The effects of olive orchard diversifications on greenhouse gas emissions and its influencing factors

Abstract Purpose In recent years, intercropping in olive groves has become a sustainable practice for mitigating climate change. Therefore, the objective of this study was to determine whether crop diversification in rainfed olive groves modifies carbon dioxide (CO 2 ), nitrous oxide (N 2 O), and methane (CH 4 ) emissions and key chemical and enzymatic properties of the soil in the short term. Materials and methods A field experiment was conducted under semi-arid Mediterranean conditions using four treatments: a conventional olive monocrop (CP) and three crop diversification systems: saffron ( Crocus sativus ) (D-S), oats and vetch ( Vicia sativa and Avena sativa ) (D-O) and lavandin ( Lavandula × intermedia ) (D-L). CO 2 , N 2 O, and CH 4 emissions were measured periodically using closed static chamber techniques. Simultaneously, soil samples were analyzed to determine physicochemical parameters (pH, total nitrogen (TN), total organic carbon (TOC), P available, K, and Fe) and enzymatic activities (β-1,4-glucosidase (BG), leucine aminopeptidase (LA), N-acetylglucosaminidase (NAG), Arylsulfatase (AS) and phosphatase (AP) and dehydrogenase (DH)) in order to evaluate the interactions between soil properties and gas fluxes. Results and discussion The results showed that CO 2 emissions were significantly higher in D-S (385.2 mg CO 2 m -2 h -1 ) and D-O (335.2 mg CO 2 m -2 h -1 ) compared to CP, which was attributed to increased microbial and root activity promoted by the vegetation cover. In contrast, N 2 O fluxes (0.002 mg N 2 O m -2 h -1 in CP, 0.007 in D-S, 0.001 in D-O, and − 0.002 in D-L) and CH 4 (–0.2 mg CH 4 m -2 h -1 in CP, 0.1 in D-S, 0.2 in D-O, and 0.2 in D-L) did not show significant differences between all treatments ( p > 0.05 ), probably due to the prevailing semi-arid conditions. D-O had higher values of P available, Fe, and TN, while D-S and D-L stood out for higher values of K and TOC, both compared to CP. Enzymatic activities were particularly higher in D-S and D-O, specifically BG, LA, and AS. In addition, positive and significant correlations were observed between CO₂ accumulation and several soil parameters: in D-S, with POC, total Zn, exchangeable Na, total Cu, and BG, LA, and AS activities; and in D-L, with POC, exchangeable Na, total Mn, P available, TN, and LA and AS activities, highlighting that these indicators contribute to the regulation of greenhouse gas (GHG) emissions. Conclusion It was concluded that crop diversification in rainfed olive groves increases CO 2 emissions in the short term due to intensified biological activity, but at the same time improves soil fertility and biochemical functionality. However, long-term monitoring is required to determine whether these systems contribute to carbon stabilization and net sequestration, ensuring their potential as sustainable strategies for climate change mitigation in Mediterranean agroecosystems.