Influence of seeding rates on the formation of productivity of winter rape agrocenoses (Brassica napus L. Oleifera)

Abstract

The influence of sowing rates on the growth, development and formation of seed productivity of winter rape hybrids Pancher and Fencer is highlighted. A structural analysis and comparison of indicators of the individual state of plants at the seeding rate of winter rape recommended by the manufacturer of 500 thousand seeds/ha and reduced rates of 400, 300 and 200 thousand seeds/ha, which model the possible oss of plants in the sowing during the autumn-winter period, were carried out. It was noted that at a sowing rate of 500 thousand units/ha before entering winter (BBCH 15–18), the diameter of the root collar of the hybrids was 0.82–0.84 cm, and the height of the point above the soil level was 2.18–2.35 cm. In the variant with a sowing rate of 200 thousand seeds/ha, the diameter of the root collar of Pancher hybrid increased to 1.13 cm, and that of the Fencer hybrid — 1.11 cm, while the height of the growth point above the soil level of the hybrids was at the level of 1.77–1.88 cm. In the pre-harvest period (BBCH 93–95), the height of winter rape plants was not uniform and largely depended on the seeding rate, i.e., the greater the number of plants per square metre, the taller they were. Thus, at a sowing rate of 500 thousand seeds per hectare, the average height of Pancher winter rape plants was 167 cm, while that of the Fencer hybrid was 173 cm. With a decrease in the seeding rate to 200 thousand seeds/ha, the height of plants also decreased to 156 cm in Pancher hybrid and to 168 cm in Fencer hybrid. At the recommended sowing rates of winter rape (500 thousand units/ha), the number of branches in the hybrids was 6-7 units/plant, the number of pods was 328–386 units/plant, and the weight of 1000 seeds was 2.97–3.15 g. The yield of Pancher hybrid in this variant was 4.37 t/ha, while the yield of the Fencer hybrid was 4.55 t/ha. It was noted that reducing the seeding rate to 400 and 300 thousand units/ha did not significantly reduce the yield of hybrids. However, already at a sowing rate of 200 thousand units/ha, the yield reduction in hybrids was more significant and amounted to 0.68–0.75 t/ha with a yield of 3.62–3.87 t/ha. Studies have shown that winter rape plants have a high compensatory capacity and are able to form high productivity indicators both at the recommended sowing rates (500 thousand units/ha) and at reduced rates (300– 400 thousand units/ha). However, from a practical point of view, it is not necessary to reduce the sowing rates by 40–50% of the recommended ones, as plants may be damaged or destroyed in the autumn-winter period due to drought, freezing, rooting and damage by mouse-like rodents. The revealed peculiarity of winter rape allows determining the limit of rape density at which high and stable productivity, and therefore profitability of production, is ensured.