Microbial dynamics in maize-growing soil under different tillage and residue management
Microorganisms are involved in the fertility-related processes of agricultural fields. The long-term impact of tillage and residue management on soil microorganisms was studied over the growing season, in a sandy loam to loamy sand soil of southwestern Quebec. Tillage and residue treatments had been first imposed in fall 1991, on a maize (Zea mays L.) monoculture. Treatments consisted of no till, reduced tillage, and conventional tillage with crop residues either removed from (-R) or retained on (+R) experimental plots, laid out in a randomized complete block design. Soil microbial biomass carbon (SMB-C), soil microbial nitrogen (SMB-N) and phospholipid fatty acid (PLFA) concentrations were measured four times over the 2001 growing season i.e., in May 7 (preplanting), June 25, July 16, and September 29 (prior to corn harvest). The effect of time was larger than those of tillage or residue treatments. While SMB-C showed little seasonal change (160 μg C g-1 soil), SMB-N was responsive to post emergence mineral nitrogen fertilization, and PLFA analysis showed an increase in fungi and total PLFA throughout the season. The effect of residue was more pronounced than that of tillage, with increased SMB-C and SMB-N (61% and 96%) in +R plots compared to –R plots. This study illustrated that measuring soil quality based on soil microbial components must take into account seasonal changes in soil physical and chemical conditions.
soil microbial biomass
phospholipid fatty acid profile
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