Response of sweet pepper plants to foliar application of compost tea and dry yeast under soilless conditions

Background: Sweet pepper is considered one of the most important vegetable crops cultivated for local consump‐ tion and exportation. Under greenhouse conditions, the effects of different rates of yeast and compost tea on vegeta‐ tive growth, leaves mineral content, fruit yield and quality were studied for two consecutive years 2018/2019 and 2019/2020 under soilless conditions. Nine treatments of compost tea (CT) and or dry yeast (DY) were applied using control (sprayed with distilled water); CT (10L/fed.); CT (20 L/fed.); DY (3 g/L); DY (6 g/L); CT (10L/fed.) + DY (3 g/L); CT (20L/fed.) + DY (3 g/L); CT (10L/fed.) + DY (6 g/L) and CT (20L/fed.) + DY (6 g/L). Results: Results showed that the mixture of compost tea and dry yeast at a rate of 20 L./fed. plus 6 g/L, respectively, had significantly increased vegetative growth, fruit physical quality (length, diameter and fresh weight), total yield, leaves mineral content (N, P and K) and fruit nutritional value content (calcium and vitamin C). The maximum return or profit comes from the CT (20 L/fed) + DY (6 g/L) followed by CT (20 L/fed) + DY (3 g/L.) Conclusion: It is clear that all treatments enhanced the yield and the fruit physical parameters of the studied plants as well as all treatments are economically feasible including the control treatment. However, looking at the Revenue/ Cost ratio (R/C), one can find that the maximum net revenue comes from the mixture of CT (20 L/fed) plus DY (6 g/L) with a net revenue about 192.72 L.E./m and R/C ratio of 1.90, followed by CT (20 L/fed) + DY (3 g/L.).


Background
Sweet pepper (Capsicum annuum L), Solanaceae family, is an important summer vegetable crop due to its high nutritional and medicinal value. It contains various nutrients, rich in thiamine, riboflavin, niacin, antioxidants, flavonoids, vitamin C and vitamin A (Igbokwe et al. 2013). The average cultivated area of pepper in the open field was about 97 thousand feddan in 2015, with a production capacity of about 615 thousand tons. Under protected cultivation, sweet pepper is cultivated in 25 thousand greenhouses with an area estimated at 2320 feddan, representing about 2.39% of the total cultivated pepper area, but its capacity production amounted to about 95 thousand tons, representing about 15.45% of the total productive capacity of the pepper crop in Egypt according to Ministry of Agriculture Statistics, (2016).
Compost tea became more valuable for applications in organic farming. It is produced by extracting useful microbes from compost and/or vermi-compost, thus obtaining a highly concentrated microbial solution. Compost tea gives positive effects for plants, because it contains chelated micronutrients for easy absorption by plants, bioactive molecules and microorganisms that protect the roots and the plant from pathogens and diseases. Moreover, it provides nutrients to plants, thus improving plant growth and health (Ingram and Millner 2007;Azza and Hendawy 2010). Compost tea produces Abd-Alrahman and Aboud Bull Natl Res Cent (2021) 45:119 plant hormones, mineralizes nutrients to available form to plants and fixes nitrogen (Abou-El-Hassan et al. 2014;Hatam et al. 2015). The effects of compost tea are shortlived so the applications must be repeated to supply plants and soil surface with nutrients and/or beneficial microbes (Ingham 2005).
Active dry yeast is a natural biofertilizer that improves plant growth and yield. It is rich in protein, vitamin B, thiamin, riboflavin, pyridoxines amino acids and cytokinin (Abdelaal et al. 2017;Nagwa et al. 2020). Also, one of the benefits of yeast is the release of carbon dioxide, which is reflected in improving net photosynthesis (Ahmed et al. 1998) and convert the non-soluble form of phosphorus to soluble one (available form for plant) (Agamy et al. 2013;Kalayu 2019).
Soilless culture is a technology for growing plants in nutrient solution with or without the use of growing media, such as sand, peat moss, vermiculite, etc., to supply mechanical support for plants (Pardossi et al. 2011). It has many advantages, such as steady and high-quality production (Veys 1997), earliness, high yield, cleaner production as well as minimum herbicide and pesticide residues in the fruit (Manukyan et al. 2004). Substrate media may significantly affect plant growth (Alsmairat et al. 2018) where media with low bulk density and highwater holding capacity enhances plant aeration and root penetration (Deepagoda et al. 2013). It has been reported that the substrate physical and chemical properties affect the production quality and quantity, such as yield, flower size and number, fruit sugar and phenolic compounds (Al-Ajlouni et al. 2017).
Therefore, this work aimed to study the effect of compost tea and active dry yeast on growth, fruit physical quality, total yield, leaves mineral content and fruit nutritional value (calcium and vitamin C) of sweet pepper under peat moss: perlite media.

