Mitigating Drought-Induced Yield Loss Risk for Durum Wheat through Optimized Planting Schedule and Irrigation in Southern Italy

The Mediterranean cropping systems continue to face drought risk, with the changing climate intensifying its effects. Adaptation strategies are essential and must be assessed for their efficacy to guarantee their sustainability and relevance in specific regions, thereby enhancing adoption and optimizing resource utilization. This study investigated two climate adaptation strategies, namely shifting planting date (mid-November, late-November, or early-December) and adjusted irrigation (full, 75%, 50%, 25% deficit irrigation (DI), and rainfed), in reducing drought-induced yield loss risk (i.e., the magnitude of the yield loss and the likelihood of its occurrence) for durum wheat in the two provinces of Basilicata (Matera and Potenza) in southern Italy.

The study employed crop and probabilistic modeling to simultaneously assess the effectiveness of shifting planting dates and irrigation adjustments while quantifying the yield loss risk caused by drought. The crop model, CSM-CERES Wheat, was utilized in simulating the yield at different management combinations initialized using the weather (1991–2023), soil, and management data. Copula functions were used to model the dependency structure between drought intensity and yield anomaly calculated from the simulated yield, allowing the assessment of drought-induced yield loss risk.

Drought-induced yield loss risk in Matera was characterized by a relatively high likelihood of experiencing yield reductions with probabilities ranging from 36.6% to 78.4%, whereas Potenza exhibited negligible to low probabilities with the exception for early-December planting under rainfed condition (i.e., 55.9%). Shifting the planting date to mid-November and increasing irrigation levels reduced the likelihood of drought-induced yield loss, with significant results observed in Potenza. In Potenza, planting durum wheat in mid- to late-November under rainfed conditions showed a low risk of yield loss due to drought. This suggests that durum wheat can be grown with little or no irrigation. However, in Matera, even with full irrigation, yield loss risk was marginally high during intense dry conditions.

In Matera under rainfed conditions, substantial yield loss estimates (i.e., 70% likelihood) for late-November and early-December planting were 0.1 and 0.7 t ha^-1, respectively, for moderate drought severity (-0.84 > spei ≥ -1.28), while for exceptional droughts (spei < -2.33), yield loss estimates were 4.0 and 1.2 t ha⁻¹, respectively. In Potenza, substantial yield loss was only experienced for early-December planting under rainfed conditions during extreme  (-1.65 > spei ≥ -2.33) to exceptional drought, with estimated yield losses of 0.1 and 0.5 t ha⁻¹, respectively.

The results demonstrated that shifting the planting date to mid-November and implementing deficit and full irrigation largely mitigated drought‑induced yield loss risk in Basilicata, most notably in Potenza. Earlier planting and minimal irrigation in Potenza can help reduce yield loss risk due to drought. In Matera, on the other hand, early planting combined with full and deficit irrigation also mitigated the impact of drought except during extremely dry conditions, indicating additional or alternative adaptation strategies to cope with its impact.