Abstract
Although chemical fertilizers increase crop productivity, they have undesirable effects on the environment, soil fertility, and negatively influence fruit shelf life and quality. Therefore, the application of plant biostimulants and biostimulant-like substances has become necessary to improve the availability and absorption of nutrients, enhance growth, yield, quality, and tolerance to abiotic and biotic stresses, and serve as an alternative to mineral fertilizers. Therefore, this study investigated the influence of zeolite, kaolin (KL), and chitosan (Cs) in alleviating abiotic stress and improving productivity and quality of strawberry plants. Strawberry plants were soil fertilized by zeolite at 0, 2, and 3 kg and then they were sprayed with 2% g/L KL + 500 ppm Cs, 4% KL + 1000 ppm Cs, and 6% KL + 1500 ppm Cs. The individual application of zeolite improved the performance of strawberry plants, and its influence greatly increased with the combination spraying of different combinations from KL + Cs. The highest increments resulted from the application of 3 and 2 kg of zeolite combined with the spraying of 4% KL + 1000 ppm Cs and 6% KL + 1500 ppm Cs compared to non-treated plants.
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Influence of Zeolite, Kaolin, and Chitosan on the Growth and Productivity of Strawberry
Walid F. A. Mosa,a,* Khalid F. Almutairi,b,* Krzysztof Górnik,c and Lidia Sas-Paszt c
Although chemical fertilizers increase crop productivity, they have undesirable effects on the environment, soil fertility, and negatively influence fruit shelf life and quality. Therefore, the application of plant biostimulants and biostimulant-like substances has become necessary to improve the availability and absorption of nutrients, enhance growth, yield, quality, and tolerance to abiotic and biotic stresses, and serve as an alternative to mineral fertilizers. Therefore, this study investigated the influence of zeolite, kaolin (KL), and chitosan (Cs) in alleviating abiotic stress and improving productivity and quality of strawberry plants. Strawberry plants were soil fertilized by zeolite at 0, 2, and 3 kg and then they were sprayed with 2% g/L KL + 500 ppm Cs, 4% KL + 1000 ppm Cs, and 6% KL + 1500 ppm Cs. The individual application of zeolite improved the performance of strawberry plants, and its influence greatly increased with the combination spraying of different combinations from KL + Cs. The highest increments resulted from the application of 3 and 2 kg of zeolite combined with the spraying of 4% KL + 1000 ppm Cs and 6% KL + 1500 ppm Cs compared to non-treated plants.
DOI: 10.15376/biores.20.1.1771-1793
Keywords: Productivity; Nutritional status; Soil fertility; Strawberry
Contact information: a: Plant Production Department (Horticulture-Pomology), Faculty of Agriculture, Saba Basha, Alexandria University, Alexandria 21531, Egypt; b: Department of Plant Production, College of Food Science and Agriculture, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia; c: The National Institute of Horticultural Research, Konstytucji 3 Maja 1/3, 96-100 Skierniewice, Poland;
* Corresponding authors: walidmosa@alexu.edu.eg; almutairik@ksu.edu.sa
INTRODUCTION
Strawberry is one of the most important berry fruits that is highly consumed and accepted by people worldwide (D’Urso et al. 2015). It has an attractive taste, fine flavor, distinctive aroma, bright red colour, sweetness, and juicy texture, making it a delightful fruit. Moreover, strawberry is rich in essential minerals such as K, Ca, and P, phytochemicals, fiber, antioxidants, and vitamins, particularly vitamins C and B9. Thus, it is beneficial to human health (Fernandes et al. 2012). It can be eaten fresh, and is used for preparing jelly, ice cream, juice, chocolates, and wine (Kumar et al. 2017). In Egypt, strawberry is one of the most important export crops; the cultivated area is 15.836 hectares and the production is 638.842 tons (FAO 2022). However, it is sensitive to high temperature.
Chemical fertilizers are simpler to apply than organic fertilizers; however, they negatively impact naturally occurring soil microorganisms that boost soil fertility (Verma et al. 2014). The overuse of chemical fertilizers has caused significant environmental impacts and increased production costs (Wang et al. 2018; Fang et al. 2021). Besides, they pollute the undersoil water, increase air pollution, and raise soil acidification, which in turn decreases the organic compounds in the soil (Havlin et al. 2005).
