Purpose

Both earthworm (Eisenia fetida L.) and phosphorus (P)-releasing (PR) bacteria, including organic P-mineralizing (OPM) and inorganic P-solubilizing (IPS), are able to convert difficult-to-use P into phytoavailable P. However, there is a undesirable gap between soil P mobilization and root P acquisition when mycorrhization is enhanced. The aim of this study was to investigate the combined effects of earthworm and PR bacteria on soil P mobilization, mycorrhizal colonization, and P acquisition of maize (Zea mays L.).

Materials and methods

This study consisted of three parallel experiments. Firstly, a 90-day microcosm experiment was carried out to test the diversified effects of earthworm, OPM bacterium Bacillus megaterium, and IPS bacterium Kluyvera intermedia, on available P concentration in an autoclaved soil with or without P amendment. Secondly, a 16-week greenhouse pot experiment was conducted to compare the differential effects of earthworm, B. megaterium, and K. intermedia on P mobilization, mycorrhizal colonization, and P acquisition of maize in the same autoclaved soil receiving chemical fertilizers and Funneliformis caledonium. Thirdly, a microplot experiment was established to verify the combined effects of earthworm and PR bacteria on P mobilization and mycorrhizal P acquisition of maize in a field where the soil used in the former two experiments were collected.

Results and discussion

In the microcosm experiment, earthworm significantly increased soil available P concentration coupled of declined soil pH regardless of P amendment, while B. megaterium and K. intermedia further enhanced P mobilization in P-fertilized soils. In the greenhouse experiment, PR bacteria and earthworm co-increased mycorrhizal colonization and plant biomass, as well as soil alkaline phosphatase (ALP) activity and available P concentration compared to the control, and individual P acquisition compared to the single inoculation treatments. In the field experiment, both PR bacteria and earthworm significantly increased mycorrhizal colonization and tended to increase soil ALP activity, available P concentration, root biomass, and individual P acquisition, while the combined inoculation significantly increased ALP activity and available P concentration, and thereby individual P acquisition by 29% relative to the control.

Conclusions

Combined inoculation of PR bacteria and earthworm greatly increased soil available P concentration and maize P acquisition and grain yield. Although the combined inoculation had a lower root mycorrhizal colonization than the single inoculation treatments due to the greatly increased amounts of readily soluble P, it had a higher mycorrhization level than the control. These observations suggest that the combined application could enhance soil P mobilization and be expropriated to elaborate indigenous mycorrhizal fungal function.

中文翻译：

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释放磷（P）的细菌和worm（Eisenia fetida L.）是否可以增强玉米（Zea mays L.）的土壤P迁移和菌根P吸收？

目的

worm （Eisenia fetid a L.）和磷（P）释放细菌（包括有机P矿化（OPM）和无机P增溶（IPS））都能够将难以使用的P转化为可利用的磷P。但是，当菌根增加时，土壤P的动员与根系P的获取之间存在不希望的差距。这项研究的目的是探讨蚯蚓对土壤磷素动员，菌根和玉米的对采集（综合影响和PR细菌玉米L.）。

材料和方法

这项研究包括三个平行的实验。首先，进行了为期90天的缩影实验，以测试worm，OPM细菌巨大芽孢杆菌和IPS细菌克鲁维拉中间培养基对有或没有P改良剂的高压灭菌土壤中有效P浓度的影响。其次，16周温室盆栽试验以比较蚯蚓，的不同影响巨大芽孢杆菌，和K.中间P上动员，菌根和P采集玉米在相同的灭菌土接收化肥和Funneliformis caledonium。第三，建立了一个微样试验，以验证worm和PR细菌在收集前两个实验所用土壤的田地中对玉米的P动员和菌根磷吸收的联合作用。

结果和讨论

在微观实验中，worm不管磷的修正如何，worm都会显着增加土壤有效磷的浓度，再加上土壤pH的降低，而巨大芽孢杆菌和中间芽孢杆菌磷肥土壤中磷的迁移进一步增强。在温室试验中，与对照相比，PR细菌和worm共同增加了菌根定植和植物生物量，以及土壤碱性磷酸酶（ALP）活性和有效P浓度，与单次接种处理相比，单个P获得量增加。在田间试验中，PR细菌和earth均显着增加了菌根定植，并倾向于增加土壤ALP活性，有效磷浓度，根生物量和单个磷的获取，而联合接种显着提高了ALP活性和有效磷浓度，从而单个相对于对照，P采集量增加了29％。

结论

PR细菌和worm的联合接种大大提高了土壤中有效磷的浓度，增加了玉米的磷获取量和谷物产量。尽管由于易溶P的量大大增加，所以联合接种的根真菌菌落定植量比单次接种处理的菌落定植量低，但与对照相比，它的菌根水平更高。这些观察结果表明，联合施用可增强土壤磷的动员，可用于改善本地菌根真菌的功能。