Speaker
Description
Agro-ecosystem models can be useful to assess a wide range of spatial and temporal diversification strategies, as they are able to capture the crops interactions with heterogeneous soil and environment. The models can support the design of diversified field arrangements with limited experimental efforts. However, a prerequisite for their ability to capture these heterogeneities is the adequate simulation of soil water dynamics, as water availability is one major driver for crop growth. The simulation of soil water dynamics is dependent on the layering of the soil profile, particle size distribution (sand, silt and clay) and soil hydraulic parameters which are often derived by employing pedotransfer functions. Additionally, the model requires information on soil bulk density, which influences these parameters. Therefore, in this study we calibrated and validated an agro-ecosystem model, implemented within the SIMPLACE modelling framework (Enders et al., 2023), by using the HYPRES and the German Manual of Soil Mapping (Sponagel et al., 2005) pedotransfer functions and by adjusting bulk density for the top- and subsoil. The agro-ecosystem model was previously calibrated and validated for crop growth and phenological development of rapeseed, barley, winter wheat, winter rye, sunflower, maize, soybean and lupine. Experimental data were collected in the 70 ha “patchCROP” landscape experiment, located within a young moraine landscape in Brandenburg, Germany. A total of 12 soil profiles were used for this study. Soil texture was manually assessed in the field. Additionally, a subset of augers was analyzed in the laboratory for particle size distribution. This data was then used to extrapolate and correct the soil textural classes from the manual readings. The soil showed a strong heterogeneity, particularly in the subsoil, ranging from fully sandy profiles to profiles with a loamy layer in the subsoil. In addition, volumetric water content data from soil moisture sensors at the experimental site was used to evaluate model performance for the calibration and validation steps. The sensors were positioned at depths of 30, 60 and 90 cm at 12 locations within the field. The distance from the soil moisture sensor to the soil auger location was always smaller than 4 m. Calibration and validation was carried out by using weather data from an on-site weather station, crop management, phenology data and the soil auger information. For the simulation of the soil water balance, the SimComponent <SlimWater> was used, which employs a tipping-bucket approach by dividing the soil profile into layers of 5 cm thickness. 7 soil profiles were used for calibration and 5 for validation over a time span of 2 years. The calibrated model was able to reasonably simulate the seasonal dynamics of the soil water balance. The model set-up using soil hydraulic properties based on HYPRES was able to better capture soil moisture dynamics as it effectively captured most of the crops' water extraction patterns, as well as the differences in soil moisture due to soil texture. The model error was largest after intense rain events for soils with a loamy texture in the subsoil. While the maximum simulated and observed moisture level agreed, the model tended to underestimate the duration required for a substantial increase in subsoil moisture content. For textures with relatively high clay contents, the simulations showed a mean absolute error of <6% for the volumetric water content, while under sandy conditions the mean absolute error was <3%.
Enders, A., Vianna, M., Gaiser, T., Krauss, G., Webber, H., Srivastava, A.K., Seidel, S.J., Tewes, A., Rezaei, E.E., Ewert, F., 2023. SIMPLACE — a versatile modelling and simulation framework for sustainable crops and agroecosystems 1–18. https://doi.org/10.1093/insilicoplants/diad006
Sponagel, H., Grottenthaler, W., Hartmann, K.J., Hartwich, R., Janetzko, P., Joisten, H., Kühn, D., Sabel, K.J., Traidl, R. (Eds.), 2005. Bodenkundliche Kartieranleitung (German Manual of Soil Mapping, KA5), fifth ed. Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover.
| Keywords | agro-ecosystem models; soil heterogeneity; soil moisture simulation; diversified cropping systems |
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