Immobilisation des champignons filamenteux: aspects fondamentaux et appliques. (Fusarium moniliforme un modele)

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 20379 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Effects of glyphosate application and nitrogen fertilization on the soil and the consequences on aboveground and belowground interactions

International audienceThe application of nitrogen (N) and herbicides are commonly used to fertilize crops and protect them against weed development, but are also considered as soil and environment pollutants. Even so, the individual and combined non-target effects of N fertilizers and herbicides on multitrophic interactions within agrosystems are not well known. From soil samples collected in the field, we examined the effects of the direct application of glyphosate and/or N fertilization on microbial activities and soil nutrient status. In addition, we investigated the increase in biomass and, nutrient acquisition of the bean (Phaseolus vulgaris) and the consequences of the applications of N and glyphosate on the performance of the herbivore aphid (Aphis fabae). From soils that did (N +) or did not receive (NO) synthetic N fertilization over a 6-year period, we assessed the effects of glyphosate (CK, without glyphosate; FR, field rate of glyphosate) and N fertilization (N +, with N fertilization; NO, without N fertilization) applications in a mesocosm experiment for 75-days. Following the 75 day treatment, the biological and physiological consequences, both belowground and aboveground were determined. The growth of arbuscular mycorrhizal fungi (AMF) and dehydrogenase activity, were negatively affected following N + fertilization and the application of the FR of glyphosate, while in the absence of glyphosate, alkaline phosphatase (AIP) activity was reduced. Functional microbial responses were unaffected by both. N and glyphosate, even when applied in combination. Conversely, the N fertilization significantly increased the nitrate content (NO3-) in,the CK soils and the total N in the FR soils, compared to CK/NO and FR/NO soils. The combined effects of glyphosate and nitrogen fertilization (FR/N +) significantly decreased the soil C:N ratio, but significantly increased nitrification compared to CK/NO and FR/NO soils. The FR/N + treatments positively affected plant performance, improving the total chlorophyll, sucrose, ammonium, amino acid content, and pod biomass, compared to the CK/NO and FR/NO soils. Unlike glyphosate, which did not appear to exert an effect when applied alone or in combination, N fertilization significantly increased aphid nymph survival. The non-metric multidimensional scale allowed us to establish belowground and aboveground interactions with glyphosate and N fertilization. We conclude that glyphosate and N fertilization have negative effects on soil microflora and potential pests, but do not necessarily affect belowground and aboveground interactions, and may offer equal or superior benefits to crop productivity

Does nitrogen fertilization history affects short-term microbial responses and chemical properties of soils submitted to different glyphosate concentrations? - Fig 2

<p><b>Values of (A) average well color development and (B) Shannon diversity index <i>H</i>’ of culturable microbial communities on BIOLOG ecoplates of glyphosate-free and glyphosate-treated soils under two N fertilization histories.</b> Different letters denote significant differences according to Tukey HSD test (<i>P</i> < 0.05) among all fertilization and herbicide treatments at each incubation time (1, 8, 15 days). CK: glyphosate-free, FR: field rate, 100FR: 100 × field rate, N+: N-fertilized for 6 years, N0: unfertilized for 6 years.</p

Principal component analysis based on correlations between soil microbial and chemical parameters at each incubation time (1, 8, 15 days).

<p>N+\CK: fertilized soils and glyphosate-free (black circles), N+\FR: fertilized soils and field application rate of glyphosate (black triangles), N+\100FR: fertilized soils and 100 times the field application rate of glyphosate (black squares), N0\CK: unfertilized soils and glyphosate-free (white circles), N0\FR: unfertilized soils and field application rate of glyphosate (white triangles), N0\100FR: unfertilized soils and 100 times the field application rate of glyphosate (white squares), DH: dehydrogenase activity, AlP: alkaline phosphatase activity, URE: urease activity, AWCD: average well color development, <i>H</i>’: Shannon index, CEC: cation exchange capacity, TOC: total carbon organic, TN: total nitrogen, Soil.C.N: soil C:N ratio, pH: hydrogen potential, PO₄: available phosphorus content, NO₃: nitrate content, NIT: average net nitrification rate, Moisture: soil moisture.</p

Principal component analysis based on the data of the carbon substrates groups from Biolog EcoPlates at each incubation time (1, 8, 15 days).

<p>N+\CK: fertilized soils and glyphosate-free (black circles), N+\FR: fertilized soils and field application rate of glyphosate (black triangles), N+\100FR: fertilized soils and 100 times the field application rate of glyphosate (black squares), N0\CK: unfertilized soils and glyphosate-free (white circles), N0\FR: unfertilized soils and field application rate of glyphosate (white triangles), N0\100FR: unfertilized soils and 100 times the field application rate of glyphosate (white squares).</p

Average net nitrification rate in glyphosate-free and glyphosate-treated soils under two fertilization histories over a 15-days incubation period at 22°C.

<p>Different letters indicate a significant difference according to Tukey HSD test (<i>P</i> < 0.05). CK: glyphosate-free, FR: field rate, 100FR: 100 × field rate, N+: N-fertilized for 6 years, N0: unfertilized for 6 years.</p

Summary of the measured effects of glyphosate application / nitrogen history combinations on soil biological and chemical parameters at 15 days following glyphosate application in the laboratory incubation.

<p>Effects of treatments on variables are coloured by green as positive, and red as negative while the absence of clear effect was coloured by blue. DH: dehydrogenase activity, AlP: alkaline phosphatase activity, URE: urease activity, AWCD: average well color development, <i>H</i>’: Shannon index, PO₄: available phosphorus content, NO₃: nitrate content, NIT: average net nitrification rate.</p

Soil chemical properties measured at each incubation time (1, 8, 15 days) under two N fertilization histories and three doses of glyphosate application.

<p>Soil chemical properties measured at each incubation time (1, 8, 15 days) under two N fertilization histories and three doses of glyphosate application.</p