The influence of growth regulators on the yield of sunflower hybrids in the steppe zone of Ukraine: analysis and forecast

Vitalii Pichura; Larysa Potravka; Yevhenii Domaratskiy; Roman Stupen; Denys Breus

doi:10.2478/oszn-2026-0004

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The influence of growth regulators on the yield of sunflower hybrids in the steppe zone of Ukraine: analysis and forecast

Environmental Protection and Natural Resources

Volume 37 (2026): Issue 2 (June 2026)

By: Vitalii Pichura, Larysa Potravka, Yevhenii Domaratskiy, Roman Stupen and Denys Breus

Open Access

|May 2026

Figures & Tables

Location of the study area and schematic diagram of the strip-plot arrangement of sunflower hybrid crops at the experimental fields of the Mykolaiv State Agricultural Research Station in 2019–2021

Table 1.

Main Timeline of the Experiments

Year	Sowing Date	Harvest Date
2019	24/04	26/08
2020	29/04	22/08
2021	10/05	12/09

Climatic conditions of the sunflower growing season in 2019–2021: a – mean monthly air temperature (°C); b – precipitation amount (mm)

Seasonal NDVI distribution of sunflower hybrids in the experimental field (2019)

Seasonal NDVI distribution of sunflower hybrids in the experimental field (2020)

Seasonal NDVI distribution of sunflower hybrids in the experimental field (2021)

Table 2.

Yield of Sunflower Hybrids Depending on Factors A (Hybrid), B (Plant Growth Regulator), and C (Study Year), (t/ha)

Hybrid (A)	Regulator (B)	2019	2020	2021	Mean
Oplot	Control	2.82	1.98	2.88	2.56
	Architect™	3.07	2.01	3.12	2.73
	Helafit Combi	3.10	2.04	3.11	2.75
Hector	Control	1.92	1.54	2.04	1.83
	Architect™	2.14	1.68	2.23	2.02
	Helafit Combi	2.10	1.72	2.22	2.01
DSL403	Control	2.44	1.83	2.54	2.27
	Architect™	2.55	1.88	2.86	2.43
	Helafit Combi	2.60	1.93	2.90	2.48
P64HE133	Control	2.71	1.90	2.92	2.51
	Architect™	2.88	1.95	3.05	2.63
	Helafit Combi	2.89	2.02	3.10	2.67
8KH477KL	Control	2.22	1.68	2.41	2.10
	Architect™	2.37	1.71	2.96	2.35
	Helafit Combi	2.37	1.74	3.09	2.40

Effect of multifunctional plant growth regulators on the productivity increase of sunflower hybrids in the steppe zone

Table 3.

Results of Analysis of Variance (GLM) of the Effects of Year, Hybrid, and Plant Growth Regulator on Sunflower Yield under a Non-Replicated Strip-Plot Field Experiment

Source of variation	df	SS	MS	F	p
Year	2	6.9618	3.4809	131.2198	< 0.0001
Hybrid	4	2.9755	0.7439	28.0416	< 0.0001
Regulator	2	0.3722	0.1861	7.0150	0.0034
Hybrid × Regulator	8	0.0219	0.0027	0.1033	0.9988
Error	28	0.7428	0.0265	–	–

Table 4.

Least Significant Difference (LSD_0.05), (t/ha)

Source of variation	n	LSD_0.05, t/ha
Factor A (Hybrid)	9	0.157
Factor B (Regulator)	15	0.122
Factor C (Year)	15	0.122
Interaction A×B	3	0.272

Table 5.

Multiple Comparison of Mean Yield Values by Regulator Factor (Tukey HSD, p ≤ 0.05)

Regulator	Yield, t/ha (mean)	Δ to Control, t/ha	Δ, %	Tukey group
Control	2.33	—	—	a
Architect™	2.51	+0.18	+7.7	b
Helafit Combi	2.55	+0.22	+9.4	b

Table 6.

Effect of Foliar Application of Plant Growth Regulators on Sunflower Yield (Average for 2019–2021)

Hybrid	Control	Architect™	Helafit Combi	ΔA, t/ha	ΔA, %	ΔH, t/ha	ΔH, %
Oplot	2.56	2.73	2.75	+0.17	+6.6	+0.19	+7.4
Hector	1.83	2.02	2.01	+0.19	+10.4	+0.18	+9.8
DSL403	2.27	2.43	2.48	+0.16	+7.0	+0.21	+9.3
P64HE133	2.51	2.63	2.67	+0.12	+4.8	+0.16	+6.4
8KH477KL	2.10	2.35	2.40	+0.25	+11.9	+0.30	+14.3

[i] Note: ΔA – yield increase from Architect™; ΔH – yield increase from Helafit Combi

Spatial differentiation of the generalised values of the NDVI for sunflower hybrids from 2019 to 2021: a – cartograms; b – histogram; c – cumulative curve

Cartograms of distribution of the crop yields of sunflower hybrids in 2019–2021

Spatial differentiation of sunflower hybrid productivity in 2019–2021: a – graph of spatial differentiation; b – histogram; c – cumulative curve

Table 7.

