Olive mill waste and glyphosate‐based herbicide addition to olive grove soils: effects on microbial activities and their responses to drying–rewetting cycles

Abstract

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.

Challenges of soil carbon sequestration in the NENA region

“…Further, frequent cultivation, irrigation with saline water and soil salinity rise in coastal areas exert significant effects on soil microbial functional properties. For instance, 3 months after the application of glyphosate-based herbicide to the soil under olive trees in coastal Lebanon, lipase activities significantly decreased (Boukhoudoud et al, 2017). Soil classification and SOC mapping help to identify hotspots that need to be improved or require special management measures and bright spots with satisfactory C accumulation levels that need to be protected.…”

Microbiome Associated with Olive Cultivation: A Review

“…The effect of agronomic practices that are usually applied to olive trees, such as residue addition and glyphosate herbicide, on the soil microbial community was studied by Boukhdoud et al [ 27 ] in Alpilles, near the city of Marseille (southeastern France). They observed significant changes in the catabolic profiles of cultivable microbial communities and higher lipase activity in the soil after 2 months of glyphosate application, leading to a reduction in functional diversity.…”

“… Subjects covered in the selected papers, in percentage, addressing the effect of management with different soil microorganisms, and in different edaphic conditions, between brackets. Microbial diversity [ 8 , 10 , 12 , 17 , 26 ], Catabolic diversity [ 10 , 11 , 27 ], Microbial density [ 9 , 15 , 17 , 19 , 22 , 23 , 25 , 28 , 37 ], AMF colonization [ 13 , 23 , 29 , 30 , 31 , 32 , 33 , 34 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 48 , 49 ], Soil enzymes [ 14 , 17 ], N 2 fixing [ 19 , 21 ]. …”

Environmental Drivers of Microbial Functioning in Mediterranean Forest Soils

“…In the Mediterranean context particularly, where forests are subjected to specific constrains such as drought stress, heat waves, low nutrient availability and recalcitrant organic compounds [13] we still lack a clear understanding of factors controlling microbial C metabolism and driving soil C dynamics. Experimental determination of drivers has helped to develop which drivers may be of importance on Mediterranean soils (i.e., soil OM quality and water availability [14,15]), but a more accurate determination of drivers from measurements done in situ will give greater insight to the mechanisms maintaining microbial communities' structures and functions in these soils.…”