The Effect of Chosen Biostimulants on the Yield of White Cabbage

Abstract

An open-field study evaluated the effects of four biostimulants (Asahi, Optysil, Optycal, and Tytanit) on the yield and chemical composition of two white cabbage cultivars (‘Caraflex’ and ‘Alfredo’). Although the biostimulants did not significantly impact the marketable yield, all treatments led to a significant increase in ascorbic acid content. The influence on dry matter, sugars, phenols, and antioxidant activity varied by cultivar but generally did not result in inferior outcomes compared to the control. The effect on nitrate levels also varied, with Optysil and Asahi showing some adverse effects depending on the cultivar.

1. Introduction

White cabbage is one of the six main vegetables cultivated in Poland, with an 18% share in the production of vegetables grown in the field, which makes it a crop of high economic value in that country [1]. The yield and its quality depend largely on environmental factors and agricultural technology, but currently relying only on the latter does not allow for achieving the best results. To keep cabbage production economically profitable, there is an urgent need for other solutions which could improve yields. One of them is using preparations, especially biostimulants, enhancing the resistance of plants to unfavourable environmental factors. Being natural and environmental friendly substances, such preparations currently play an important role in horticultural practise [2,3]. According to the European Biostimulants Industry Council (EBIC) [4], the largest market for biostimulants in 2012 was Europe, where they were applied on over 6.2 million hectares. The definition and concept of plant biostimulants are constantly being refined, but generally they are considered to be substances containing organic and mineral compounds or their mixtures whose function, when they are applied to plants or the rhizosphere, is to stimulate natural processes to enhance nutrient uptake and efficiency, tolerance to biotic and abiotic stresses, and crop quality [5,6,7,8]. Biostimulants may include hormones, enzymes, proteins, amino acids, vitamins, trace elements, and other biologically active compounds [5,9,10]. Although biostimulants contain nutrients, they work differently from fertilizers [11,12,13,14]. Their influence on plants does not result from their ability to directly regulate metabolism and their action can be multidirectional. The crucial feature distinguishing biostimulants from bioregulators and hormones is that biostimulants improve plant metabolic processes without changing their natural pathway [15].

Biostimulating formulations available commercially make use of a wide range of diverse active compounds. Preparations such as those containing Ti, Si, Ca, or nitrophenols are known to promote good effects in plant production.

Titanium activates metabolic processes during the growth and development of plants and boosts the photosynthesis and absorption of nutrients [16]. Many studies have demonstrated a positive effect of titanium application in the form of, e.g., sprays, on plant crops. Titanium was found to enhance pollen grain vigour, increase the rate of nutrient uptake, and to improve the health condition of plants [17]. Dobromilska [18] showed that the application of Tytanit spray improved the yield of tomato plants.

Silicon is an element which can enhance plant tolerance to biotic and abiotic stresses by making plants rigid and strong. It can be introduced to plants in root or foliar application using different sources, i.e., sodium silicate, calcium silicate, calcium silicate. The fortification of plants with this element has improved their resistance to diseases, insect attacks, and unfavourable climatic conditions [19,20,21,22,23,24,25].

Cabbage is a crop with very high requirements for calcium. The sufficient supply of this element is a necessary precondition for increasing cabbage yield [26]. Calcium also plays a crucial role in preventing tipburn, a frequent disorder of cabbage heads caused by Ca deficiency in the youngest parts of plants [27,28]. Thus, the use of preparations containing calcium activators is an option allowing for the obtaining of a high quality yield of cabbage crops. Calcium can be applied to plants in different forms, with prohexadione-calcium being of particular relevance [29].

Phenolic compounds, as effective antioxidants at low concentrations, influence various biochemical and physiological processes in plants. Components of Asahi SL, a commercially available mixture of sodium ortho- and para-nitrophenolates with sodium 5-nitroguaiacolate, are easily metabolized by plants into other phenolics which are involved in mitochondrial energy-generating processes [15]. Applied exogenously, they strengthen the cell walls of plants, and increase the resistance of plants to temperature and water stress, mechanical damage, and disease infections. They have been shown to have a positive effect on limiting the severity of diseases caused by Alternaria [30]. In addition, they play an important role in the metabolism of nitrogen in plants and in cytoplasmatic transport, contributing to increased plant productivity [31].

