Threshing force of paddy as affected by loading manner and grain position on the panicle

Abstract

Threshing force, which is the force that separates a grain from the panicle, has a great importance in evaluating losses over design and application of harvesting and threshing machines. In addition, it is important to know the shattering habit of rice varieties in rice breeding program. In this study, the threshing force of two improved rice cultivars Dorfac and Kadous (long-grain), and three local cultivars of Hashemi, Alikazemi (long-grain), and Binam (medium-grain) was determined. The threshing force was measured at three portions of upper, middle, and lower of the panicle and three loading manners as tension, bending perpendicular to the front of the grain (type 1) and bending perpendicular to the side of the grain (type 2). The results revealed that cultivars, loading manners and the grain position on the panicle significantly (P < 0.01) affected the threshing force. The highest threshing force of 0.887 N was obtained from the lower portion of the panicle under tension loading; while the least threshing force of 0.267 N was determined for grains from the upper portions of the panicle under bending force of type 2. In the case of tension loading, the highest threshing force value pertained to long-grain cultivars.