Comparison of Dry Land Wheat Grain Harvest Losses in Different Types of Chaff Collector Combine Harvesters in Kurdistan Province

In conventional combine harvesters, wheat chaff is typically removed from the end of the machine and deposited on the field surface. Depending on the wheat cultivar, cultivation method, and growing conditions, the amount of chaff produced can range from 0.8 to 1.5 times the amount of grain harvested per hectare (Tavakoli, 2012). On average, this translates to an annual production of approximately 14 million tons of chaff, which is valued at around $240000000 based on regional prices in 2018-2019 ($1000 per kilogram). If collected, these chaff residues could be used as animal feed for livestock. Additionally, the long stems protruding from the back of conventional combine harvesters can interfere with subsequent cultivation efforts. Chaff combine harvesters have a similar structure to conventional machines, but feature a modified end that includes a tank and blower for collecting and depositing crushed chaff. Apart from the threshing unit, all other components of the harvester remain unchanged.

This study was conducted in 2019 in dryland wheat fields to determine the performance of Chaff combine harvesters in Kurdistan province. The study used 15 combine harvesters, including John Deere models equipped with chaff threshers from Shiraz, Bookan, and Hamedan, as well as the Hamedan Barzegar specific chaff collector combine. These combines were evaluated and compared based on natural losses, head and chaff storage losses, field capacity, purity percentage, and yield in field conditions in Kurdistan province. The total number of combines evaluated was 15, using a completely randomized design. Among these, 33% belonged to Shiraz company (5 samples), 33% to Bookan (5 samples), 20% to Hamedan (3 samples), and 14% to Hamedan Barzegar (2 samples). Sampling included measurement of natural losses, header losses, threshing tank losses (losses of the threshing unit, separating unit, and cleaning unit), and quality losses (broken grains and impurities) in the combine tank.

The results showed that the average yield, natural loss, and combine loss were 1,698.14 kg.ha-1, 2.39%, and 4.92%, respectively. In terms of the loss rates in different parts of the combine, 43.49% was related to the chaff storage of the combine, and 56.50% was related to the combine head.The natural loss rate in this province was 2.39%. The total combine loss was 5.18%, with 40.44% of that related to chaff storage and the rest related to the combine head. The results also showed a significant difference between the treatments in terms of field capacity, chaff storage loss, and purity percentage at a probability level of 5%.The total loss of the Hamedan Barzegar combine was 6.67%, which was higher than the other combines. The chaff storage loss of the Shiraz, Bookan, Hamedan, and Hamedan Barzegar combines were 0.87%, 2.64%, 0.78%, and 4.28%, respectively, showing a significant difference at a 5% level. There was also a significant difference between the treatments in terms of total grain loss.Based on these results, it is recommended to use the Hamedan, Bookan, Shiraz, and Hamedan Barzegar combines, with total losses of 4.33%, 4.33%, 4.52%, and 6.56%, respectively.

The average purity of harvested grains was 96.62%, and there was no significant difference between the combine harvesters in this regard.There was a significant difference between the combines in terms of field capacity at a probability level of 5%. The field capacity of the Bookan, Hamedan Barzegar, Hamedan, and Shiraz combine harvesters were 0.83, 0.87, 0.83, and 0.73 hectares per hour, respectively.In Kurdistan province, the average grain combine loss in dryland wheat harvesting with chaff combine harvesters was 4.92%, which is higher than in other provinces.The loss in the chaff tank of the Shiraz, Bookan, Hamedan, and Hamedan Barzegar combine harvesters was 0.87%, 2.64%, 0.78%, and 4.28%, respectively. Regardless of head losses, the loss in the Hamedan combine was less than other combine harvesters.The total losses of the Hamedan Barzegar, Bookan, Shiraz, and Hamedan combine harvesters were 6.56%, 4.32%, 4.52%, and 4.30%, respectively, with the Hamedan Barzegar and Hamedan combine harvesters having the highest and lowest losses, respectively.Based on the results obtained from this study, using the Hamedan combine is recommended in the dryland conditions of Kurdistan due to its low losses, high purity, and field capacity.