Precipitation gradient and crop management affect N2O emissions: Simulation of mitigation strategies in rainfed Mediterranean conditions

Abstract

In Mediterranean areas high precipitation variability and crop dependence on soil water availability make the interaction between climate and agricultural management a key issue for mitigating N2O emissions. In this study we used the STICS model to capture the effect of a water deficit gradient and precipitation variability on N2O emissions and mitigation strategies (i.e. N fertilizer type, grain legumes introduction in crop rotations and crop residues management) in a rainfed Mediterranean transect (HWD-Senés, MWD-Selvanera and LWD-Auzeville, i.e. high, medium and low water deficit, respectively). The model was first tested against a database of daily N2O fluxes measured during twelve growing seasons of winter crops at the LWD site. Several scenarios were then run on each site, always over 9 successive growing seasons to take into account precipitation variability. STICS showed a good ability to simulate the driving variables of N2O fluxes at the daily time scale. The mean observed and simulated cumulative emissions during the growing season were 0.71 and 0.82 kg N2O-N ha-1 , respectively. The simulated N2O emissions (mean of all scenarios) decreased with increasing water deficit being 2.51, 0.65 and 0.26 kg N2O-N ha-1 yr-1 for LWD-Auzeville, MWD-Selvanera and HWD-Senés, respectively, which is consistent with published results. The lower N2O emissions in the driest sites were not only related to lower fertilization rates but also to other factors associated with the Mediterranean characteristics, particularly, the drier water regime. Simulated N2O emissions were highly sensitive to the interannual variability of the climatic conditions. According to the simulations, urea fertilizer would lead to slightly higher N2O emissions (+6 and +8%) than ammonium-and calcium nitrate, respectively. The incorporation of winter pea in the traditional cereal-based Mediterranean rotations would reduce by ca. 22% the N2O emissions in HWD-Senés without changing wheat yields. Differently, in MWD-Selvanera and LWD-Auzeville, N2O emissions would remain unchanged since the emissions associated to the decomposition of low C:N ratio pea residues would 3 counteract the lower application of N fertilizer. The systematic removal of crop residues at LWD-Auzeville would decrease the N2O emissions by 20%. However, this practice seems not recommendable if tillage is practiced due to the concomitant decrease of soil organic matter, fact that would worsen the C footprint of the system and increase the susceptibility to soil erosion. Our work highlights the interest of combining experimental and modelling approaches to account for climatic variability and evaluate long-term effects of N2O mitigation practices under Mediterranean conditions.

No-tillage reduces long-term yield-scaled soil nitrous oxide emissions in rainfed Mediterranean agroecosystems: A field and modelling approach

“…The emission of N2O associated to denitrification is then calculated as a variable fraction of the denitrification rate depending on pH and WFPS. A more detailed description of N2O emission simulation by STICS can be found in Plaza-Bonilla et al (2017). Independent data from the two datasets obtained were used to calibrate the model.…”

“…Rainfed Mediterranean agroecosystems are characterized by the low magnitude and high variability of precipitation and the high evapotranspiration rates, severely limiting crop yield potential. In these areas, winter cereals show a good adaptation given the partial synchrony of their water needs with the distribution of precipitation and the key contribution of the soil water recharge period (Lampurlanés et al, 2016;Plaza-Bonilla et al, 2017). In different rainfed Mediterranean areas of Spain reduced and no-tillage (NT) systems have been introduced during the last three decades aimed to reduce costs and mitigate soil erosion (Moreno et al, 2010).…”

Cover crops mitigate direct greenhouse gases balance but reduce drainage under climate change scenarios in temperate climate with dry summers

“…Agriculture can also mitigate the GHG balance via carbon (C) sequestration (Smith et al., ). Agronomic practices can be improved by generating more C residues via higher biomass production, which sequesters more C in the soil (Collins, Rasmussen, & Douglas, ), and by improving N management to reduce N 2 O emissions (Plaza‐Bonilla, Léonard, Peyrard, Mary, & Justes, ).…”

“…Justes, Mary, and Nicolardot (2009) parameterized the decomposition module and demonstrated that the model predicts crop residue decomposition well, including that of fresh cover crop residues for a wide range of C:N ratio. The model was also determined to simulate correctly many effects of cover crops on nitrate leaching, soil C dynamics and CO 2 emissions, soil N 2 O emissions, and water and temperature stress on plants (Constantin, Beaudoin, Launay, Duval, & Mary, 2012;Plaza-Bonilla et al, 2017;Vuichard et al, 2016). Constantin et al (2012) shown that STICS was satisfactory for predicting long-term N mineralization from cover crops based on 13-17 years of experimental data from three contrasted pedoclimatic sites.…”

“…These authors shown that STICS was satisfactory for predicting changes in organic soil C in most experiments, with a mean rRMSE of only 3.9%. Plaza-Bonilla et al (2017) recently demonstrated that STICS was able to satisfactorily predict the effects of climate scenarios and cropping systems on N 2 O emissions under Mediterranean conditions and for wet and dry regions. Finally, we parameterized and validated the STICS model for the emergence of various cover crop species, which make it possible to have specific parameters for a wide range of species used as cover crops .…”