The aim of this study was to determine the effect of selected biostimulants applied in the open-field cultivation of two early cultivars of white-headed cabbage (‘Caraflex’ and ‘Alfredo’) on the yield and chemical composition of the crop.

2. Material and Methods

2.1. Research Site

The open-field experiment on the cultivation of white cabbage was carried out in 2016–2017, with harvest planned at the end of summer. The experimental plots were located in the Vegetable Experimental Station in Kraków-Mydlniki (50°08′ N, 19°85′ E). The soil type is Fluvic Cambisoil (Humic), according to the classification of the Food and Agriculture Organization of the United Nations [32], containing 3.4% organic matter, with pH = 6.9.

2.2. Material

Two white cabbage cultivars (hybrids F₁) from Bejo Zaden B.V. were tested: ‘Alfredo’, which forms spherical heads weighing 2–4 k and whose vegetation period is about 90 days, and ‘Caraflex’, with spherical-conical heads weighing 1–2 kg and a vegetation period of about 80 days.

Four biostimulants were applied: Asahi, Optysil, Optycal, and Tytanit.

Asahi SL (ARYSTA LifeScience, Warsaw, Poland) is composed of three phenolic compounds: sodium para-nitrophenolate PNP (0.3%), sodium ortho-nitrophenolate ONP (0.2%), sodium 5-nitroguaiacolate 5NG (0.1%), and water.

Optycal (INTERMAG Company, Oklusz, Poland) contains 350 g CaO per 1 kg of preparation.

Optysil (INTERMAG Company, Olkusz, Poland) contains 200 g SiO₂ in 1 dm³ of solution.

Tytanit (INTERMAG Company, Olkusz, Poland) contains 8.5 g of Ti in 1 dm³ of solution.

The control plants were plants not treated with biostimulants.

2.3. Methods

Transplants were produced in multipots containing 96 cells, each with a volume of 0.053 dm³. They were planted out at a spacing of 75 × 40 cm on plots 6 m² containing 20 plants. The experiment was designed as a randomized block with four replications. The agronomic treatments were applied in accordance with the requirements of the species [33]. The biostimulants were applied four times in a foliar spraying with the addition of Faster adjuvant (containing sodium salts of alkyl derivatives of C10–C13 benzenesulphonic acids). The doses of biostimulants used were as follows: Asahi and Optysil 0.5 dm³ ha⁻¹, Optycal 1.5 kg ha⁻¹, Tytanit 0.3 dm³ ha⁻¹. The trial schedule is presented in

Table 1. The course of experiments in 2016 and 2017.

Operation	2016	2017
Seed sowing Transplant planting-out Application of biostimulants Harvest ‘Caraflex’ ‘Alfredo’	27 May 26 June 8 and 25 July; 1 and 8 August 8 September 19 September	22 May 27 June 13, 20, and 27 July; 4 August 4 September 20 September

The results of the treatments were determined on the basis of obtained yields of marketable heads of the two cabbage cultivars, their dry matter and the content of sugars, vitamin C, total phenolics, nitrates, and DPPH scavenging ability.

.

2.4. Chemical Analyses

The analyses were carried out according to standard methods.

Dry matter was estimated after drying fresh plant material at 105 °C to constant weight.

Soluble sugar content was evaluated using the anthrone colorimetric method. The optical density of ethanol extracts after reaction with anthrone reagent was measured at 625 nm on a Helios Beta spectrophotometer (Thermo Fisher Scientific Inc., Carlsbad, CA, USA). The content of soluble sugars was calculated using the calibration curve of glucose as standard.

The content of L-ascorbic acid was assessed using the Tillman’s method. Plant material was mixed with CH₃COOH, extracted for 30 min, and then titrated with 2.6-dichlorophenolindophenol (Tillman’s reagent, Merck Group, Wien, Austria).

Total phenolic content was determined in 80% methanol extracts of plant material by the photometric method with the Folin–Ciocalteu reagent, using gallic acid as standard.

The radical scavenging activity (RSA) of 80% methanol extracts of plant material was tested with DPPH as a stable free radical. The decrease in absorbance was monitored at 517 nm using a UV-VIS spectrophotometer (Thermo Electron Corporation, Cambridge, UK). The RSA of plant extracts was expressed as the percentage of stable free radical DPPH (2,2-diphenyl-1-picrylhydrazyl) neutralization after 15 min from the start of the reaction.

