Abstract
Agricultural practices contribute considerably to emissions of greenhouse gases. So far, knowledge on the impact of organic compared to non-organic farming on soil-derived nitrous oxide (N2O) and methane (CH4) emissions is limited. We investigated N2O and CH4 fluxes with manual chambers during 571 days in a grass-clover– silage maize – green manure cropping sequence in the long-term field trial “DOK” in Switzerland. We compared two organic farming systems – biodynamic (BIODYN) and bioorganic (BIOORG) – with two non-organic systems – solely mineral fertilisation (CONMIN) and mixed farming including farmyard manure (CONFYM) – all reflecting Swiss farming practices–together with an unfertilised control (NOFERT). We observed a 40.2% reduction of N2O emissions per hectare for organic compared to non-organic systems. In contrast to current knowledge, yield-scaled cumulated N2O emissions under silage maize were similar between organic and non-organic systems. Cumulated on area scale we recorded under silage maize a modest CH4 uptake for BIODYN and CONMIN and high CH4 emissions for CONFYM. We found that, in addition to N input, quality properties such as pH, soil organic carbon and microbial biomass significantly affected N2O emissions. This study showed that organic farming systems can be a viable measure contributing to greenhouse gas mitigation in the agricultural sector.
Highlights
With a share of 10–12% in carbon-dioxide equivalents (CO2-eq.), agriculture contributes substantially to global greenhouse gas (GHG) emissions[1]
Even though considerable parts of Steiner’s biodynamic philosophy and practices lie beyond scientific judgement, a fair share of the available peer-reviewed research results from controlled field experiments as well as case studies show effects of biodynamic farming on yield, soil quality and soil biodiversity[15,16,17,18,19]. It has not been tested whether the effects of biodynamic farming on GHG emissions differ from other organic farming systems
N2O flux dynamics were best explained by soil moisture expressed as water-filled pore space (WFPS) (p < 0.0001), followed by soil nitrate concentrations (p = 0.021)
Summary
With a share of 10–12% in carbon-dioxide equivalents (CO2-eq.), agriculture contributes substantially to global greenhouse gas (GHG) emissions[1]. Even though considerable parts of Steiner’s biodynamic philosophy and practices lie beyond scientific judgement, a fair share of the available peer-reviewed research results from controlled field experiments as well as case studies show effects of biodynamic farming on yield, soil quality and soil biodiversity[15,16,17,18,19]. It has not been tested whether the effects of biodynamic farming on GHG emissions differ from other organic farming systems
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