Experimental site and cultivation method
An experiment was conducted in the farm of the Central Laboratory for Agricultural Climate Research Centre (CLAC), Dokki, Giza, Egypt, during the two successive winter seasons of 2018/2019 and 2019/2020 to study the effect of different compost tea and active dry yeast rates on growth, fruit quality and yield of sweet pepper plants.
Sweet pepper cv. Gedeon F1 Hybrid seedlings were obtained from the Central Laboratory of Agriculture Climate (CLAC). Each seedling was transplanted in a fiveliter pot (Neveen 2016) filled with a well-mixed media of perlite: peat moss (1:1: v/v). The physical and chemical characteristics of the used media are listed in Table 1.
The experiment contained nine treatments, with three replicates for each treatment. Seedlings were transplanted in pots under greenhouse conditions during the first week of October in both seasons, in plots of 3 m × 1 m arranged in completely randomized design. Each plot contained 48 pots and each pot contained one seedling. The distance between seedlings was 25 cm. This is done through drip irrigation system, which is running through the pots of the sweet pepper rows.
These pots were irrigated by Cooper nutrient solution (Cooper 1979), which adapted according to El-Behairy, (1994). Where desired initial concentration was maintained by dilution of the stock with tap water as illustrated in Table 2. Electrical conductivity (EC) of the nutrient solution was maintained between (2 and 2.2) m. mhos-1 and pH was kept between 6 and 6.5.
Three weeks after transplanting and for three consecutive weeks, the plant leaves were sprayed with aqueous solution of yeast (15L/feddan) and compost tea by one of the above-mentioned concentrations each week, early in the morning, while the control plants sprayed by distilled water (Table 3).

Compost tea extraction
Compost tea was extracted by adding 10 L of water to a liter of compost. Compost tea was left at room temperature for four days. After that, compost tea was filtered to avoid clogging of the spraying equipment. The chemical composition of the used compost tea is illustrated in Table 4. EC, soluble ions and pH were determined according to Jackson (1973). Available phosphorus and available potassium have been evaluated according to Black 1965 and total nitrogen has been determined according to Jackson (1973).
Active dry yeast (Saccharomyces cerevisiae) was dissolved in warm water (38 ○ C) followed by adding sugar at a ratio of 1:1 to active growth and reproduction of yeast and was left for two hours before spraying according to Morsi et al (2008). The chemical analysis of the used active yeast is shown in Table 5.

Measurements and data collection Vegetative measurements
The vegetative measurements were determined after 120 days from transplanting in both seasons during the flowering stage. Five plants were randomly chosen from each plot and transferred to laboratory to record the following data: Plant length (cm); number of leaves/ plants, number of branches/ plants, leaves fresh weight (g/plant) and leaves dry matter (%), plant leaves area (cm 2 ).

Chemical measurements
Determination of mineral content Oven-dried samples from leaves were grinded and used to estimate total nitrogen and phosphorus contents using Kjeldahl and colorimetric methods, according to Cottenie (1980). Potassium content was measured according to Chapman and Pratt (1982) using flame photometer method.
Fruit yield The fruits were harvested when having attained full size for fresh use. Fruit diameter (cm), fruit length (cm), fruit weight (g), total yield kg/pant then total yield kg/m 2 were estimated.

Fruit chemical content and nutritional value:
a. Determination of vitamin C (mg/100 g): randomly selected samples from the fresh fruits were analyzed to measure ascorbic acid (vitamin C) content according to AOAC (1990). b. Determination of Calcium content: Oven-dried samples from fruits were grinded and used to estimate Calcium. It was measured with an atomic absorption spectrophotometer (FAO 1980).

Economic evaluation
The benefit cost ratio was determined according to (Nahed, et al. 2015) by dividing the gross return (LE / m 2 ) on total variable cost (LE /m 2 ).
Total cost was determined by the cost of substrate + plastic pots + seedling + foliar application (compost tea and dry yeast) + nutrient solution + irrigation equipment.
Total yield for the two seasons was summed and multiplied by an average market price to represent the total income (Table 6).
• Net revenue = Revenue-Total cost • The Revenue to Cost (R/C) ratio was calculated to represent the profit percentage.

Statistical analysis
The experiment data were statistically analyzed using Mstatic (M.S.) software. Mean comparison of the different treatments was tested as illustrated by Snedecor and Cochran (1982), where, means with the same letters are not significantly different at 5% level of significance according to (Duncan 1955).

Effect of compost tea, dry yeast and their mixtures on physical quality and total yield
Results showed that mixture of compost tea and active dry yeast treatments enhanced fruit physical quality and total yield compared with the control treatment as shown in (Table 8). The highest values of all physical quality and total yield were obtained by the mixture of CT (20L/fed.) + DY (6 g/L). The fruit diameter of CT (20L/fed.) + DY (6 g/L)-treated plants increased (6.17, 5.90 cm) as compared with control (3.27, 3.13 cm) in the first and second seasons, respectively. Moreover, the fruit length of CT (20L/fed.) + DY (6 g/L)-treated plants increased by (8.77 and 10.02). The fruit weight (g) also increased by (117.62 and 122.68) in the first and second seasons, respectively. Similarly, total yield (kg/plant) of 20L/fed. (CT) + 6 g/L (DY)-treated plants increased by (2.06 and 2.18) as compared with control (1.09 and 1.21) in the first and second seasons, respectively.

