Carbon storage and nitrous oxide emissions of cropping systems in eastern Washington: A simulation study

Abstract

Conservation tillage is an agricultural strategy to mitigate atmospheric greenhouse gas (GHG) emissions. In eastern Washington, we evaluated the long-term effects of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) on soil organic carbon (SOC) storage and nitrous oxide (N 2 O) emissions at three dryland and one irrigated location using the cropping systems simulation model CropSyst. Conversion of CT to NT produced the largest relative increase in SOC storage (ΔSOC, average yearly change relative to CT) in the top 30 cm (11.8 in) of soil where ΔSOC ranged from 0.29 to 0.53 Mg CO 2 e ha -1 y -1 (CO 2 e is carbon dioxide [CO 2 ] equivalent of SOC; 0.13 to 0.24 tn CO 2 e ac -1 yr -1). The ΔSOC were less with lower annual precipitation, greater fallow frequency, and when changing from CT to RT. Overall, ΔSOC decreased from the first to the third decade after conversion from CT to NT or RT. Simulations of ΔSOC for the conversion of CT to NT based on a 0 to 15 cm (0 to 5.9 in) soil depth were greater than the ΔSOC based on a 0 to 30 cm depth, primarily due to differences among tillage regimes in the depth-distribution of carbon (C) inputs and the resultant SOC distribution with depth. Soil erosion rates under CT in the study region are high, posing deleterious effects on soil quality, productivity, and aquatic systems. However, an analysis that includes deposition, burial, and sedimentation on terrestrial and aquatic systems of eroded SOC indicates that the substantial erosion reduction obtained with RT and NT may result only in minor additional SOC oxidation as compared to CT. Simulated N 2 O emissions, expressed as CO 2 equivalent, were not very different under CT, RT, and NT. However, N 2 O emissions were sufficiently high to offset gains in SOC from the conversion of CT to RT or NT. Thus, reducing tillage intensity can result in net C storage, but mitigation of GHG is limited unless it is coupled with nitrogen (N) fertilizer management to also reduce N 2 O emission. . Tillage operations that mix crop residues with soil and decrease soil aggregation facilitate microbial degradation of soil organic matter (Balesdent et al. 2000;Six et al. 2004a). Therefore, a shift from high physical disturbance conventional tillage (CT) to reduced tillage (RT) to no-tillage (NT) can increase SOC storage (Allmaras et al. 2000;Huggins et al. 2007). Crop rotations that increase carbon (C) inputs from roots and residues can also increase the storage of SOC (Huggins et al. 1998;Huggins et al. 2007).In addition to SOC storage, reduction of nitrous oxide (N 2 O) emissions also contributes to mitigate the climate impact of agriculture. According to the US Environmental Protection Agency (2011), agriculture contributes 7.4% of total greenhouse gas (GHG) emissions in the United States, with approximately 70% due to N 2 O production from agricultural soil management (e.g., nitrogen [N] fertilizer). Crop management and N fertilization strategies that limit the availability of mineral N for N 2 O production can he...

Evaluating Carbon Footprint Behavior in the Agriculture and Energy Sectors: A Review

“…Con respecto de los sistemas de cultivo, (Stöckle et al, 2012) se evaluó comportamiento de GEI durante la preparación de tres suelos secos y uno irrigado, según el tipo de labranza (convencional, reducida y cero). Este estudio utilizó «CropSyst», un modelo de simulación de sistemas de cultivo múltiple que ha sido usado en el Pacífico Noroccidental de EE.UU.…”

“…Regarding cropping systems, Stöckle et al (2012) evaluated the GHG effects of conventional, reduced, and no tillage at one irrigated and three dry land locations, using a multiyear, multicrop, and daily time step cropping systems simulation model, called CropSyst. This model has been used in the US Pacific Northwest (Pannkuk, Stöckle, & Papendick, 1998), and many other world locations (Wang & McGlinchy, 2009).…”

Modeling of Soil Carbon Storage Capacity Using Farm Management Factors in Drylands

“…The systematic random sampling (Yu et al, 2012) was performed in each quadrate. Soil samples from the 4 corners of the quadrates and their center were taken from depth of 0-30 cm (Stöckle et al, 2012) and mixed as a composite sample. Totally 95 composite soil samples are placed into the plastic bags and transferred to the laboratory.…”

Comparison of Greenhouse Gas Offset Quantification Protocols for Nitrogen Management in Dryland Wheat Cropping Systems of the Pacific Northwest

“…The accuracy of emission reductions for the iPNW could also be improved through development of regional emission factors (Tier II or Tier III) and might be achieved through field measurements or employing existing biophysical models, such as CropSyst (Stockle et al, 2012), and assessment frameworks, such as BioEarth (Adam et al, 2014). However, lower input models (e.g., COMET-Farm) rather than high input process-based models (e.g., CropSyst, DNDC) would likely reduce transaction costs associated with project development and verification (Li, 2000;Stockle et al, 2012).…”