Alelopatski uticaj ekstrakata korovskih vrsta Abutilon theophrasti Med. I Xanthium strumarium L. na useve soje i kukuruza / Allelopathic influence of the extracts of weed species Abutilon theophrasti Med. and Xanthium strumarium L. on the crops of soybean and maize

Aphenomenon called allelopathy has been examined and explained through general, historical and scientific frameworks of scientific researches, first of all laboratory experiments, providing data on its cross-section of origin, development, current condition and future potential. It is possible to distinguish allelopathy from other mechanisms of plant community since its harmful effect appears as a result of the release of allelochemicals. For this reason it is also different from its competition. Allelopathy is considered to be one of the bases of sustainable agriculture, thus becoming a priority field of study in developed countries. The aim of this research was to determine the allelopathic influence of the extract of weed species A. theophrasti and X.strumarium on the initial growth of soybean and maize germs, as well as to determine the concentration of extracts of the examined weed species that have a negative impact on the germination of soybean and maize in laboratory conditions. Within field conditions, the aim of the research was to determine the concentration of the examined extracts of weed species that have a negative impact on the yield of test plants, as well as to determine the number of the examined weed plants per m2 that have a negative impact on germination, emergence and yield of soybean and maize. The extracts of weed species A. theophrasti prepared with different solutions confirmed the existence of significant allelopathic influence on the percentage of germination of soybean and maize. Ethyl-acetate extract applied in the highest possible concentration caused the highest percentage of soybean germination. Treatments with water and hexanol extracts had a stimulating effect on the length of the underground and over-ground part of soybean germs. Ethyl-acetate extract of weed species A. theophrasti caused the lowest percentage of germination of maize. In other words, it confirmed the strong allelopathic influence of the extract. Methanol extract was next on the list, while the last three extracts (water, hexanol and butanol) also confirmed the similar percentage of germination under allelopathic influence. The length of the underground and over-ground part of germs for all the applied extracts confirmed their allelopathic influence. Ethyl-acetate extract had the highest inhibitory effect on the length of the underground and over-ground part of maize. The application of the extracts of weed species X. strumarium also confirmed the allelopathic influence on the germination of soybean and maize as well as on the underground and over-ground part of the seed germs. Water and methanol extracts had a highly inhibitory effect in all four applied concentrations. Hexan extract in three applied concentrations of larger amount (0,04-0,01 g/ml) caused equal germination of soybean. Also, it is determined that this extract has stimulating influence on the length of the underground part of soybean, while the same concentration had the significant inhibitory effect on the length of the over-ground part. Ethyl-acetate extract of weed species X. stumarium in concentration of 0,04 and 0,02 g/ml caused 100% of soybean germination, while two concentrations with the lower amount of extract caused a smaller percentage of germination. However, concentration of 0,04 g/ml had a strong inhibitory effect on the length of the underground part of germs, while smaller concentrations had a stimulating effect on the length of the underground part of germs. The length of the over-ground part of germs showed a strong inhibitory effect of all four applied concentrations. The extracts of weed species X. strumarium confirmed the allelopathic influence on maize in laboratory conditions. The seeds treated by methanol extract resulted in the lowest percentage of germination, while the seeds treated by hexanol extracts had the highest percentage of germination. The length of the underground and over-ground part of the germ of maize also confirmed the significant inhibitory influence. Application of the smallest concentration of hexanol extract had a stimulating effect on the length of the underground part of germs, confirmed by high germination of seeds treated by that concentration. Experiments done in field conditions confirmed the results obtained in laboratory conditions. Soybean treated by water extract of weed species A. theophrasti resulted in reduced yield in the amounts of 37,96-63,50%, while maize yield was reduced in the amount of 13,68-39,47%. Methanol extract also had a significant allelopathic influence, reducing yield from 21,05-37,37% in corn crops, while in soybean crops the percentage of reduced yield was from 42,34-60,58%. Yield of soybean treated by water extracts of weed species X. strumarium was reduced in the amounts of 40,88-45,26%, while yield of maize went down in the amount of 10,53-30,26% pro rata to applied concentrations of extracts. Methanol extract reduced the amount of plant yield from 20,26-36,32% in maize, while the percentage