Green pea harvesting losses as dependent upon crop condition and combine harvester operating mode | Visina gubitaka u žetvi zelenog graška u zavisnosti od stanja useva i režima rada kombajna

This paper presents results of a two-year study on the use of a Herbort-461 combine harvester in harvesting green pea grains. The focus of the study was to reach an optimal operating mode of the combine harvester for minimum grain loss and damage during harvesting of green peas of different maturity groups. Pea harvesting losses occurring at both the header and the threshing device were evaluated. Header losses made up of uharvested pea pods were induced by length of the growing season of individual cultivars and ground evenness. The lowest average grain losses in late maturity cultivars on even ground accounted for about 2% of the total yield. Grain losses in unharvested pods increased with an increase in the size of microdepressions in the ground. The highest losses in unharvested pods were recorded in early maturity cultivars on extremely uneven ground (17.34% average yield) due to the fact that ground microdepressions prevented the combine harvester from harvesting the pods of these cultivars normally developing low to the ground. As compared to the upright pea crop, the average header losses in all cultivars of the lodged crop were 2.08% and 16.39% higher on even and uneven ground respectively. Header pea losses were determined upon passage of the combine harvester by gathering grains, manually removing and separating the remaining pods from the stems and weighing them.Thresher grain losses were determined in unthreshed pods and free grains in the threshed material. The degree of grain loss and damage is dependent upon number of revolutions of the drum, and sieve mesh size and cleanliness. Threshing quality was assessed by removing broken and visibly damaged grains from the sample taken from the harvester bunker. The best performance was achieved at 300 rev/min of the drum, with lowest grain losses and grain damage being 1.1-1.8% and 0.9-1.2% respectively. During this operating mode, thresher losses in unthreshed pods were 8-9%. Grain losses and grain damage decrease but grain losses in unharvested unopened pods increase as the number of revolutions of the drum decreases. Under operating conditions, the harvesting efficiency of the combine harvester ranged from 0.4-0.6 ha/h on smooth ground and 0.2-0.4 ha/h on uneven ground.