Mineralization of nitrogen from15N labelled fungi, soil microbial biomass and roots and its uptake by barley plants

• The availability of nitrogen in15N labelled fungi, soil microbial biomass (Ca(15NO3)2 immobilized by addition of glucose), barley roots and Ca(NO3)2 to barley plants was investigated in a greenhouse experiment. Samples of above-ground plant biomass were taken five times during 76 days. During this time, and at the start of the experiment, the C and N contents of the soil microbial biomass were determined. Microbial biomass-C decreased during the first 41 days, and then increased back to pre-treatment levels. Only 2% of the total soil15N was found in the microbial biomass two days after additions of Ca(15NO3)2. At the final sampling 76 days later, 17% of the15N remaining in soil was found in the microbial biomass. In the other tratments, microbial biomass-N accounted for 20% of remaining soil15N in the one that had received fungi, 29% in the one with barley roots and 35% in the Ca(NO3)2 plus glucose treatment. At harvest, 38% of the soil15N at day 0 added as Ca(NO3)2-N, 29% of fungal-N, 10% of N immobilized in the soil microbial biomass and 7% of N in barley roots was recovered in the above-ground plant biomass.It can be concluded that nitrogen in the native soil biomass is resistant to mineralization and plant uptake. The use of laboratory grown organisms for mineralization studies will overestimate the plant availability of nitrogen in soil microorganisms.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Markvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Soil Science (hsv//eng)

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Jordbruksvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Agricultural Science (hsv//eng)

Nyckelord

barley; chloroform fumigation; fungi; 15N-nitrate; microbial biomass N; mineralization; roots

Publikations- och innehållstyp

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