Microbial biomass and N transformations in two soils cropped with annual and perennial species
1996
Chantigny, M.H. | Prevost, D. | Angers, D.A. | Vezina, L.P. | Chalifour, F.P.
A field study was undertaken to determine the effects of different plant species on soil microbial biomass and N transformations in a well drained silty clay loam (Typic Dystrochrept) and a poorly drained clay loam (Typic Humaquept). The crop treatments were faba bean (Vicia faba L.), alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), bromegrass (Bromus inermis L.), reed canarygrass (Phalaris arundinacea L.), and wheat (Triticum aestivum L.). Measurements of microbial biomass C, denitrification capacity, and nitrification capacity were performed periodically in the top 2-10 cm of soil. On most sampling dates, all three parameters were higher under perennial than under annual species. The nitrification capacity was positively affected by the level of N applied to each species (r= 0.65** for the silty clay loam and 0.84*** for the clay loam) and not directly by the plant. The differences found in microbial biomass C were significantly correlated with the water-soluble organic C present under each plant species (r= 0.74*** for the silty clay loam and 0.90*** for the clay loam), suggesting differences in C deposition in the soil among plant species. In the silty clay loam, the denitrification capacity was positively related to the amount of organic C found under each plant species, while in the clay loam, it was dependent on the amount of N applied to each species. There was less denitrification activity per unit biomass under legume species than under gramineae, suggesting that, depending on their composition, root-derived materials may be used differently by soil microbes.
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