Seed losses during the harvesting of oilseed rape (Brassica napus L.) at on-farm scale

In the Italian environments, the rapeseed (Brassica napus L.) is subjected, at ripening, to a seed shattering causing significant losses that reduce the yield and increase the oilseed rape seedbank in the soil. Meteorological events and mechanical harvesting are the main factors affecting the extent of seed dispersal. Lacking the availability of works investigating the actual losses during the harvest at large scale, the Consiglio per la sperimentazione e la ricerca in agricoltura, Unità di ricerca per l’ingegneria agraria (CRA-ING) has conducted a study in order to determine the effective seed losses at on-farm scale. The amount of losses of two combine headers, traditional for wheat and specific for oilseed rape harvest, was compared. The rapeseed header had a hydraulic sliding cut-bar and two vertical electric blade on both sides in order to reduce the pulling and tearing action between the cut-off plants and those still standing. The seed losses were evaluated before and during the harvesting by using plastic trays placed on the ground within the crop rows. The trays were arranged in a layout allowing the estimation of the seed losses of three different sectors of the combine headers. The results have demonstrated that, at farm level, the use of a specific oilseed rape header adapted and optimized for the crop requirements allows to obtain a level of seed losses (0,97% of total production), below the values reported in literature. For rapeseed, the higher losses are localized at the final parts of the head, where the plants are strictly intertwined.