Yield and Antioxidant Quality of Habanero Chili Pepper by Supplementing Potassium with Organic Products

Abstract

Habanero chili pepper has great economic importance in Mexico, but its production is limited due to different factors that affect quality. Given the high demand and prices of the fruit, the production of this crop is spreading to other regions in search of new production systems. The aim of this research work was to assess the yield and antioxidant components of the fruit by supplementing potassium from organic sources. The “Campeche”, “Palenque”, and “Jaguar” varieties were studied in five NPK treatments; replacing the % of potassium with humus and compost: (T1) 240-200-120+50% of K from liquid earthworm humus; (T2) 240-200-180+25% of K from liquid earthworm humus; (T3) 240-200-120+50% of K from vermicompost; (T4) 240-200-180+25% of K from vermicompost; and (T5) 240-200-240 (control, 100% chemical nutrition). For yield components, there were significant differences, highlighting the importance of the nutrition source for the yield and weight of fruits per plant. The control (T5) presented a value of 39 t·ha⁻¹ and was similar to treatments T2 and T3 with a supplement of 25 and 50% organic K. For the polar and equatorial diameter of fruit, as well as for plant height and leaf area, treatments supplemented with 50% organic K (T1 and T3) were more effective. For the varieties evaluated, no differences in yield and fruit weight were found; however, Campeche produced more fruits per plant with a greater equatorial diameter, while Palenque obtained fruits with a greater polar diameter and taller plants. The results of antioxidant compounds show that organic K supplementation improves the quality of total carotenoids, β-carotenes, and xanthophylls compared to 100% chemical fertilization, since total carotenoid content is improved by 54.2%, β-carotenes by 46.4%, and xanthophylls by 37.8%, respectively. The Campeche variety was the one that presented the best fruits with the highest antioxidant quality. These results indicate a positive effect of the combined application of chemical fertilizer with worm humus on yield and its components in pepper and other crops and show an economic, ecological, and sustainable alternative to the production of habanero chili pepper.

1. Introduction

Mexico has distinguished itself as one of the countries with the greatest genetic diversity of chili pepper. The most cultivated species of Capsicum are native to Central and South America. They include C. annuum, C. frutescens, C. baccatum, C. pubescens, and C. chinense. From an agricultural-commercial point of view, the most important species is C. annuum, native to Mexico [1,2,3]. In the last few years, habanero chili pepper has been booming. It is grown in Mexico throughout the year; however, the production conditions are not the most suitable, affecting the yield and quality of the fruit. Therefore, multiple techniques have been developed to make the available resources more efficient, with the goal of standardizing the quality of this product [4,5]. One of the trends is the conservation of agricultural systems through the use of sustainable agriculture, which is based on natural non-polluting products such as composts, earthworm humus, and seaweeds. Such agriculture represents a way to achieve food safety [6]. In addition to this, Yuan et al. [7] and Verma et al. [8] state that there are important factors fostering the conversion from conventional to organic agriculture, such as counteracting the price increase in chemical fertilizers. In just the first six months of 2022, the USD value of chemical fertilizer imports in Latin America and the Caribbean increased by an average of 137%, in comparison with the same period in 2021. [9,10] propose a quantity between 140 to 150 kg·ha⁻¹ of K to produce 28 t·ha⁻¹. On their side, Borges et al. [11] suggest a quantity of 130–120–160 of N, P₂O₅, and K₂O for the production of habanero chili pepper.

Other studies report that the Capsicum genus requires from 50 to 300 kg·ha⁻¹ of K because this nutrient is essential for plant growth. K is absorbed by the roots in its ionic form (K⁺), participates in different biochemical and metabolic processes, and is related to fruit quality. An adequate supply of K also increases the resistance to pests, diseases, and abiotic stress [12]. According to FAO, the production of K as potassium oxide (K₂O), reached 44.5 million tons in 2018, 87% of which was used for agricultural purposes. On the other hand, there is a fertilizer crisis that has triggered a shortage and scarcity of these products in the global market, leading to cost increases. From the end of 2020 until early 2022, the increase in the cost per kg of N, P, and K from urea, MAP (monoammonium phosphate), and KCl (potassium chloride) was approximately one dollar [13]. Furthermore, agriculture is extremely sensitive to climate changes that affect crop development; so good agricultural practices in protected production systems are nowadays considered part of fresh fruit and vegetable safety assurance programs [14,15]. One advantage of these protected production systems is minimizing the restrictions that bad weather conditions impose on crops, creating more direct jobs per hectare, producing safe crops, and increasing production by up to five times in comparison to open field production systems. Therefore, the production of organic crops under greenhouse conditions is quite attractive and habanero chili pepper is among the most frequently grown crops under this production system [16].

On the other hand, the habanero chili pepper is of great importance worldwide because it is a source of phytochemical compounds that benefit human health [17]. Menichini et al. [18] mention that, apart from its pleasant flavor, consuming the Capsicum chínense habanero chili pepper has potential health benefits thanks to the high content of phytochemicals present in the fruit. For thousands of years, chilies have been selected based on their spiciness, color, flavor, and later by vitamin content. The pungency in the fruit is attributed to the production of capsaicinoids in the placenta. The color of the fruit is due to a combination of pigments: chlorophylls, carotenoids, and anthocyanins accumulating in the fruit’s wall or pericarp. The resulting color is green, yellow, and purple in the immature stages, while in ripe stages the color is yellow, red, or orange. The flavor is partially the result of monoterpenoids and aliphatic aldehydes, which also accumulate in the fruit’s wall. The vitamin content, specifically ascorbic acid, varies a lot within different species, and the habanero chili pepper has one of the highest contents of this vitamin [19]. However, climate conditions such as temperature, light intensity, type of soil, compost, fertilization, the increase in carbon dioxide concentration in the atmosphere and the application of compounds from natural origins can have an effect on the antioxidant content and activity of harvested fruits. Other factors that can impact the activities of antioxidants include genotype variations, maturity, cultural practices, and management [20].

