International audienceThis research examines how agricultural practices commonly used in Lebanese olive tree orchards (no-tillage, co-culture with Vicia sativa L. var. sativa and conventional tillage) affect soil microbial and chemical characteristics, and whether this depends on geographical context (coastal or inland areas). Four coastal and four inland sampling sites were selected, and at each site three practices were considered (one practice per plot). For each plot (200m(2)), 20 soil samples were taken and homogenized to obtain a composite sample from which soil was characterized chemically and microbiologically. Differences in chemical properties (smaller N content and alkyl C fraction in the coastal area) depended on geographical location rather than on agricultural practices. For microbial properties, catabolic structure varied with geographical location; the index of catabolic diversity was larger in the coastal area. Importantly, the basal respiration was similar in both areas although the soil contained less nitrogen (N) in the coastal area. The negative effect of conventional tillage on microbial functioning of the soil was observed only in relation to geographical location. We found that this effect was reduced by co-culture, for example with Vicia sativa L. var. sativa. Our study reveals that geographical location affects how agricultural practices affect soil properties (in the coastal area, enhanced mineralization of labile C and change in microbial catabolic profile). This suggests that soil management should take into account the environmental conditions specific to coastal areas, which enhance the adverse effects of conventional tillage. Consequently, this type of management should not be implemented in coastal areas of the Mediterranean

• FTIR-ATR was used to test land use effect on soil chemical properties. • Soil chemical signature differs between olive-tree orchards and Mediterranean forests. • Climate (Humid vs Sub humid, coastal vs inland area) also shapes soil properties. • PLS modeling confirmed that FTIR-ATR is a useful tool to predict land use.

The objective of this experimental study was to determine the effect of agronomic practices usually implemented in olive groves (addition of olive mill waste and herbicides) on soil microbial communities and to test whether drought enhanced such effects. For that purpose, mesocosms containing soil cores from olive groves were incubated for 5 months under either of the three treatments: (i) addition of olive mill waste (OMW), (ii) addition of glyphosate‐based herbicide (Gly treatment) and (iii) both treatments. Half of the mesocosms were subjected or not (controls) to drying–rewetting cycles (D/Rw) for 1 month (1 D/Rw) or 3 months (3 D/Rw). In the controls, 2 months after the Gly treatment, higher lipase activities were observed compared with no practice treatment as well as a significant change in catabolic profiles of cultivable microbial communities. Three months later, lipase activities significantly decreased under the Gly treatment. Addition of OMW together with Gly treatment counteracted the negative effect of the herbicide on lipase activities. After three D/Rw cycles, Gly treatment modified catabolic profiles and induced a decrease in functional diversity. Overall, the combination of glyphosate‐based herbicide with OMW was a conservative practice that maintained soil functioning and led to a better response to D/Rw cycles.