Placement of Pseudomonas sp. DSMZ13134 around NH4+-based fertilizer depots in maize stimulates root exploitation of the fertilizer depot in soil

Publikations-Art

Kongressbeitrag

Autoren

Nkebiwe, P.M., Weinmann, M., Weber, N., Neumann, G., Müller, T.,

Erscheinungsjahr

2015

Tagungsname

Unsere Böden, unser Leben. Jahrestagung der Deutschen Bodenkundlichen Tagung 2015

Tagungsort

München

Tagungsdatum

September 2015

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.