Given the high demand and high prices that habanero chili pepper reaches in the market, it is necessary to develop new production technologies to increase the yield and quality of the fruit. One of these options is the use of agricultural byproducts as an alternative in areas where agricultural inputs are scarce, expensive, and of low quality, leading to low yields. The goal of this research work was to determine whether the rates of chemical fertilization supplemented with potassium from organic sources such as vermicompost and earthworm humus can improve the yield, as well as the physical and biochemical antioxidant quality of habanero chili peppers grown under greenhouse conditions.

2. Materials and Methods

2.1. Study Site

The study was conducted in 2022 a spring-summer cycle in a tunnel-type green-house at the Department of Horticulture, Universidad Autonoma Agraria Antonio Narro (UAAAN) in Saltillo, Coahuila, Mexico (25°21′24″ N latitude, and 101°02′05″ W longitude, at an altitude of 1765 masl). The temperature to control the thermostats from the cooling system was on average 30/15 °C max/min, respectively, and maximum and minimum relative humidity during the experiment fluctuated between 70% and 40%. Average photosynthetically active radiation registered at solar noon was 302 μmol m ⁻² s ⁻¹.

2.2. Vegetal Material

Three varieties of habanero chili pepper were studied: (1) “Campeche” (Creole variety collected in the state of Campeche, Mexico with orange-colored fruits), (2) “Palenque” (belonging to VITAGRO LDTA USA with red fruits), and (3) “Jaguar” (owned by the National Institute of Forestry, Agriculture and Livestock Research (INIFAP), and is registered in the National Catalog of Plant Varieties (CNVV) of the National Service of Inspection and Certification of Seeds (SNICS) with the definitive registration number Num. CHL-008-101109 and breeder’s title No. 0664., with orange-colored fruits.

2.3. Establishment of the Experiment

The seeds were planted in polystyrene trays with 200 cavities, using Premier Sphagnum Peat moss as the substrate (Premier Horticulture INC. Quakertown, PA, USA) and mineral perlite (Termolita by Hortiperl, Nuevo Leon, Mexico) at a ratio of 60:40, respectively. At 50 days after planting, when the seedlings reached an approximate height of 12 cm and had 3 to 4 true leaves, transplanting was carried out in 16 L polyethylene bags. These bags were filled with the same substrate in the same proportions. The topological arrangement was a double row with a spacing of 40 cm between rows and 30 cm between plants, arranged in a triangular pattern at a distance of 1.70 m between beds, achieving a planting density of 3.9 plants m⁻². A drip irrigation system was used with a rate of 0.5 until an increase to 2 L∙h⁻¹ per emitter according to the phenological stage. Each nutrient solution was prepared in an 1100 L container using a pump with a flow rate of 600 L∙h⁻¹. Nutrition was based on 3 applications: the first one at transplanting, the second one 15 days after transplanting, and the third one at flowering. The applications were modified throughout the crop cycle according to the phenological stages of the genotypes.

2.4. Assessed Variables

2.4.1. Agronomic Variables

Weight of fruits per plant (PFP) was measured in g, for which three plants per treatment were harvested and obtained from the sum of all the fruits of six cuts using an electronic scale (PS-5 Portion Control Scale ±5 g), and later an estimate was made in t∙ha⁻¹ to determine Yield (REND). Average fruit weight (PPF) in g was estimated considering the ratio between total fruit weight/number of fruits. The Number of Fruits per Plant (NFP) was calculated at the end of the harvest, counting all fruits obtained throughout the harvest cycle. Polar diameter (DPF) and equatorial diameter of the fruit (DEF) in cm were obtained by taking 2 fruits at random from two cuts (third and fourth) and measuring with an Autotec digital Vernier (Model:12 Inch-300MM). Final leaf area (AFF) was measured in cm² with a LI-COR model LI-3000A leaf area meter. This was done at the beginning of the production stage by taking three intermediate leaves with a southeast orientation from three plants per treatment. Final plant height (AFP) in cm was measured with a measuring tape from the base of the stem to the plant apex at the end of the production season.

2.4.2. Variables for Fruit Quality

These were determined in fresh fruits and measured in the Laboratory of Mineral Nutrition and tissue culture of the Department of Horticulture, UAAAN.

The capsaicin content (CAP) was determined in the physiological maturity stage following the method described by Bennet and Kirby [21], with a Bio-145025 BIOMATE-5 spectrophotometer (Thermo Electron Corporation, Madison, WI, USA) at a wavelength of 286 nm. In order to determine the capsaicin concentration in the samples, a calibration curve of this compound was built (Sigma-Aldrich, San Luis, MO, USA) within a range of 0 to 1.2 mg mL⁻¹. Readings were recorded in triplicate for each sample and capsaicin content was expressed in Scoville units (SHU).

Vitamin C content (VC) was determined with the methodology reported by Padayatt et al. [22]. A total of 10 g of the weight of fresh fruit were weighed and placed in a mortar and crushed with 10 mL of hydrochloric acid at 2% (v/v). The blend was homogenized in 40 mL of distilled water. It was filtered through gauze and collected in an Erlenmeyer flask. A total of 10 mL of the supernatant were taken and titrated with 2,6-dichlorophenolindophenol (1 × 10⁻³ N) when the solution reached a pink color.

The content of VC was determined using the following formula:

$$\mathrm{Vitamin}\mathrm{C}(\mathrm{mg}100\mathrm{g}\mathrm{Fresh}\mathrm{Fruit}\mathrm{Weight})=\frac{\mathrm{mL}\mathrm{used}\mathrm{of}2.6\mathrm{dichlorophenolindophenol}\times 0.088\times \mathrm{total}\mathrm{volume}\times 100}{\mathrm{Aliquot}\mathrm{volume}\times \mathrm{sample}\mathrm{weight}\mathrm{g}.}$$

