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More microbes in organic soil

Two types of soil bacteria, strongly magnified.

Active organic soils: Two types of soil bacteria. (Photo: Fotolia sciencerfvideo.mov)

Soils in organic farming contain on average 59 percent more biomass from microorganisms, which are up to 84 percent more active compared to those in conventional farming. These were the findings of a global meta study by FiBL, which has recently been published in the academic journal PLOS ONE.

(Frick, 25 September 2017) Soils in organic farming contain on average 59 percent more biomass from microorganisms, which are up to 84 percent more active compared to those under conventional farming. These were the findings of a global meta study by FiBL that took 57 systematically selected international publications (149 pairwise comparisons) into account. The study was published in PLOS ONE, a renowned international scientific journal of the Public Library of Science (PLOS).

Further results of the study:

  • The metabolism of microbes in organic soils is significantly more active, which in turn leads to a faster conversion of organic matter like compost into plant-available nutrients.
  • The positive effect of organic farming on the activity of microbes is significantly increased in warm and dry climates.
  • Organic fertiliser, a diverse crop rotation and the inclusion of leguminous plants in the crop rotation have positive effects on microbial abundance and activity.
  • Organic farming has a positive effect on the soils’ pH and soil carbon, which in turn has a positive effect on the microbes.

The paradox: Lower yields in organic farming

Large amounts of microbial biomass and an active soil life provide an excellent base for a high crop yield. However, the paradox is that the yields in organic farming are on average still 20 % lower. This is due to the lack of adapted varieties in organic farming and the avoidance of chemical plant protection agents and synthetic fertilisers as well as herbicides. However, there is mounting evidence that organic farming systems using adapted varieties produce more stable yields in drought conditions. The higher biomass in the soil is also significant for the climate: Organically farmed soils contain more humus, which helps in the sequestration of the greenhouse gas CO2.

Further information

FiBL contacts

FiBL study on microbial biomass

Studies on yields and humus formation in organic farming

Weblinks

Supporter

This work is supported by the "2013-2014 BiodivERsA/FACCE-JPI joint call" for research proposals with the Swiss National Fond (SNF) in the framework of the programme NRP 68 "Soil as a Resource".

Partner

Justus Liebig University in Giessen

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