Permaculture Management of Arable Soil Increases Soil Microbial Abundance, Nutrients, and Carbon Stocks Compared to Conventional Agriculture

Conventional agricultural practices severely deplete the soil of essential organic matter and nutrients, increasing its vulnerability to disease, drought, and flooding. Permaculture is a form of agroecology adopting a whole ecosystem approach to create a set of principles and design frameworks for enriching soil fertility, but there is little scientific evidence of its efficiency. This study compares two permaculture managed sites with a conventional arable site to investigate the effect of permaculture management on soil fertility. We used phospholipid fatty acid analysis to estimate microbial abundance and diversity and related these to measured soil nutrients and carbon stocks. The potential of permaculture management to mitigate soil greenhouse gas emissions was assessed during a laboratory soil incubation and measurement of greenhouse gases via gas chromatography. Overall, the permaculture managed allotments had three times higher microbial biomass, one and a half times higher nitrogen, and four times higher carbon content than the arable site. Permaculture soils had larger carbon dioxide and nitrous oxide fluxes compared to arable soil, but all sites had a mean negative flux in methane. Permaculture management by use of organic amendments and no-dig practices provides a constant slow release of nutrients and build-up of organic matter and carbon and consequently promotes greater bacterial and fungal biomass within the soil.