Abstract
The excessive use of chemical fertilizers in agriculture not only causes a decrease in soil fertility but also has negative effects on the environment, natural resources, and human health. Therefore, environmentally friendly practices, such as the use of organic fertilizers (OFs) and plant biostimulants that increase yield and fruit quality can be effective in solving these problems. In the present research study, we investigated the impact of using an OF alone and in combination with as a biostimulant different doses of humic acid (HA) on plant growth parameters, yield, fruit characteristics, and leaf mineral nutrient concentrations in plants of the Monterey and Albion strawberry varieties. As a result of this study, we determined that the combined application of the OF and HA increased the yield, fruit quality, plant growth, and nutritional elements in the crop compared with using the OF alone. In addition, the Monterey variety plants treated with OF and HA (5.0 L·ha−1) in T3 offered the best results among the different treatment groups and varieties. With this treatment, we obtained the highest total yield (262.42 g/plant), fruit weight, total soluble solids (TSS), and TSS/acid ratio, as well as increased growth parameters, and mineral nutrient concentrations in leaves. These results are hopeful for enhancing organic strawberry production.
Strawberry (Fragaria ×ananassa Duch) is one of the most popular fruits in the world by virtue of its taste, aroma, color, and ability to grow under different environmental conditions. Strawberries are rich in nutritional compounds, such as sugars, minerals, vitamin C, and vitamin E, as well as bioactive compounds, such as flavonoids, anthocyanins, and phenolic acids (Giampieri et al. 2015; Negi et al. 2021; Skrovankova et al. 2015). Moreover, strawberry fruits are thought to reduce the risk of cardiovascular diseases, inflammation, obesity, diabetes, cancer, and other chronic diseases (Almli et al. 2019). According to Food and Agriculture Organization (FAO) data, in 2022, the total strawberry production area in the world increased to 397,603 ha, and the production amount reached 9,569,864 tons. Regarding the latter, in 2022, China ranked first, with 3,354,803 tons, and the United States ranked second, with 1,261,890 tons. Turkey currently ranks third in strawberry production globally, with 728,112 tons (FAO 2024).
Chemical fertilizers, pesticides, and fungicides are extensively used to increase yield in conventional strawberry farming. However, using chemical fertilizers and pesticides for long periods of time and in large amounts can cause yield reductions, as well as environmental pollution and human health problems. Equally, the lack of pesticide residues in strawberries is crucial to ensuring that the fruits are safe for consumption, particularly in children, who commonly consume this fruit. In addition, consumer demand for organic products has increased significantly in recent years (Röös et al. 2018), as organic products have become important in the global market in line with demands.
Therefore, the widespread implementation of organic farming methods is necessary, given the ability of such methods to enhance soil structure during production while remaining humane and environmentally friendly. The use of biostimulants may be effective in achieving these goals. Biostimulants are various substances and microorganisms that positively affect plant growth and increase the utilization of plant nutrients (Calvo et al. 2014; Povero et al. 2016). Plant biostimulants are classified into six nonmicrobial and three microbial categories (Colla and Rouphael 2015). Some of these are seaweed extracts, HAs, fulvic acids (FAs) (Battacharyya et al. 2015; Canellas et al. 2015), and arbuscular mycorrhizal fungi (AMF) (Rouphael et al. 2015), which promote plant growth rhizobacteria (PGPR) (Ruzzi and Aroca 2015). In recent years, humic substances, especially HAs and FAs, have been recognized as plant biostimulants with positive effects on plant growth and development (Canellas et al. 2015; Conselvan et al. 2017; Garza-Alonso et al. 2022).
