Interaction of cultivated plants and weeds in ten-field crop rotations

At the Department of General Agriculture of the Uman University of Horticulture the study of allelopathic relationships of cultivated and weedy plants was conducted for a long time in a stationary experiment with 10-field crop rotations: typical option 11 – the first field – corn for green mass; the second is winter wheat; the third – sugar beets; the fourth – barley with clover seeding; the fifth – clover; the sixth – winter wheat; the seventh – sugar beets; the eighth – peas; the ninth – winter wheat; the tenth is corn. In variant 1 corn was grown in the third field instead of sugar beets in the standard variant; in variant 2 instead of corn in the tenth field – sunflower, in va riants 7 and 8 – sugar beets and winter wheat, respectively. In variant 4 maize was grown in the last three fields of the typical variant 11. The test crop in our experiment was corn for green mass, therefore, in the final year of the second crop rotation the species composition of weeds in these crops plantations was determined. It turned out that in a typical crop rotation chicken millet and yellow bristle were the main polluters. The proportion of these weeds increased in crop rotations 1 and 4, and decreased in crop rotation 7, where the proportion of broad-leaved weeds increased. The total number of weeds decreased in crop rotation 2, where sunflowers were grown instead of corn in the tenth field. A positive relationship has been established between the root residues of crops and weed seeds germination in the following paired combination: corn – chicken millet; sugar beets – white quinoa; sugar beets – common amaranth and sugar beets – yellow bristle. In another vegetation experiment the soil taken from the rhizosphere of corn contributed to chicken millet germination, and the soil from sugar beets stimulated seeds germination of white quinoa and common amaranth. The soil from sunflower rhizosphere significantly reduced seed germination intensity of common amaranth and yellow bristle. Water extracts from chicken millet and yellow bristle had a negative effect on the initial corn growth, the extracts from white quinoa practically did not affect both growth indicators, and the extracts from common amaranth contributed to corn plants height while simultaneously increasing their weight.