Estimation of greenhouse gases (N₂O, CH₄ and CO₂) from no-till cropland under increased temperature and altered precipitation regime: A DAYCENT model approach

Greenhouse gas (GHG) emissions play an important role in regulating the Earth surface temperature. GHG emissions from soils are sensitive to climate change and land management practices. According to general circulation model (GCM) predictions, the Earth will experience a combination of increased temperature and altered precipitation regimes which may result in an increase or a decrease of GHG exchange. The effect of climate change on GHG emissions can be examined through both experiments and by applying process-based models, which have become more popular. The performance of those models can be improved significantly by appropriate calibration procedures. The objectives of this study are to: (i) calibrate the DAYCENT model using advance parameter estimation (PEST) software and to (ii) examine simulated GHG dynamics at daily and seasonal time-scales under a climate change scenario of increased temperature (2°C) and a precipitation regime change where 40% of precipitation during the dry season was redistributed to the wet season. The algorithmic calibration improved the model performance by reducing the sum of weighted squared residual differences by up to 223% (decreased from 1635 to 505g N₂O-Nha^-1 d^-1) for N₂O and 22% (decreased from 623 to 507% WFPS) for water filled pore space (WFPS) simulation results. In the altered climate scenario, total N₂O and CO₂ fluxes decreased by 9% (from 2.31 to 2.10kg N₂O-Nha^-1yr^-1) and 38% (from 1134.08 to 699.56kg CO₂ ha^-1yr^-1) respectively, whereas CH₄ fluxes increased by 10% (from 1.62 to 1.80kg CH₄ ha^-1yr^-1). Our results show a larger impact of altered climate on CO₂ as compared to N₂O and CH₄ emissions. The main difference in all GHG emissions was observed in summer period due to drought conditions created by reduced precipitation and increased temperatures. However, the GHG dynamics can also be attributed to no-till practices which play an important role in changing the soil moisture conditions for aerobic and anaerobic microsites. These results are based on a process-based model, therefore, we suggest performing experimental studies to examine the GHG emissions under increased temperature and especially under altered precipitation regimes.