Nitrate content was determined calorimetrically by the method of Cataldo et al. [34].

2.5. Meteorological Data

There was less rainfall in each month of the growing season (May–August) of 2016 than in the corresponding period of 2017 (Figure 1). In 2017, rain events were less frequent but more intense, while 2016 had more regular rainfall. The highest air temperatures in 2016 were noted in June and July, as opposed to in 2017—in May and July.

2.6. Statistical Analysis

Statistical analysis was performed by a two-way ANOVA and Tukey t-test at p ≥ 0.05 using Statistica 13.3 (StatSoft). The first factor was the type of biostimulant and the second was the cabbage cultivar. All results were expressed as the means from two observation years. Homogenous groups were marked by the same letters.

3. Results

The obtained yield ranged from 40.98 to 56.05 t ha⁻¹ (

Table 2. The effect of cultivar and biostimulant on the marketable yield of cabbage (t ha⁻¹).

Cultivar	Biostimulant					Mean
	Control	Asahi	Optycal	Optysil	Tytanit
‘Alfredo’ ‘Caraflex’ Mean	56.05 b 43.21 ab 49.63 A	53.95 ab 47.17 ab 50.56 A	53.11 ab 42.67 ab 47.89 A	53.35 ab 47.01 ab 50.18 A	48.76 ab 40.98 a 44.87 A	53.04 B 44.21 A -

Values marked with the same letters are not significantly different at p < 0.05. Lowercase letters indicate the significance of the interaction between the factors (biostimulant and cultivar), while uppercase letters indicate the significance of the biostimulant (in the last row) or cultivar (in the last column).

). In both years of the study, only the cultivar had significant influence on the marketable yield of cabbage—the yield of ‘Alfredo’ was 20% higher than that of ‘Caraflex’. The effect of biostimulants was statistically insignificant; however, the marketable yield of ‘Caraflex’ was observed to be higher after the application of Asahi and Optysil compared to the control plants.

Independently of the cultivar, less dry matter was observed in plants sprayed with Tytanit than in those treated with Asahi (

Table 3. The effect of cultivar and biostimulant on the dry matter in cabbage heads (% f.m.).

Cultivar	Biostimulant					Mean
	Control	Asahi	Optycal	Optysil	Tytanit
‘Alfredo’ ‘Caraflex’ Mean	7.29 ab 7.52 ab 7.40 AB	7.52 ab 7.62 b 7.57 B	7.16 ab 7.35 ab 7.25 AB	7.16 ab 7.56 b 7.36 AB	6.84 a 7.20 ab 7.02 A	7.19 A 7.45 B -

Values marked with the same letters are not significantly different at p < 0.05. Lowercase letters indicate the significance of the interaction between the factors (biostimulant and cultivar), while uppercase letters indicate the significance of the biostimulant (in the last row) or cultivar (in the last column).

). The differences in dry matter between the control and treated plants were not always statistically significant. The ‘Alfredo’ plants, which generally produce less dry matter than ‘Caraflex’, had the lowest share of dry matter (6.84%) when treated with Tytanit, while the highest share was observed for the ‘Caraflex’ plants treated with Asahi (7.62%).

Similarly to the case of dry matter, the content of soluble sugars (

Table 4. The effect of cultivar and biostimulant on the content of soluble sugars in cabbage heads (% f.m.).

Cultivar	Biostimulant					Mean
	Control	Asahi	Optycal	Optysil	Tytanit
‘Alfredo’ ‘Caraflex’ Mean	2.90 abc 3.34 e 3.12 AB	3.02 d 3.29 e 3.15 B	2.84 ab 3.20 de 3.02 AB	2.99 de 3.13 de 3.06 AB	2.74 a 3.24 de 2.99 A	2.90 A 3.24 B -

Values marked with the same letters are not significantly different at p < 0.05. Lowercase letters indicate the significance of the interaction between the factors (biostimulant and cultivar), while uppercase letters indicate the significance of the biostimulant (in the last row) or cultivar (in the last column).

) in the heads of ‘Alfredo’ was lower (by 12%) compared to ‘Caraflex’. A positive impact of Asahi and Optysil application (an increase in sugar content as compared to the control) was noted only for ‘Alfredo’. The use of Tytanit and Optycal had no effect on sugar content in “Alfredo’, while for ‘Caraflex’ this was the case for every biostimulant tested.

