Javascript is not activated in your browser. This website needs javascript activated to work properly.
You are here

Plant-microbial competition for nitrogen uncoupled from soil C:N ratios

  • Katarina Månsson
  • Per Bengtson
  • Ursula Falkengren-Grerup
  • Göran Bengtsson
Publishing year: 2009
Language: English
Pages: 1908-1916
Publication/Series: Oikos
Volume: 118
Issue: 12
Document type: Journal article
Publisher: Wiley-Blackwell

Abstract english

A green house experiment was designed to test the idea that competition for inorganic nitrogen (N) between plants and heterotrophic microorganisms occurs in soils with high C:N ratios, qualifying for N limited microbial activity, but not at low C:N ratios. The short- term (24 h) N-15 uptake by the grass Festuca gigantea and microorganisms in planted and unplanted soils was determined, and the bacterial activity was measured by the H-3-thymidine incorporation technique. Two deciduous forest soils, with C:N-ratios of 20 and 31, and the 20 soil amended with litter to a C:N ratio of 34, were used. A novel and important part of the experimental design was the preparation of the unplanted reference soil with plants present until the competition assay started by the addition of N-15 labelled ammonium (NH4+) or nitrate (NO3-). The results suggested that plants and soil microorganisms competed for mineral N but under influence of other factors than the soil C:N ratio. The plants reduced the microbial uptake of NH4+ and NO3- in the soil with low C:N ratio, which also had the lowest bacterial activity. The plants had a larger N uptake than microorganisms in the two natural soils but smaller in the litter-amended, and their presence enhanced the bacterial activity, especially in the latter soil. The litter-amended soil with its high C:N ratio and easily decomposable C was the soil that best fulfilled the criteria for competition, including a net consumption of mineral N during the assay, the lowest plant uptake of mineral N due to the high N immobilization by microorganisms, and a reduced microbial N-15 uptake-to-bacterial activity in the presence of plants. Thus, other factors, such as the decomposability of the soil C and the bacterial activity, were more important than the soil C:N ratio to the outcome of plant-microbial competition for N.


  • Biological Sciences
  • Ecology


  • Microbial Ecology
  • ISSN: 1600-0706
Per Bengtson
E-mail: per [dot] bengtson [at] biol [dot] lu [dot] se



+46 46 222 37 60


Sölvegatan 37, Lund


Research group

Microbial Ecology


Doctoral students and postdocs

PhD students, main supervisor


PhD students, assistant supervisor

Jian Li

Experimental setup