Anaerobic digestion is increasingly used in Europe to treat organic substrates and produce biogas as a renewable energy source. The residual matter (digestate) is used in agriculture as an organic fertilizer. The study aims at assessing the impact of digestate application in the field on earthworms from the short term (few hours) to the long term (two years), and at investigating under laboratory conditions the role of ammonia and earthworm behavior on digestate toxicity in the short term. First, we studied earthworm communities in fields fertilized with digestates, cattle effluents, or chemical fertilizers for two years. Earthworm abundance was assessed before and after the fertilization event of the third year. Earthworm mortality at the soil surface was also assessed immediately after fertilization. Next, the toxicity of digestate or ammonia solutions on Aporrectodea caliginosa and Lumbricus terrestris was measured in microcosms (110 cm(3)) to better understand the short-term toxicity (two weeks). Finally, we spread digestate (40-80 t ha(-1)) on soil columns (5300 cm(3)) and used X-ray tomography after two weeks to assess the burrowing behavior of earthworms in the cores. Earthworm abundance was 150% higher in the fields treated for two years with digestates or cattle effluents compared to the field treated with chemical fertilizers. 0.5 to 2% of adult earthworms died at the soil surface a few hours after liquid digestate and cattle slurry spreading (18 to 24 t ha(-1)). The digestate (10% to 20% (fresh digestate/dry soil)) and ammonia were also lethal to earthworms in the microcosms within two weeks. In contrast, no mortality occurred inside soil columns two weeks after digestate spreading; A. caliginosa avoided the soil surface with high digestate inputs. This case study highlighted the potential short-term toxicity of digestate (a few hours), which evolved towards a neutral to positive impact in the field in the longer term (from two weeks to two years). Further research is needed to understand the impact of diverse solid and liquid digestates on soil macrofauna in different soils.

At the time of spring pre-emergent herbicide application, the soil surface in conservation agriculture is most of the time covered by cover crops (CC) mulches. The state of these mulches depends on their destruction date and on the selected species. Sorption and degradation of C-14-S-metolachlor on and within 8 decaying CC-covered (2 species x 4 initial decomposition state) soils corresponding to conservation agriculture were compared to its fate in bare soil (BS) corresponding to conventional agriculture. C-14-S-metolachlor and its metabolites distribution between mineralized, extractable and non-extractable (NER) fractions was determined at 5 dates during a 20 degrees C/84-d period. Herbicide mineralization was weak (<2%) for both CC and BS. Extractability of C-14 in BS was intermediate between CC that were decomposed 28 or 56 days and 0 or 6 days before application. Degradates consisted in up to 43% of total radioactivity, with specificities according to the CC or soil compartment. NER formation was equivalent in BS and in the much decomposed CC amended microcosms, and was stronger in less decomposed CC. S-metolachlor DT50 was 23-d in BS, and 9, 15, 39 and 25-d for CC ordered by increased decomposition state at the time of application. These results were attributed to the proportion of C-14 intercepted by CC, and to higher levels of organic matter and microbial activity in less decomposed CC as compared with more decomposed ones. Then the state of decomposition level of CC residues determines the behaviour of SMOC (S-metolachlor) sprayed on the mulch in the conditions of conservation agriculture. (C) 2018 Elsevier B.V. All tights reserved.

The recycling of exogenous organic matter (EOM) through agriculture is an efficient way to enhance soil organic matter (SOM) and to supply crops with readily available nutrients. It can also cause environmental damage, such as nitrate leaching. Characterisation of EOM to predict the C and N dynamics of mineralisation when applied to cropped soils is essential to improve its use in agriculture. The measurement of C and N mineralisation through soil laboratory incubation of 18 types of EOM and EOM biochemical fractionation were used to parameterise the NCSOIL model to simulate the mineralisation kinetics of C and N. The soil type did not significantly interfere with EOM mineralisation and parameterisation, enabling extrapolation of the parameters for one soil to other soil types. Four groups of EOM were distinguished based on their C and N dynamics: (1) stable compost, (2) more reactive compost and stable manure, (3) manure and (4) very reactive EOM as sludge and litter that should be used as fertiliser. The use of easily accessible indicators, such as I-ROC (Lashermes et al., 2009) and the measured organic C:N ratio (CNEOM) was appropriate for parameterising groups 1 and 4. Regression relating the optimised resistant pool size and Van Soest fractions and CNEOM was found (R-2 of 0.967) to improve the pool sizes for the remaining EOM. Further research is required to improve the parameterisation. (C) 2016 Published by Elsevier Ltd.

The increasing use of cover crops (CC) may lead to an increase in glyphosate application for their destruction. Sorption and degradation of 14C-glyphosate on and within 4 decaying CC-amended soils were compared to its fate in a bare soil. 14C-Glyphosate and its metabolites distribution between mineralized, water-soluble, NH4OH-soluble and non-extractable fractions was determined at 5 dates during a 20 °C/84-d period. The presence of CC extends 14C-glyphosate degradation half-life from 7 to 28 days depending on the CC. 14C-Glyphosate dissipation occurred mainly through mineralization in soils and through mineralization and bound residue formation in decaying CC. Differences in sorption and degradation levels were attributed to differences in composition and availability to microorganisms. CC- and soil-specific dissipation patterns were established with the help of explicit relationships between extractability and microbial activity.