Humic substances are known to significantly improve global soil fertility by increasing plant growth and nutrient uptake, thereby reducing the toxicity of pollutants in the atmosphere. These substances have recently been considered a potential tool to face global environmental challenges due to strong demands for safe food and sustainable agriculture (Gautam et al. 2021). HAs are among the most essential parts of humic substances (Pekcan et al. 2018). HAs positively affect the physical, chemical, and biological properties of soil, including texture, structure, water-holding capacity, cation exchange capacity, pH, soil carbon content, enzymes, nitrogen cycle, and nutrient availability (Ampong et al. 2022; Bhatt and Singh 2022). In addition, HA increase the microbial population of the soil, including beneficial microorganisms (Aghaeifard et al. 2016). Soil C content can be a direct measure of soil health. To reduce carbon emissions that cause climate change and its negative effects on the environment, HA treatments that can continuously provide C to the soil are used (Ampong et al. 2022). HA compounds can exert diverse biochemical effects on plants, operating at the cell wall, membrane, and cytoplasmic levels. These effects may encompass heightened photosynthesis and respiration rates, augmented protein synthesis, and plant hormone-like activity (Chen and Aviad 1990).
It has been reported that HA treatments increase nutrient uptake and yield in plants such as yellow passion fruit (Cavalcante et al. 2013), onion (Bettoni et al. 2016), apples (Zydlik et al. 2021), and tomatoes (Alenazi and Khandaker 2021). In addition, among their many beneficial effects, they reduce the negative effects exerted on plants by abiotic stress conditions, such as disrupted water balance (Man-Hong et al. 2020), drought (Shen et al. 2020), and salinity (Khaled and Fawy 2011; Saidimoradi et al. 2019), and the uptake of toxic heavy metals (copper, lead, cadmium, etc.) present in the soil by plants (Wu et al. 2017).
HAs positively affect plant development, yield, and fruit quality depending on the plant species, soil structure, treatment doses, and growing conditions of the plant. However, the correct treatment and dosage of HAs are essential to increasing yield in strawberry cultivation. Nonetheless, research on this subject considering strawberries is limited, as available studies mainly focus on the use of chemical fertilizers. Therefore, further research is needed to determine the appropriate HA dosage and treatment method to increase plant growth and yield in organic strawberry cultivation. This study was carried out to improve plant nutrition in organic strawberry production to increase yields and enrich product quality. Considering these facts, in the present study, we examined the effects of treatments applying an OF alone and in combination with different doses of HA on vegetative growth, yield, fruit quality, and plant nutrition in plants of the Albion and Monterey strawberry varieties.
Materials and Methods
Trial area and plant material.
The trial was conducted in 2021–22 at the treatment area of Osmaniye Korkut Ata University, Osmaniye, Turkey (37.04084 N, 36.22048 E). This region has a Mediterranean climate, and its elevation is 121 m above sea level. Fresh seedlings of Albion and Monterey varieties bred by the University of California and sourced from an agricultural company, Ciltar (Adana, Turkey), were used as material in the experiment (Shaw and Larson 2006, 2009). Albion is a day-neutral variety whose most important feature is its extraordinary fruit quality. In addition, this variety is resistant to anthrochnosis, verticillium, and phytophthora. On the other hand, Monterey is a medium-neutral day variety with a noteworthy aroma. Despite being vulnerable to mildew, Monterey is an early-maturating plant with a firm plant structure (Turemis and Agaoglu 2013).
Throughout the 7-month study period, varying amounts of liquid HA and a single dose of a liquid OF were tested. HA was derived from leonardite, an ecologically benign alternative, and as a source, we used a “Lifos” preparation (Osmanlı Organik Gübre Tarım A.Ş, İncesu, Kayseri, Turkey), which included 15% organic matter, 15% HAs + FAs, and 2.5% potassium. The OF used in this study was “Biofarm” (Camli Yem Besicilik, Bornova, Izmir, Turkey), which contained 40% organic matter (21% organic carbon) and crucial elements, like nitrogen (3%), phosphorus (1%), and potassium (2.5%).
Soil sampling, treatment, and analysis.
