Sowing rate effect the performance and seed quality of pea cultivars in the eastern forest-steppe of Ukraine
Authors: Popov S. I. , Hlubokyi O. M. , Avramenko S. V. 
Published: May 2023

Purpose. To assess the sowing rate effect on the performance and seed quality of pea cultivars in the Eastern Forest-Steppe of Ukraine.
Materials and methods. The study was conducted in the stationary crop rotation of the Plant Production Institute named after V.Ya. Yuriev of NAAS in 2018–2021 on basic mineral fertilization at a dose of N30P30K30. The soil was typical mid-humus slightly-leached chernozem. The forecrop was spring cereals. Zoned pea cultivars Oplot and Metsenat were investigated in the experiments. The sowing rate was 0.8 million, 1.0 million, 1.2 million, and 1.4 million seeds/ha. The farming techniques, except for the issues under investigation, were conventional the zone. The data were processed by analysis of variance.
Results and discussion. Under the instable weather in 2018–2021, on average, the largest numbers of pods and seeds per plant and the highest 1000-seed weight in the pea cultivars were recorded at the sowing rate of 0.8 million seeds/ha. The increase in the rate to 1.4 million seeds/ha resulted in a significant decline in these parameters: by 10.9−11.4%, 16.0–18.3% and 5.3–7.8%, respectively. The differences in the 1000-seed weight between the ‘1.0 million seeds/ha’ and ‘1.2 million seeds/ha’ variants as well as between ‘1.2 million seeds/ha’ and ‘1.4 million seeds/ha’ variants were insignificant: 2.3−2.4 g and 4.1−9.5 g, respectively. The pre- harvest plant density was vary similar regardless of the sowing rates: 0.75−1.12 million plants/ha in Oplot and 0.74−1.11 million plants/ha in Metsenat. At the same time, the pre-harvest plant survival decreased when the sowing rate was raised: 79.3−80.0% (depending on the cultivar) at 1.4 million seeds/ha vs. 85.0−87.0% at 1.0 million and 1.2 million seeds/ha. The highest pre-harvest plant survival (92.5−93.8%) was recorded when the both cultivars were sown at the rate of 0.8 million seeds/ha. Thus, pea cultivars were able to self-regulate their plant density at different sowing rates.
On the average across the four years in the ‘0.8 million seeds/ha’ variant, the performance of Oplot amounted to 2.67 t/ha. When the sowing rate was increased to 1.2 million and 1.4 million seeds/ha, the performance rose by 0.35 t/ha and 0.41 t/ha or by 13.1% and 15.4%, respectively. At the same time, the increase in the sowing density to 1.4 million seeds/ha did not significantly boost the seed yield compared to the ‘1.2 million seeds/ha' variant. In Metsenat, the differences in the yield depending on the sowing rate were smaller (2.51−2.75 t/ha).The biggest yield was noted at the sowing rate of 1.2 million seeds/ha and there was a downward trend in the plant performance as the plant density was increased.
Under the most favorable weather in 2020 and 2021, the highest yields were obtained when the cultivars were sown at the rates of 1.2 million and 1.4 million seeds/ha, without any significant difference between them. In 2020, the maximum yield was given by Oplot (4.09 and 4.20 t/ha, respectively, which was by 14.2% and 17.3% higher than that in the ‘0.8 million seeds/ha’ variant). Metsenat responded more weakly to the favorable weather. When the sowing density was raised from 1.0 million seeds/ha to 1.4 million seeds/ha, the yield was 3.59–3.77 t/ha; the desirable gain in the seed yield of 0.20 t/ha or 5.6% was provided at the rate of 1.2 million seeds/ha. In unfavorable 2018, there was no significant difference in the yields from the cultivars between the studied variants.
There were differences in the seed quality of the cultivars depending on weather and sowing rate. On average across the sowing rates, Oplot had a higher content of protein in seeds: 21.35%, which was by 0.26% higher than in Metsenat. On average across the study years, a higher content of protein in seeds were noted with the sowing rate of 0.8 million seeds/ha: 1.68% in Oplot and 21.40% in Metsenat. As the sowing rate was increased to 1.0 million and 1.2 million seeds/ha, the protein content in seeds reduced by 0.20–0.37%; when the rate was increased to 1.4 million seeds/ha - by 0.65– 0.67%. Regardless of the sowing rate, Oplot produced a higher yield and accumulated more protein in seeds than Metsenat.
Conclusions. On average under the unstable weather in 2018−2021, the highest indicators of the pea performance were recorded at the sowing rate of 0.8 million seeds/ha, and its increase to 1.4 million seeds/ha led to their reduction. The pre-harvest plant density differed insignificantly between the cultivars related to the sowing rates, plant survival rates decreased with increasing sowing density. The pre-harvest highest survival of plants was achieved at the rate of 0.8 million seeds/ha − 92.5−93.8%. The pea cultivars were able to self-regulate their plant density.
On the average across the four years in the ‘0.8 million seeds/ha’ variant, the yield from Oplot was 2.67 t/ha, increasing by 0.35 and 0.41 t/ha or by 13.1 and 15.4% at the sowing rates of 1.2 million and 1.4 million seeds/ha, respectively. 1.2 million seeds/ha turned out to be the optimal sowing rate, and an increase in the sowing density led to a reduction in the plant performance.
There were differences in the seed quality of the cultivars depending on the weather and sowing rate, in particular, the highest content of protein in seeds was detected in Oplot sown at the rate of 0.8 million seeds/ha.