Heads of ‘Caraflex’ contained 8% more ascorbic acid than heads of ‘Alfredo’ (

Table 5. The effect of cultivar and biostimulant on the content of ascorbic acid in cabbage heads (mg 100 g⁻¹ f.m.).

Cultivar	Biostimulant					Mean
	Control	Asahi	Optycal	Optysil	Tytanit
‘Alfredo’ ‘Caraflex’ Mean	40.39 a 45.86 d 43.13 A	42.73 bc 49.61 e 46.17 BC	43.73 cd 49.51 e 46.62 C	40.85 ab 52.83 f 46.84 C	41.53 ab 48.58 e 45.06 B	41.85 A 49.28 B -

Values marked with the same letters are not significantly different at p < 0.05. Lowercase letters indicate the significance of the interaction between the factors (biostimulant and cultivar), while uppercase letters indicate the significance of the biostimulant (in the last row) or cultivar (in the last column).

). Regardless of the cultivar, all biostimulants caused an increase in ascorbic acid content in comparison with the control. However, there were differences between the cultivars when it comes to the response to the biostimulants, as reflected in the level of ascorbic acid. For ‘Caraflex’, the increase in the content of this compound was noted after every treatment, especially with Optysil. By contrast, the response of ‘Alfredo’ to this biostimulant was the weakest, and a significant increase as compared to the control was brought about only by Asahi and Optycal.

‘Caraflex’ was also found to have significantly (49%) higher total phenolic compounds than ‘Alfredo’ (

Table 6. The effect of cultivars and biostimulant on total phenolic compounds in cabbage heads (mg g⁻¹ f.m.).

Cultivar	Biostimulant					Mean
	Control	Asahi	Optycal	Optysil	Tytanit
‘Alfredo’ ‘Caraflex’ Mean	0.381 ab 0.529 c 0.455 A	0.344 a 0.605 de 0.474 A	0.437 b 0.595 cde 0.516 B	0.371 ab 0.516 c 0.493 AB	0.409 ab 0.544 cd 0.477 AB	0.388 A 0.578 B -

Values marked with the same letters are not significantly different at p < 0.05. Lowercase letters indicate the significance of the interaction between the factors (biostimulant and cultivar), while uppercase letters indicate the significance of the biostimulant (in the last row) or cultivar (in the last column).

). With respect to the effect of biostimulants on the total phenolic content, clearly the best results were achieved by Optycal, Optysil, and Tytanit, regardless of the cultivar. The response of each cultivar to the treatments was nevertheless different. For ‘Alfredo’, none of the biostimulants contributed to a significant change in the phenolic content, whereas for ‘Caraflex’, Asahi caused the greatest increase.

As shown in

Table 7. The effect of biostimulant and cultivar on DPPH radical scavenging activity (%).

Cultivar	Biostimulant					Mean
	Control	Asahi	Optycal	Optysil	Tytanit
‘Alfredo’ ‘Caraflex’ Mean	2.86 a 6.18 b 4.52 AB	2.03 a 5.55 b 3.79 A	3.05 a 6.26 b 4.65 B	2.09 a 6.26 b 4.18 A	2.24 a 5.28 b 3.76 A	2.45 A 5.91 B -

Values marked with the same letters are not significantly different at p < 0.05. Lowercase letters indicate the significance of the interaction between the factors (biostimulant and cultivar), while uppercase letters indicate the significance of the biostimulant (in the last row) or cultivar (in the last column).

, ‘Caraflex’ exhibited 2.4-fold higher antioxidant activity than ‘Alfredo’. Neither of the tested preparations affected this trait.

The nitrate content of ‘Caraflex’ exceeded that of ‘Alfredo’ by 110.79 mg per kg f.m. (

Table 8. The effect of cultivar and biostimulant on the content of nitrates in cabbage heads (mg NO₃ kg⁻¹ f. m.).

Cultivar	Biostimulant					Mean
	Control	Asahi	Optycal	Optysil	Tytanit
‘Alfredo’ ‘Caraflex’ Mean	610.65 bc 667.01 cd 638.83 A	482.43 a 758.71 e 620.57 A	561.20 ab 721.59 de 641.40 A	733.70 de 725.96 de 729.83 B	561.20 ab 629.89 bc 595.55 A	589.84 A 700.63 B -

Values marked with the same letters are not significantly different at p < 0.05. Lowercase letters indicate the significance of the interaction between the factors (biostimulant and cultivar), while uppercase letters indicate the significance of the biostimulant (in the last row) or cultivar (in the last column).

