Evaluating the STICS Soil-Crop Model on durum wheatchickpea intercropping system under the semi-arid conditions of Southern Tunisia

Soil-crop models provide critical insights for designing and assessing innovative cropping systems, particularly for improving sustainability in water-limited regions. However, accurately modeling intercropping systems particularly those involving grains and legumes continues to pose a significant challenge in agricultural research. This study focuses on the initial calibration and evaluation of the STICS soil-crop model for a durum wheat-chickpea intercropping system in Mediterranean semi-arid conditions. Field experiments were conducted during 2020–2021 and 2021–2022 cropping seasons in the Medenine region, Tunisia, with comparison between the intercropping and monoculture systems. The Model performance was evaluated using Aboveground Plant Nitrogen (AGPN) as an indicator of nitrogen uptake. The STICS model demonstrated satisfactory predictive capacity across most simulations, with efficiency (EFF) values ranging from 0.56 to 0.80. Grain yield predictions were reasonably accurate, as indicated by a normalized root mean square error (NRMSE) of ≤ 37%, particularly for durum wheat (EFF ≥ 0.55). The model effectively simulated the soil water content, achieving an efficiency (EFF) of ≥ 0.51 and an NRMSE of ≤ 25%, especially in the chickpea plots. However, the predictions of the soil nitrogen stock were less accurate in the chickpea monocultures, with efficiency values ≤ 0.38 and NRMSE ≥ 44%. The intercropping simulations showed moderate accuracy, with efficiency values up to 0.41. These findings highlight the potential complementary interactions between durum wheat and chickpeas in using nitrogen and carbon resources. This study contributes to the development of sustainable agricultural practices tailored to Mediterranean climates, supporting climate adaptation and resource efficiency.