Formation of the photosynthetic-active surface of sunflower hybrid plants depending on fertilizer standards

Abstract

Sunflower (Helianthus annuus L.) is one of the most widespread, highly productive and export-oriented oilseeds in the agricultural sector of Ukraine. The main key to growing consistently high yields of sunflower is the creation of prerequisites for increasing the productivity of their photosynthesis, that is, the synthesis of the maximum amount of organic matter per unit area of the leaf surface for a certain period of time. It was experimentally established that the use of fertilizers, especially nitrogen fertilizers, has a positive effect on the development of leaf surface of sunflower plants. According to the results of a short-term field experiment, it was found that in the conditions of the Left-Bank Forest-Steppe of Ukraine, an increase in the content of nutrients in the soil by applying mineral fertilizers provided an increase in the leaf area of sunflower hybrids of different maturity groups. It was found that the early-ripening hybrid Oreol formed the maximum leaf area (29.6 thousand m²/ha) when applying mineral fertilizers at a dose of N70P100K80. It was established that the reduction of the dose of nitrogen and phosphorus fertilizers was accompanied by a decrease in the size of the leaf surface area, compared to the variant of applying the maximum dose of mineral fertilizers, the difference was 8.1‒10.1 %. The mid-early hybrid formed almost the same leaf area, in particular 30.6 and 30.5 thousand m²/ha, for the application of both the full dose of mineral fertilizers N70P100K80 and only nitrogen-phosphorus mineral fertilizers at a dose N70P100. The application of N70P100 was better for the leaf surface growth of the mid-season hybrid Drive, where it was 31.0 thousand m²/ha. The application of medium doses of fertilizers, in particular N50P70 and N70P100, by the influence on the leaf surface area formation of sunflower plants occupied an intermediate position. The exceeding of the control, by leaf area, was 17.7 and 19.7 %. It was established that, on average for the variants of the experiment, the leaf surface area of the early-ripening hybrid Oreol was the smallest and amounted to 27.2 thousand m²/ha. The leaf surface area of the mid-early hybrid Drive and mid-ripening hybrid Cadet was almost the same, but compared to the previous hybrid it was higher by 4.6‒4.9 %.