Fizyczne i biologiczne aspekty mechanicznej separacji nasion buka zwyczajnego (Fagus sylvatica L.)

Paweł Tylek


Obtaining certified seed material requires a number of physical actions which in turn call for the knowledge of rules governing separation processes. The latter are based on the differences in some physical and mechanical properties between the components of seed mixtures. This kind of knowledge is further required for designing and building various sub-assemblies of the machinery and equipment used to improve seed material, and for operating effectively seed cleaners and mechanical seed sorters as well as other machinery used in the seed processing. Both contemporary and older designs of separators utilise the experience of practitioners rather than the theoretical concepts rooted in the deep knowledge of the agrophysics of seeds. Therefore, it is necessary to perform a detailed analysis of the separation-related properties of beechnuts, including the features that have not yet been considered in forestry but should be taken into account when designing future universal separators. An analysis of the relevant body of literature indicates that the knowledge acquired to date does not encompass most of the physico-mechanical properties of seeds of the common beech (Fagus sylvatica L.). In view of the above, it was hypothesised that a set of the physico-mechanical properties of a beech seed, which may be related to separation, is influenced by the degree of development of the seed embryo. To examine this hypothesis, beech seeds were classified into three measurement fractions according to the stage of development of the embryo and the estimated seed germination capacity. In order to determine some of the characteristics it was necessary to adapt and modify the known and yet imperfect methods of measurement, and sometimes even to design original measuring stands. The use of filming methods necessitated developing algorithms for computerised image processing. The results of the studies showed that the mass, density, critical velocity of transportation and elasticity, as well as, to a limited extent, the size and shape of a beechnut depend on the degree of development of the seed embryo. By contrast, the external friction of seeds or their susceptibility to roll cannot be regarded as separating characteristics. The highest effectiveness of mechanical separation can be obtained by basing the process on the mass and density of seeds. For density, the optimum separation limit for dividing beechnuts into fractions is the value of 0.9 g•cm-3, for seed with ca. 10% moisture content. The size of beechnuts is characterised by three positively correlated basic dimensions. Among those linear dimensions, the most effective separating feature is thickness, followed by length and width, but it is only thickness that permits separation of seeds with insufficiently developed embryos from those properly formed. Taking into account the specific shape of a beechnut with its cross-section in the form of an equilateral triangle, sifting beechnuts through a sieve with round-shaped mesh requires selecting an appropriate sieve mesh, i.e. the one that is ca. 15% larger than the nominal width of seeds. To ensure the effective pneumatic separation of beechnuts, the minimum range of regulation of the velocity of vertical air stream should be 7-10 m•s--1. Such values, however, are unattainable for many universal separators. The effectiveness of beech seed separation in an air stream requires also longer-than-standard pneumatic ducts. In the course of the studies it was also noted that the traditional method used to dry beechnuts in order to prepare them for storage fails in ensuring uniform final moisture content. The most valuable seeds, i.e. vital ones with large seed embryos, show a significantly higher moisture content than other seeds, well above the commonly adopted standards. This is perhaps the reason behind a drop in the germination capacity of seeds during storage.
Other language title versionsPhysical and biological aspects of the mechanical separation of seeds of the common beech (Fagus sylvatica L.)
Book typeMonograph
Author Paweł Tylek (FoF / IoFUaFT / DoFMech)
Paweł Tylek,,
PublisherUniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW [80]
Publishing place (Publisher address)Kraków
Issue year2010
Book series /Journal (in case of Journal special issue)Zeszyty Naukowe Uniwersytetu Rolniczego im. Hugona Kołłątaja w Krakowie. Rozprawy, ISSN 1899-3486, (0 pkt)
Publication size in sheets9
Languagepl polski
Score (nominal)20
Citation count*4 (2015-12-27)
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