Soil analysis was made before the trial. This soil analysis determined that the soil of the trial area was clayey–loamy and low in organic matter (Table 1).
Properties of soil at experimental site.
On 25 Oct 2021, the planting beds were prepared, and the drip irrigation pipes were placed on the stretcher and then covered with black plastic mulch. For the experiment, we used fresh seedlings, which were planted on 27 Oct 2021 using the triangular planting method at 30 × 30-cm intervals. The abbreviations of the treatments used in the study are as follows: T1: OF; T2: OF + HA (2.5 L·ha−1); T3: OF + HA (5.0 L·ha−1); T4: OF + HA (7.5 L·ha−1).
In the trial, doses of 2.5 L·ha−1, 5.0 L·ha−1, and 7.5 L·ha−1 liquid HA and 60 L·ha−1 organic liquid fertilizer were applied drip-wise every 15 d throughout the growing season. The treatments were administered on a weekly basis from March to the end of the experiment, as plant growth and fruit development accelerated as the weather became warmer. The seedlings were placed in a low tunnel to protect them from harsh weather conditions (e.g., the winter cold) until March. The strawberry harvest started in March and lasted until the end of June.
Total yield per plant, fruit weight, pH, TSS, and acid content were measured in this study. For pomological analysis, 20 fruits at the fully ripened stage were randomly taken from each replication. Fruit juice pH was measured in juice extracted from 20 randomly selected fruits in each replicate every 15 d using a pH meter (Hanna Instruments, Smithfield, RI, USA) (Kaska et al. 1986).
To determine titratable acidity, samples of 1 mL of fruit juice were obtained from 20 randomly selected fruits in each replicate and increased in quantity to 50 mL using pure water; then, the mixture was titrated with 0.1 M sodium hydroxide (NaOH) until the pH value was 8.1 Calculations to determine the percentage of citric acid were performed every 15 d (Adak et al. 2003; Ozdemir et al. 2001). TSS was measured in juice obtained from 20 randomly selected fruits in each replicate every 15 d using a digital refractometer (Atago PAL-1 pocket digital refractometer; Atago, Tokyo, Japan). The TSS/acid ratio (taste) was calculated by dividing the measured TSS (%) by the total acidity (% of citric acid) values.
In April, leaf samples, 15 fully mature leaves of 10 plants per replicate, were collected for mineral nutrient analysis. Nitrogen, phosphorus, potassium, calcium, magnesium, iron, and zinc contents in leaves were determined. To prepare the leaves for analysis, they were washed with tap water and distilled water before being dried in an oven at 65 °C until they reached a constant weight. The samples were dry-ashed in a muffle furnace at 550 °C for 6 h. Next, 3.3% HCl acid was added to the ashes, and the obtained solution was filtered using blue-band filter paper. Potassium, calcium, magnesium, iron, and zinc concentrations were determined using an atomic absorption spectrophotometer (Jones 2001). The latter was set to 430-nm wavelength to measure phosphorus levels, and Barton’s method was used (Dasgan et al. 2023; Jones 2001). For nitrogen analysis, a 0.2-g ground sample was digested with 5 mL of concentrated H2SO4 at 380 °C using a selenium tablet in the combustion unit of a Kjeldahl apparatus for 1 h until the color turned pale. Then, distillation was performed with 28% NaOH according to a standard Kjeldahl protocol, and titration was performed with 0.01 N H2SO4. The total nitrogen (N) in leaves was calculated from the amount of H2SO4 consumed in the titration (Dasgan et al. 2023; Jones 2001).
Leaf area measurements were conducted on three randomly selected plants from each replicate by using a Digimizer Image Analyzer (v. 5.3.5; MedCalc Software Ltd., Ostend, Belgium). At the end of the experiment, the root length, root thickness, stem diameter, and root and stem dry matter (DM) amounts were determined in five plants selected from each replicate of the treatments. The stem diameters of these five plants were measured with a digital caliper at the intersection of the root and stem. Root thickness was measured with a digital caliper. To determine the amount of DM in the roots and stems, their fresh weights were measured; then they were dried in an oven at 65 °C until they reached a constant weight. Finally, the DM ratios were calculated (Turemis and Kaska 1995).
