Photosynthetic activity of safflower under the effect of the elements of cultivation technology
Authors: Kalenska S. M. , Hordyna N. Yu. 
Published: May 2024

Purpose. To establish the peculiarities of the formation of photosynthetic indicators of safflower varieties as affected by the elements of cultivation technology, specifically row width, row spacing, and sowing rate, in the Right Bank Forest Steppe of Ukraine.
Methods. The research was carried out in 2021–2023 at the Agronomic Research Station of National University of Life and Environmental Sciences of Ukraine. The soil type was typical low-humus chernozem. The design of the field experiment provided for the study of the influence of the following factors: factor A – varieties: ‘Dobrynia’ and ‘Soniachnyi’; factor B – row width: 19, 38 and 57 cm; factor C – sowing rate: 100, 200 and 300 thousand seeds/ha.
Results. The leaf area of safflower increased as the row width and sowing rate increased, which emphasizes the importance of optimizing the location of plants in the field for reaching effective photosynthesis and subsequent crop formation. In particular, at the time of flowering, in the ‘Dobrynia’ variety, the leaf area was 32.7, and in ‘Soniachnyi’ 31.2 thousand m2/ha; the varieties in general differed by 1.5 thousand m2/ha, which exceeded the value of the smallest significant differences by experience. At the same time, it was determined that the average leaf area for a row spacing of 19 cm was 30.7 thousand m2/ha. Increasing the row width to 38 cm contributed to the leaf area formation of 31.4 thousand m2/ha, which is 0.6 thousand m2/ha more than in the previous treatment. At a row spacing of 57 cm, the crops had a leaf area of 33.8 thousand m2/ha, which was 3.1 thousand m2/ha more than at a row spacing of 19 cm. Sowing rate of 100 seeds/ha resulted in leaf area of 31.0 thousand m2/ha, while sowing rates 200 and 300 thousand seeds/ha ensured a leaf area increase of 1.50 and 1.53 thousand m2/ha, respectively. In the budding stage, the highest content of the chlorophylls a and b in safflower plants was noted for row width of 38 cm and sowing rates of 200 and 300 thousand seeds/ha. The content of chlorophylls was 5.21 and 5.24 5.19 and 5.22 mg/g of dry matter, respectively, in ‘Dobrynia’, and 5.19 and 5.22 mg/g of dry matter in ‘Soniachnyi’.
Conclusions. The highest parameters of the photosynthetic potential were obtained for row width of 57 cm and sowing rates of 200 and 300 thousand units/ha: in ‘Dobrynia’, 0.89–90 million m2 × day/ha in the period of budding – flowering, and 1.21–1.23 million m2 × day/ha in the period flowering – full maturity; in ‘Soniachnyi’ 0.93–0.94 million m2 × day/ha and 1.35–1.36 million m2 × day/ha, respectively. The parameters of net photosynthetic productivity (NPF) of crops in the period from flowering to full maturity in ‘Dobrynia’ was 1.59 g/m2 per day, and 1.47 g/m2 per day in ‘Soniachnyi’. At the same time, for a row width of 19 cm, the NPP was 1.73, and at 38 cm 1.76 g/m2 per day, and for a row spacing of 57 cm it was 1.11 g/m2 per day, which is 0.6 g/m2 per day less than for a row spacing of 19 cm. At the sowing rates of 100, 200 and 300 thousand seeds/ha, the NPP was, respectively, 1.29, 1.65, and 1.65 g/m2 per day. In ‘Soniachnyi’, the highest NPP indicators were obtained for a row spacing of 38 cm and a sowing rate of 300,000 plants/ha: 2.02 g/m2 per day; in ‘Soniachnyi’ for a row spacing of 19 and 38 cm and a seeding rate of 300,000 seeds/ha: 1.86 g/m2 per day for both options.