Design and evaluation of fertilization rule-based strategy with APSIM-Wheat Model: For a climate responsive and risk proofing fertilization in Morocco

Crop simulation models are essential decision support tools, particularly in regions with highly variable climates, as they help farmers optimize crop management practices. In Moroccan rainfed areas, nitrogen (N) and phosphorus (P) fertilization strategies are critical for making informed decisions about the timing and quantity of application to maximize income. This research presents an innovative rule-based approach that integrates the APSIM crop simulation model to enhance nitrogen (N) and phosphorus (P) fertilization recommendations, tailored specifically for implementation at farmers' field levels. This study compares four N- and P-fertilization strategies: two rule-based strategies derived from the APSIM model using historical climate data and current-year rainfall, and two recommendations from empirical models commonly used by Moroccan farmers and advisers (Fertimap and NPK-engine). The study tested the impact of these four fertilization schemes on wheat yield, plant nutrient content, and farmers' gross margins in field trials at two sites, El-Jadida and Ksar-Lkbir, during the 2021/2022 growing season, which experienced contrasting rainfall patterns. A subsequent risk analysis evaluated the agronomic and economic efficiency of these strategies across ten growing seasons (2012-2021), considering variations in fertilizer and wheat market prices. The results indicate that the APSIM-based decision rules, which integrate historical climate data and current in-season rainfall, were the most effective in 2021/2022. This approach optimized farmers' gross margins in El-Jadida and minimized economic losses in Ksar-Lkbir. The risk frequency analysis highlighted the superiority of APSIM-based decision rules, particularly those incorporating current-year rainfall, during favorable seasons. However, differences between the strategies were less pronounced in other seasons. Overall, the APSIM-based decision tools, which combine historical climate data with current in-season rainfall, and the NPK-engine tool were identified as the most effective strategies for minimizing economic risk in Morocco's variable and often harsh climate.