Characteristics of the region and experimental site
The field trial with corn (Zea mays L.) and common sunflower (Helianthus annuus L.) was conducted between 2023 and 2025 as a multi-year trial at the Institute of Plant Biology and Environmental Sciences, Faculty of Agrobiology and Food Resources at the Slovak University of Agriculture in Nitra. Geographically, the trial site is located in the western part of the Žitavská upland at an altitude of 170–175 m above sea level. The research site is characterized by flat terrain with medium-heavy loamy soils; the soil type is classified as Orthic Luvisol (HMa). The trial site is situated in a maize-growing production area and is classified as a very warm agro-climatic region, with an average precipitation of 320.3 mm during the months of April to September. The trail was carried out simultaneously focusing on both corn and common sunflower.
The aim of the trial was to compare the efficiency of AZOTER® bacterial product (containing asymbiotic bacteria and, depending on the specific product AZOTER® F/SC, in combination with the mycoparasitic fungi Trichoderma atroviride and Conithyrium sp.) applied to the soil during seedbed preparation, as well as the combination of soil-applied AZOTER® F and foliarly-applied microbial preparation AZOTER® L at various nitrogen application rates (reduced by 30% or 50%) on the yield parameters of corn (Zea mays) and common sunflower (Helianthus annuus), compared to control variants—specifically the variant fertilized with full NPK nutrition. The fertilization dosage for the purpose of the trial was determined based on agrochemical analysis to achieve full nutrient balance at the experimental site. This trial monitored and verified the efficiency of the bacterial components of AZOTER® F and AZOTER® L under nitrogen reduction conditions; other fertilization parameters (P, K) remained constant across all fertilized variants. The trial was conducted over a three-year period to verify the results over a longer time horizon, always taking into account the agrochemical requirements of the site.
A. CORN
Variants of the trial
The experiment with corn was conducted in several variants, including control groups – an unfertilized control and a control fertilized with a full dose of NPK – as well as variants involving the application of AZOTER® F and AZOTER® L at different nitrogen fertilization rates. The trial was established using conventional farming practices and was carried out in three replicates over a three-year period from 2023 to 2025. In each respective year, the full NPK fertilization dose was determined based on a prior agrochemical soil analysis. The required nitrogen application rate varied annually according to the specific needs of the site as identified by the agrochemical analysis. The AZOTER® F and AZOTER® L products were subsequently tested at various nitrogen fertilization levels compared to the selected full N dose, focusing on achieved yields and nitrogen fertilizer savings. In the variant where the nitrogen dose was reduced by 30% compared to the monitored full N dose, AZOTER® F was applied at the standard recommended rate (10 l.ha⁻¹ with 150–200 l of water, applied pre-sowing with immediate incorporation into the soil). In the variant with the nitrogen dose reduced by 50% compared to the monitored full N fertilization dose, AZOTER® F was applied at the standard recommended rate (10 l.ha⁻¹; 150–200 l H₂O, applied pre-sowing with immediate incorporation into the soil), followed by a subsequent application of AZOTER® L product (10 l.ha⁻¹; 150–200 l of water, applied at the 6–8 leaf growth stage of the analyzed crop).
The impact of AZOTER® F and AZOTER® L bacterial preparations on corn (Zea mays) yields under nitrogen reduction conditions compared to full NPK fertilization.
| Fertilization variant | Yield in t.ha-1 | Average results achieved 2023–2025 | ||||
| 2025 | 2024 | 2023 | Yield (t.ha-1) | Yield increase (t.ha-1) | N application rate difference(kg.ha-1) | |
| 100% N dose | 7,80 | 7,52 | 7,73 | 7,68 | – | – |
| 70% N dose + AZOTER® F | 8,32 | 8,32 | 8,12 | 8,25 | + 0,57 | – 69,77 |
| 50% N dose + AZOTER® F + AZOTER® L | 8,20 | 8,48 | 7,80 | 8,16 | + 0,48 | -114,95 |
Graph 1: Corn (Zea mays) yield in t.ha⁻¹ across different fertilization variants and the application of AZOTER® F and AZOTER® L preparations (2023–2025)
Results (Corn)
In the experiment, the influence of AZOTER® F and AZOTER® L products was monitored at various rates of nitrogen fertilization on corn yield. Other fertilization parameters (P, K) remained unchanged across the individual fertilized variants. The results of the three-year trial confirmed the positive impact of the bacterial product AZOTER® F (pre-sowing application) and the combination of the soil bacterial product AZOTER® F (pre-sowing application) with the foliarly applied microbial product AZOTER® L (application at the 6–8 leaf growth stage) on corn yield formation. The results verified the positive influence of the AZOTER® F product on soil with an adequate nutrient supply, both in the variant combined with a full dose of NPK fertilization and in variants with nitrogen fertilization reduced by 30% and 50%. The findings indicate that the application of AZOTER® products had a positive effect on yield while simultaneously reduction in the nitrogen fertilization rate.
In the variant with a 30% reduction in the total nitrogen dose combined with the application of a standard dose of AZOTER® F between 2023 and 2025, the averaged results for the entire three-year trial period showed a yield of 8.25 t/ha. This represented an average yield increase of 0.52 t/ha (with annual yield growth values ranging from +0.39 t/ha to +0.80 t/ha).
Compared to the full N-fertilization variant, this formed a percentage increase of 7.42% (annual increases ranged from +5.05% to +10.64%), while achieving an average nitrogen fertilizer saving of 69.77 kg/ha (annual saving values in individual years ranged from 37.63 to 88.56 kg/ha).
