProjektDEA

Lessons from a landmark 1991 article on soil structure: distinct precedence of non-destructive assessment and benefits of fresh perspectives in soil research

In 1991, at the launch of a national symposium devoted to soil structure, the Australian Society of Soil Science invited Professor John Letey to deliver a keynote address, which was later published in the society’s journal. In his lecture, he shared the outcome of his reflexion about what the assessment of soil structure should amount to, in order to produce useful insight into the functioning of soils. His viewpoint was that the focus should be put on the openings present in the structure, rather than on the chunks of material resulting from its mechanical dismantlement. In the present article, we provide some historical background for Letey’s analysis, and try to explain why it took a number of years for the paradigm shift that he advocated to begin to occur. Over the last decade, his perspective that soil structure needs to be characterised via non-destructive methods appears to have gained significant momentum, which is likely to increase further in the near future, as we take advantage of recent technological advances. Other valuable lessons that one can derive from Letey’s pioneering article relate to the extreme value for everyone, even neophytes, to constantly ask questions about where research on given topics is heading, what its goals are, and whether the methods that are used at a certain time are optimal