Influence of sowing dates and methods of weed control on the growth, development and productivity of sunflower in direct seeding technology
When cultivating sunflower using direct seeding technology, its yield largely depends on the time of sowing and the effectiveness of weed control. The purpose of the research is to study the influence of sowing dates and methods of weed control on the growth, development and productivity of sunflower cultivated using direct seeding technology in the zone of unstable moisture in the Stavropol territory. Methods. Field studies were conducted in the experimental field of the North Caucasus Federal research center (zone of unstable moisture of the Stavropol territory) in 2018-2019, where the objects of research were sunflower crops on April 5-10, April 25-30 and May 15-20, cultivated using direct seeding technology with herbicides according to the following scheme: without the use of herbicides (control), spraying of weeds with a continuous herbicide from the group of glyphosates 5-7 days before sowing sunflower (glyphosate), glyphosate + soil herbicide, which was sprayed on plots after sowing the crop, and glyphosate + herbicide “Euro-Lightning”, used in the phase of 3-4 pairs of real sunflower leaves. Results. It was found that the transfer of sunflower sowing dates from April to the second decade of may leads to an increase in field germination of seeds, reducing the negative impact of atmospheric and soil drought during the growing season of the crop, which ensures the formation of a significantly greater vegetative mass of plants compared to the April sowing dates. The highest yield is formed by sunflower when sown in the second decade of May with the pre-sowing application of a continuous herbicide from the group of glyphosates in combination with a soil herbicide (2.45 t/ha) and the same glyphosate with the spraying of crops with “Euro-Lightning” herbicide in the phase of 3-4 pairs of leaves - 2.41 t/ha. Sowing sunflower in April, as well as the refusal to use herbicides or only pre-sowing spraying of the soil with glyphosate leads to a significant decrease in crop yield.