INFLUENCE OF SOWING DATES ON PHOTOSYNTHETIC ACTIVITY AND SUNFLOWER YIELD IN DIRECT SOWING TECHNOLOGY

Abstract

When using the technology of direct sowing, which is becoming increasingly widespread in the Stavropol Territory, mulch is formed on the surface of the soil from the
plant residues of previous crops as a result of the absence of tillage. In the spring it slows
down soil warming, which can have a significant impact on the choice of the optimal sowing
dates for spring crops. The purpose of the research was to establish the influence of sowing
dates on the photosynthetic activity of crops and the yield of sunflower when it was cultivated
using direct sowing technology in the conditions of unstable soil moisture zone of the Stavropol Territory. The experiment was conducted on the field of the FSBSI “North Caucasus
FARC” in 2018-2020. On average, over three years of research, sunflower plants of May
sowing dates (May 15-20) had a large leaf index in the flowering stage – 3,78 m2/m2, which
was 36,2 and 43,9% higher in comparison to the crops of the first and third ten-day period of
April. At the same time, the photosynthetic potential and the net productivity of photosynthesis for the entire growing season were also significantly higher at May sowing – 1,96 million
m2×day/ha and 11,0 g/m2×day. This allowed sunflower plants of this sowing dates to form a
significantly larger green matter, as a result of which the highest yield was obtained – 2,34
t/ha, which was significantly 0,84-0,73 t/ha higher than sunflower sowing on April 5-10 and
25-30. With the postponement of the sowing dates, the quality of the seeds improved – the oil
content increased from 49,4 to 54,0%. This made it possible to obtain the greatest oil harvest
– 1264 kg /ha, which was 41,4-31,1% more than when sowing in April.