Modelling scenarios of soil properties and managements in olive groves at the micro-catchment scale with the AnnAGNPS model to quantify organic carbon

Authors: TAGUAS, ENACAMACION - University Of Cordova (UCO), Spain; Bingner, Ronald - Ron; MOMM, HENRIQUE - Middle Tennessee State University; Wells, Robert - Rob; Locke, Martin

Submitted to: Catena
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2021
Publication Date: 4/13/2021
Citation: Taguas, E.V., Bingner, R.L., Momm, H.G., Wells, R.R., Locke, M.A. 2021. Modelling scenarios of soil properties and managements in olive groves at the micro-catchment scale with the AnnAGNPS model to quantify organic carbon. Catena. 203:105333. https://doi.org/10.1016/j.catena.2021.105333.
DOI: https://doi.org/10.1016/j.catena.2021.105333

Interpretive Summary: Technology has been developed to assess the impact of agricultural practices on organic carbon. Changes in agriculture and forestry can potentially increase soil-carbon storage and reduce atmospheric carbon dioxide that is, in part, contributing to factors affecting global climate change. Currently, 48% of the world’s olive oil is produced in Spain, and there is clear concern over the carbon balance in the context of climate change and the loss of productivity. In this study various scenarios were prepared for use in simulations of a small catchment containing extensive olive groves that included 6 different soil types, 3 different managements involving no till, conventional tillage, and cover crops, 3 types of fertilization and 2 contrasting reach organic carbon half-lifes. The soil organic carbon pools were only significant for fertilizer applications and where degradation in channels associated with very large catchments because of long travel times produced. The most significant parameters derived from the sensitivity analysis were soil texture, saturated hydraulic conductivity and Curve Numbers associated with exported organic carbon, soil organic carbon, fertilization parameters and the rate of decomposition of residues. This technology can be helpful in understanding how carbon is cycled and distributed on the landscape and can provide a valuable tool in guiding policy-makers in land-use management planning as they may impact terrestrial carbon sequestration.

Technical Abstract: Soil organic carbon (SOC) stock changes are crucial in identifying risk of desertification in fragile areas such as the Mediterranean Basin and to fulfill global conventions for environmental protection. In Spain, 48% of the world’s olive oil is produced with 2.6 Mha dedicated to the crop, and there is clear concern over the carbon balance in the context of climate change and the loss of productivity. In this work, 108 scenarios were prepared with the model AnnAGNPS in a small catchment of extensive olive groves by considering 6 different soil types (with textures sandy, S; sandy loam, Slo; loam, L; clay loam, Clo; silty loam clay, SiLoC; clay, C), 3 different managements (no till, NT; conventional tillage, CT, and cover crop, SC), 3 types of fertilization (two organic at rates of 40 and 80 kg.ha-1, F2 and F3, and another inorganic F1 with 100 kg.ha-1) and 2 contrasting reach organic carbon half-life time (0.1 day-730 days). The consistency of the simulated values of annual OC attached to sediment and of variations of ground SOC (h=200 mm) were evaluated and compared in the context of the region of Andalusia, Spain. In addition, the most significant parameters to consider in the subsequent calibration process were also identified. There were significant differences in annual values of exported OC exported for the scenarios of soil and management, ranging between 0.0 kg.ha-1 and 368.9 kg.ha-1. In addition, S and SC showed the lowest variability intervals, while Clo and NT had the highest OC values and variation ranges. For the SOC pools, the effects of soil and fertilization types were more evident than that of management. The combination C-SC-F3 presented the maximum increase of SOC (0.150 mg OC.g-1soil.y-1) as a result of the maximum OC inputs while the combination Slo-NT-F1 presented the minimum (0.080 mg OC.g-1soil.y-1). Finally, the most significant parameters derived from the sensitivity analysis were soil texture, saturated hydraulic conductivity and Curve Numbers for the annual exported OC and ground OC, the fertilization parameters and the rate of decomposition of residues. Although a proper calibration was not carried out, the consistency of parameterization based on the abundance of experimental studies supports the use of AnnAGNPS for simulating the OC loss in agricultural catchments.