Impact of reduced tillage on greenhouse gas emissions and soil carbon stocks in an organic grass-clover ley – winter wheat cropping sequence

Maike Krauss, Reiner Ruser, Torsten Müller, Sissel Hansen, Paul Mäder, Andreas Gattinger - Agriculture, Ecosystems & Environment Volume 239, 15 February 2017, Pages 324–333

Farm Table says:

This is the very first study comparing climate impacts of tillage systems in organic arable farming, and amazingly, this paper proves to have a unique approach in interpreting a whole new set of data.

A Complete Overview of Reduced Tillage

  • Conservation tillage has proven to be advantageous in terms of soil erosion control and water conservation and e.g. no-till farming (NT) is widely adopted, particularly in dryer regions. However, no-till can reduce yields and seems profitable only in combination with other measures of conservation agriculture like improved crop rotations and residue management.
  • The scope of this study was to monitor N2O and CH4 trace gas fluxes for two years and to assess SOC stocks in an organic long-term tillage trial. In interaction with tillage systems, two organic fertilizer types were included to assess the impact of different C and N availabilities. The cropping sequence included a grass-clover ley and winter wheat as typical crops in organic rotations found on European farms.
  • Organic reduced tillage aims to combine the environmental benefits of organic farming and conservation tillage to increase sustainability and soil quality. In temperate climates, there is currently no knowledge about its impact on greenhouse gas emissions and only little information about soil organic carbon (SOC) stocks in these management systems.
  • We therefore monitored nitrous oxide (N2O) and methane (CH4) fluxes besides SOC stocks for two years in a grass-clover ley – winter wheat – cover crop sequence.
  • The monitoring was undertaken in an organically managed long-term tillage trial on a clay rich soil in Switzerland. Reduced tillage (RT) was compared with ploughing (conventional tillage, CT) in interaction with two fertilisation systems, cattle slurry alone (SL) versus cattle manure compost and slurry (MC).

 

Derivative Conclusion

This study filled important knowledge gaps about the impact of organic reduced tillage on greenhouse gas emissions, SOC stock changes and its potential for climate change mitigation.

  • organic reduced tillage increased SOC stocks after 13 years compared to ploughing in slurry fertilized plots and that tillage system effects were of minor importance in terms of N2O and CH4 emissions when the cropping seasons were considered. N2O fluxes after single tillage events were however higher in the reduced system. We further observed that
  • fertilizing with manure compost increased N2O emissions and SOC stocks compared to fertilization with slurry with little effects on CH4 uptake.

 

The results indicated that reduced tillage and manure compost application were both valuable measures for climate change mitigation in relation to the traditional ploughing system with slurry application due to the domination of SOC sequestration in the first decade after conversion. N2O fluxes were triggered by actual pedoclimatic conditions and influenced by soil biochemical properties. To reduce the impact of tillage operations on N2O emissions, it is recommended to reduce tillage frequency and to adjust tillage timing to cold and dry soil conditions whenever possible.

2017 - Switzerland - Maike Krauss, Reiner Ruser, Torsten Müller, Sissel Hansen, Paul Mäder, Andreas Gattinger - Agriculture, Ecosystems & Environment Volume 239, 15 February 2017, Pages 324–333
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