Many studies on biostimulants and nutrient-based fertilizers of olive trees have been focused on the ability of these products to increase olive productivity and ameliorate oil quality. However, little information is available on their effects on rhizosphere microbial communities; whereas it is well known that microorganisms associated with plants play a key role on the productivity and the health of their host. The aim of this study was to evaluate the effects of foliar application of a biostimulant and nutrient fertilizers on photosynthesis, carbohydrate profile of the roots and soil microbial community structure. Specific attention was paid to arbuscular mycorrhizal (AM) fungi. The phospholipid fatty acid (PLFA) 16:1ω5 and the neutral lipid fatty acid (NLFA)16:1ω5 in the roots (intraradical mycelium) and in the soil (extraradical mycelium) were used as biomarkers for AM fungi. Experimentation consists of the annual foliar application of six nutrient-based treatments during two successive growing seasons: TC (untreated trees), T₁ (nitrogen-based fertilizer), T₂ (biostimulant rich in boron, magnesium, sulfur, manganese and amino acids), T₃ (products rich in phosphorus, potassium and boron), T₄ (product rich in phosphorus, calcium and zinc), T₁₂ (application of T₁ and T₂) and T₁₂₃₄ (application of T₁, T₂, T₃ and T₄). At the end of the experiment, statistical analysis revealed a significant modification of macronutrient and micronutrient profiles of olive leaves, which caused a significant increase of photosynthesis and induced quantitative changes in the most of individual root sugars, essentially the translocated forms of sugars (sucrose and mannitol). Foliar application of fertilizers and biostimulant increased the PLFA biomarkers indicative of Gram-positive bacteria (i15:0, i16:0), Gram-negative bacteria (16:1ω7, 16:1ω9, cy17:0, 18:1ω7 and cy19:0) and actinobacteria (10Me16:0). The level of NLFA 16:1ω5 in both the rhizosphere and roots, increased significantly under foliar fertilization, however the level of PLFA 16:1ω5 did not appear to be significantly influenced, suggesting that spore and vesicle formation was more sensitive to foliar fertilization than the hyphae development. The NLFA 16:1ω5/PLFA 16:1ω5 ratio, in the roots of olive trees, showed a significant increase, indicating that AM fungi allocated high carbon to storage structures following foliar fertilization. Our study provides evidence that foliar fertilization induces rapid changes in specific microbial groups, which in turn increase the rhizosphere carbon metabolism.

许多关于橄榄树生物刺激素和营养基肥料的研究都集中在这些产品提高橄榄产量和改善油质的能力上。然而，关于它们对根际微生物群落影响的信息很少。而众所周知，与植物相关的微生物对其宿主的生产力和健康起着关键作用。本研究的目的是评估叶面施用生物刺激素和营养肥料对光合作用、根的碳水化合物分布和土壤微生物群落结构的影响。特别关注丛枝菌根 (AM) 真菌。磷脂脂肪酸 (PLFA) 16:1ω5 和中性脂脂肪酸 (NLFA)16：根（根内菌丝体）和土壤（根外菌丝体）中的 1ω5 用作 AM 真菌的生物标志物。试验包括在两个连续的生长季节期间每年对六种基于营养的处理进行叶面喷施：TC（未经处理的树木）、T₁（氮基肥料）、T ₂（富含硼、镁、硫、锰和氨基酸的生物刺激素）、T ₃（富含磷、钾和硼的产品）、T ₄（富含磷、钙和锌的产品） )、T ₁₂（T ₁和T _{2 的应用}）和T ₁₂₃₄（T ₁、T ₂、T ₃和T _{4 的应用）}）。在实验结束时，统计分析显示橄榄叶的宏量营养素和微量营养素谱发生了显着变化，这导致光合作用显着增加并诱导了大部分根糖的数量变化，主要是糖的易位形式（蔗糖和甘露醇）。叶面施肥和生物刺激素增加了指示革兰氏阳性菌（i15:0、i16:0）、革兰氏阴性菌（16:1ω7、16:1ω9、cy17:0、18:1ω7和cy19:0）的PLFA生物标志物) 和放线菌 (10Me16:0)。根际和根中NLFA 16:1ω5的水平在叶面施肥下显着增加，但PLFA 16:1ω5的水平似乎没有受到显着影响，表明孢子和囊泡的形成对叶面施肥比菌丝发育更敏感。橄榄树根部的 NLFA 16:1ω5/PLFA 16:1ω5 比率显示出显着增加，表明 AM 真菌在叶面施肥后将高碳分配给储存结构。我们的研究提供的证据表明，叶面施肥会引起特定微生物群的快速变化，进而增加根际碳代谢。