Effects of Soil Tillage on CO2 Emissions Caused by Soil Respiration and Fuel Combustion.

Agricultural soils as well as their management are significant sources for atmospheric carbon dioxide. Soil CO₂ efflux is mainly caused by soil respiration while management induced emissions originate from fossil fuel combustion. Enormous potential for reducing these emissions lies in the adoption of reduced or no-till management strategies instead of conventional treatment.
With the intention to assess the impact of soil management on CO₂ emissions and carbon dynamics of cropland a research project of three years duration has been started in 2007. Five agricultural fields which are part of long-term tillage treatment experiments have been chosen as study sites. They differ in climatic conditions, soil texture, slope and crop rotation. Three different tillage systems are investigated: Conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). RT and NT use cover crops during the winter period.
Soil CO₂ emissions are measured with a portable soil respiration system in intervals of about one week, but also in relation to management events. Concurrent soil temperature and soil water content are measured and soil samples are taken for chemical and microbiological analyses.
CO₂ emissions caused by machine use are indirectly determined by measuring the fuel consumption of the tractor for each management operation.
First results indicate a high spatial variation of soil CO₂ fluxes even within one plot. Referred to CT plots calculated carbon losses for vegetation period 2007 amounted to 65-94% for NT plots while for the different RT plots they ranged between 84 and 128%.
Measurements of CO₂ emissions due to fuel combustion for soil management and sowing winter wheat in autumn 2007 showed the following results: CT 180,8 kgCO₂/ha, RT: 89,4 kgCO₂/ha, NT: 19,5 kgCO₂/ha. This means a reduction of about 50% for RT and 90% for NT referring to CT.