For quantification of total carotenes (CT), β-carotenes (βC), and xanthophylls (Xa), the technique described by Silverstein et al. [23] was used, which is based on the colorimetric method with a Genesys 10S UV-spectrophotometer. Vis was used (Thermo Scientific, Waltham, MA, USA, 0245.1), adjusted to a wavelength of 454 nm for CT, 440 nm for βC, and 474 for Xa, to quantify the absorbances (Abs) of analyzed samples, which were read in triplicate and the content was obtained using following formulas:

$$\mathrm{C}\mathrm{T}\mathrm{m}\mathrm{g}/0.1\mathrm{kg}=\frac{\mathrm{Abs}454\times 3857\times \mathrm{volume}}{\mathrm{W}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{g}.}\left(100\right)$$

$$\mathsf{\beta }-\mathrm{c}\mathrm{a}\mathrm{r}\mathrm{o}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{e}\mathrm{s}\mathsf{\mu }\mathrm{g}/\mathrm{mL}=\frac{\mathrm{Abs}440\times 3857\times \mathrm{volume}}{\mathrm{W}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\mathrm{g}.}\left(100\right)$$

$$\mathrm{X}\mathrm{a}\mathrm{n}\mathrm{t}\mathrm{h}\mathrm{o}\mathrm{p}\mathrm{h}\mathrm{y}\mathrm{l}\mathrm{l}\mathrm{s}\mathrm{mg}/\mathrm{kg}=\frac{\mathrm{Abs}474\times \mathrm{deviation}\mathrm{factor}\mathrm{of}\mathrm{the}\mathrm{spectrophotometer}}{\mathrm{weight}\mathrm{g}\times 236}\left(\mathrm{F}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l}\mathrm{d}\mathrm{i}\mathrm{l}\mathrm{u}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\times 1000\right)$$

2.5. Experimental Design and Statistical Analysis

For the assessed variables, three factors were analyzed: (A) Nutrition, (B) Variety, and (C) A×B Interaction. The experimental design was based on fully randomized blocks with a split-plot arrangement [24] and three repetitions. In large plot (A), the nitrogen (N) and phosphorus (P) requirements were used at 100% in all treatments and sources were completely chemical, using phosphonitrate (03-33-00 from FertiMax SA de CV, Puebla, Mexico) and phosphoric rock (24% P₂O₅ from Fosforita de Mexico SA de CV, Puebla, Mexico) with adjusting requirements with nitric and phosphoric acid (GNS Agricola, Torreon, Coahuila, Mexico), while for potassium nutrition (K), chemical fertilization with potassium sulfate (00-00-50 soluble potassium K₂O from FertiMax SA de CV, Puebla, Mexico) was used in combination with organic fertilization (liquid earthworm humus and vermicompost produced in a productive project of the UAAAN distributed by Management of University Companies, Saltillo, Coahuila, Mexico) and applying them three times according to the phenological stage. In small plot (B) were the three varieties of habanero chili pepper described above. With this, the following NPK treatments were established; (T1) 240-200-120+50% of K from liquid earthworm humus; (T2) 240-200-180+25% of K from liquid earthworm humus; (T3) 240-200-120+50% of K from vermicompost; (T4) 240-200-180+25% of K from vermicompost, and (T5) 240-200-240 (control, 100% chemical nutrition). To calculate the quantities, the nutritional analysis shown in

Table 1. Nutritional value of solid and liquid vermicompost, as well as the recommended rate for habanero chili pepper [11].

	N	P	K	Ca	Mg	Na	B	Fe	Cu	Mn	Zn	PH
				ppm
Recommended doses	240 *	200 *	240 *	168.0	48.7	23.0	0.4	3.2	0.0	1.9	0.2
Liquid earthworm humus	0.06 ++	0.08 ++	14.4 ++	21.0	22.0	136.0	27.3	17.0	1.8	3.2	2.5	8.2
Vermicompost	0.16 +	0.108 +	24.3 +	11.0	23.0		15.7	15.0	1.8		0.3	7.2

* The doses of N, P, K are given in Kg ha⁻¹, ++ = mL/L, + = g/ Kg.

was used.

The statistical difference between factors was analyzed using an analysis of variance (ANOVA), and means were compared with Tukey’s test (p ≤ 0.05) using the statistical package SAS^® V. 9.0 [25].

3. Results and Discussion

3.1. Yield Components

When analyzing the assessed variables for factor A (nutrition), REND, PFP, and DEF showed significant differences (p ≤ 0.05), whereas in PPF, DPF, AFF, and AFP, the differences between the nutrition treatments were highly significant (p ≤ 0.01). However, in NFP, there were no differences among the treatments. For factor B (varieties), highly significant differences were found (p ≤ 0.01) in variables PPF, NFP, DPF, and DEF; however, no differences were found in REND and PFP among different varieties, or in A×B interactions. The results show that the source of nutrition is the most important factor in increasing the yield of habanero chili pepper crops under greenhouse conditions. Variables PFP and REND (t·ha⁻¹), show a positive effect only in factor A, with significant differences; while variables PPF, DEF, and AFF show differences that occur in the three factors studied: nutrition (A), varieties (B), and nutrition*varieties (A×B). However, variable NFP is only affected by factors B and A×B, while for variables DPF and AFP the difference occurred in factors A and B (

Table 2. Sum of the squares of habanero chili pepper yield variables in five K nutrition treatments (A Factor) and three varieties (B Factor) under greenhouse conditions.

Variation Source	GL	Measured Squares
		REND (t·ha−1)	PFP (g)	PPF (g)	NFP	DPF (cm)	DEF (cm)	AFF (m2)	AFP (cm)
Blocks	2	13.7 ns	9100 ns	0.212 ns	2313 *	0.010 ns	0.034 ns	8.08 *	42.2 *
Nutrition (A)	4	118 *	77,810 *	3.42 **	423 ns	0.190 **	0.071 *	33.1 **	70.4 **
Error A	8	41.1	26835	0.433	819	0.045	0.005	6.58	25.8
Variety (B)	2	15.9 ns	10,607 ns	13.0 **	4633 **	0.260 **	0.297 **	7.36 *	25.4
A×B Interaction	6	58.0 ns	38,189 ns	1.34 **	2903 **	0.025 ns	0.070 *	8.36 *	53.2 **
Error B	20	27.4	18,031	0.212	648	0.040	0.023	2.37	12.8
CV (%)		15.4	15.4	8.29	15.3	5.85	6.54	18.8	5.74

*, ** Significant at p ≤ 0.05, 0.01, ns: not significant, REND: yield t·ha⁻¹, PFP: weight of fruits per plant, PPF: average fruit weight, NFP: number of fruits per plant: DPF: polar diameter of fruit, DEF: equatorial diameter of fruit, AFF: final foliar area of the plant, AFP: final plant height, CV (%): coefficient of variation.