Statistical analysis.
The experiment was set up according to a split-plot experimental design in randomized blocks with three replicates and 20 plants in each replicate.
The obtained data were statistically analyzed with MSTAT-C software (version 1.2; Michigan State University, East Lansing, MI, USA) (Farid and Eisensmith 1986). The LSD (least significant difference) test was used to determine the differences between the means at P < 0.05.
Results and Discussion
Plant growth parameters.
The effects of the treatments on root length, root thickness, stem diameter, root and stem DM amounts, and leaf area were found to be significant (Table 2). The longest roots, 25.08 cm and 24.53 cm, were observed in plants treated with T3 and T4, respectively. Cay and Kaynas (2016) reported that the root length of Sweet Ann strawberry variety under leonardite treatment was greater than that of the control (17.90 cm).
Effects of treatments on strawberry plant features.
Among the root thickness data examined, the highest value, 1.54 mm, was found in plants treated with T3 (Table 2). Similar to root length, the lowest value for root thickness was obtained with the T1 treatment (1.10 mm). The stem diameter values obtained with the T2, T3, and T4 treatments (13.67 mm, 14.36 mm, and 14.22 mm, respectively) were higher than those obtained with the T1 treatment (11.74 mm). The highest DM amount in the roots was observed in plants treated with T3 (34.40%), and the lowest one was observed in plants treated with T1 (29.32%). Among the varieties, the highest amount of DM in the roots was detected in the Monterey variety, with 33.27%. The variety × treatment interactions were determined in the T4 and T3 treatments of the Monterey variety, with 36.47% and 35.26%. In this study, we observed the highest stem DM amounts, 24.03% and 23.74%, in plants treated with T4 and T3, respectively.
As can be seen in Table 2, there were significant differences in plant leaf area among treatment groups. The highest value was found in plants treated with T3 (803.35 cm2/plant). In the Monterey variety, we recorded a value of 782.31 cm2/plant. Rafeii and Pakkish (2014) reported that the best results in terms of leaf area in the Camarosa strawberry variety were obtained with treatment based on HA in the flowering stage. Rzepka-Plevnes et al. (2011) and Derkowska et al. (2015) also observed an increase in strawberry leaf area with HA treatment. Eshghi and Garazhian (2015) similarly found that HA treatments increased the leaf area in Paros strawberry cultivar plants, with the maximum value, 533.4 cm2, being obtained with the foliar HA treatment.
The effects of HA on plant growth parameters probably include complex formation of HA and mineral ions, the catalysis of HA by enzymes in the plant, the effect of HA on respiration and photosynthesis, and the stimulation of nucleic acid metabolism (Rafeii and Pakkish 2014). In addition, humic substances (HSs) can increase root size by causing changes in root structure through the formation of lateral roots and by increasing root hair production through hormone-like activity (auxin, gibberellin, and cytokine-like activities) (Canellas et al. 2011; Trevisan et al. 2010). Aisha et al. (2014) reported that HA treatment increased turnip root growth and root productivity, and Barzegar et al. (2022) reported that root development in radish increased with soil HA application.
Total yield per plant.
