Uticaj fizičkih osobina na kvalitet semena useva / Influence of physical properties on cropI seed quality

The physical properties of seeds that will be investigated are: germination, shape and dimensions, sphericity, volume, size of individual seeds, seed mass porosity, static coefficient of friction on the familiar surface, moisture, bulk density, net density, weight of 1000 seeds and the dependence of compressive strength of the deformation force. The analysis of these physical properties will be made with corn, soybean, sunflower, wheat and barley. Within each type of seed, the analysis of two or three varieties or hybrids that are from the new collection of scientific and research institutions in this field is planned to be made. The creation of such database will be of great importance for seed finishers in Serbia. Today there is no adequate information on these physical characteristics presented as a whole. Thanks to the efforts of geneticists, hybrids or varieties of these crops emerge every year and soon find their place in agriculture. Often problems occur in processing the seeds during their transportation through gravity pipes, in determining the inclination of the sieve of the seed purifiers or the choice of the sieve openings as well as in the working process of gravity separators.The shape of individual maize, soybean, sunflower, wheat and barley is not regular, that is to say, it is not in the known proper form such as cube, cuboid, sphere, pyramid, cone or cylinder.Therefore, it is defined through description (Mohsenin, 1980) as a rotund, round with two ends flattened, oblong, conical, oval, invert oval, elliptical, edged elliptical, uneven, scarred, etc. This method of determining is, however, bound with the subjective error (Babić, 2000), and from the engineering aspects another way of defining should be chosen. The defining and measuring of the sphericity of seeds is one way of comparison with the pellet seeds (Mohsenin, 1980; Babić, 2000). The volume of uneven geometric object is usually measured by the volume, mass or pycnometre method (Mohsenin, 1980) and is calculated based on the three different measured sizes by the regression analysis. Porosity seed mass in a pile is defined as the ratio of volume of space and the total volume of material (Babić, 2000; Mohsenin, N., 1980). The coefficient of friction (-) on the basis of the Coulomb39;s law (Mohsenin, N., 1980) is defined as the ratio of the friction - Ftr (N) and the force normal to the surface of contact - Fn (N). The humidity wheat, barley, maize, soybean and sunflower seeds can be different for the time of collection, and it is dried down to its balance value as prescribed by the Regulation on the quality of seeds of agricultural plants: The Official Journal of SFR Yugoslavia 47/1987, which totals 11.0% for sunflower seeds, 14.0% for soybeans and between 13.5 and 14.0% for other crops. Bulk density of seeds is defined as the ratio of the mass and the total volume (the sum of volumes of the seed and the space between seeds) whereas the net density (Mohsenin, 1980) is the ratio of seed mass and volume of the seeds (capacity of the space between seeds). The mass of 1000 grains of a plant depends only on the seed moisture. This value increases along with the rise in humidity, which is confirmed by measurement results for wheat by Al-Mahasneh et al. (2007), where it ranges from 32.57 g at grain moisture contents of 9.3% to 51.95 g at moisture content of 41.5%. Seed germination should be high and it is prescribed in the Regulation on the quality of seeds of agricultural plants: The Official Journal of SFR Yugoslavia 47/1987. The seeds of field crops in the research are of different shapes and materials, and therefore react differently to the action of an external force, which may be in the area of plastic deformation, or in permanent damage, i.e. cracking the seeds. Being familiar with the values of the physical properties of seeds, and the seeds of wheat, corn, soybeans, barley and sunflower is necessary for the design and development of new seeds, but also for the control and management of existing equipment, transportation, processing and storage. The physical properties that will be investigated in this paper depend only on the shape and dimensions, surface conditions, moisture and seed composition. This is the reason why there are no analytical expressions for their calculation.