Optimization of Mechanized Quinoa (Chenopodium quinoa Willd.) Harvesting in Mediterranean Conditions: Technical and Environmental Aspects

Quinoa attracts growing interest thanks to its nutritional value, biomass potential, and tolerance to cold, salinity, and drought, making it suitable for Mediterranean environments. Harvesting can be carried out with conventional wheat combine harvesters, although specific adjustments are required to ensure efficient seed–biomass separation and minimize losses. This study examined technical and environmental aspects of mechanized quinoa harvesting in southern Italy to identify the most effective threshing drum (TD) speed that limits losses while ensuring adequate seed separation. Field trials conducted in Puglia in 2022 and 2024, using modified combine harvesters and TD speeds between 600 and 900 rpm, showed wide variability in seed losses across settings. The 700-rpm setting yielded minimal losses in 2022 (Threshing Index, TI 6%), but proved inadequate in 2024 (TI 93%), as uneven ripening and lower yields compromised threshing efficiency. Conversely, 900 rpm produced the highest losses in 2022 (TI 67%) and the lowest cleaning efficiency with the highest residue percentage in 2024, confirming excessive mechanical aggressiveness. In 2024, 650 rpm showed relatively low losses (53%), but these were affected by reduced yield and incomplete detachment (TI 50%). In both years, 750 rpm provided the most stable performance, offering a balanced compromise between efficient seed detachment (TI 23% in 2022; 55% in 2024) and moderate seed losses (25% and 63%, respectively). Adaptive harvesting strategies, focused on appropriate machinery calibration and optimized agronomic practices, could promote the sustainable integration of quinoa into Mediterranean crop diversification systems.