). Such results are consistent with those mentioned by Salas et al. [26]. These authors consider that organic products can modify such variables; concluding that it is possible to use compost tea as a substitute for chemical fertilization in fodder production to improve quality. Coupled with the fact that organic fertilizers, in addition to providing nutrients to plants, improve the physical, chemical, and biological properties of the soil, increasing the unitary production of chili peppers and improving the quality of the fruit. In addition, Eghball [27] and Aram and Rangarajan [28] mention that in organic fertilizers, 80 to 90% of potassium is unavailable in the first year. However, Joshi et al. [29] mention that this type of organic fertilizer has low nutritional content and is slow-release, so they have to be supplemented with chemical fertilization to achieve better results.

The results of the Tukey mean comparison test (p ≤ 0.5) show that the REND is impacted by the application of 50% of K from organic nutrition based on liquid earthworm humus and by 25% of K from organic nutrition based on vermicompost, obtaining the results of 31 and 30 t∙ha⁻¹, respectively. The best yield was presented by the control (204N-200P-240K) with 39 t∙ha⁻¹. However, T2 and T3 showed a yield increase of up to 34 t∙ha⁻¹ in comparison with T1 and T4, indicating that the lower concentration of liquid humus and the higher concentration of vermicompost led to yield improvement (Figure 1).

Similar results were reported by Ramírez et al. [30], who found that habanero chili pepper plants grown under greenhouse conditions can reach an average yield of 46 t·ha⁻¹, with a higher number of flowers and fruits, as well as a small fruit size. This is in contrast with what was reported in the field, which resulted in a smaller number of fruits, but with bigger fruit size, resulting in a higher fruit yield per hectare.

Regarding factor B, there were no significant differences. Under these experimental conditions, the yield was 32 and 34 t∙ha⁻¹, which demonstrates that varietal selection does not play an important role in the decision-making process when aiming to obtain competitive yields above the domestic average. Nevertheless, the production of habanero chili peppers under greenhouse conditions increases the yield four times when compared with open-field production, with average values of 35 t·ha⁻¹ and 8 t·ha⁻¹, respectively [31]. Furthermore, Borges et al. [11] concluded that according to the production targets proposed (28 t·ha⁻¹ of fresh fruit), the results showed that the soils require an application of 108 to 150 kg·ha⁻¹ of K.

On the other hand, PPF represents a very interesting and attractive pattern for production, as well as for the market. Furthermore, PPF is an indicator of the final price to the consumer, since most potential buyers are swayed by the physical appearance of the product. The mean comparison (p ≤ 0.01) shows that the control has a higher weight, with a value of 6.56 g versus treatments T1, T2, T3, and T4, which had an average of 5.32 g, respectively. The treatment with 50% of K from vermicompost T3 produced the highest weight of 5.68 g (Figure 2). Significant differences were found for this variable (p ≥ 0.01) in factor B, where V3 had the highest weight of 6.58 g, followed by V2 with 5.34 g, and V1 showed the lowest weight of 4.76 g.

Based on the mean comparison applied to variable PFP, significant differences were found (p ≤ 0.05). The control (T5) stood out with an average weight of 1000 g of fruit per plant, while the plot nourished with T4 exhibited the lowest weight with a value of 769 g (

Table 3. Mean comparison of factor A and factor B yield variables in habanero chili peppers under greenhouse conditions.

	PFP (g)	REND (t∙ha−1)	PPF (g)	NFP	AFF (m2)	AFP (cm)	DPF (cm)	DEF (cm)
T1	803 ± 19.5 b	31.3 ± 0.83 b	5.21 ± 0.16 bc	159 ± 9.20 a	1.13 ± 0.12 a	63.8 ± 0.99 a	3.43 ± 0.15 ab	2.48 ± 0.09 a
T2	884 ± 29.5 ab	34.5 ± 0.57 ab	5.36 ± 0.71 bc	173 ± 8.66 a	0.84 ± 0.09 b	60.8 ± 1.17 ab	3.43 ± 0.14 ab	2.35 ± 0.06 ab
T3	876 ± 30.9 ab	34.2 ± 0.91 ab	5.68 ± 1.31 b	167 ± 7.15 a	0.67 ± 0.05 b	64.2 ± 1.33 a	3.70 ± 0.08 a	2.37 ± 0.06 ab
T4	769 ± 28.7 b	30.0 ± 0.71 b	4.97 ± 1.01 c	172 ± 9.56 a	0.66 ± 0.02 b	58.2 ± 1.12 b	3.31 ± 0.12 b	2.24 ± 0.07 b
T5	1010 ± 19.3 a	39.4 ± 0.81 a	6.56 ± 0.90 a	159 ± 10.6 a	0.78 ± 0.04 b	64.8 ± 1.45 a	3.40 ± 0.11 b	2.32 ± 0.01 ab
Varieties
(1) Campeche	840 ± 36.7 a	32.8 ± 0.95 a	4.76 ± 0.73 c	183 ± 9.12 a	0.86 ± 0.11 a	62.2 ± 1.42 ab	3.57 ± 0.09 a	2.50 ± 0.02 a
(2) Palenque	873 ± 40.3 a	34.1 ± 0.77 a	5.34 ± 0.53 b	167 ± 9.29 ab	0.85 ± 0.09 a	64.5 ± 1.65 a	3.48 ± 0.17 ab	2.34 ± 0.02 b
(3) Jaguar	893 ± 39.7 a	34.8 ± 0.83 a	6.58 ± 0.89 a	148 ± 11.4 b	0.73 ± 0.05 a	55.7 ± 2.31 b	3.31 ± 0.15 b	2.22 ± 0.09 b

The means with the same letter within each column are equal (Tukey, α = 0.05). Media ± standard deviation of three repetitions. PFP: fruit weight per plant, REND: yield, PPF: average fruit weight, NFP: number of fruits per plant, AFF: final foliar area of the plant, AFP: final plant height, DPF: polar diameter of the fruit, DEF: equatorial diameter of the fruit.