Three-way ANOVA results for sunflower yield explained by Hybrid, Year and NDVI_phase indices (GLM)

Source of variation	df	SS	MS	F	p	η²	Partial η²
Hybrid (A)	4	2.98	0.745	28.04	<0.0001	0.19	0.31
Year (C)	2	6.96	3.481	131.22	<0.0001	0.44	0.67
NDVI phase (D)	2	1.84	0.920	34.67	<0.0001	0.12	0.29
A × C	8	0.64	0.080	3.02	0.011	0.04	0.09
A × D	8	0.51	0.064	2.41	0.031	0.03	0.07
C × D	4	0.73	0.182	6.87	0.0003	0.05	0.14
A × C × D	16	0.58	0.036	1.36	0.148	0.04	0.06
Error	210	5.57	0.0265	–	–	–	–
Total	254	19.81	–	–	–	1.00	–

[i] Note: η² – proportion of explained variance; Partial η² – partial effect size of factors in the GLM model

Table 8.

Parameters of OLS Models for Forecasting Yield of Sunflower Hybrids Based on Phase-Specific NDVI Indices (Combined Data for 2019–2021)

Hybrid	β ₀	β₁ NDVI_16-19	β₂ NDVI_61-67	β₃ NDVI_79-80	R₂	RMSE	MAE	MAPE, %
8KH477KL	−1.960	16.780	7.098	−0.583	0.979	0.078	0.062	2.81
DSL403	−1.363	1.454	6.067	9.598	0.972	0.072	0.052	2.33
Hector	−0.609	14.556	4.232	−2.925	0.919	0.076	0.051	2.60
Oplot	−0.106	9.787	0.822	16.552	0.952	0.113	0.092	3.90
P64HE133	−1.547	18.034	5.034	6.533	0.978	0.076	0.056	2.44

Level of approximation of the universal yield forecasting model for the sunflower hybrid Oplot based on data from 2019–2021

Table 9.

Parameters of OLS Models for Forecasting Yield of Sunflower Hybrids Based on the Integrated NDVI_year Index (Differentiated by Year-Type Moisture Regime, 2019–2021)

Year	Hybrid	n	a	b	R²	RMSE	MAE	MAPE, %
2019	8KH477KL	74	0.402	6.346	0.973	0.010	0.008	0.34
	DSL403	126	0.506	6.535	0.832	0.016	0.013	0.50
	Hector	127	0.281	5.838	0.857	0.016	0.012	0.58
	Oplot	183	0.402	8.415	0.832	0.030	0.023	0.76
	P64HE133	112	0.450	7.816	0.931	0.017	0.014	0.50
2020	8KH477KL	417	0.430	4.645	0.712	0.025	0.020	1.19
	DSL403	618	0.310	5.614	0.859	0.019	0.014	0.72
	Hector	698	0.299	4.905	0.848	0.017	0.012	0.73
	Oplot	818	0.257	6.430	0.899	0.022	0.018	0.87
	P64HE133	578	0.434	5.377	0.689	0.027	0.021	1.08
2021	8KH477KL	363	0.705	6.544	0.833	0.043	0.035	1.26
	DSL403	364	0.219	7.791	0.978	0.023	0.013	0.45
	Hector	363	0.518	5.853	0.986	0.024	0.017	0.78
	Oplot	361	0.345	9.943	0.969	0.035	0.028	0.94
	P64HE133	364	0.166	8.679	0.966	0.026	0.015	0.51

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DOI: https://doi.org/10.2478/oszn-2026-0004 | Journal eISSN: 2353-8589 | Journal ISSN: 1230-7831

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Language: English

Page range: 1 - 23

Published on: May 4, 2026

Published by: National Research Institute, Institute of Environmental Protection

In partnership with: Paradigm Publishing Services

Keywords:

NDVI,

yield,

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© 2026 Vitalii Pichura, Larysa Potravka, Yevhenii Domaratskiy, Roman Stupen, Denys Breus, published by National Research Institute, Institute of Environmental Protection
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Volume 37 (2026): Issue 2 (June 2026)

The influence of growth regulators on the yield of sunflower hybrids in the steppe zone of Ukraine: analysis and forecast

Figures & Tables

Figure 1.

Table 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Table 2.

Figure 6.

Table 3.

Table 4.

Table 5.

Table 6.

Figure 7.

Figure 8.

Figure 9.

Table 7.

Table 8.

Figure 10.

Table 9.

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