Impact of the New European Greening Rules on Regional CO2 Fluxes in the Intensively Used Northern Rur Catchment, Germany

In order to address environmental and sustainability issues, in 2015 the European Commission replaced the Single Farm Payment Scheme by a Basic Payment including a “greening” payment that is worth about 30% of the total payment. A prerequisite for greening payments includes to maintain an “ecological focus area” covering at least 5% of the area of holding. This request can alternatively be achieved by sowing nitrogen fixing catch/cover crops in the off season (generally in fall and winter). Therefore, it is assumed that the proportion of catch/cover crops will increase from 2015 onwards at the expense of bare soil fields. In particular, with regard to more frequently occurring mild weather conditions during fall and winter, this increase in catch/cover crops will have significant impact on agricultural area CO₂ fluxes and annual carbon budgets.

The goal of this study is to evaluate this change in agricultural practice on local and regional carbon fluxes and budgets. As a first attempt, we compare parallel Eddy Covariance (EC) measurements of CO₂ fluxes from two nearby sites. Site one was cultivated with winter wheat followed by the regional catch crop oil radish (Raphanus sativus) and site two with winter wheat (Triticum aestivum) followed by a second cultivation period of winter wheat. From the harvest of winter wheat on, the results show major differences between both sites due to prolonged CO₂ uptake of the oil radish. In contrast the bare soil and small winter wheat plants of field two show only minor uptake during fall. Hence, respiration processes dominate that period.

In addition to this comparison, the daily courses of net CO₂ flux and soil respiration of three different catch/cover crops: greening mix, oil radish, white mustard (Sinapis alba) were observed on a random basis. Therefore, we compared measurements of a net flux chamber and soil respiration chamber against EC data. All three catch/cover crops show significantly higher CO₂ uptake rates than our EC test fields, (i) cultivated with winter barley (Hordeum vulgare), and (ii) without vegetation.

To allow an assessment of the change in CO₂ fluxes and budgets on regional scale, a land use comparison based on satellite images for the years 2014 and 2015 will be applied in combination with statistical information from local authorities. By using these results, a first regional evaluation of the impact of the new greening policies on carbon fluxes and budgets for the northern Rur catchment will be carried out.