Densely rooted rhizosphere hotspots induced around subsurface NH4 +-fertilizer depots: a home for soil PGPMs?

Nkebiwe, Peteh Mehdi; Neumann, Günter; Müller, Torsten

doi:10.1186/s40538-017-0111-y

Cited by 13 publications

(31 citation statements)

References 47 publications

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“…Secretion of phosphohydrolases by soil bacteria (alkaline phosphatases), fungi and plant roots (acid phosphatases) is an important factor mediating the hydrolysis of organic phosphate esters in soils, thereby increasing the plant-availability of phosphate anions in soils (Neumann and Rö mheld, 2002;Khan et al, 2009;Jones and Oburger, 2011). Comparing different fungal and bacterial PGPM strains, Nkebiwe et al (2017) reported particularly high secretory alkaline phosphatase activities in the growth media of the investigated PGPM strain Proradix under conditions of P limitation. Accordingly, Proradix inoculation significantly increased the activity of alkaline phosphatase in the rhizosphere of inoculated maize plants supplied with nitrate fertilization and tested under standard conditions (pH 8.2, 30°C) according to the method of Tabatabai and Bremner (1969), with a similar trend in acid phosphatase (Tab.…”

Section: Effects On Rhizosphere Chemistrymentioning

confidence: 99%

“…Rhizosphere soil samples were collected by shaking off root-adhering soil, which was immediately frozen in liquid N and stored at -80°C. Acid and alkaline phosphatase activities were determined based on the p-nitrophenyl phosphate method (Tabatabai and Bremner, 1969) with modifications according to Nkebiwe et al (2017) with 200 mM Naacetate buffer (pH 5.2) for acid phosphatase or 200 mM Naborate buffer (pH 8.2) for alkaline phosphatase. Additional measurements were taken at the rhizosphere pH measured for plants supplied with nitrate or stabilized ammonium fertilization, using 200 mM Na-acetate buffer adjusted to the respective pH values.…”

Section: Rhizosphere Phosphatase Activitiesmentioning

confidence: 99%

“…2A). Proradix has been previously characterized as PGPM strain with particularly high P-solubilizing potential, associated with intense ammonium-induced acidification of artificial growth media (Nkebiwe et al, 2017). However, the improved performance of Proradix with respect to plant growth promotion in combination with stabilized ammonium supply instead of nitrate fertilization (Tab.…”

Section: Effects On Rhizosphere Chemistrymentioning

confidence: 99%

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The role of N form supply for PGPM‐host plant interactions in maize

Mpanga

Gomez-Genao

Moradtalab

et al. 2019

J. Plant Nutr. Soil Sci.

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The form of nitrogen (N) supply has a significant impact on rhizosphere chemistry and root growth responses of higher plants. The respective effects are also employed as management options to improve nutrient acquisition and to minimize nutrient losses in cropping systems. However, surprisingly little is known concerning the interactions with rhizosphere biota. In this study, we investigated the effects of selected bacterial and fungal inoculants with proven plant growth‐promoting and phosphate (P)‐solubilizing potential (plant growth‐promoting microorganisms, PGPM) in maize with nitrate or stabilized ammonium supply, on soils with limited P availability and sparingly soluble rock phosphate (Rock‐P) applied as P fertilizer. The combination of the bacterial inoculants Pseudomonas sp. DSMZ 13134 (Proradix) and Bacillus amyloliquefaciens FZB42 with ammonium sulphate fertilization, stabilized with the nitrification inhibitor 3,4‐dimethylpyrazole‐phosphate (DMPP), resulted in a superior shoot biomass production (79–111%) and shoot P accumulation (109–235%) as compared with nitrate supply. This effect could be partially attributed to (1) ammonium‐induced rhizosphere acidification via increased root extrusion of protons, (2) promotion of root hair elongation, and (3) increased shoot concentrations of hormonal growth regulators (indole‐3‐acetic acid, zeatin, gibberellic acid). The effects, induced by the microbial inoculants were mainly related to increased root length development (43–44%), associated with a 60% increase in auxin production potential. No inoculant effects were detected on root hair elongation or on chemical modifications of the rhizosphere involved in P solubilisation, such as rhizosphere acidification, release of carboxylates or secretory phosphohydrolases. However, the ammonium‐induced stimulation of root hair elongation increased preferential sites for root colonization by the selected inoculants, which may explain the increase in rhizosphere abundance of PGPMs, exemplarily recorded for the fungal inoculant Trichoderma harzianum OMG16 (210%). The presented data suggest a network of positive interactions between stabilized ammonium fertilization and plant growth‐promoting functions of various bacterial and fungal PGPM inoculants. This offers perspectives to increase the efficiency and the reproducibility of PGPM‐assisted fertilization strategies.

