Multi-criteria optimization for mitigation model of greenhouse gas emissions from abandoned grassland

The most of agricultural area lies under permanent grasslands (3488 M ha, or 69%) and generates considerable GHG emissions as thus increasing global climate change. Grasslands cover some 1.2 M ha, or 50% of agricultural area in Lithuania. Accounting of GHG emission generated in grassland ecosystems may be important when evaluating and interpreting measurements of fluxes at both regional and ecosystem levels. Therefore, biosphere-atmosphere interactions were investigated on a clay loam topsoil over silt loam (Calc(ar)i-Endohypogleyic Luvisol) in differently managed grassland ecosystems of the Training Farm of Aleksandras Stulginskis University in 2009-2010. The following was carried out within the frame of the European Projects COST. The objective of this investigation was to determine the impact of fertilizers, their rates, and combinations on both GHG emission and productivity in abandoned semi-natural sward as well as cultural pasture. GHG emission measurements were carried out between June and September, when meteorological conditions were optimal for intensive plant and soil biota physiological processes, in absence of frosts stress. Gradual decline in GHG fluxes was observed during the vegetation period due to a decreasing supply of environmental components - organical substrates, fertilizers, activity of microorganisms - as well as their interaction with humidity and temperature (HTC ranged from 2.0 to 0.9). There was strong correlation observed between mean N2O, CO2, and CH4 emission during vegetation period on the one hand, and NPK (r = 0.9, 0.8 and 0.9) with monomial nitrogen fertilizers (r = 0.8 and 0.6) on the other. The fuzzy multi-criteria decision making method TOPSIS was applied when choosing the best compromise fertilizing regime. Fertilizing option N180P120K150 was chosen as the most suitable for supporting soil fertility and ensuring low emission rate in this particular case.