Intensity of Organic Farming Influences Soil Health and Biodiversity
DR. DEREK H. LYNCH
Professor, Dalhousie University, Canada
Organic farming globally, broadly aspires to be an agroecological farming system – i.e. to develop productive farming systems while also maintaining on farm biodiversity and ecological cycles above and belowground. This goal is centred around a general commitment to ‘feed the soil’ – i.e. to maintain the levels of organic matter (soil organic carbon; SOC) in soil and in doing so optimize soil biological life and soil health. These key aspirational goals of organic farming overlap closely with recent global interest in regenerative agriculture and in enhancing SOC storage and soil health on all agricultural lands as a climate mitigation and adaptation strategy
Sampling to assess earthworm abundance and diversity in a seeded organic corn field. Photo credit: Stephanie Lavergne.
But are organic farms narrowly restricted by organic certification regulations and standards with respect to their options for farm management practices as they attempt to achieve these agroecological goals of maintaining SOC, soil health and soil biodiversity? My mini-review, using data primarily from Canada, provides evidence that rather than being a homogenous farming system, a spectrum of intensity of farm management approach exists within all organic farming sectors (whether cropping or livestock based), and that this variation in management approach determines soil agroecological outcomes. Additionally, this variation in intensity of management appears to reflect more strongly differences in farmer philosophy and approach to organic farming, rather that other factors such as the size or scale of the organic farm.
The study demonstrated that, whether livestock or cropping based, within each farming sector, organic farms differ in the diversity of crops and other vegetation managed over time and space on the farm, the amount and frequency of imported and applied nutrients, and the frequency of soil tillage or disturbance. These are key management factors influencing SOC storage in soil and its dynamics (or flux), soil health and soil biodiversity. In general, reduced intensity of organic management and enhanced overall diversity of vegetation on farm (including cash crops, cover crops and even weeds) was found to be linked to improved outcomes with respect to SOC status and soil health (especially soil physical and biological properties). Soil microbial biomass and activity, soil fungal abundance and diversity, including of beneficial symbiotic mycorrhizal fungi, appears to also increase under less intensive management conditions on organic farms. However, the study also notes that lower intensity should not be confused with zero farm inputs. Maintaining and avoiding farm deficiencies in critical nutrients such as phosphorus, which if severe can undermine plant productivity and thus farm carbon cycling, is also a key consideration for optimizing the intensity of management and maintaining soil health and biodiversity on organic farms.
While this study focused on organic farming, refining our understanding of farm management intensity and how it is linked to soil carbon status, soil health and biodiversity may be key to advancing these agroecosystem attributes and services from all of agriculture.
Read the review: Lynch, D.H. (2022). Soil health and biodiversity is driven by intensity of organic farming in Canada. Frontiers in Sustainable Food Systems, 6, 826486. DOI: https://doi.org/10.3389/fsufs.2022.826486