Functional diversity of soil bacteria as affected by management practices and phenological stage of Phaseolus vulgaris

This study focused on the effect of management regime and crop developmental stage on soil bacterial functional diversity by using GN Biolog plates. The fields examined were: a grazed grassland (Gr), 2 conventional cultivations differing in the amount and the quality of chemical inputs (C-1 and C-2) and 5 fields cultivated organically for 14, 10, 8, 5 and 2 years respectively. All agricultural lands were cultivated with Phaseolus vulgaris L. Sampling was conducted at seedling emergence, in the mid-growth and after harvest. Low values of diversity were recorded in grassland and conventional fields with the lowest ones in C-2 field. in organic fields, diversity was not related to the age of organic cultivation. However, despite diversity similarities a gradual evolution in community functionality was recorded that parallel changes in the rate of substrate consumption. Increased catabolic activity and diversity followed by changes in the composition of consumed wells occurred in the middle of the phaseolus growth period. Finally, the effect on catabolic profiles of crop developmental stage in conjunction with seasonally varying abiotic conditions was of greater magnitude than that of management regime. The temporal changes in bacterial functionality were totally absent at the C-2 field. (C) 2008 Elsevier Masson SAS. All rights reserved.