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Castor (Ricinus communis L.) is an oilseed species that can be grown as a semi-perennial in Mediterranean environments, including the coastal areas of Sicily. The present study investigated the optimization of cultivation techniques for castor, with the crop being maintained over a two-year period, through the evaluation of different agronomical inputs in order to increase seed yield. The effects of irrigation (I) and nitrogen fertilization (N) on the seed and oil yield and their components were assessed in castor cultivated in a typical semi-arid environment. Four levels of irrigation (I0, I30, I60, and I100: 0, 30, 60, and 100% of crop evapotranspiration—ETm restoration, respectively) as the main plot and three levels of nitrogen fertilization (N) (0, 60, and 120 kg N ha−1) as the sub-plot were considered. Irrigation mostly affected the number of racemes per plant, the number of capsules per raceme, and the seed weight. The oil content was, on average, 39.2% and 45.6% for the first and second year, respectively. The highest seed yield was obtained by I100N120 treatment (4154.0 kg ha−1); however, the combination of a high soil nitrogen level (N120) and medium water availability (I60) resulted in satisfactory seed and oil yields. The reduction in the irrigation water to an intermediate level could be also an environmentally friendly strategy not significantly affecting yields. [ABSTRACT FROM AUTHOR]

Increasing air temperature due to changing climate is projected to decrease the length of the growing season, hasten vegetative development and maturation, and ultimately affect yield of many C3 crops. Previous multilocation trials highlighted strong relationships between thermal trends in the interval "beginning of flowering‐end of grain filling" and grain yield, and protein content in durum wheat (Triticum turgidum subsp. durum (Desf.) Husn.). With the aim to confirm these relationships, nine durum wheat genotypes, including old (Capeiti 8, Senatore Cappelli and Trinakria) and modern (Amedeo, Arcangelo, Mongibello, Simeto, and Svevo) varieties and a Sicilian landrace (Russello) were grown at three different sites representing a climate gradient in Sicily, Italy. Moreover, the effect of post‐anthesis heat stress on these durum wheats was further investigated in two contrasting environments: open‐field (control—C) and greenhouse heat stress (HS). HS shortened the interval "beginning‐end of flowering" of 1.5 days across genotypes, and the "end of flowering‐beginning of grain filling" and maturation of 4.9 days, with a range of 1 day in Arcangelo to 11 days in Cappelli. Advances in main phenophases significantly decreased kernel weight (KW) and grain yield (GY), whereas grain protein content (PC) increased. As expected, a negative relationship was observed between GY and PC, while positive relationships were found for GY and grain‐filling duration (GFD), and GY and KW. Genotypes responded differently to heat stress, as evidenced by the net photosynthesis, transpiration rate, instantaneous water use efficiency and dry matter accumulation in kernels. Genotypes were ranked according to the heat susceptibility index (HSI): Amedeo, Arcangelo, Capeiti 8, Svevo and Trinakria resulted heat‐tolerant. These varieties were characterized by an early trigger of dry matter accumulation in kernels under HS (Amedeo, Arcangelo and Trinakria), or showed similar length of the GFD (Capeiti 8) between environments. The multilocation trial confirmed a negative relationship between maximum temperatures and grain yield, and a positive relationship between minimum temperatures and protein content during grain–filling periods. Research focusing on agronomic strategies, phenology and breeding for tolerance to heat stress is of strategic importance to cope with the detrimental effect of global warming in semi‐arid climates. [ABSTRACT FROM AUTHOR]

• Castor might be grown as rainfed crop in semi-arid Mediterranean environments. • Autumn or winter sowings allowed to increase phenological intervals and seed yield. • Photoperiod corrected growing degree unit equations showed the lowest variability. • Suitable areas for autumn sowings were identified in Sicily. Castor (Ricinus communis L.) is an oilseed crop holding great promise for semi-arid environments. In regions where minimum temperature during winter is high enough to allow plants to survive, it would be worth to explore the adaptability of the species by performing autumn sowings, thus enabling rainfed cropping systems. A two-year field experiment under different sowing times (from November to June) was conducted in Southern Italy using castor Hy. Hazera. Autumnal sowings extended the plant vegetative period; nevertheless, flowering was simultaneous with all sowing dates. Only with the latest spring sowing (that of June) both floral induction and seed ripening were postponed. Seed yield with January and February sowings was the highest (3.92 Mg/ha on average). Using the wide variability of temperature and photoperiod conditions of the different growing periods, thermal and photothermal sums to predict the length of the main phenological intervals were calculated using different models. Overall, the best predicting model was that using sums of thermal units from minimum temperatures > 8 °C and maximum temperatures of 30 °C minus the degrees exceeding 30 °C, multiplied by photoperiod. The model allowed to develop zonation maps predicting the latest sowing date and the earliest seed ripening date in Sicily for autumn-spring and spring-summer growing season. The zonation procedure indicates that castor can be sown in autumn in coastal areas, while spring sowings are more suited to colder inland and hilly areas of Sicily. The work might find practical application to individuate suitable Mediterranean areas to grow castor in winter sowings. [ABSTRACT FROM AUTHOR]