). The highest level of nitrates was noted after using Optysil (729.83 mg)—it was significantly higher than the level found in other combinations, where it ranged from 595.55 mg (Tytanit) to 641.40 mg (Optycal). Optysil most strongly affected the nitrate content in ‘Alfredo’—it exceeded significantly that of the control, while the other biostimulants were observed to have either no effect or even to reduce the nitrate content in this cultivar. ‘Caraflex’ had the highest nitrate content after Asahi, well above the control, while the other biostimulants did not affect this trait.

4. Discussion

The present investigation on the application of four plant biostimulants containing nitrophenols, Ca, Si, and Ti, in the open-field cultivation of white cabbage aimed to determine whether such treatment contributed to yield improvement. The studies on the effect of biostimulants on crop production have so far produced inconsistent results. In the experiment described in this paper, the marketable yield of cabbage was not affected by the examined preparations, which agreed with the results obtained by Heckman [11], who tested two biostimulants (mixtures of humic acids and plant extracts) and found no positive effect on the yield of spring cabbage. On the other hand, Hassan and Obaid [35] obtained a higher yield of ‘Galaxy’ head cabbage sprayed with a silicon solution at a concentration of 3 mL dm⁻³, and Kováčik et al. [36] observed that the use of Mg-Tytanit resulted in an increased yield of oilseed rape seeds and that crops treated with biostimulant three times gave higher yields than those treated twice. According to Hara and Sonoda [26], cabbage head yield increased with the increase in Ca, Mg, or S concentration in the culture solution from 0 to 100 ppm Ca. In turn, sprays of CaCl₂ or calcium chelate had no effect on cauliflower productivity [27,28], but in the case of Chinese cabbage the largest head weight was obtained when the plants were sprayed at first with Tytanit and after 4 days with Wapnovit, a preparation containing calcium [37].

The Tytanit preparation did not have any positive effect on the average potato tuber weight [38]. Neither was Tytanit found to significantly influence the yield of tested strawberry cultivars [17]. At the same time, however, there were numerous reports of the beneficial effects of biostimulants on plant growth. Czeczko and Mikos-Bielak [31] observed that spraying plants with Asahi at a concentration of 0.1% significantly increased the yield of leek, celeriac, and potato. Similarly, Dobrzański et al. [39] reported a positive impact of this preparation on the yield of onion. Asahi (0.1%) and Tytanit (0.05%) preparations were found to enhance the marketable yield of carrot roots by reducing the share of small and unmarketable roots in the total yield [40]. A study carried out on celery demonstrated a significant effect of foliar fertilization with various Tytanit concentrations. The highest yield was observed after a single spray with a 3.6% solution while double spraying resulted in insignificant changes in the yield [41]. The application of titanium at an annual dose of 960 g Ti·ha⁻¹ caused a significant increase in the marketable yield of greenhouse tomato culture on rockwool [42]. Three- and fourfold spraying (at 10 day intervals) of the cherry tomato cultivar ‘Picolino’ with 0.03% Tytanit significantly increased the yield and limited the formation of non-commercial fruit [18]. Borkowski et al. [43] reported that tomatoes ‘Admiro’ treated with silicon (twice with 1% of liquid potassium silicate Silvit using 0.5 dm³ solution per plant) gave a higher yield than the control, but more fruit with blossom-end rot was observed in the treated sample. According to Xu et al. [25], foliar spraying with biostimulants improved the tomato yield by increasing the uptake of nitrogen and potassium. In case of herbs, foliar application with 0.05% Tytanit increased the yield of thyme (Thymus vulgaris) by 16.0% and contributed to a reduction in the share of stalks in herb [44]. The growth stimulators (Asahi SL 0.1% and Tytanit 0.05%) applied in foliar spraying twice in the vegetation period contributed to a better growth of sweet basil plants and a significant (by 28–31% in comparison with the control) increase in herb yield [45].

