Photosynthetic activity of winter rye plants (Secale Cereale L.) in dependence on cultivation conditions in the Northern Steppe of Ukraine

Abstract

Topicality. Today, studying the influence of agrotechnical methods on the photosynthetic activity of plants and the grain productivity of modern winter rye varieties, depending on the predecessors, sowing dates and mineral nutrition, allows to achieve full biological potential of plants and determine the optimal technological parameters for increasing grain yield in the Northern Steppe of Ukraine. Purpose. To conduct investigations on the peculiarities of photosynthetic activity of modern winter rye varieties depending on their predecessors against the background of different sowing dates and the mineral nutrition content in the soil and climatic conditions of the Northern Steppe. Materials and Methods. In 2018–2021, the research was conducted on the basis of the Experimental Farm "Dnipro" of the State Enterprise Institute of Grain Crops of NAAS of Ukraine. There were four factors in the experiment. The winter rye varieties Pamiat Khudoierka and Stoir were sown after sunflower and spring barley in the early (5–10 September), optimal (20–25 September) and late (5–10 October) dates. Results. Winter rye, sown after spring barley, had a larger leaf area, leaf index and higher values of photosynthetic potential compared to the experimental variants where this crop was sown after sunflower. The maximum values of these parameters were observed in plants of different varieties when sown on 20–25 September with N45 applied on frozen-thawed soil after both predecessors. Over the years of research, annual average values of leaf area in the heading stage of plants grown after stubble predecessor for Pamiat Khudoierka variety were 50.4 thousand m2/ha, Stoir variety – 52.9 thousand m2/ha, and after sunflower – 46.6 and 48.5 thousand m2/ha, respectively. These variants also had the highest photosynthetic potential of the crop, which was 2.59 and 2.76 million m²-days/ha in Pamiat Khudoierka and Stoir varieties grown after spring barley, and 2.40 and 2.52 million m²-days/ha after sunflower, respectively. According to our research results, it was found that the highest yield of Stoir variety was obtained by sowing winter rye after spring barley and sunflower in the most optimal date, namely 20–25 September, and applying nitrogen at the rate of 45 kg a.i./ha in early spring, which was, depending on the predecessor, 6.47 and 5.03 t/ha, respectively. Conclusions. Therefore, according to the results of the conducted research, it was found that the maximum leaf surface area (52.9 thousand m2/ha), leaf index (5.3) and photosynthetic potential (2.76 million m²-days/ha) were formed by Stoir variety at sowing on 20–25 September after spring barley and nitrogen fertilisation of 45 kg a.i./ha in early spring on frozen-thawed soil. In addition, the maximum yield level of Stoir variety was achieved under such conditions after spring barley and sunflower, which was 6.47 and 5.03 t/ha, respectively. Key words: winter rye, variety, predecessor, sowing date, photosynthetic activity of plants, leaf area, photosynthetic potential of crops, yield