The effect of the treatments on total yield per plant was found to be significant (Fig. 1). The yield obtained by using HA with the OF was higher than that obtained by using the OF alone. The highest total yield was 262.42 g/plant in the T3 treatment of the Monterey variety, and the lowest yield was 138.44 g/plant in the T1 treatment of the Albion variety. The increase in yield may have been because HA treatments allow the strawberry plant to more easily absorb macro- and micronutrients from the soil (Zydlik et al. 2021). In addition, Canellas et al. (2015) reported that HSs cause an increase in cell membrane permeability, allowing nutrients to enter the plant more efficiently. Eshghi et al. (2013) and Mufty and Taha (2021) observed the highest yield in their HA treatment experiments following application of foliar HA and seaweed treatments. In addition, positive effects of HAs on fruit yield in strawberries have also been reported elsewhere (Eshghi and Garazhian 2015). Moreover, Gholami et al. (2019) revealed that HA and vermicompost treatment increased nutrient uptake and yield in chicory. Kishor et al. (2021) reported that soil and foliar HA treatment improved yield and quality, as well as economic profitability, in coffee. Finally, Zydlik et al. (2021) concluded that the treatment of soil with an activator containing HA resulted in higher yield in apples.
Effects of treatments on yield per plant (g/plant): (A) treatments, (B) cultivars, (C) treatment × cultivar. Means that differ significantly at a 5% level are indicated by different letters. T1: OF; T2: OF + HA (2.5 L·ha−1); T3: OF + HA (5.0 L·ha−1); T4: OF + HA (7.5 L·ha−1). OF = organic fertilizer; HA = humic acid.
Citation: HortScience 59, 8; 10.21273/HORTSCI17902-24
Average fruit weight.
The treatments significantly affected the average fruit weight (Fig. 2). The largest fruits were detected in the T3 (18.14 g) and T4 (17.72 g) treatments of the Monterey variety and the T3 (17.51 g) treatment of the Albion variety. The smallest fruits were observed in the T1 treatment of the Albion variety. Although fruit size in strawberries is a variety-specific characteristic, environmental factors and practices can also influence this trait. HAs significantly increase the rate of photosynthesis, respiration, and plant hormone-like activities in plants; as a result, the number and weight of fruits increase due to the increase in the number of flowers blooming on the plant (Chen and Aviad 1990). Eshghi et al. (2013) reported that HA increased the primary fruit weight of strawberries, which may have been due to more nutrients having reached or been transported to the fruits. Moreover, Aghaeifard et al. (2016) emphasized that HAs play a vital role in this context by minimizing fruit dropping, improving the delivery of beneficial nutrients (phosphorus and potassium) to the plant, and directly preventing nutrient deficiencies and disorders in the plant.
Effects of treatments on average fruit weight (g): (A) treatments; (B) cultivars; (C) treatment × cultivar. Means that differ significantly at a 5% level are indicated by different letters. T1: OF; T2: OF + HA (2.5 L·ha−1); T3: OF + HA (5.0 L·ha−1); T4: OF + HA (7.5 L ·ha−1). OF = organic fertilizer; HA = humic acid.
Citation: HortScience 59, 8; 10.21273/HORTSCI17902-24
Also, Aghaeifard et al. (2016), Ullah et al. (2017), and Zydlik and Zydlik (2023) observed that foliar HA treatment in different strawberry varieties increased the number of fruits and fruit weight. One study found that foliar HA, brassinosteroid, and seaweed extract treatments positively affected fruit set, leaf macros, and micronutrient contents in apricot (Al-Saif et al. 2023).
Fruit juice pH, TSS, acidity, and TSS-to-acid ratio.
In this study, the effects of treatments on pH, TSS, acidity, and TSS/acid ratio were found to be significant (Table 3). The highest pH value was found in fruits treated with T1 (3.66), T3 (3.65), and T4 (3.65). When comparing varieties, a pH value of 3.70 was obtained in fruits of the Monterey variety. Considering treatments, the highest TSS value was obtained with T3 (11.27%), and the lowest value was obtained with T1 (10.24%) (Table 3). Eshghi and Garazhian (2015) illustrated that HA treatments increased the TSS value in fruits of the Paros strawberry variety. Similarly, Alkharpotly et al. (2017) reported that the TSS values in fruits of the Festival strawberry variety treated with HA only were 11.47% in 2014/2015 and 11.63% in 2015/2016. In addition, HA treatment-led increases in TSS value in fruits were also reported by Aminifard et al. (2012), in pepper; by Mohamadineia et al. (2015), in grape; and by Al-Saif et al. (2023), in apricot.