). When Borges et al. [11] grew habanero chili peppers with different nutritional levels of N, P₂O₅, and K₂O (240-240-240, 120-120-120, and 000-000-000), they found that fruit yield presented a significant response to increases in nutrition and moisture levels; reaching an average of 1391 g of fruit per plant at the level with the highest nutrition and highest usable moisture. Nevertheless, in this essay, factor B did not produce significant differences among varieties. Villa et al. [32] assessed the response of habanero chili peppers to three planting densities and three nutrient solutions under greenhouse conditions with a semi-controlled climate. The results indicate that there was a positive response in fruit yield by increasing the concentration of the nutrient solution.

In variable NFP, the form of potassium fertilization did not have any influence on plant fruiting since the results were the same as the control (T5) (Table 3). This may be due to the use of organic fertilizers in addition to K. These organic fertilizers have a high quantity of micronutrients as well as humic and fulvic acids that work as chelates within the substrate. However, there was a significant difference (p ≤ 0.05) in varieties V1 and V2; which were higher than V3 with values of 183, 167, and 148 fruits per plant, respectively. Ramírez et al. [30] mention that on average, the habanero chili pepper yields 280 fruits, but as a consequence, 60% of the fruits are not suitable for commercialization.

The AFF was improved by T1, showing a better response with an area of 1.13 m², in comparison with T2, T3, T4, and T5 which had between 25% and 42% less area (Table 3). Villa et al. [32] assessed the response of habanero chili peppers at three planting densities and three nutrient solutions under greenhouse conditions with a semi-controlled climate. Regarding the foliar area index (IAF), the combination of a nutrient solution at medium concentration with an intermediate population density showed the highest IAF. In the same study, the variable was improved by supplementing 50% of K from liquid earthworm humus. Likewise, Swart et al. [33] mentioned the influence of temperature on the growth and development of plants from the genus Capsicum. At a temperature of 21.1/18.7 °C (day/night), the plants showed a greater amount of branching before anthesis, as well as an important correlation with the foliar area. However, the type of variety played an important role in such a variable, as confirmed by this study where factor B was 15% lower in V3 versus V1 and V2.

The AFP was improved by treatments T1, T3, and T5, obtaining an average height of 64 cm, demonstrating that fertilizing with 50% of K from liquid earthworm humus or vermicompost will lead to similar results as fertilizing 100% with chemical nutrition. These results agree with the investigations carried out by Gómez et al. [34] because, with the applications of organic fertilizers (compost), the height of the plant increased by 48%. Nieto-Garibay et al. [35] report that with the use of 50 t·ha⁻¹ of compost, the habanero pepper crop reaches a greater plan height (73.2 cm). By the same token, differences between varieties were found, particularly V2 with a value of 64.5 cm followed by V1 with 62.2 cm. V3 plants had a shorter length of 55.7 cm. In the case of variables DPF and DEF, the supplementation of K played a determinant role in achieving good quality, and the biggest size was obtained in the plot supplied with T3. In factor B, there were also significant differences, whereby V1 showed the highest DPF (3.57 cm) and DEF (2.50 cm). The DEF was enhanced by the use of organic products, even though the treatments based on supplementation with organic K had similar results to the control (T5) (Table 3). Rodríguez et al., [36] used nutrient solutions from vermicompost in tomato production, but they did not find any difference in the thickness of the pericarp, nor in the equatorial and polar diameters of the fruit, highlighting the fact that organic fertilizers can be an option to obtaining high-quality fruits.

Regarding the interactions (A×B) for variable PPF, T3 and T5 on V3 showed superior results to the rest of the combinations, with values of 7.43 and 7.80 g, respectively. Regarding NFP, T2 on V2 showed the highest number of fruits, resulting in lower fruit weight, in contrast with T3 on V3, which showed the lowest number of fruits (118) but with higher weights (

Table 4. Mean comparison of the interaction factor A×B (fertilization×varieties) PPF: average fruit weight, NFP: number of fruits per plant, AFF: final foliar area of the plant, AFP: final height of the habanero chili pepper plant grown under greenhouse conditions.

	PPF (g)	NFP	AFF (m2)	AFP (cm)
T1V1	5.00 ± 0.30 efg	169 ± 9.6 bcd	1.24 ± 0.39 ab	62.4 ± 2.50 bcd
T1V2	5.23 ± 0.15 def	120 ± 8.6 f	1.37 ± 0.20 a	64.7 ± 1.95 bc
T1V3	5.40 ± 0.36 cde	189 ± 10.9 abc	0.79 ± 0.18 de	64.1 ± 2.62 bc
T2V1	5.26 ± 0.45 de	165 ± 9.8 cd	1.06 ± 0.30 bc	62.1 ± 1.23 bcd
T2V2	4.56 ± 0.37 fg	207 ± 7.5 a	0.71 ± 0.18 e	64.5 ± 2.01 bc
T2V3	6.30 ± 0.53 b	148 ± 10.7 def	0.76 ± 0.14 e	55.6 ± 3.32 e
T3V1	4.26 ± 0.51 g	202 ± 8.9 ab	0.59 ± 0.15 e	61.4 ± 2.84 bcd
T3V2	5.36 ± 0.62 cde	181 ± 9.4 abcd	0.68 ± 0.16 e	65.1 ± 2.12 bc
T3V3	7.43 ± 0.48 a	118 ± 8.2 f	0.73 ± 0.35 e	66.1 ± 3.01 b
T4V1	3.60 ± 0.36 h	188 ± 9.2 abc	0.69 ± 0.05 e	55.7 ± 3.63 e
T4V2	5.33 ± 0.32 de	167 ± 5.8 bcd	0.65 ± 0.05 e	58.3 ± 2.81 e
T4V3	6.00 ± 0.43 bc	160 ± 7.1 cde	0.64 ± 0.07 e	60.5 ± 3.87 cde
T5V1	5.66 ± 0.15 bcd	192 ± 8.7 abc	0.74 ± 0.11 e	63.7 ± 3.16 bcd
T5V2	6.23 ± 0.20 b	159 ± 4.2 cde	0.84 ± 0.14	58.7 ± 3.05 e
T5V3	7.80 ± 0.26 a	125 ± 6.2 ef	0.76 ± 0.09 e	72.0 ± 2.64 a

The means with the same letter within each column are equal (Tukey, α = 0.01). Media ± standard deviation of three repetitions. (T1) 240-200-120+50% of liquid humus; (T2) 240-200-180+25% liquid humus; (T3) 240-200-120+50% vermicompost; (T4) 240-200-180+25% vermicompost; (T5) 240-200-240 npk (control) and three varieties (1): Campeche, (2): Palenque, and (3): Jaguar.

