Mechanical Harvesting of Castor Bean (<em>Ricinus communis</em> L.) with a Combine Harvester Equipped with Two Different Headers: A Comparison of Working Performance

Castor bean (Ricinus communis L.) is a promising industrial crop suitable for cultivation in marginal conditions in the Mediterranean area, but the mechanical harvesting of the seeds is still usually performed manually. In this manuscript, the authors present a preliminary test to assess the effectiveness of equipping a combine harvester with a sunflower header to mechanically harvest castor beans. Machinery performance, seed loss from impact (ISL) and cleaning systems (CSL), and seed cleaning were evaluated and compared with the results obtained from the same combine harvester equipped with a cereal header. According to the results, no statistically significant difference in CSL was found. Values ranged from 162. 41 kg dry matter (DM) ha−1 in the cereal header to 145.56 kg DM ha−1 in the sunflower header, corresponding, respectively, to 8% w/w and 7% w/w of the potential seed yield (PSY). Using the sunflower header significantly lowered ISL (158.16 kg DM ha−1, i.e., 8% w/w of PSY) in comparison with the cereal header (282.02 kg DM ha−1, i.e., 14% w/w of PSY). This suggests more gentle cutting and conveying capability of the sunflower header to harvest the plants without losing capsules. On the other hand, the use of different headers did not significantly affect the cleaning of the seeds which averaged at 20% of the total seeds collected in both cases. In conclusion, the study highlights that a conventional combine harvester equipped with a sunflower header could be the first step towards the development of a fully mechanized harvest phase in castor beans which triggers lower seed loss and does not negatively affect the cleaning capacity of the combine harvester. Further studies are also encouraged to confirm these findings in other hybrids