Effects of treatments on strawberry fruit features.
Furthermore, the acidity values obtained with the treatments were between 0.64% and 0.67% in the current study. The highest acidity value, 0.67%, was obtained with the T2 treatment, and the lowest one, 0.64%, was obtained with the T1 treatment (Table 3). Similarly, previous studies reported that HA treatment increased the fruit acidity value in pepper (Aminifard et al. 2012), in fruits of the Paros strawberry variety (Eshghi and Garazhian 2015), and in fruits of the Camarosa strawberry variety (Aghaeifard et al. 2016).
There were also significant differences among treatments regarding the TSS/acid ratio (taste) (Table 3). The highest TSS/acid ratio, 17.32, was observed in fruits treated with T3. Although the variety × treatment interactions for the TSS/acid ratio were statistically insignificant, the highest TSS/acid ratio, 18.95, was observed in T3-treated fruits of the Monterey variety.
In addition to external quality parameters, such as color, size, and shape, internal quality parameters, such as pH, taste (TSS/acid), and acidity, which are at the basis of fruit quality definition, are also important for consumers (Roussos et al. 2022). In strawberry, Martínez-De la Cruz et al. (2022) reported that treatments based on HSs and a rhizobacteria-based biostimulant increased fruit quality; a similar result was reported by Chakraborty et al. (2023), who researched treatments based on HAs and seaweed.
Plant nutrient analysis in leaves.
The differences among the treatments in terms of total nitrogen, phosphorus, potassium, calcium, iron, and zinc concentrations in leaves were significant (Table 4). Among the treatments, the highest nitrogen concentration, 2.45%, was identified in leaves treated with T3, and the lowest one, 2.13%, was determined in leaves treated with T1. Mills and Jones (1996) reported that the nitrogen sufficiency level in leaves was between 2.10% and 4.00%. In this study, the nitrogen concentration in all treatment groups was within the sufficiency limits. HSs increase the uptake of nitrates and other nutrients by increasing root plasma membrane H +-ATPase activity, contributing to cell wall loosening, cell growth, and organ growth (Conselvan et al. 2017). Previous studies reported that HA treatment increased leaf nitrogen concentration in rapeseed (Jannin et al. 2012), pistachio (Razavi Nasab et al. 2019), and strawberry (Mufty and Taha 2021). In addition, Zydlik and Zydlik (2023) indicated that the leaf nitrogen concentration in strawberry under foliar HA treatment was in the range of 2.13% to 2.18%.
Effects of treatments on nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn) contents in strawberry leaves.
The leaf phosphorus concentration ranged between 0.26% and 0.33%. In the present study, the highest phosphorus concentration, 0.33%, was found in leaves treated with T3. Mills and Jones (1996) reported that the phosphorus sufficiency level in leaves was between 0.20% and 0.45%. Therefore, the phosphorus concentration in all treatment groups was within the adequacy limits. Aghaeifard et al. (2016) stated that treatment with HA caused a 39.11% increase in phosphorus (%P) in plants of the Camasosa strawberry variety, and Zydlik and Zydlik (2023) illustrated that foliar HA treatments in Rumba strawberry resulted in a leaf phosphorus value in the range of 0.24% to 0.28%.
In the present study, the leaf potassium concentration of the treatments varied between 1.93% and 2.33%, and the potassium concentration of the T3 treatment (2.33%) was higher than that of the other treatments. In the cultivar × treatment interactions, the highest potassium concentration was observed in the T3 treatment of the Monterey cultivar, with 2.34%. Similarly, Mills and Jones (1996) reported that the sufficiency level in leaves was between 1.10% and 2.50%. Thus, in this study, the potassium concentration in all treatment groups was within the potassium sufficiency limits. In the Camasosa strawberry variety, Aghaeifard et al. (2016) observed the highest potassium value, 1.29%, in the HA-only treatment group and the lowest, 0.76%, in the control, which had received no treatment.