).

AFF increased with T1, because within this treatment, varieties 1 and 2 were superior to the other interactions. On the other hand, for variable AFP, the control was superior to the other combinations with a value of 72.0 cm. This result implies that supplementation with K from organic sources has an effect on the aforementioned variable. Jayanthi et al. [37] mention that the positive effect of the combined application of chemical fertilizer with worm humus on the yield and its components in pepper and other crops shows the possibility of saving chemical fertilizer by substituting a part of it with worm humus without affecting performance. In similar studies with Solanum lycopersicum L., it was evidenced that the application of doses of 10.5 t ha⁻¹ of vermicompost + 20% NPK and 11.5 t·ha⁻¹ of vermicompost + 25% NPK caused an increase in the number of flowers and fruits per plant and the weight of the fruit, when compared with the 100% NPK treatments of the recommended dose and 3.50 t·ha⁻¹ of vermicompost [38].

The positive results obtained in yield with the application of the mixture of chemical fertilizer and worm humus (T4) compared to T1 (100% chemical fertilizer) may be related to the potential use of worm humus for ground amendments. Numerous researchers reported the beneficial effect of earthworm humus on different physiological processes and indicators of growth, as well as the development of pepper and other crops, such as the number of flowers emitted and fruit yield [39]. On the other hand, the addition of earthworm humus to the substrate mixture could influence some important changes in the physical and chemical properties of the soil, such as increased water retention capacity, cation exchange, availability of potassium, as well as other ions such as calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu), which have essential functions in the activity of numerous enzymes and are involved in essential biochemical and physiological processes for the growth and development of plants [37].

In the case of varieties, no significant yield differences were obtained between chemical and organic fertilization, regardless of the combination. Similar results were reported by Terada et al. [40], who examined the effects of soluble chemical and organic fertilizers on the quality and growth of a Micro-Tom tomato. They found that, for example, the number of leaves, yield, and mean weight per fruit did not differ significantly when the two types of fertilization were applied. Wu et al. [41] investigated the individual and combined effects of chemical and organic fertilizers on the growth and fruit yield of tomato cv. ‘Changfeng 5′ and determined that the total yield was slightly higher when the organic fertilizer was applied.

3.2. Components of the Biochemical-Antioxidant Quality

Solanaceae plants such as C. annum and C. chínense produce secondary metabolites that protect them from pathogens. Moreover, secondary metabolites can be of great importance in the human diet, like vitamin C, capsaicinoids, and carotenes. The European Scientific Committee on Food reports that the per-capita consumption in Europe and the United States is 1.5 mg; while in Mexico, India, and Thailand, people consume an average of 25–200 mg of capsaicin [42].

Table 5. Sum of the squares of the biochemical-antioxidant variables of habanero chili pepper in five nutritional treatments with K (A Factor) in three varieties (B Factor) grown under greenhouse conditions.

FV	GL	Capsaicin (CAPs: mg/Kg)	Vitamin C (VC: mg/100 g)	Carotenoids (CT: mg/100 g)	β-Carotenes (Βc: mg/mL)	Xanthophylls (Xa: mg/Kg)
Blocks	2	25,455 ns	102 ns	241 ns	1.6 ns	191 ns
Nutrition (A)	4	27,838 ns	5225 **	2097 **	19.3 **	242 ns
Error A	8	31,275 ns	80 ns	530 ns	1.5 ns	71.2 ns
Variety (B)	2	7174 ns	1453 **	3882 **	24.4 **	5639 **
Interaction (A×B)	6	14,796 ns	3147 **	25522 **	2.2 **	275 **
Error B	20	17,605	69	278	0.7	97.6
CV (%)		7.5	4.5	33.2	17.6	28.7

** Significant at p ≤ 0.05, 0.01, ns: not significant, CV (%): Coefficient of variation.

shows the mean squares from the analysis of the biochemical-antioxidant variables in habanero chili peppers, highlighting that no difference was found at any level in CAPs. However, the VC, CT, βC, and Xa variables showed higher variation because there were significant differences between factors A, B, and A×B.

The mean comparison shows that variable CAPs are not impacted by the use of K-supplementing organic products (

Table 6. Mean comparison of factor A and factor B of the biochemical-antioxidant variables of habanero chili peppers grown under greenhouse conditions.

	CAPs. mg/Kg	VC mg/100 g	CT mg/100 g	βC mg/mL	Xa mg/Kg
T1	1735 ± 46.7	198 ± 3.27 a	1.70 ± 0.03 ab	6.95 ± 0.57 a	36.4 ± 3.48
T2	1737 ± 35.6	149 ± 2.26 c	1.55 ± 0.04 b	5.36 ± 0.46 b	38.6 ± 2.61
T3	1730 ± 37.9	200 ± 3.67 a	1.29 ± 0.05 b	4.25 ± 0.38 bc	39.2 ± 3.54
T4	1799 ± 41.4	164 ± 4.07 b	2.33 ± 0.03 a	3.73 ± 0.56 c	30.7 ± 2.57
T5	1857± 45.9	199 ± 5.65 a	1.07 ± 0.02 b	3.31 ± 0.42 c	27.4 ± 2.08
Varieties
(1) Campeche	1749 ± 30.4	171 ± 7.9 b	2.17 ± 38.1 a	6.14 ± 0.66 a	56.8 ± 3.37 a
(2) Palenque	1773 ± 35.8	186 ± 5.8 a	1.40 ± 42.4 b	4.36 ± 0.57 b	24.8 ± 2.67 b
(3) Jaguar	1793 ± 29.8	189 ± 4.1 a	1.21 ± 48.8 b	3.66 ± 0.71 b	21.8 ± 3.02 b

The means with the same letter within each column are equal (Tukey, α = 0.05). Media ± standard deviation of three repetitions. CAs: Capsaicin, VC: Vitamin C, CT: total carotenoids, βC: β-carotenes; Xa: xanthophylls.