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Section: Effects On Rhizosphere Chemistrymentioning

confidence: 99%

Section: Rhizosphere Phosphatase Activitiesmentioning

confidence: 99%

Section: Effects On Rhizosphere Chemistrymentioning

confidence: 99%

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The role of N form supply for PGPM‐host plant interactions in maize

Mpanga

Gomez-Genao

Moradtalab

et al. 2019

J. Plant Nutr. Soil Sci.

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“…In an investigation with Bacillus-, Pseudomonas-, and Trichoderma-based inoculants in maize on six different soils in five countries with eight different types of fertilizers based on recycling products from organic and inorganic waste materials, Thonar et al [12] reported superior performance particularly in combination with composted animal manures. Nkebiwe et al [13,14] found beneficial effects by combination of microbial inoculants with placement of stabilized ammonium fertilizers.…”

Section: Introductionmentioning

confidence: 99%

“…Based on these findings, we hypothesised that the selection of suitable combinations of microbial inoculants with organic or inorganic fertilizers could be a key factor for the development strategies to improve the fertilizer use efficiency with support of microbial inoculants. Therefore, in this study we compared the performance of greenhouse tomato, supplied with different types of fertilizers (municipal waste compost, poultry manure, rock phosphate, stabilized ammonium) in combination with selected microbial inoculants with proven plant growth-promoting and phosphate-solubilizing properties, pre-selected in the studies of Thonar et al [12] and Nkebiwe et al [13,14]. To also consider the potential impact of different soil properties, the experiments were conducted on two contrasting soils from Ghana with low P availability, and moderately acidic and alkaline pH in face of the significance of soil pH for P fixation in soils.…”

Section: Introductionmentioning

confidence: 99%

Soil Type-Dependent Interactions of P-Solubilizing Microorganisms with Organic and Inorganic Fertilizers Mediate Plant Growth Promotion in Tomato

et al. 2018

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The use of plant growth-promoting microorganisms (PGPMs) as bio-effectors (BEs) to improve the nutrient acquisition of crops has a long history. However, limited reproducibility of the expected effects still remains a major challenge for practical applications. Based on the hypothesis that the expression of PGPM effects depends on soil type and the properties of the applied fertilizers, in this study, the performance of selected microbial inoculants was investigated for two contrasting low-fertility soils supplied with different organic and inorganic fertilizers. Greenhouse experiments were conducted with tomato on an alkaline sandy loam of pH 7.8 and an acidic loamy sand of pH 5.6 with limited phosphate (P) availability. Municipal waste compost, with and without poultry manure (PM), rock phosphate (RP), stabilized ammonium, and mineral nitrogen, phosphorus and potassium (NPK) fertilization were tested as fertilizer variants. Selected strains of Bacillus amyloliquefaciens (Priest et al. 1987) Borriss et al. 2011 and Trichoderma harzianum Rifai (OMG16) with proven plant growth-promoting potential were used as inoculants. On both soils, P was identified as a major limiting nutrient. Microbial inoculation selectively increased the P utilization in the PM-compost variants by 116% and 56% on the alkaline and acidic soil, while RP utilization was increased by 24%. This was associated with significantly increased shoot biomass production by 37-42%. Plant growth promotion coincided with a corresponding stimulation of root growth, suggesting improved spatial acquisition of soluble soil P fractions, associated also with improved acquisition of nitrogen (N), potassium (K), magnesium (Mg), and calcium (Ca). There was no indication for mobilization of sparingly soluble Ca phosphates via rhizosphere acidification on the alkaline soil, and only mineral NPK fertilization reached a sufficient P status and maximum biomass production. However, on the moderately acidic soil, FZB42 significantly stimulated plant growth of the variants supplied with Ca-P in the form of RP + stabilized ammonium and PM compost, which was equivalent to NPK fertilization; however, the P nutritional status was sufficient only in the RP and NPK variants. The results suggest that successful application of microbial biofertilizers requires more targeted application strategies, considering the soil properties and compatible fertilizer combinations.

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