The increasing popularity of avocado (Persea americana) fruit has led to a rise in environmental impacts of avocado production. There is an urgent need to adopt sustainable nutrient practices in avocado nurseries and orchards to reduce nitrogen (N) pollution without compromising productivity. However, there is little understanding of how avocado rootstocks respond to different N fertilisation strategies. We investigated the effects of a plant growth-promoting rhizobacterium (PGPR) from the genus Paraburkholderia on growth of Reed avocado seedlings fertilised with either inorganic N fertiliser (iN) or combined inorganic N with organic manure-based fertiliser (iNoN). We studied plant growth and N acquisition, mineral N (NH₄⁺-N and NO₃⁻-N) in leachate, potting-mix physicochemical properties, and rhizosphere microbial communities. PGPR increased N uptake efficiency (NUpE) in seedlings fertilised with iNoN by 23% compared with iNoN without PGPR, 120% compared with iN without PGPR, and 71% compared with iN with PGPR. No significant differences in growth or mineral N leaching were observed between the iNoN and iN treatments. However, both uninoculated and PGPR-inoculated plants with iNoN fertiliser had greater plant N uptake and rhizosphere microbial-biomass N than uninoculated plants with iN fertiliser. Potting medium with iNoN fertiliser had higher N retention than with iN fertiliser, regardless of PGPR inoculation. Our results provide evidence that PGPR effects on N uptake efficiency are regulated by N form and N availability. The beneficial effects of PGPR inoculation when co-applied with a combination of inorganic and organic N fertiliser indicate that PGPR-based technologies can improve nitrogen recovery in avocado nurseries.

鳄梨（Persea americana）果实的日益普及导致鳄梨生产对环境的影响增加。迫切需要在鳄梨苗圃和果园采用可持续的营养做法，以在不影响生产力的情况下减少氮 (N) 污染。然而，人们对鳄梨砧木对不同施氮策略的反应知之甚少。我们研究了来自Paraburkholderia属的植物生长促进根际杆菌(PGPR)对使用无机氮肥 (iN) 或无机氮与有机肥基肥料 (iNoN) 施肥的里德鳄梨幼苗生长的影响。我们研究了植物生长和 N 获取、矿物 N（NH ₄ ⁺ -N 和 NO ₃^--N) 在渗滤液、盆栽混合物的理化特性和根际微生物群落中。与没有 PGPR 的 iNoN 相比，PGPR 使使用 iNoN 施肥的幼苗的氮吸收效率 (NUpE) 提高了 23%，与没有 PGPR 的 iN 相比提高了 120%，与有 PGPR 的 iN 相比提高了 71%。在 iNoN 和 iN 处理之间没有观察到生长或矿物 N 浸出的显着差异。然而，与未接种 iN 肥料的未接种植物相比，未接种和接种 iNoN 肥料的植物具有更高的植物 N 吸收和根际微生物生物量 N。无论是否接种 PGPR，使用 iNoN 肥料的盆栽培养基都比使用 iN 肥料具有更高的氮保留量。我们的结果提供证据表明 PGPR 对 N 吸收效率的影响受 N 形式和 N 可用性的调节。