); however, there are numerous reports mentioning that capsaicin may vary. Kozukue et al. [43] and Broderick and Cooke. [44] assessed different capsaicinoids in Capsicum plants, using placenta, pericarp, and fruit seeds at several plant stages, and found differences in each one of them. Habanero chili pepper stood out for its highest total capsaicin content of 2260.9 µg/g, versus 18 µg/g found in a jalapeño chili pepper variety. The values obtained for capsaicin coincide with the range reported by Manju and Sreelathakumary [45], where the content of habanero chili pepper varies from 1.2 to 3.59% in fresh fruit weight. On the other hand, Eyal et al. [46] and Sanju et al. [47] report that capsaicin and hydro-capsaicin represent 90% of chili’s pungency, but these characteristics can vary depending on the planting density and the season of the year in which they are produced. Similar results to that research work were reported by Borges et al. [11], who concluded that the capsaicin content in habanero chili pepper fruits grown using different nutritional levels of N, P₂O₅, and K₂O (240-240-240, 120-120-120, and 000-000-000) did not show any significant response.

There were differences in the treatments assessed for VC. Treatments T3, T5, and T1 showed the best response with an average value of 199 mg/100 g of fresh weight, while treatments T2 and T4 showed a lower content with values of 149 and 164 mg/100 g of fresh weight. Therefore, by supplementing with 50% of organic K from liquid earthworm humus or vermicompost, the content of VC is the same as the results obtained by using 100% chemical fertilization. It is important to note that VC is a natural antioxidant that reduces the risk of immunological diseases, chronic-degenerative diseases such as cardiovascular disorders, and neurodegenerative diseases like Parkinson’s and Alzheimer’s, as well as cancer, diabetes, and cataracts [48].

For the variety factor (A), the highest value was obtained by the “Jaguar” and “Palenque” varieties, with an average value of 188 mg/100 g of fresh weight. These results coincide with the reports of Nuez et al. [49], emphasizing that the content of vitamin C is influenced by diverse agronomic factors such as open field or greenhouse production, irrigation, maturity stage of the fruit, nutrition, and cultivars.

Several differences were found in CT (p ≤ 0.05). T4 had the best response with 2.33 mg/100 g followed by T1 with 1.70 mg/100 g, indicating that the use of organic products improves the concentration of these antioxidant groups since the control (T5) showed the lowest value (1.07 mg/100 g). These results coincide with the report of Kopsell et al. [50], showing that the nutritional fertility regime can have an effect on the accumulation of plant carotenoids. The variety factor had higher values in “Campeche” than in “Palenque” and “Jaguar”, by 35.5 and 44.3%, respectively. Moreno et al. [51] worked with different types of chili peppers for the quantification of carotenoids, finding the highest quantity in a habanero chili pepper variety through fresh sampling.

In the assessment, βC was also improved by the addition of an organic K supplement. The best value was obtained at the plot irrigated with T1, showing a value of 6.95 mg/mL, which was 52.3% higher than the control (T5) (Table 6). The “Campeche” variety was superior (p ≤ 0.05) to the “Palenque” and “Jaguar” varieties by 28.8 and 40.3%, respectively. That value is 0.72 mg/mL higher than the value reported by Mínguez and Hornero [52], who reported 6.23 mg/mL of β-carotenes in the fruits of yellow peppers. When it comes to the consumption of fresh fruit, appearance is crucial, and color is the first parameter to be considered in the consumption decision. In pepper crops, the color is modified by organic agricultural practices, in contrast with traditional agriculture; however, this can be the result of many environmental components to which the plant is exposed [33]. For variable Xa, there were no significant differences between the types of K fertilization, but there were differences in the variety factor. The “Campeche” variety stood out with a value of 56.8 mg/Kg, while the “Palenque” and “Jaguar” varieties showed a lower content of 23.2 mg/Kg, representing a 59% difference with respect to the “Campeche” variety (Table 6).

These results are similar to those found by Rusu et al. [53] in the tomato crop, where they observed that biological fertilization was found to have a positive effect on the accumulation of polyphenols, lycopene, and β-carotene in tomato fruits, which suggests that it can be a viable alternative to chemical fertilization in terms of producing premium quality products. Additionally, organic fertilization increased the nutritional value of the tomatoes.

3.3. Interaction of Antioxidant Means

When Tukey’s means test (p ≤ 0.05) was applied to the interaction level, the results showed changes in VC. The combination of T5 with V3 achieved the highest value, which was similar to T4 with V2, and this combination in turn was 100% higher than the lowest value expressed by T4 with V1. These results confirm the findings of Duerte et al. [54], who stated that organic fertilization can help to increase the content of VC in citrus, although this will depend on the species and the cultivar. The lowest value was 110 mg/100 g, while the highest value was 227 mg/100 g of fresh fruit weight under essay conditions. Such values surpassed the reports of Manju and Sreelathakumary [45] who, while working with 32 genetic materials, found that the ascorbic acid content in habanero chili pepper varies from 61.8 to 136 mg/100 g of fresh fruit weight, as well as presenting good additive genetic parameters, thus establishing that Vitamin C can be improved through selection (

Table 7. Means comparison of the interaction A×B (fertilization×varieties) for the biochemical-antioxidant variables of habanero chili pepper grown under greenhouse conditions.