Reducing chemical fertilizer use while increasing organic fertilizers represents a forward-looking strategy for balanced agricultural management, and this approach regulates nutrient supply to the soil, enhancing both soil productivity and crop quality (Chen 2006). Sustainable agricultural practices prioritize the health of both soil components and crop plants, along with beneficial microbes (Narula and Dudeja 2013).
Using organic fertilizers can enhance soil nutrient levels and boost soil enzyme activity (Kilic et al. 2021). The usage of organic fertilizers has numerous advantages such as reducing the cost, improving the soil construction, texture, and airing, enhancing the soil water holding capacity and improving the growth root system (Liu et al. 2010), increasing soil organic matter, and consequently improving the soil fertility (Moe et al. 2017; Jin et al. 2022). Additionally, organic fertilizers affect the physicochemical properties of orchard soils and the sugar, acid, and solid content of fruit (Yadav et al. 2016).
Zeolite-coated fertilizers possess a greater capacity to absorb and hold water and retard the rates of nutrient release from the soil, particularly sandy and sandy loam soil (Syukur and Sunarminto 2013). Additionally, natural zeolites are effective soil-improving substances and have a good capacity to hold water and nutrients, and they improve the rates of infiltration, conductivity, cation exchange capacity, and prevent water losses from profound leaking (Enamorado-Horrutiner et al. 2016), and they could be utilized as fertilizer and chelating agents (Tsintskaladze et al. 2016). Moreover, natural zeolites markedly enhance fertilizer efficiency and reduce the environmental impact of chemical fertilizers in agriculture due to their high surface area, porosity, ion exchange capacity, and ability to retain and gradually release nutrients and water (Lahori et al. 2020).
Kaolin (KL) particle film technology has been developed as an efficient, eco-friendly solution to mitigate heat and light stress, reduce water deficits, and promote the cultivation of high-quality fruits and vegetables (Boari et al. 2015) by reflecting solar radiation off the tree canopy surface (Gullo et al. 2020; Ali et al. 2021). Moreover, it is believed to work as an anti-transpirant, enhancing water use efficiency (Brillante et al. 2016), effectively lowering temperature and sunburn, which in turn enhances productivity and improves both the physical and chemical qualities of fruit across various tree species compared to the control (Khalifa et al. 2021). Spraying of KL forms a white film of particles on the leaves, leading to the activation of the photosynthetic rate (Torres-Quezada et al. 2018). KL is a mineral compound characterized by a high amount of kaolinite, and it has been used for alleviating environmental stresses such as heat and drought in different crops. It is also a non-toxic and eco-friendly natural antitranspirant that enhances growth traits, yield, and its components, meanwhile, it can help mitigate the adverse effects of water deficiency, although it may increase leaf temperature if the plant is not under drought stress (Mphande et al. 2020).
Appling of chitosan (Cs) has been demonstrated as a strategy to alleviate the negative effect of abiotic stress, stimulate plant growth, and improve the yield and quality of crops (Jabeen and Ahmad 2013). It also can improve plant tolerance to abiotic stresses such as salt, drought, and low temperatures (Hassan et al. 2021; Kocięcka and Liberacki 2021; Wang et al. 2021). The impact of Cs may be attributed to the release of nitrogen, which is then utilized in the synthesis of components for the photosynthetic system (Shangguan et al. 2000). It acts as a growth promoter by enhancing nutrient absorption capacity in plants (Malekpoor et al. 2016; Balal et al. 2017). Additionally, Cs is a natural, low toxic, and economical compound, consisting of an amino polysaccharide obtained by alkaline deacetylation from chitin and other decomposable substances of crabs and shrimp shells. Therefore, it is considered an eco-friendly product (Mohamed et al. 2018). Cs is favored for its various properties; water-soluble (Golkar et al. 2019), bioactive (Turk 2019; Bakhoum et al. 2020), antimicrobial (Gerami et al. 2020), and non-toxic characteristics (Sen et al. 2020) to enhance stress tolerance and boost plant performance by activating multiple stress-related enzymes. Therefore, this study focused on studying the influence of zeolite combined with different combinations of KL + Cs as to improve the growth, productivity, and fruit quality attributes of strawberry.