The literature’s reports also vary as to the chemical composition of crops obtained with the use of various substances supporting the growth and development of plants, and this applies to both nutritional and non-nutritional ingredients that together determine the quality of vegetables. In this experiment, all used preparations, especially Optysil, had a clearly positive influence only on the content of ascorbic acid in cabbage heads, which was confirmed by Hassan and Obaid [35], Silva et al. [46], and Aleyashe and Obaid [47], for white and Chinese cabbage. As for dry matter, sugars, phenolic content, and antioxidant activity, their impact was uncertain, frequently different depending on the cultivar, but in the majority of cases comparable to the control. Similarly, divergent results were obtained by other authors investigating the effect of biostimulants on the yield quality of vegetables or fodder plants. Truba and Sosnowski [48] found out that Tytanit changed the content of fibrous fractions in plant cell walls of Medicago and Trifolium. Wadas and Kalinowski [49] noted that Tytanit did not affect the content of dry matter and nitrogen, phosphorus, potassium, calcium, magnesium, or sulphur in potato tubers. Kleiber and Markiewicz [42] showed that tomato fruit treated with Tytanit in doses of 80 and 480 g Ti·ha⁻¹ had the highest vitamin C content compared to the control and other Ti concentrations applied, but no significant effect of this preparation was identified for the content of dry matter and sugars in fruit, or active acidity. Tomatoes treated with the Asahi SL biostimulator were characterized by the highest content of dry matter, P, K, Mg, Na, and Zn. In addition, they were distinguished by the highest amount of bioactive components (vitamin C and polyphenols) and the highest antioxidant potential [50]. Czeczko and Mikos-Bielak [31] reported that Asahi increased the content of reducing sugars and phenolic compounds in the tested vegetables (potato, tomato, celery, leek), thus improving their antioxidant properties, but in most cases lowered the content of protein and vitamin C. In another study, foliar application of calcium in the form of Pro-Ca preparation improved total soluble sugar content in the heads of Chinese cabbage [29].

The biostimulants investigated in the present work affected the content of nitrates in the cabbage heads; for Optysil, the effect was unfavourable since its application led to their significant increase, especially in ‘Alfredo’. On the other hand, according to D’Imperio et al. [51], in other brassica crops, namely tatsoi (Brassica rapa L., Tatsoi group) and mizuna (Brassica rapa L., Mizuna group), the nitrate content was reduced by Si treatments, which stands in contrast to the results obtained in the present experiment. Other studies on nitrogen content in plant crops also reported various effects of stimulant treatments. The application of Asahi SL at a concentration of 0.1% significantly reduced the total nitrogen levels in eggplant fruit (cv. ‘Black Beauty’) [52]. In the present investigation, the content of nitrates was higher in ‘Caraflex’ but lower in ‘Alfredo’ compared to the control after the application of Asahi. This preparation was also found to significantly reduce N (as % of air-dry weight) in sweet basil herb, while Tytanit did not cause the change [45].

5. Conclusions

• The constant need to improve the yield quantity and quality of cabbage, which is one of the most important vegetable crops, forces the search for new agrotechnics. The use of biostimulants can be helpful in this regard. These types of substances improve the condition of plants, are environmentally friendly, and therefore play an important role in agricultural practise. Many studies have been carried out, but the reaction of plants to these substances is not always the same. The use of biostimulants in plant production is expected to positively impact the yields and quality of crops. However, biostimulants may bring about no yield improvement or their effect may be both favourable and unfavourable. As a result of our research, the treatment of two cabbage cultivars with the investigated biostimulants (Asahi, Optycal, Optysil, and Tytanit) did not affect the yield in comparison with the control. In general, the yield of cabbage and the content of selected compounds in the cabbage heads were found to more strongly depend on the cultivar than on the use of biostimulants. A higher marketable yield was achieved from the cultivar ‘Alfredo’ than from ‘Caraflex’. However, ‘Caraflex’ had a higher content of dry matter, soluble sugars, ascorbic acid, total phenolic compounds, and nitrates as well as showing a higher antioxidant activity. The biostimulants, in turn, were found to have a clearly positive effect only on the content of ascorbic acid. Their influence on the content of dry matter, soluble sugars, phenolic compounds, and on the antioxidant activity of cabbage heads was not clear. Optysil significantly increased the level of nitrates in the plants of both tested cultivars, while the other biostimulants either had no effect on this feature or every preparation affected it differently in each cultivar.
• Current research has confirmed the belief that the effect of biostimulants on cabbage yield exists, but that this is not positive in every case; therefore, further studies on other ways of biostimulant use, e.g., different doses, times of application, together with a wider range of tested cultivars, are necessary.