Abstract The present study was conducted on onion variety ‘Punjab Naroya’ in a factorial randomized block design during 2016−17 and 2017−18 in a loamy sand alluvial soil of semi-arid region. There were 14 treatments consisting of two factors. Factor I comprised two levels of mineral fertilizers (100% NPK and 75% NPK) and factor II consisted of six combinations of microbial inoculants along with a control. Microbial inoculants were applied through root dipping of seedlings for 30 min before transplanting. The study was aimed to identify microbial consortia that can reduce the use of mineral fertilizers by 25% without any loss in bulb yield and to identify microbial consortia that can act as potential supplement to recommended dose of mineral fertilizers (100% NPK) in improving bulb yield of onion. We have identified two treatments viz., 100% NPK + T6 (Azotobacter sp. + Sphingobacterium sp. + Burkholderia sp.) and 100% NPK + T1 (Azotobacter sp. + Bacillus sp.) that have registered 12.0% and 7.5% increase in bulb yield over uninoculated control (100% NPK). The study has also led to the identification of three treatments viz., 75% NPK + T6, 75% NPK + T1 and 75% NPK + T5 (Azotobacter sp. + Bacillus sp. + Burkholderia sp.) manifesting 8.6%, 6.1% and 3.7% higher bulb yield over uninoculated control (100% NPK). Besides, various microbial inoculants significantly improved the plant growth parameters (plant height, number of leaves), yield attributes (bulb yield, 20-bulb weight and equatorial diameter of bulb), bulb quality attributes (ascorbic acid, total soluble solids, pyruvic acid and dry matter) and reduced the physiological loss in weight during 15–120 days of storage at room temperature. The triple inoculation treatment with Azotobacter sp. + Sphingobacterium sp.+ Burkholderia sp. gave the best results for most of the traits followed by dual inoculation treatment with Azotobacter sp. + Bacillus sp. However, the soil chemical (pH, electrical conductivity, organic carbon, available nitrogen, phosphorus and potassium) and microbial properties (bacterial, actinomycetes and fungal count) exhibited non-significant improvement after harvest of onion crop. The interaction effects between mineral fertilizers and PGPRs were non-significant for all the traits. Therefore, it can be concluded that the integrated utilization of these microbial inoculants as root dip of seedlings along with 75% NPK offers the scope of reducing the application of mineral fertilizers to onion crop by 25% without any loss in bulb yield and to reduce environmental pollution.

中文翻译：

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在田间条件下利用植物促生长根际细菌作为幼苗浸根提高球茎产量和减少洋葱矿物肥料的使用

摘要 本研究于 2016-17 年和 2017-18 年期间在半干旱地区的壤质砂冲积土中以因子随机区组设计对洋葱品种 'Punjab Naroya' 进行了研究。有14个治疗由两个因素组成。因子 I 包括两种水平的矿物肥料（100% NPK 和 75% NPK），因子 II 由六种微生物接种剂组合和对照组成。在移栽前通过幼苗浸根30分钟施用微生物接种剂。该研究旨在确定可以在不降低球茎产量的情况下将矿物肥料的使用量减少 25% 的微生物聚生体，并确定可以作为推荐剂量矿物肥料 (100% NPK) 的潜在补充剂以改善球茎的微生物聚生体洋葱产量。我们已经确定了两种治疗方法，即 100% NPK + T6（固氮菌属 + 鞘氨醇菌属 + 伯克霍尔德菌属）和 100% NPK + T1（固氮菌属 + 芽孢杆菌属）与未接种的对照（100 % NPK）。该研究还确定了三种处理方法，即 75% NPK + T6、75% NPK + T1 和 75% NPK + T5（固氮菌+芽孢杆菌+伯克霍尔德菌）分别为 8.6%、6.1%和未接种对照（100% NPK）相比，球茎产量高 3.7%。此外，各种微生物菌剂显着改善了植物生长参数（株高、叶数）、产量属性（球茎产量、20 球重和球茎赤道直径）、球茎质量属性（抗坏血酸、总可溶性固形物、丙酮酸和干物质）并在室温下储存 15-120 天期间减少了重量的生理损失。固氮菌三重接种处理。+ 鞘氨醇杆菌 + 伯克霍尔德菌。对大多数性状给出了最好的结果，然后用固氮菌进行双重接种处理。+ 芽孢杆菌 然而，洋葱作物收获后土壤化学（pH、电导率、有机碳、有效氮、磷和钾）和微生物特性（细菌、放线菌和真菌数量）没有显着改善。矿物肥料和PGPRs之间的交互作用对所有性状都不显着。所以，