Résumé
Nitrogen (N) availability is crucial to maintaining crop productivity in
agroecosystems, driven primarily by soil microbial processes such as
nitrification and denitrification. Weeds are an integral part of
agroecosystems and are involved in many processes related to the N cycle,
but how weed management could shift plant-microbe interactions and thus
N-cycling is yet to be determined. Using a network of 15 Mediterranean
vineyards, we quantified the effect of five years of different weed
management practices (chemical weeding, tillage, mowing) on the
aboveground and belowground functional properties of weed communities and
soil microbial N-cycling. Specific root length (SRL) of the tilled and
mowed weed communities were 30 % and 44 % lower than in the
herbicide-treated weed communities. Soil pH and texture were the main
drivers of soil microbial activity as quantified by substrate-induced
respiration (SIR), potential denitrifying enzyme activities to SIR ratio
(PDEA:SIR) and potential nitrifying to denitrifying enzyme activity ratio
(PNEA:PDEA). Acidic soils with a low sand content had high SIR while
alkaline soils with low sand content had high PDEA:SIR. PNEA:PDEA was
negatively related to soil pH. • SIR was also impacted by the management:
mowed weed communities had 58 % higher SIR compared to herbicide-treated
communities. Weed communities with high SRL were associated with soils
with a higher nitrifying enzyme efficiency per unit of respired carbon.
Synthesis and applications: Overall, our findings indicate that
vineyard weed management influences the potential nitrifying enzyme
activities by modifying the root strategies of weed communities. This
study highlights that the design of sustainable weed management strategies
should incorporate unintended effects on soil microbial communities and
N-cycling.23-Sep-2024 --