Peculiarities of the Sorghum bicolor (L.) Moench and S. orysoidum productivity formation under the effect of sowing timing in the western part of the Forest Steppe of Ukraine

Abstract

Purpose. To investigate the effect of sowing dates of sorghum bicolor and soryz on growth, development and productivity in the conditions of the western part of the Forest Steppe of Ukraine.
 Methods. The following methods were used in the experiments: field, laboratory and mathematical-statistical.
 Results. It was established that, on average over the years of research, the plants of sorghum bicolor and soryz formed higher productivity when the sowing was carried out in the period from beginning to the middle of May, when the soil temperature at a depth of 10 cm exceeded 12°C. At the same time, field germination was 83.2% and 87.1% in sorghum bicolor variety ‘Dniprovskyi 39’, and 80.3% and 82.5 % in soryz variety ‘Samaran 6’. Sowing in late April reduced the field germination by 2.1–8.7 % on average in the experiment The vegetation period for early sowing period was the longest and amounted to 115 days in sorghum bicolor and 116 days in soryz; under optimal sowing conditions, it decreased from 2 to 8 days. The tillering of plants depended on the varietal characteristics and averaged 1.2–1.3 tillers per plant in sorghum bicolor and 1.2–1.4 tillers per plant in soryz. Plant height was 110–116 cm in sorghum bicolor variety ‘Dniprovskyi 39’ and 111–109 cm in soryz variety ‘Samaran 6’. Stem diameter ranged from 1.5 cm to 1.6 cm. The leaf area during the period of “panicle emergence-flowering” reached a maximum for the sowing in the beginning and middle of May and was 30.11 thousand m2/ha and 28.30 thousand m2/ha in sorghum bicolor ‘Dniprovskyi 39’, and 28.43 and 26.96 thousand m2/ha in soryz variety ‘Samaran 6’, respectively. Optimum sowing timing contributed to the formation of high crop productivity, specifically, the grain yield was 3.43 t/ha and 3.67 t/ha, biomass yield 31.83 t/ha and 33.77 t/ha, respectively in ‘Dniprovskyi 39’, and 3.5 and 3.7 t/ha, 29.5 and 37.83 t/ha, respectively, in ‘Samaran 6’.
 Conclusions. It was found that germination energy and laboratory germination of seeds depended on variety, while field germination depended on sowing conditions, such as temperature and soil water content. It was foundd that the early sowing (in the late April) compared to the optimal time (early May and the middle of May) reduced grain yield of ‘Dniprovskyi 39’ variety by 10.1–14.8% and ‘Samaran 6’ by 17.1–21.6%; biomass by 21.9–26.5% and 12.4–31.7%, respectively. Biometric indicators of plant growth and development, as well as the net productivity of photosynthesis, were also higher for sowing seeds at optimal period. Therefore, sowing sorghum in the early and middle May is recommended for the western part of the Forest Steppe of Ukraine.