Fate of realistic maize herbicides mixtures and impacts on soil microbial communities

Transcription

1 Fate of realistic maize herbicides mixtures and impacts on soil microbial communities Joly Pierre Besse-Hoggan, P., Bonnemoy, F., Perrière, F., Bohatier, J. and Mallet, C. Pesticide Behaviour in Soils, Water and Air 2-4 September 213 York, UK

2 Herbicides in environment - Possible transfer of herbicides molecules after spraying on cultures Herbicides Microbial communities Pool of organic matter Primary and secundary productions - Important literature on the impact of herbicides sprayed alone at exaggerated or realistic doses Lo, 21 ; Puglisi, 212 (review) IMPACT on ecological processes and biochemical cycles

3 Herbicides in environment Laws EU Policy Ecophyto 218 Guidelines SAU Around 4% / yr UIPP 211 Use of mixtures Quantity decreases / Number of molecules rises LACK of knowledge on the effects of pesticides mixtures

4 Study case : replacement of Atrazine atrazine 23 max. 3 kg/ha/yr MIXTURE of pesticides! < 3 kg/ha/yr

5 Experimentation design S-metolachlor mesotrione nicosulfuron Dual Gold Safeneur Callisto Milagro Herbicides used alone or in mixture (2 or 3 molecules) Microcosms study (5 replicates/condition/date of sampling) Following an application schedule (sequential pollution) days

6 Experimentation design Experimental conditions : - Limagne clay-rich soil - Sieved at 4mm - Humidity at 5% of WHC - Room temperature at 2 C ± 2 C - Day/Night cycle (14h/1h)

7 Experimentation design Herbicides & metabolites concentrations (HPLC) Total microbial community Specific communities (involved in nitrogen cycle and phototrophic organisms) Abundance / Diversity / Activities

8 Results Fate of herbicides

9 Percentage of herbicide initial input remaining Fate of herbicides S-metolachlor contained in the commercial formulation Dual Gold Safeneur DG Day of treatment

10 Percentage of herbicide initial input remaining Fate of herbicides S-metolachlor contained in the commercial formulation Dual Gold Safeneur DG DG (DG/C) Day of treatment

11 Percentage of herbicide initial input remaining Fate of herbicides S-metolachlor contained in the commercial formulation Dual Gold Safeneur DG 6 DG (DG/C) 4 DG (DG/M) Day of treatment

12 Percentage of herbicide initial input remaining Fate of herbicides S-metolachlor contained in the commercial formulation Dual Gold Safeneur DG 6 DG (DG/C) DG (DG/M) 4 DG (DG/C/M) Day of treatment

13 Fate of herbicides - Different S-metolachlor dissipation kinetics between mixtures - Presence at day 12 at around 2 to 4% of the initial input - Total dissipation of mesotrione after 91 days whatever the considered treatement - Slow dissipation of nicosulfuron - At day 12, more than 6% of the initial input remains

14 Results Nitrogen cycle NO 3 - NH 4 + NO 2 - NO nitrification denitrification

15 N-NH4+ (µg.g -1 dry soil) Ammonium (NH 4+ ) Co DG C M DG/C DG/M C/M DG/C/M Day of treatment

16 N-NH 4 + (µg.g -1 soil dw ) Ammonium (NH 4+ ) e 2.5 e de Co 2 DG C a b c ab c abc a c bc cd bc abc ab a a b ab b M DG/C DG/M C/M DG/C/M Day of treatment

17 N-NO 3 - (µg.g -1 of soil dw ) Nitrates (NO 3- ) c bc c b ab ab c bc a ab bc bc c a b a ab a Co DG C M DGC 6 DGM CM 4 DGCM Day of treatment

18 Archeal amoa gene (copies.ng -1 DNA tot.) Bacterial amoa gene (copies.ng-1 DNA tot.) Abundance of nitrifying communities NH 4 + NO 2 - amoa Archeal (AOA) / Bacterial (AOB) Differences at days 22 and 28 only 3 25 AOA 12 1 AOB 2 15 Co DG C M 8 6 Co DG C M 1 DG/C DG/M 4 DG/C DG/M 5 C/M DG/C/M 2 C/M DG/C/M Day of treatment Day of treatment

19 Impact of herbicides mixtures on the nitrogen cycle Day 28 NO 3 - Day 56 Pool of O.M. NH 4 + NO 2 - NO Nitrification AOA abundance Sensitive communities 1 2 Mixture of 2 or 3 herbicides Analyses in terms of activities are needed, in order to confirm hypothesis 1 results The increase of ammonium quantities can also be linked to the action of herbicides mixtures on sensitive communities (hypothesis 2)

20 Results Phototrophic communities

21 Phototrophic communities Shifts in soil surface colonization by phototrophic communities Analyses of diversity and pigments abundance

22 peak intensity (AU) Phototrophic communities HPLC analysis of pigments content fucoxanthin chlorophyll a retention time (min.)

23 Co DG C M DGC DGM CM DGCM Total percentage Co DG C M DGC DGM CM DGCM Pigment (µg.g-1 soil dw) Phototrophic communities Shifts in soil surface colonization by phototrophic communities 16 Day 56 Day 91 Day Fucoxanthin Chlorophyll a

24 Phototrophic communities 1% Cloning-sequencing Day 91 9% 8% 7% 6% 5% 4% Xanthophyceae Diatom Chlorophyceae 3% 2% 1% % T DG C M DGCM

25 Conclusion Herbicides mixtures, at the recommended field rate, change the molecules dissipation rate and temporally impair the microbial communities NO 3 - Pool of O.M. NH 4 + NO 2 - NO Sensitive communities (phototrophic ) Mixture of 2 or 3 herbicides Nitrification AOA abundance Resistant communities (degrading) metabolites

26 Perspectives of this work Analyses currently running in order to confirm the results Limagne soil (clay dominant) Versailles soil (silt dominant) Use another type of soil and analyse the behaviour and the impact of the herbicides mixtures with these new parameters Ecosphère Continentale et Côtière

27 Thank you for your attention Looking for a Post Doctoral position! Contact : pijoly@gmail.com Isolation of pesticide-degrading bacteria by Most Probable Number (MPN) method using tetrazolium salts; Magalie Stauffert; Clermont Université; France Isolation and characterization of edaphic herbicide-degrading fungal strains after exposure to a mixture of herbicides; Magalie Stauffert; Clermont Université; France Biodegradation of sulcotrione herbicide in a Vertic dark soil: impact of pesticide/soil/bacteria interactions; Edith Dumas; Clermont Université; France Poster session A, today, 5 p.m. to 6:3 p.m.