EXPERIMENTAL
Applied Treatments, Location, and Experimental Design
The experiments were conducted using a split-plot design with three plots (replicates) on the festival strawberry variety, where each plot contained ten plants. The plants were cultivated in rows. The distance between rows was 40 cm and between plants in the same row 25 cm under drip irrigation. Strawberry plants were planted at the start of October 2022 and 2023 seasons in a private orchard in the Nubaria region, Beheira governorate, Egypt. Each plot was fertilized with zeolite with 0, 2, and 3 kg at the start of the plantation as the main factor, then they were sprayed with the combinations of 2% g/L KL + 500 ppm Cs, 4% KL + 1000 ppm Cs, and 6% KL + 1500 ppm Cs as a submain factor compared to untreated trees as a control (Table 1). The plants were sprayed four times: mid-November 2022 (vegetative growth and flowering period), December 01, 2022 (flowering and fruiting period), March 01, 2023 (fruiting period), and April 01, 2023 (fruiting period). The same treatments were performed again in the second season of 2023/2024, where the total volume of the spraying solution was 2 L. Physical and chemical analysis of the experimental soil is given in Table 2, and the weather data in Table 3.
Table 1. The Applied Treatments
Table 2. Soil Analysis
O.M: organic matter
Table 3. Weather Data During the Experimental Period 2022/2023 to 2023/2024
Vegetative Growth Attributes
After 120 days from transplanting throughout the two experimental seasons, in the two growing seasons, plant height (cm), number of leaves per plant, and leaf area were measured. Leaf chlorophyll content was measured in fresh leaves by taking an average of ten readings. The flower number and the number of crowns were estimated.
Fruit Yield
The yield per plant (g) was determined as the weight of all harvested fruits from each plot during February and March over the harvested season up to mid May, and then the total yield per hectare was calculated.
Fruit Quality
Fruit physical characteristics
The average fruit weight was calculated as the average of 40 fresh fruits. Fruit firmness was measured using a Chatillon Pressure Meter Equipped with a Plunger (Hongqi Instrument (Changxing) Company, Zhejiang, China). Fruit length and diameter were measured using a digital Vernier caliper.
Fruit chemical characteristics
Twenty ripe fruits were chosen randomly from each experimental plot at a full ripe stage to measure the percentage of total soluble solids content (TSS) using the hand re-fractometer. Titratable acidity (TA%), samples of 100 g fruits from each experimental plot at a full ripe stage were randomly chosen to determine the titratable acidity of juice by titration with 0.1 NaOH solution, according to the method described in (AOAC 2005). The content of vitamin C (mg/ 100 mL juice) was determined by titration using 2,6-dichloro phenol indophenol (Nielsen 2017). Anthocyanin content (mg/100 g F.W.) was determined according to Nangle et al. (2015). The phenol-sulfuric acid method was used to estimate the total sugars using 1.0 mL of sample treated with 1.0 mL of 5% phenol and 5.0 mL of concentrated H2SO4 and measured at 485 nm, while reduced sugars were estimated using the 3,5-dinitro salicylic acid (DNS) method using 2.0 mL of the sample and 1.5 mL of DNS at 80 °C for 10 min and measuring at 510 nm (Lam et al. 2021). Non-reduced sugars were the difference between them.
Mineral Content in the Leaves
At the end of seasons 2022/2023 and 2023/2024 seasons, 40 leaves from each plot (Arrobas et al. 2018) were dried at 70 °C until constant weight and then ground and digested using H2SO4 and H2O2 until the solution became clear to determine nitrogen content using the micro Kjeldahl method (Wang et al. 2016), phosphorus content using the Vanadomolybdo method (Wieczorek et al. 2022), and potassium content was determined using a flame photometer (Asch et al. 2022). Micronutrients, such as iron, manganese, and zinc, were determined using atomic absorption spectrophotometry.