In the variant with a 50% reduction in the total nitrogen dose combined with the application of standard doses of AZOTER® F and AZOTER® L between 2023 and 2025, the averaged results for the entire three-year trial period showed a yield of 8.16 t/ha. This represented an average yield increase of 0.48 t/ha, which, compared to the full N-fertilization variant, forms a percentage increase of 6.2%. This was achieved with an average nitrogen fertilizer saving of 114.95 kg/ha (with annual saving values ranging from 63.21 to 142.60 kg/ha-1).
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B. COMMON SUNFLOWER
Experimental variants
The trial with common sunflower was conducted using several variants, including controls—an unfertilized control and a control fertilized with a full dose of NPK—as well as variants involving the application of AZOTER® F and AZOTER® L at various nitrogen fertilization rates. The experiment was established using conventional farming practices and was carried out in three replicates over a three-year period from 2023 to 2025.
In each selected year, a full dose of NPK fertilization was determined based on a prior agrochemical soil analysis. The required nitrogen application rate varied annually according to the specific site requirements identified by the analysis. The AZOTER® F and AZOTER® L products were subsequently tested at different nitrogen fertilization levels compared to the full N-dose, focusing on achieved yields and nitrogen fertilizer savings. In the variant with a 30% reduction in nitrogen compared to the full N-dose, AZOTER® F was applied at the standard recommended rate (10 l/ha–1 with 150–200 l of water, applied pre-sowing with immediate incorporation into the soil).
In the variant with a 50% reduction in nitrogen compared to the full N-fertilization dose, a combination of AZOTER® F and AZOTER® L was used. AZOTER® F was applied at the standard recommended rate (10 l/ha-1; 150–200 l H₂O, applied pre-sowing with immediate soil incorporation). This was followed by a subsequent application of AZOTER® L (10 l/ha-1; 150–200 l water, applied at the 6–8 leaf growth stage of the analyzed crop).
Impact of AZOTER® F and AZOTER® L bacterial products on common sunflower yield under reduced nitrogen conditions compared to a full NPK dose.
| Fertilization variant | Yield in t.ha-1 | Average results achieved
2023-25 |
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| 2025 | 2024 | 2023 | Yield (t.ha-1) | Yield increase (t.ha-1) | Difference in N application rate (kg.ha-1) | |
| 100% N dose | 3,60 | 3,24 | 3,14 | 3,33 | – | – |
| 70% N dose + AZOTER® F | 4,05 | 3,72 | 3,36 | 3,71 | + 0,383 | -60,06 |
| 50% N dose + AZOTER® F + AZOTER® L | 3,90 | 3,55 | 3,29 | 3,58 | + 0,253 | -99,88 |
Graph 2: Common sunflower yield (t/ha) under different fertilization variants and the use of AZOTER F and AZOTER L products between 2023 and 2025
Results (Common sunflower)
In the experiment, the influence of AZOTER® F and AZOTER® L products was monitored at various nitrogen fertilization rates on the yield of corn. Other fertilization parameters (P, K) remained constant across the individual fertilized variants.
The results of the three-year trial confirmed the positive impact of the bacterial product AZOTER® F (pre-sowing application) and the combination of the soil bacterial product AZOTER® F (pre-sowing application) with the foliarly applied microbial product AZOTER® L (application at the 6–8 leaf growth stage) on common sunflower yield formation. The results verified the positive influence of the AZOTER® F product on soil with an adequate nutrient supply, both in the variant combined with a full dose of NPK fertilization and in variants with nitrogen fertilization reduced by 30% and 50%. The findings indicate that the application of AZOTER® products had a positive effect on yield while simultaneously reduction in the nitrogen fertilization rate.
In the variant with a 30% reduction in the total nitrogen dose combined with the application of a standard dose of AZOTER® F between 2023 and 2025, the averaged results for the entire three-year trial period showed a yield of 3.71 t/ha-1. This represented an average yield increase of 0.383 t/ha-1 (with annual yield growth values ranging from +0.22 t/ha-1 to +0.48 t/ha-1). Compared to the full N-fertilization variant, this formed a percentage increase of 11.52% (annual increases ranged from +7.0% to +12.5%), while achieving an average nitrogen fertilizer saving of 60.06 kg/ha-1 (annual saving values in individual years ranged from 47.33 to 80.8 kg/ha-1).
In the variant with a 50% reduction in the total nitrogen dose combined with the application of standard doses of AZOTER® F and AZOTER® L between 2023 and 2025, the averaged results for the entire three-year trial period showed a sunflower yield of 3.58 t/ha-1. This represented an average yield increase of 0.253 t/ha-1, which, compared to the full N-fertilization variant, forms a percentage increase of 7.6%. This was achieved with an average nitrogen fertilizer saving of 99.88 kg/ha-1 (with annual saving values in individual years ranging from 79.07 kg/ha-1 to 133.85 kg/ha-1).
Conclusion
The results obtained from the 2023–2025 monitoring period demonstrate a synergistic effect of the soil and foliar application of AZOTER® F and AZOTER® L bacterial products on the production levels of both corn and common sunflower. The application of these biological products allowed for a reduction in mineral nitrogen doses by up to 50% without a decline in yield levels. Furthermore, there was an increase in nutrient use efficiency, an improvement in soil microbial activity, and significant economic savings on nitrogen fertilizer inputs. The findings of this three-year trial clearly demonstrate the possibility of optimizing nitrogen nutrition without a negative impact on yield. Simultaneously, a positive environmental and economic effect is achieved through reduced input costs and a more sustainable approach to the soil environment.
Authors:
doc. Ing. Ivan ČERNÝ, PhD., SUA in Nitre,
doc. Ing. Ladislav VARGA, PhD., SUA in Nitre
The experiment was carried out in cooperation with: AZOTER Trading s.r.o., Dúbravská 2, 841 04 Bratislava, Slovakia
