Economic Analysis and Evaluation of Grain Losses of Two Common Straw Collecting Combine Harvester: A Case Study, Azna County, Lorestan, Iran

Wheat, is the most important crop in the world. In Iran, wheat is the most important and strategic agricultural crop, due to its vital role in providing food and feeding livestock. Because wheat harvesting operation has a significant share of total grain losses, it is considered as the most important and sensitive stage of production. Recently, in Iran, the need for straw to feed livestock has increased sharply, and since wheat is the main source of straw production, changes have been made in the configuration of the grain combine harvester so that in addition to collecting grain, it can crush and collect straw. These combine harvesters are known as straw collecting combine harvesters. The growing need for straw, along with the high cost and difficulty of straw collecting, has made straw collecting combine harvesters more popular, especially in areas where animal husbandry is common alongside agriculture. Despite facilitating and increasing the possibility of straw collection by this type of combine harvesters, in many cases grain losses have increased. Therefore, it is necessary to investigate the amount of grain losses in this type of combine harvester and determine the factors affecting its losses.

This study was conducted to investigate the effect of ground speed and wheat yield on grain loss in a straw collecting combine harvester. The use of this type of harvester was also analyzed economically. Two models of JD-1055 and JD-1165 combine harvesters were considered for evaluation. The experiments were performed in a split factorial design in the form of a randomized complete block design. Grain yield (at three yield levels: less than 2 Ton ha-1, 2 to 5 Ton ha-1, and more than 5 Ton ha-1) was the main factor and the other two treatments, the model of combine harvester and the ground speed (with three levels: 1, 1.5 and 3 km h-1) were factorially placed in subplots. Loss components including head loss, combine harvester body loss, end loss, threshing unit loss, cleaning unit loss, and quality losses were measured and compared with that of a conventional grain combine harvester. Field capacity and harvesting cost were also measured for both types of combine harvesters. Finally, based on cost-benefit analysis, the straw collecting combine harvester was compared with the conventional combine harvester economically.

The results showed that in addition to the main effects, the two-way and three-way interactions were also significant for the studied factors on head loss, body loss, end loss, threshing unit loss, cleaning unit loss, and quality losses of straw collecting combine harvester. The losses of the straw collecting combine harvester are strongly affected by the ground speed and the grain yield. The percentage of grain loss in low yields (less than 2 Ton ha-1) was significantly higher than that of medium (2 to 5 Ton ha-1) and high yields (more than 5 Ton ha-1). The average loss of JD-1055 was less than JD-1165, mainly because of more loss in threshing and cleaning units. The highest total losses, with a rate of 10.54%, were related to JD-1165 in low yields, while the lowest percentage of total losses, at a rate of 2.54%, was related to JD-1055 in medium grain yield and low speed(1 km h-1). The total grain losses of conventional combine harvesters obtained about 3.22% while the total grain losses of straw collecting combine harvesters were approximately 5.44%. In general, the losses of straw collecting combine harvester were about 2.22% more than that of the conventional combine harvester. The economic evaluation showed that in the region where animal farming is common along with agriculture, the use of straw collecting combine harvester is more economical than a conventional combine harvester.

Combine harvester model, grain yield, as well as ground speed of the combine harvester affects the grain losses in different units of a straw collecting combine harvester as well as total losses. As the grain yield and the feed rate increase, the total losses of this combine decrease at first but increase again in high yields. Adjusting the feed rate helps reduce the end losses and total losses of straw collecting combine harvester. In the study area, using a straw collecting combine harvester is more economical than a conventional combine harveste