Statistical Analysis
The results were statistically analyzed by using a Split Plot Design in three replicates, where soil addition of zeolite was the main factor and spraying of KL + Cs combination was the submain factor using CoHort Soft-ware 6.311 (Pacific Grove, CA, USA). The least significant difference at 0.05% (LSD0.05) was applied to compare the treatment means (Snedecor and Cochran 2021).
RESULTS AND DISCUSSION
Vegetative Growth Parameters
Spraying strawberry plants with the combination of KL + Cs solely or combined with the soil addition of zeolite greatly improved the leaf chlorophyll content, numbers of flowers, and crowns compared to untreated plants (Fig. 1). Additionally, the results significantly improved the leaf chlorophyll content by the addition of 3 kg of zeolite combined with 6 % KL + 1500 ppm Cs, which is the superior treatment rather than the other treatments. Numbers of flowers and crowns were statistically improved by the addition of 3 or 2 kg zeolite to the soil combined with the exogenous spraying of 6% KL + 1500 ppm Cs, 4% KL + 1000 ppm Cs, and 2% KL + 500 ppm Cs compared to untreated plants.
The addition of zeolite to the soil singly and with the spraying of KL and Cs greatly improved the leaf number per plant, leaf area, and plant height over untreated trees (Table 4). The addition of 3 or 2 kg of zeolite combined with the spraying of 6% KL + 1500 ppm Cs and 4% KL + 1000 ppm Cs greatly enhanced the number of leaves per plant, plant height, and leaf area compared to the control plants. Additionally, the spraying of 6% KL + 1500 ppm Cs was also effective in improving these parameters. Moreover, the highest increments in these parameters were noted by the soil addition of 3 kg zeolite combined with 6% KL + 1500 ppm Cs, which is the superior treatment during the experimental period.
Table 4. Effect of the Zeolite Soil Addition Combined with the Spraying of KL and Cs on the Leaf Number, Plant Height, and Leaf Area of Strawberry
Note: Treatments with the same letter in each column indicate no significant differences between them.
Fruit Weight and Fruit Yield
The results showed that there was an improvement in individual fruit weight, fruit yield were obviously improved by the soil addition of zeolite at 3 or 2 kg combined with the spraying of 6% KL + 1500 ppm Cs or 4% KL + 1000 ppm Cs respectively, compared to untreated plants (Fig. 2). Additionally, the spraying of 6% KL + 1500 ppm Cs and 4% KL + 1000 ppm Cs also were more effective in improving the same parameters than the spraying of 2% KL + 500 ppm Cs compared to untreated trees. The results indicated that the most efficient treatment was the application of 3 kg of zeolite to the soil combined with the spraying of 6% KL + 1500 ppm Cs compared to the other applied treatments.
Fruit Physical Characteristics
Spraying strawberry plants fertilized with zeolite by the mixture of KL + Cs positively increased the fruit length, fruit diameter, and fruit firmness compared to nontreated plants (Table 5). The best results in fruit length, fruit diameter, and fruit firmness were noted by the addition of 3 kg zeolite and spraying the plants with the 6% KL + 1500 ppm Cs. Additionally, the fruit length and fruit diameter were also greatly improved with the addition of 3 kg zeolite combined with the spraying of 4% zeolite + 1000 ppm Cs in the two experimental seasons.
Table 5. Effect of the Zeolite Soil Addition Combined with the Spraying of KL and Cs on the Fruit Length, Diameter, and Fruit Firmness of Strawberry
Note: Treatments with the same letters in each column indicate no significant differences between them
Fruit Chemical Characteristics
Spraying of 6% KL + 1500 ppm Cs and 4% KL + 1000 ppm Cs greatly increased the fruit content from TSS %, anthocyanin, and vitamin C, and their effect was greatly increased by the soil addition of zeolite at 3 or 2 kg. Meanwhile, they greatly reduced the fruit content from acidity compared to untreated trees (Fig. 3). Additionally, the results demonstrated that the most positive influence was obtained by the 3 kg zeolite combined with 6% KL + 1500 ppm Cs, which is the best treatment compared to nontreated plants during the testing period. Moreover, the spraying of 6% KL + 1500 ppm Cs was more effective in improving these parameters than the spraying of 4% KL + 1000 ppm Cs or 2% KLl + 500 ppm Cs.