Effect of compost tea, dry yeast and their mixture on leaf mineral content
There were significant increases due to compost tea and or dry yeast applications in terms of leaf mineral contents, i.e., N, P and K compared with the control treatment (Table 9). Nitrogen, phosphorus and potassium concentrations in the treated plants by mixture of CT (20L/fed.) + DY (6 g/L) increased in the first and second season, respectively, as compared to control.
The lowest values of the mentioned parameters were recorded by control in both seasons.

Effect of compost tea, dry yeast and their mixture on fruit nutritional values
Nutritional values (calcium and vitamin C) of sweet pepper fruits were significantly increased due to all applications of compost tea and/or dry yeast treatments compared with the control in both seasons as shown in Table 10. Calcium percentage and vitamin C (mg/100 g) content in the treated plants by mixture of CT (20L/ fed.) + DY (6 g/L) significantly increased (2.01 and 2.14) and (89.33 and 94.52) as compared to control (1.48 and 1.59) and vit. C (72.49 and 75.23) in the first and second seasons, respectively.

Economic feasibility
Economic feasibility is a criterion that can be used to evaluate the benefit in terms of economic value or cash return investment. In this study the sum of the total fixed cost is calculated once for the two seasons and the variable costs were estimated for one season and multiplied by two representing the total cost, while the total yield for the two seasons were summed and multiplied by an average market price to represent the total revenue. The difference between the total cost and the total revenue is the profit. The Revenue to Cost (R/C) ratio was calculated to represent the profit percentage, where its value reflects the economic feasibility of the proposed treatments. When the R/C ratio is less than one the proposed treatment is not feasible in terms of cost to revenue aspects. In contrast if the R/C ratio is greater than one the project is profitable. Table 11 represents the results of the conducted economic feasibility study for these proposed treatments. It is clear that all treatments are economically feasible including the control treatment; however, looking at the R/C ratio, one can find that the maximum return or profit comes from the compost tea (20 L/fed) and yeast (6 g/L) mixture, followed by compost tea (20 L/fed) and yeast (3 g/L) mixture as indicated by the treatment order column in Fig. 1.

Discussion
Results reported that foliar spray of sweet pepper with the mixture of CT (20L/fed.) + DY (6 g/L) is the most suitable under soilless culture, which ranked the first in all vegetative growth characters, total yield, fruit quality, and chemical composition. It could be attributed to the dual effect of compost tea and dry yeast on plant metabolism, which promotes cell division, amino acids  and vitamin synthesis which improves plant growth (Matter and El Sayed 2015). Consequently, the plants received the benefit of both factors at the same time.
The positive impact of compost tea on plants may return to supply them with chelated microelements and increase elements availability which make them easier for plants absorption. Also, these fertilizers supply plants with nutrients and useful microorganisms that increased the time for the stomata to remain opened.
Our results agree to a great extent with those obtained by (Gharib et al. 2008 andAzza &Hendawy 2010). They showed that vegetative growth and oil yield and quality of sweet marjoram (Majorana hortensis) and Borago officinalis plants, respectively, were increased by foliar application of compost tea. In addition, dry yeast plays an important role in secretion of some growth promoters, such as cytokines that induces cell reproduction and differentiation, controlling shoot and root development and chloroplast maturation (Abdelaal et al. 2017 andNagwa et al. 2020). Also, the effect of adding dry yeast on improving vegetative growth may be due to the fact that many physiological and biological processes take place in the leaves, in addition to the leaves being an effective method for better absorption and transport of nutrients inside the plant (AL-Karawi et al. 2018). Moreover, the importance of dry yeast for improving the vegetative growth characters, yield and quality of sweet pepper may be due to its content of nutrients like nitrogen as shown in Table 5. Several authors have been attributed this bio-stimulatory effect to its influence on the nutritional signal transduction producing growth regulators and crushing harmful microorganisms (El-Ghadban et al. 2003). Also, El-Tohamy and El-Greadly (2007) studied the promoting effect of foliar application of dry yeast on snap beans plants, and it increased growth, yield and quality. Our findings are similar with the findings of Azza and Hendawy (2010) on borage plants. Also, Gomaa and Mohamed (2007) studied the combined effect of organic and bio-fertilizers on guar plants, and found that the highest yield was obtained from the mixture application of 20-ton manure and rhizobium + yeast (40 L/feddan).

Conclusion
The application of compost tea and dry yeast significantly enhanced the fruit chemical and physical characteristics of sweet pepper plants for the two studied seasons. The combination of the two fertilizers was superior compared to each one alone. Using 20 L./fed. of compost tea + 6 g/L. of dry yeast resulted in the highest vegetative growth, yield, physical and chemical qualities of sweet pepper plants. Moreover, economically speaking this treatment also was the highest in terms of benefit to cost ratio compared to all other treatments. As a general recommendation from this study, the foliar spraying mixtures of organic and bio-fertilizer (compost tea and active dry yeast) to sweet pepper plants produced the highest yield and better fruit quality. Also, this means that decreasing the quantity of mineral fertilization which increases the net income to the growers and reduces the environment pollution caused by extensive application of mineral fertilizers.
Abbreviations CT: Compost tea; DY: Dry yeast; R/C: Revenue to cost ratio.