The Combined Effect of Mycorrhization and Olive Mill Wastewater on Biomass Productivity and Physiological Performance in Young Olive Plants

Abstract

The study aims to determine the optimal dose of olive mill wastewater (OMW) for maximum mycorrhization and to assess the biomass, physiological, and biochemical tolerance of mycorrhizal olive plants to stress induced by this wastewater. The study involved injecting Rhizopha-gus irregularis into young olive trees (Olea europaea L.) under greenhouse conditions. At rates of 100, 150, and 200 m³/ha, OMW is applied to the soil surrounding each olive tree. For comparison, a non-inoculated group was added as a control. Dry matter, mycorrhization rate, leaf relative water content (RWC), foliar nutrients (N, P, and K), and a number of physiological and biochemical parameters were among the variables that were assessed. When arbuscular mycorrhizal fungi and olive mill wastewater were combined at a rate of 100 m³/ha, the results showed significant increases in dry matter (22.5%), Leaf relative water content (16.32%), potassium levels (38.46%), stomatal conductance (30.4%), and photosynthesis compared to the control. However, high olive mill wastewater doses (150 and 200 m³/ha) caused water stress: Compared to non-mycorrhizal plants (NM), the decrease in mycorrhizal plants (M) was less pronounced. Leaf relative water content dropped by 14.9% and 21.27% in mycorrhizal plants and by 22.22% and 28.88% in non-mycorrhizal plants. Under these high doses of Olive mill wastewater, the mycorrhization rate dropped significantly by as much as 30% and 45% respectively. All OMW treatments increased proline and sugar content as stress responses. Consequently, our study reveals that the optimal application of 100 m³/ha of OMW, combined with Rhizophagus irregularis, enhances the growth and performance physiology of young olive plants while increasing mycorrhization rates, stomatal conductance, and photosynthetic efficiency. This synergy between OMW and AMF also promotes better plant resilience to water stress by activating biochemical mechanisms such as increased proline and sugar levels. Additionally, AMF mitigates the negative effects of high OMW doses, highlighting its crucial role in managing the risks associated with wastewater application.

Keywords

• olive mill
• wastewater
• arbuscular mycorrhizal fungi
• olive plants
• photosynthetic