Modeling carbon sequestration under zero-tillage at the regional scale. II. The influence of crop rotation and soil type

For policy decisions with respect to CO2-mitigation measures in the agricultural sector, national and regional estimations of the efficiency of such measures are required. The conversion of ploughed cropland to zero-tillage is discussed as an option to reduce CO2 emissions and promises at the same time effective soil and water conservation. Based on the upscaling of simulation results with the soil and land resources information system SLISYS-BW, estimations of CO2-mitigation rates in relation to crop rotations and soil type have been made for the state of Baden-Wurttemberg (Germany). The results indicate considerable differences in the CO2-mitigation rates between crop rotations ranging from 0.48 to 0.03 Mg C ha(-1) a(-1) for winter cereals-spring cereals-rape rotations and winter cereals-spring cereals-corn silage rotations, respectively. The efficiency of the crop rotations is strongly related to the total carbon input and in particular the amount of crop residues. Among the considered soil types, highest CO2-mitigation rates are associated with Cumulic Anthrosols (0.62 Mg C ha(-1) a(-1)) and the lowest with Gleysols (-0.01 Mg C ha(-1) a(-1)). An agricultural extensification scenario with conventional plowing but conversion of the presently applied intensive crop rotations to a clover-clover-winter cereals rotation indicated a CO2-mitigation potential of 466 Gg Ca-1. However,the present high market prices for cereals and increasing demand for energy production from biomass encourages an intensification of the agricultural production and an excessive removal of biomass which in future will seriously reduce the potential for carbon sequestration on cropland. (C) 2009 Elsevier B.V. All rights reserved.