Measuring culturable microbial populations and filamentous microbial growth in soil of wheat plots subjected to crop rotation and monoculture

Marais A. ; Hardy M.B. ; Morris C.D. ; Botha A. (2010)


Crop management practices, Including the addition of fertilisers, often lead to different microbial communities in agricultural soils. Soil dilution plates were used to enumerate yeasts, basldiomycetous fungi, general heterotrophic microbes, as well as actinomycetes in soils sampled at three times (winter, spring, early summer) within and between rows of plots planted to a wheat monoculture and wheat-legume rotation. An adapted version of the buried slide technique was used to measure the numbers of filamentous microbes in the soil. Seasonal changes (July- November) were evident in all measured microbial populations in both plots sampled. Whereas most microbe populations showed similar or declining numbers from winter (July) to spring (September), general heterotrophic counts increased slightly in the monoculture plot, while filamentous growth increased within crop rows in the monoculture plot. Biolog EcoPlates™ were used to give an indication of spatio-temporal changes In the soil bacterial metabolic profile. A seasonal shift occurred in the ability of the bacterial community to assimilate carbon sources with more organic acids utilised in November than in July. Fungi, capable of anaerobic growth, occurred more abundantly In the soil of the monoculture plot. This study Indicated the efficacy of using simple culture methods, in combination with the buried slide method, to detect fine-scale and short-term temporal changes in the abundance and metabolic activity of important microbial populations in soils subjected to different agronomic practices.

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