	VC (mg/100 g)	CT (mg/100 g)	βC (mg/mL)	Xa mg/Kg
T1V1	212 ± 2.78 bc	1.74 ± 0.05 bcd	8.83 ± 0.98 a	50.1 ± 3.58 b
T1V2	179 ± 2.90 ef	1.85 ± 0.02 bc	6.60 ± 0.70 bc	31.3 ± 3.85 cde
T1V3	203 ± 3.42 cd	1.49 ± 0.01 bcde	5.43 ± 1.00 de	27.7 ± 4.27 def
T2V1	123 ± 3.45 bcd	1.99 ± 0.05 b	7.63 ± 0.97 b	76.8 ± 2.56 a
T2V2	163 ± 2.76 gh	1.80 ± 0.05 bcd	4.43 ± 0.26 ef	19.0 ± 1.53 f
T2V3	160 ± 2.30 h	0.86 ± 0.02 e	4.06 ± 0.56 gh	20.1 ± 2.08 f
T3V1	213 ± 3.30 bc	1.08 ± 0.02 e	6.23 ± 0.47 cd	66.1 ± 3.20 a
T3V2	193 ± 3.66 de	1.33 ± 0.01 de	3.50 ± 0.36 i	32.7 ± 2.93 cd
T3V3	194 ± 3.15 de	1.45 ± 0.04 cde	3.03 ± 0.51 i	18.8 ± 3.78 f
T4V1	110 ± 3.72 j	4.69 ± 0.01 a	3.76 ± 0.61 hi	43.9 ± 2.06 bc
T4V2	221 ± 3.09 ab	1.17 ± 0.01 e	4.43 ± 0.37 ef	24.1 ± 2.13 f
T4V3	160 ± 2.99 h	1.14 ± 0.02 e	3.00 ± 0.17 i	23.9 ± 1.82 f
T5V1	195 ± 3.86 d	1.32 ± 0.03 e	4.23 ± 0.39 g	46.9 ± 2.72 b
T5V2	176 ± 3.77 fg	0.82 ± 0.01 e	2.90 ± 0.27 i	16.9 ± 1.55 f
T5V3	227 ± 2.90 a	1.07 ± 0.01 e	2.80 ± 0.40 i	18.4 ± 1.47 f

The means with the same letter within each column are equal (Tukey, α = 0.01). Media ± standard deviation of three repetitions. (T1) 240-200-120+50% of liquid humus; (T2) 240-200-180+25% liquid humus; (T3) 240-200-120+50% vermicompost; (T4) 240-200-180+25% vermicompost; (T5) 240-200-240npk (control) and three varieties (1): Campeche, (2): Palenque, and (3): Jaguar. Variables: VC: vitamin C, CT: total carotenoids, βC: β-carotenes, Xa: xanthophylls.

).

The carotenoids synthesis study is crucial for research because it can counteract biotic and abiotic limitations through the mediation of reactive oxygen species [55]. The means test (p ≤ 0.05) applied to the interaction factor (A×B) of the carotenoids variable showed that T4 with the “Campeche” variety was superior, achieving a value of 4.69 mg/100 g of fresh fruit weight. The control with the “Palenque” variety proved to be inferior (240-200–240 NPK). Such results are similar to what was found by Pérez et al. [56] while working with traditional, organic, and integrated agriculture. These authors assessed the total carotene content in pepper fruits, finding that the variable is superior under organic agriculture with a value of 3231 mg/Kg, followed by integrated agriculture with 2493 mg/Kg. Traditional agriculture obtained values of 1829 mg/Kg. It must be noted that β-carotenes are very important for the elimination of free radicals, both in plants and in humans. Therefore, under the conditions of this research work, such antioxidants were increased using organic fertilizers. In the means comparison test, T1 in combination with the “Campeche” genotype showed the highest content, with a value of 8.83 mg/mL. The lowest value was found in the control with the “Palenque” and “Campeche” genotypes, reaching 2.90 and 2.80 mg/mL, respectively. The Xanthophylls variable in the combination of nutritional treatments and varieties assessed showed significant differences (p ≤ 0.05), with treatment T2 standing out in combination with the “Campeche” variety and T3 with the same variety, with values of 76.8 and 66.1 mg/Kg, respectively, while the lowest values varied. The control in combination with the “Palenque” and “Jaguar” varieties reached values of 16.9 and 18.4 mg/Kg, respectively (Table 7).

Rusu et al. [53] observed that the content of total polyphenolic compounds, lycopene, and β-carotene are improved by using varieties and fertilizers in tomatoes. In tomatoes, regardless of cultivar, ‘Cristal’ obtained higher values by up to 48% compared to chemical fertilization, and ‘Siriana’ by up to 32% compared to the same fertilization. Ayuso-Yuste et al. [57] showed that the traditional tomato varieties tested proved richer in lycopene and β-carotene than commercial ones in the last ripening stages, as seen in this investigation of the habanero chili pepper with the “Campeche” variety.

4. Conclusions

The use of organic fertilizers is an option for K supplementation since they increase the antioxidant quality of habanero chili peppers under greenhouse conditions.

The source of nutrition has a strong influence on the yield and antioxidant quality of chili fruits since by supplementing K with organic fertilizers, yields similar to a chemical dose can be obtained, while the biochemical-antioxidant quality of fruit is improved. In the case of capsaicin, it was not modified by any level of study. On the other hand, total carotenoids, vitamin C, β-carotenes, and xanthophylls are improved by organic nutrition. Moreover, it was found that different varieties of habanero chili pepper respond differently to the use of organic nutrition since they do not influence yield parameters, but they do influence the antioxidant quality, with the Campeche variety being the one with the highest content of total carotenoid, β-carotenes, and xanthophylls. It was also observed that by supplementing the % of K from liquid earthworm humus and vermicompost, it has a positive effect on the leaf area and height of the plant, as well as on the number of fruits and polar and equatorial diameter. Therefore, fruits of good size with commercial value were obtained, which suggests that using organic fertilizers may be a viable alternative to 100% chemical fertilization in terms of greenhouse production of top-quality habanero chili peppers.

In addition, the use of organic fertilizers for K supplementation increased the nutritional value of habanero chili peppers, providing an opportunity for growers to use sustainable organic fertilizers on a large scale in combination with chemical ones. It was found that 100% chemical fertilization increases yield; however, most of the fruits presented a size without commercial value.

Finally, this study emphasizes the need for more research on the efficiency of different doses of organic fertilizers, analyzing more nutritional elements and their interaction with the components of worm castings, whether liquid or solid, to determine their impact on the commercial improvement of cultivation of habanero chili pepper. This will help optimize the use of these types of fertilization and ensure that growers can produce safe and high-quality products that satisfy the growing demand for healthier food options and, on the other hand, represent an economical, ecological, and sustainable alternative in the production of habanero chili pepper.