Titre du document / Document title

Free-living nitrogen-fixing bacteria in temperate cropping systems : Influence of nitrogen source

Auteur(s) / Author(s)

DELUCA T. H. ⁽¹⁾ ; DRINKWATER L. E. ⁽²⁾ ; WIEFLING B. A. ⁽³⁾ ; DENICOLA D. M. ⁽³⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ University of Montana, School of Forestry, Missoula, MT 59812, ETATS-UNIS
⁽²⁾ Rodale Research Institute, Kutztown, PA 19530, ETATS-UNIS
⁽³⁾ Slippery Rock University, Biology Department, Slippery Rock, PA 16057, ETATS-UNIS

Résumé / Abstract

Sustainable cropping systems rely on a minimum of external inputs. In these systems N is largely acquired in animal manures and leguminous green manures. Little is known of how these organic forms of N fertilizer influence the presence and activity of free-living N₂-fixing bacteria. High concentrations of inorganic N in soil inhibit N₂-fixation in cyanobacteria and Azotobacter spp. It is likely that manure and fertilizer applications would result in concentrations of inorganic N capable of inhibiting N₂ fixation and, ultimately, the presence of these organisms. We investigated the effect of synthetic and organic N fertilizer sources on the populations and N₂-fixation potential of free-living N₂-fixing bacteria in the Farming Systems Trial at the Rodale Research Institute. Field plots received the following N treatments prior to corn (Zea mays L.) production : (1) Legume rotations and green manures supplying about 165 kg N ha^-1 ; (2) beef cattle manure applied at a rate of 220 kg N ha^-1 (plus 60 kg N ha^-1 from 1994 hay plow-down) ; or (3) fertilizer N (urea and NH₄NO₃) applied at a rate of 145 kg N ha^-1. Soil samples were collected at two depths from corn plots four times during the growing season, and analyzed for soil moisture, soil pH, numbers of N₂-fixing cyanobacteria and Azotobacter spp., extractable NH₄⁺ and NO₃^-, and potentially mineralizable N. Soil samples collected in mid-July were analyzed for nitrogenase activity (by C₂H₂ reduction) and total C and N. Populations of Azotobacter spp. and cyanobacteria were influenced only slightly by treatment ; however, cyanobacteria species composition was notably influenced by treatment. Nitrogenase activity in surface soils was greatest in legume-N plots and in subsurface plots levels were greatest in fertilizer-N plots. Populations and activity of free-living N-fixing bacteria appeared to be somewhat reduced in all plots as a result of low soil pH levels and high concentrations of inorganic N across all treatments. Annual applications of N to all plots resulted in high levels of potentially mineralizable N that in turn may have reduced non-symbiotic N₂-fixation in all plots.

Revue / Journal Title

Biology and fertility of soils   ISSN 0178-2762   CODEN BFSOEE 

Source / Source

1996, vol. 23, n^o2, pp. 140-144 (29 ref.)

Langue / Language

Anglais

Editeur / Publisher

Springer, Berlin, ALLEMAGNE  (1985) (Revue)

Mots-clés anglais / English Keywords

Bacteria ; Green manure ; Free form ; Azotobacter ; Cyanobacteria ; Leguminosae ; Zea mays ; Pennsylvania ; Temperate zone ; Cultivated soil ; Acetylene reduction assay ; Azotobacteraceae ; Dicotyledones ; Angiospermae ; Spermatophyta ; Gramineae ; Monocotyledones ; United States ; North America ; America ; Soil biology ;

Mots-clés français / French Keywords

Bactérie ; Engrais vert ; Forme libre ; Azotobacter ; Cyanobacteria ; Leguminosae ; Zea mays ; Pennsylvanie ; Zone tempérée ; Sol cultivé ; Test réduction acétylène ; Azotobacteraceae ; Dicotyledones ; Angiospermae ; Spermatophyta ; Gramineae ; Monocotyledones ; Etats Unis ; Amérique du Nord ; Amérique ; Biologie du sol ;

Mots-clés espagnols / Spanish Keywords

Bacteria ; Abono verde ; Forma libre ; Azotobacter ; Cyanobacteria ; Leguminosae ; Zea mays ; Pensilvania ; Zona temperada ; Suelo cultivado ; Azotobacteraceae ; Dicotyledones ; Angiospermae ; Spermatophyta ; Gramineae ; Monocotyledones ; Estados Unidos ; America del norte ; America ; Biología del suelo ;

Localisation / Location

INIST-CNRS, Cote INIST : 20698, 35400006626072.0080