In addition, in different turnip plants, Aisha et al. (2014) reported that organic and HA treatments increased the growth of root tissues and the percentages of nitrogen, phosphorus, and potassium as a result of the increased HA ratio. Li et al. (2019) documented that HA increased alkaline nitrogen, available phosphorus, and potassium content based on a study in which inorganic fertilizers and HA were applied to peanut.
The highest calcium content was 0.91% in the T3 treatment, and the lowest was 0.72% in the T1 treatment. Mills and Jones (1996) reported the adequacy limits for calcium as 0.60% to 2.50%, and Campbell and Miner (2000) as 0.50% to 1.50%. Therefore, the calcium content in the treatment groups in the current study were within the sufficiency limits.
Although the leaf magnesium concentration was in the range of 0.21% to 0.22%, the differences among the treatment groups were not significant. May and Pritts (1990) highlighted that the adequacy level of magnesium in leaves was between 0.20% and 0.50%. The total iron concentration in leaves was between 72.17 and 118.25 mg·kg−1, and the highest iron concentration was found in the T3 treatment (118.25 mg·kg−1). In the variety × treatment interactions, the highest iron content was observed in the T3 treatment of the Monterey variety. Mills and Jones (1996) illustrated that leaf iron content was sufficient between 50 and 250 mg·kg−1 The leaf iron content obtained in the current study was within the sufficiency range.
In the current study, the leaf zinc concentration varied between 26.29 and 49.13 mg·kg−1, and the zinc concentration of the T3 treatment (49.13 mg·kg−1) was higher than that in the other treatment groups. In the cultivar × treatment interactions, the highest zinc concentration was observed in the T3 treatment of the Monterey cultivar, with 54.25 mg·kg−1. Jones et al. (1991) reported the level of zinc sufficiency in leaves as 20 to 200 mg·kg−1, and Mills and Jones (1996) reported a range between 20 and 50 mg·kg−1. The total zinc in leaves was thus sufficient in all treatment groups in the current study.
Overall, HA treatments together with OF application provided higher leaf nutrient element contents than OF-only treatments. This finding suggests that in this study, HAs may have increased the plants’ capacity to use nutrients. Previous studies have reported that HA can increase the uptake of nutrient elements (Barzegar et al. 2022; Kołodziejczyk 2021). Nardi et al. (2017) acknowledged that HSs increased the nutrient utilization efficiency of plants. Last, Phooi et al. (2022) emphasized that HAs positively affect soil physical, chemical, and biological properties, so HAs indirectly improve plant growth by chelating nutrients for the plant.
Conclusion
HA dosage and treatment methods are among the most important factors that can affect yield and fruit quality in organic strawberry cultivation. In this study, we found that combined OF–HA treatment resulted in increased yield, fruit quality, and plant growth compared with treatment with OF alone. Among the varieties and treatment groups, the best results in terms of plant growth, fruit quality, and nutrient concentration in leaves were obtained with the treatment based on the combination of an OF and HA (5.0 L·ha−1) applied to plants of the Monterey variety. In addition, we observed that the application of HA augmented the efficacy of the OF in soil, thereby facilitating enhanced nutrient uptake by plants and concomitantly elevating both yield and fruit quality. These findings reveal the biostimulant potential of HA. Based on the results of this study, it is recommended that OFs and HAs are used together to ensure high-efficiency and-quality fruit production in organic strawberry cultivation.
Moreover, it is important to develop sustainable agricultural systems to counteract the effects of climate change on agriculture and protect human health and the environment. The combined use of OF and HA can contribute to the development of sustainable agriculture by improving the soil structure and mitigating environmental pollution, in addition to increasing yield and fruit quality.
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