Biometrical features of plants and physical properties of amaranth seeds (Amaranihus cruentus) of a population variety originating from South America and a new Polish variety Rawa have been studied. New research methods were worked out or old methods were adapted to suit specific features of this plant. Studies were carried out in the period 1995-96 (population variety) and in 1997 (variety Rawa). Alongside field experiments plot experiments with varying sowing density were conducted in order to evaluate the influence of the number of plants per 1 mL plant on the variability of biometrical features and yields. Plant and wisp height, stalk thickness, wisp mass, number of plants per 1 mL and biological yield as well as seed self-shedding were determined. Geometrical properties (thickness, width, and length) were determined for individual seeds together with their aerodynamic features, surface roughness, resistance to static loading and microstructure. Whereas seed mass was characterised by such parameters as: density, porosity, outer and inner friction, angle of repose and chute, rehological properties and qualitative features. It has been found out that Rawa variety was more uniform than population variety and gave yields that were 50% higher. Seed sowing density differentiated plant biometrical features. Seed self-shedding in different weather conditions ranged from 0,3 to 2.1% of the biological yield. Physical properties of seeds changed according to moisture levels which was described by the regression lines and curves. It was found that with moisture decrease seed thickness, and the mean values ranged from 0,58 to 0,93 mm. Seeds of Rawa variety were developed better. The weight of 1000 seeds was from 0,60 g (very dry seeds) to 0,95 g (very moist seeds). Density was increasing with the decrease in moisture from 653,3 to 842,0 kg/m3. Whereas, porosity of the seed mass decreased from 53,5 to 40,0 %. Both the angle of repose and chute were decreasing with the decrease in the coefficient of inner and outer friction while the roughness of the seed surface was increasing. Amaranth seeds appeared to be more resistant to mechanical loading. The force ranging from 10.7N (very moist seeds) to 70,6N (dry seeds) was sufficient to damage the structure of an individual seed. Aerodynamic seed features depended on such parameters as seed load bearing surface, width, length and weight. With the increase in these parameters critical velocity increased linearly, and the coefficient of volatility decreased according to the same formula.A generalised Maxwell model with three branches was used to describe the phenomena of stress relaxation in the seed mass. It led to the conclusion that amaranth seeds en mass show strong viscoelastic properties. Seed qualitative features show high nutritive value, and evaluation of their microstructure showed that they contain unique starch with kernels thet are very uniform in size (1-1,5(m). Learning about biometrical plant features and their physical properties allowed for working out agrophysical basic for the harvest technology of this plant.
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