Abstract
Plant P-acquisition from soil can be improved by rhizosphere acidification induced by exudation of protons or organic acids in neutral to alkaline soils, increased root growth and plant growth-promoting microorganisms (PGPMs). Our objective was to investigate the effect of stabilized NH4+-fertilizer placed as a subsoil depot and PGPM inoculated in and around the NH4+-depot zone on root growth, rhizosphere pH, root-colonization by PGPM around the NH4+-depot-zone, shoot N and P content, and yield. The test crop was maize (Zea mays L.). At 8 weeks after sowing on an alkaline low-P soil contained in rhizoboxes, higher root length density, lower rhizosphere pH and higher Pseudomonas sp. colonization rate was observed in the NH4+-depot zone in comparison to the corresponding soil zone in controls supplied homogenously with NO3-. Shoot N and P in plants fertilized with N as an NH4+-depot was higher than those in plants fertilized homogenously with NO3-. There was no difference in shoot weight and there was no PGPM effect on shoot growth. In two field experiments (2014 and 2015) on a neutral silt loam with moderate P availability, root length density was higher in the NH4+-depot-side of maize rows compared to opposite sides without an NH4+-depot, irrespective of PGPM treatment. In 2014 only, inoculation of Pseudomonas sp. PRORADIX DSMZ13134 led to doubling of root length density in the NH4+-depot zone. This indicated improved root exploitation of the fertilizer depot induced by PGPM inoculation under field conditions. This effect could not be reproduced in 2015 possibly due to severe drought stress. Yield of grain (2014) and silage (2015) were neither affected by placement of subsoil NH4+-depot nor inoculation with PGPMs, likely due to moderate to optimal initial levels of N and P in the field sites.
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Claims 12
Claim · model-written summary
At eight weeks in rhizoboxes, maize root length density was higher in the NH4+-depot zone than in homogenously NO3- fertilized controls.
- Treatment
- NH4+-depote0
- Outcome
- root length densitye0
- Direction
- highere0
- Comparator
- controls supplied homogenously with NO3-e0
- Setting
- rhizoboxese2
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher root length density, lower rhizosphere pH and higher Pseudomonas sp. colonization rate was observed in the NH4+-depot zone in comparison to the corresponding soil zone in controls supplied homogenously with NO3-”
e1“maize (Zea mays L.)”
e2“an alkaline low-P soil contained in rhizoboxes”
Claim · model-written summary
The maize NH4+-depot zone had lower rhizosphere pH than the corresponding control zone.
- Treatment
- NH4+-depote0
- Outcome
- rhizosphere pHe0
- Direction
- lowere0
- Comparator
- controls supplied homogenously with NO3-e0
- Setting
- rhizoboxese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher root length density, lower rhizosphere pH and higher Pseudomonas sp. colonization rate was observed in the NH4+-depot zone in comparison to the corresponding soil zone in controls supplied homogenously with NO3-”
e1“maize (Zea mays L.)”
e2“an alkaline low-P soil contained in rhizoboxes”
Claim · model-written summary
The maize NH4+-depot zone had a higher Pseudomonas sp. colonization rate than controls.
- Treatment
- NH4+-depote0
- Interactor
- Pseudomonas sp.
Pseudomonase0symbiont - Outcome
- Pseudomonas sp. colonization ratee0
- Direction
- highere0
- Comparator
- controls supplied homogenously with NO3-e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher Pseudomonas sp. colonization rate was observed in the NH4+-depot zone in comparison to the corresponding soil zone in controls supplied homogenously with NO3-”
e1“maize (Zea mays L.)”
Claim · model-written summary
Maize shoot nitrogen was higher with an NH4+-depot than with homogeneous NO3- fertilizer.
- Treatment
- NH4+-depote0
- Outcome
- Shoot Ne0
- Direction
- highere0
- Comparator
- plants fertilized homogenously with NO3-e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot N and P in plants fertilized with N as an NH4+-depot was higher than those in plants fertilized homogenously with NO3-”
e1“maize (Zea mays L.)”
Claim · model-written summary
Maize shoot phosphorus was higher with an NH4+-depot than with homogeneous NO3- fertilizer.
- Treatment
- NH4+-depote0
- Outcome
- Pe0
- Direction
- highere0
- Comparator
- plants fertilized homogenously with NO3-e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Shoot N and P in plants fertilized with N as an NH4+-depot was higher than those in plants fertilized homogenously with NO3-”
e1“maize (Zea mays L.)”
Claim · model-written summary
Maize shoot weight did not differ between the stated fertilizer treatments.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no difference in shoot weight”
e1“maize (Zea mays L.)”
e2“NH4+-depot was higher than those in plants fertilized homogenously with NO3-”
Claim · model-written summary
PGPM inoculation showed no effect on maize shoot growth.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no PGPM effect on shoot growth”
e1“maize (Zea mays L.)”
Claim · model-written summary
In field experiments, maize root length density was higher on the NH4+-depot side of rows than the opposite side, regardless of PGPM.
- Treatment
- NH4+-depote0
- Outcome
- root length densitye0
- Direction
- highere0
- Qualifier
- irrespective of PGPM treatmente0
- Comparator
- opposite sides without an NH4+-depote0
- Setting
- field experimentse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root length density was higher in the NH4+-depot-side of maize rows compared to opposite sides without an NH4+-depot, irrespective of PGPM treatment”
e1“two field experiments (2014 and 2015)”
Claim · model-written summary
In 2014, Pseudomonas sp. PRORADIX DSMZ13134 inoculation doubled maize root length density in the NH4+-depot zone.
- Treatment
- inoculation of Pseudomonas sp. PRORADIX DSMZ13134e0
- Interactor
- Pseudomonas sp. PRORADIX DSMZ13134e0symbiont
- Outcome
- root length densitye0
- Direction
- doublinge0
- Value
- doublinge0
- Qualifier
- In 2014 onlye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In 2014 only, inoculation of Pseudomonas sp. PRORADIX DSMZ13134 led to doubling of root length density in the NH4+-depot zone”
e1“maize (Zea mays L.)”
Claim · model-written summary
The inoculation effect on maize root length density was not reproduced in 2015.
- Treatment
- inoculation of Pseudomonas sp. PRORADIX DSMZ13134e2
- Interactor
- Pseudomonas sp. PRORADIX DSMZ13134e2symbiont
- Outcome
- root length densitye3
- Direction
- could not be reproducede0
- Qualifier
- possibly due to severe drought stresse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This effect could not be reproduced in 2015 possibly due to severe drought stress”
e1“maize (Zea mays L.)”
e2“inoculation of Pseudomonas sp. PRORADIX DSMZ13134”
e3“doubling of root length density”
Claim · model-written summary
Maize grain yield in 2014 was unaffected by subsoil NH4+-depot placement or PGPM inoculation.
- Treatment
- placement of subsoil NH4+-depote0
- Interactor
- PGPMse0symbiont
- Outcome
- Yield of graine0
- Direction
- neither affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yield of grain (2014) and silage (2015) were neither affected by placement of subsoil NH4+-depot nor inoculation with PGPMs”
e1“maize (Zea mays L.)”
Claim · model-written summary
Maize silage yield in 2015 was unaffected by subsoil NH4+-depot placement or PGPM inoculation.
- Treatment
- inoculation with PGPMse0
- Interactor
- PGPMse0symbiont
- Outcome
- silagee0
- Direction
- neither affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yield of grain (2014) and silage (2015) were neither affected by placement of subsoil NH4+-depot nor inoculation with PGPMs”
e1“maize (Zea mays L.)”
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