Cereals germination in mixture stand — allelopathic aspects

Mixture crops, as opposed to pure sowing crops, are characterised by more stable output, reduced expenditure on pesticides as well as smaller environment pollution thanks to the biological diversification of species. It seems mixture crops have good prospects while the pro-ecology movements are growing in popularity. The growth and development of plants, both in natural and formed ecosystems, are often modified by physical and chemical processes taking place in neighbouring plants. The most typical example of physical process of this type is competition for environmental growth factors such as water, nutrients and light. The phenomenon takes place mostly when such resources are limited. In agricultural ecosystems competition can be controlled by means of agricultural practices and pesticides which eliminate the competitors of crop plants or making up for the shortage of nutritive growth elements, e.g. fertilisation and irrigation. In natural ecosystems the phenomenon of competition leads to one species dominance over others. Apart from this purely physical phenomenon there are chemical interactions observed among plants. The possibility of using allelopathic interactions to biological weed control and the compounds themselves as natural pesticides seems to be a very important issue. This experiment aimed at describing the allelopathic interspecies interactions in mixture crops. It is assumed that dominance of a certain crop species in a mixture field may be explained by the allelopathic properties of the species for one reason. Once the allelopathic interactions of crops are determined it will be easier to explain the changes of species composition in mixtures fields. The preliminary inter-crop influences were researched in a laboratory tests performed on Petri dishes. These tests allowed determination of allelopathic effects of tested grain species on the energy and the germinating ability of seeds of other grain crop species, as well as on the length of root and aerial parts of their seedlings. Four grain crop species were tested including barley, oat, wheat and triticale. Results of the experiments showed that some crop species when grown in a mixture with other crops affect their germination energy and seedling growth. Allelopathic interaction between barley and oat was noticed in the mixture. The percentage of germinated seeds depended on the selection of species used in the mixture. The sprouts growth rate, measured by its weight, depended on the kind of mixture and, to some degree, on the selection of species. Interspecific interactions of various crops resulted from the allelopatic properties of substances released by germinating seeds and roots of growing seedlings. P5.2