This study quantifies and models the influence of the type and the degree of decomposition of cover crops (CC) on three pesticides sorption: epoxiconazole (EPX), S-metolachlor (SMOC) and glyphosate (GLY). Residues of four cover crop species were incubated for 0, 6, 28 or 56 d in controlled conditions. For each incubation time, adsorption of pesticides on CC residues was measured in batch experiments. Additionally, the biochemical and elemental composition (Van Soest fractionation, C:N, (13)C NMR spectroscopy) of CC was characterized. Mineralization of CC residues was monitored at all incubation times using CO2 trapping. Results showed that the adsorption of pesticides differed significantly according to (i) the type of molecule, (ii) the type of CC, (iii) the degree of CC decomposition and the interaction CC×decomposition time. EPX and GLY were the most (Kd ranging from 188 to 267 L kg(-1)) and the least (Kd ranging from 18 to 28 L kg(-1)) sorbed pesticides respectively. With increasing decomposition of the CC residue, sorption increased by 1.6- to 4.7-fold according to the type of pesticide and cover crop. It was significantly correlated with the net cumulative mineralization (ρ>0.7) and other indicators of biochemical composition such as C:N ratio (ρ<-0.7), the Van Soest neutral detergent soluble fraction (ρ>0.5) and the alkyl/O-alkyl C ratio determined by NMR. An innovative model based on net cumulative mineralization of CC residues is proposed to describe the pesticide sorption and appears to be a promising approach to account for the effects of decaying plant residues on the environmental fate of pesticides.

Pharmaceutical products excreted by treated animals or humans are transferred to manure or wastewater, respectively. In wastewater treatment plants, they can be degraded and/or adsorbed into sludge. Therefore pharmaceuticals may be indirectly disseminated into the environment from the recycling of organic residues in agriculture, which is largely encouraged nowadays. Even though the European regulations on this usage do not include pharmaceuticals, they are considered as emerging pollutants due to their potential activity against non-target organisms and their potential risk of transfer towards aquatic ecosystems. It is thus necessary to estimate their available concentration, mostly present in soil water or in the aqueous phase of organic residues. These analyses represent a challenge, because of the trace-level concentration of pharmaceuticals in complex matrices. We developed an analytical method for the quantification of 14 pharmaceuticals (including 8 antibiotics) in various aqueous environmental samples: soil water and aqueous fractions of pig slurry, digested pig slurry and sewage sludge, which present a wide range of dissolved organic carbon (DOC) content [1]. The analysis was performed by online solid-phase extraction coupled to ultra-high performance liquid chromatography with tandem mass spectrometry (on-line SPE-UHPLC-MS/MS). During this development, we have been particularly confronted to the importance of matrix effects in mass spectrometry analysis. Indeed, undesirable molecules present in the samples can strongly modify the MS signal of the analytes, leading to a wrong quantification and an increase of quantitation limits. We thus proposed a criterion and methods to deal with these matrix effects. The matrix effects, mostly due to ion suppression, were shown to be a function of the DOC content and its origin. They were limited in soil water which presents low DOC content (-22% to +20%), thus internal quantification by isotopic dilution allowed their correction. On the contrary, in charged matrix they could rise up to the [-38% to -93%] range. The matrix effects variability between the samples suggested DOC content cut-offs above which sample purification was required. These cut-offs depended on compounds, with concentrations ranging from 30-290 mg C/L for antibiotics up to 600- 6400 mg C/L for the most apolar compounds. When necessary, a purification method compatible with fluoroquinolones and tetracyclines was furthermore proposed. It was based on a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) extraction procedure using a new composition of salts. The overall procedure was found simple, rapid, sensitive, accurate and efficient.

We quantified the effects of tillage practice and repeated compost (municipal solid waste compost, MSW, and co-compost of sewage sludge and green wastes, SGW, compared with a control plot without compost addition, CONT) application on bromide and isoproturon transport into the tilled horizon of a loamy Albeluvisol. To do this we conducted field measurements of near-saturated hydraulic conductivity (K), bromide and isoproturon leaching in column experiments and batch isoproturon sorption measurements. While the K measurements showed that tillage practice had the major effect compared with the different organic amendments, with greater conductivities measured after ploughing and smaller Kvalues measured after sowing, the column leaching experiments showed no statistically significant effect of either the tillage practice or the compost amendments. The batch sorption coefficient, Kd, of isoproturon increased in the order CONT < MSW < SGW, while the leaching of isoproturon for the MSW and SGW was either equal, retarded or quicker compared with CONT. Rate-limited sorption of isoproturon in the CONT and SGW treatments columns was found, and the overall dissipation of isoproturon increased in the order CONT < SGW < MSW. It was suggested that irreversible sorption as well as degradation occured during isoproturon leaching.

A simplified particle-size fractionation procedure of soil organic matter was used to localize and quantify the non-extractable residues of C-14-labelled isoproturon in a soil where large amounts of bound residues were formed. Four size-fractions were isolated corresponding to non-humified organic matter in fractions (> 200 and 200-50 mu m) and humifled organic matter in fractions (50-0.2 mu m and < 0.2 mu m). The majority of C-14-isoproturon bound residues were associated with humified organic matter. In each fraction, concentrations of bound residues normalized to carbon (C) content were used as indicators of the capacity of organic matter to bind herbicide residues. Binding capacities differed among size fractions, and were greater for the more decomposed organic materials located in fractions < 50 mu m. Results were compared to previous data concerning atrazine residues and discussed in terms of the physico-chemical and microbial processes implicated in the binding properties of the different fractions.