Abstract
Abstract. The effects of tillage on soil properties, crop productivity, and global greenhouse gas emissions have been discussed in the last decades. Global ecosystem models have limited capacity to simulate the various effects of tillage. With respect to the decomposition of soil organic matter, they either assume a constant increase due to tillage or they ignore the effects of tillage. Hence, they do not allow for analysing the effects of tillage and cannot evaluate, for example, reduced tillage or no tillage (referred to here as “no-till”) practises as mitigation practices for climate change. In this paper, we describe the implementation of tillage-related practices in the global ecosystem model LPJmL. The extended model is evaluated against reported differences between tillage and no-till management on several soil properties. To this end, simulation results are compared with published meta-analyses on tillage effects. In general, the model is able to reproduce observed tillage effects on global, as well as regional, patterns of carbon and water fluxes. However, modelled N fluxes deviate from the literature values and need further study. The addition of the tillage module to LPJmL5 opens up opportunities to assess the impact of agricultural soil management practices under different scenarios with implications for agricultural productivity, carbon sequestration, greenhouse gas emissions, and other environmental indicators.
Highlights
Agricultural fields are tilled for various purposes, including seedbed preparation, incorporation of residues and fertilizers, water management, and weed control
We described the implementation of tillage-related processes into the global ecosystem model LPJmL5.0-tillage
The extended model was tested under different management scenarios and evaluated by comparing to reported impact ranges from meta-analyses on C, water, and N dynamics, as well as on crop yields
Summary
Agricultural fields are tilled for various purposes, including seedbed preparation, incorporation of residues and fertilizers, water management, and weed control. Abdalla et al (2016) found in a meta-analyses that on average no-till systems reduce CO2 emissions by 21 % compared to conventional tillage, whereas Oorts et al (2007) found that CO2 emissions from no-till systems increased by 13 % compared to conventional tillage, and Aslam et al (2000) found only minor differences in CO2 emissions These discrepancies are not surprising as tillage effects a complex set of biophysical factors, such as soil moisture and soil temperature (Snyder et al, 2009), which drive several soil processes, including the carbon and nitrogen dynamics and crop performance.
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