Photosynthetic productivity agrophytocenoses of grain sorghum under the influence of seeding rate in the Eastern Forest-Steppe of Ukraine
Authors: Rozhkov A.A. , Sviridov A.N. , Sviridova L.A. , Mogilevskaya V.V. 
Published: February 2023

These are the presented results of three-year studies on the effect of different seeding rates on the photosynthetic productivity of agrobiocenoses of grain sorghum of different ripeness groups in the conditions of the Eastern Forest-Steppe of Ukraine.

Statement of the problem. Today, the biological potential of the yield of varieties and hybrids of grain sorghum is far from being fully utilized. The correct selection of varieties and hybrids for the conditions of a particular growing area in combination with the optimal parameters of the cultivation technology, it can significantly increase the yield and stabilize the production of sorghum grain.

The aim of research was to determine the effect of seeding rates on the photosynthetic productivity of modern hybrids of grain sorghum of various ripeness groups in the conditions of the Eastern Forest-Steppe of Ukraine.

Research methodology. The research was carried out on the basis of an eight-field grain-steam-row crop rotation by the Department of Plant Production UNPCz "Experimental Field" KhNAUnd.a. V.V. Dokuchaev in 2017‒2019. The two-way field experiment was established by the method of split plots in triplicate. In the experiment, three hybrids of grain sorghum (factor A) were studied: Brigga, Aggil and Angii, in three variants of the seeding rate (factor B): 160 ths. pcs./ha, 200 and 240 ths. pcs./ha. The sowing area was 20,0 m2, accounting ‒ 12.0 m2.

Results of researches. Among the studied hybrids of grain sorghum, hybrids Aggil and Anggi formed a large leaf area. Thus, the leaf area of the hybrid Aggil during the tillering, stemming and flowering phase was 0,53 (6,9 %), 4,80 (23,0 %) and
2,92 ths. m2/ha (11,8 %) is correspondingly higher than that of the hybridBrigga. The hybrid Anggi in these phases had an excess compared with the control (hybridBrigga) was 1,02 ths. m2/ha (13,4 %), 4,58 (22,0 %) and 4,46 ths. pcs./ha (18,1 %).

With a gradual increase in the seeding rate, at the step of gradation adopted in the experiment - 40 ths. pcs./ha, the increase in the total photosynthetic potential decreased. In particular, there was an increase in the seeding rate from 160 to 200 ths. pcs./ha, this indicator on average for hybrids was increased by 19,5 %, whereas with an increase in the seeding rate from 200 to 240 ths. pcs./ha it was only by 9,8 %.

The difference in the indices of the net productivity of photosynthesis between the studied hybrids was not significant. Only tendencies of an increase in this indicator were observed in the hybrids Anggi and Aggil. The seeding rates influenced the variability of this indicator much more. With its increase, the net productivity of photosynthesis decreased. Thus, there was an increase in the seeding rate from 160 to 240 ths. pcs./ha, it decreased from 3,23 to 2,75 g/m2 per day. To a greater extent, the net productivity of photosynthesis decreased with an increase in the seeding rate from 200 to 240 ths. pcs./ha. In particular, there was an increase in the seeding rate from 160 to 200 ths. pcs./ha, this indicator decreased by 0,14 g/m2 per day, and from 200 to 240 ths. pcs./ha - by 0,34 g/m2 per day.

Keywords: grain sorghum, hybrids, seeding rates, leaf area, photosynthetic sowing potential, net productivity of photosynthesis.