physical characteristics of some native rice varieties cultivated in northern iran

background: physical characteristics of crops play an important role in designing the required machinery and apparatus for planting, harvesting, transport, processing and also storing. the aim of this study was to determine physical characteristics of some native rice varieties cultivated in northern iran, namely gerde, shafagh, tarom-e-hashemi, shiroodi and keshvari. methods: some geometrical, gravimetrical and frictional characteristics of the five varieties were determined by standard methods at their initial wet basis moisture content ranging between 10-11% (w.b.). data analysis was carried out by spss software (ver. 16.0) using one-way anova. results: among all the five studied rice varieties, the highest length, width and thickness values were measured as 8.06 mm, 3.59 mm and 2.87 mm, belonging to shafagh, gerde and shiroodi varieties, respectively which each of them had significance difference (p<0.05) with the other varieties from point of view of the mentioned characteristics. also, shafagh and keshvari revealed maximum and minimum values of volume, equivalent diameter and surface area, respectively. shafagh had also the highest rate of weight of thousand grains (25.06 g). gerde was found to be the most spherical variety and revealed the highest bulk density (0.82 kg/m3) and angle of repose (45.57º) while having minimum true density (1.41 kg/m3). conclusions: there were significant differences among the examined varieties in the case of physical properties and most of these properties were related to each other. these data could be useful for resolving some problems associated with design, development and analysis of behavior of products during post-harvest processing.