Capsicum chinense Jacq. Response to Pyrolysis-Derived Amendments and Sustainable Fertilizers in Containerized Greenhouse Systems

Abstract

The controlled-environment cultivation of Capsicum chinense Jacq. is a high-value but input-sensitive system, where optimizing fertilization management practices (FMPs) is essential for maximizing yield and fruit quality. We tested the hypothesis that targeted FMPs—biochar, wood vinegar, and Cropmax—enhance vegetative growth, pigment accumulation, and reproductive performance in three genotypes (‘Carolina Reaper’, ‘Trinidad Scorpion’, and ‘Habanero Chocolate’) under containerized greenhouse conditions. Across biometric, pigment, and yield metrics, biochar–Cropmax combinations produced the strongest responses, increasing plant height by up to 22%, leaf number by 51%, and chlorophyll content index by 36% over controls. Yield gains were substantial: ‘Trinidad Scorpion’ reached 301.79 g plant⁻¹ (+46%), ‘Habanero Chocolate’ 142.58 g (+32%), and ‘Carolina Reaper’ showed marked improvement in mean fruit mass (5.58 g). Biochar also elevated dry matter content to 10.31% and soluble solids to 8.35 °Brix. These results demonstrate that integrating biochar-based FMPs can significantly intensify C. chinense greenhouse production while aligning with sustainable horticultural objectives.

1. Introduction

Global demand for sustainable food production continues to pressure agricultural systems to enhance yields while preserving environmental integrity [1,2]. Capsicum chinense Jacq., including the high-value genotypes ‘Carolina Reaper,’ ‘Trinidad Scorpion,’ and ‘Habanero Chocolate,’ is prized for its pungency, distinctive flavor, and rich bioactive compound profile, such as capsaicin and vitamins [3,4], supporting culinary, pharmacological, and industrial markets [5]. The ‘Carolina Reaper,’ distinguished by its extremely high Scoville heat rating [6], is a key subject in capsaicinoid pharmacology [7,8] and food innovation [9]. The ‘Trinidad Scorpion’ (>1 million SHU) serves as a model for studying capsaicinoid biosynthetic pathways and sensory perception [10,11,12]. The ‘Habanero Chocolate,’ with moderate pungency, complex flavor, and unique chocolate-brown pigmentation, provides breeding potential for improving phenotypic traits and nutritional composition [13].

Optimizing growth, yield, and seed production in C. chinense Jacq. under greenhouse conditions remains challenging, particularly when balancing high productivity with sustainable resource use [14]. While prior studies have explored the effects of biochar and wood vinegar in field conditions, limited data exist on their efficacy under controlled, protected cultivation systems where water, nutrients, and environmental factors can be precisely managed. Moreover, the interaction between genotype and fertilization strategies in determining physiological, reproductive, and fruit quality traits remains insufficiently elucidated, representing a key gap in the literature.

Biochar, a pyrolysis-derived carbon-rich soil amendment, has demonstrated benefits for soil structure, nutrient retention, water-holding capacity, and carbon sequestration [15,16,17,18], while also influencing microbial community dynamics and nutrient cycling [19,20]. Its application has been associated with enhanced root development, stress resilience, and nutrient uptake across various crops [21,22]. Wood vinegar, another pyrolysis by-product, acts as a natural biostimulant, improving root growth, chlorophyll content, photosynthetic efficiency [23,24], and reducing pest and disease incidence [25,26,27,28]. Cropmax, a foliar fertilizer containing amino acids, micronutrients, and natural plant hormones, further supports nutrient assimilation, vegetative vigor, and yield potential [29]. The synergistic combination of these amendments represents a promising, environmentally sustainable approach to enhance growth, productivity, and fruit quality in greenhouse-grown C. chinense cultivars.

The present study aims to evaluate the individual and combined effects of biochar, wood vinegar, and Cropmax on vegetative growth, pigment accumulation, fruit yield, and seed viability in three C. chinense genotypes under controlled greenhouse cultivation. We hypothesize that targeted FMPs incorporating biochar, with or without wood vinegar and/or Cropmax, will significantly enhance biometric, physiological, and reproductive traits, with genotype-specific variations modulating the magnitude of the response. The outcomes are intended to inform sustainable, high-efficiency horticultural protocols for premium chili pepper production [30].

2. Materials and Methods

2.1. Experimental Site and Conditions

The study was conducted during the 2023 and 2024 growing seasons at the Vegetable Research and Development Station, Bacău, Romania (46°34′ N, 26°55′ E; 165 m a.s.l.). The site has a temperate continental climate, with a long-term mean annual temperature of 9.8 °C and precipitation of 550–600 mm. Experiments were performed in an Almería-type greenhouse covered with UV-stabilized polyethylene film. Inside, day/night temperatures were maintained at 25–30 °C/18–20 °C, a relative humidity at 60–75%, and photoperiod under natural light supplemented to a minimum of 14 h. Environmental parameters were monitored continuously through all phenological stages.

2.2. Plant Material

Three Capsicum chinense Jacq. genotypes—‘Carolina Reaper’ (CR), ‘Trinidad Scorpion’ (TS), and ‘Habanero Chocolate’ (HC)—were selected to represent a spectrum of morphological, physiological, and heat-level traits. These genotypes differ in plant architecture (Figure 1), capsaicinoid content, and adaptation to greenhouse conditions, allowing assessment of fertilization responses across contrasting genetic backgrounds.

2.3. Experimental Design

A randomized complete block design (RCBD) with three replications was used (Figure 2). Four FMPs were tested:

• Biochar + Cropmax (B_C).
• Wood vinegar + Cropmax (WV_C).
• Cropmax as a standalone application (C).
• Untreated control (Unt.).

Each genotype received all FMPs, with three plants per treatment, resulting in 12 experimental units per replication and a total of 108 pots. Plants were arranged randomly within each block to minimize microclimatic bias. All experimental units were physically separated, and precautions were implemented to prevent cross-contamination between treatments, particularly during pyroligneous extract applications.

Applications of the fertilization products were conducted using dedicated equipment for each treatment. Protective barriers and sequential application protocols were employed to eliminate drift between adjacent plants. Sampling for leaf number, branch count, and reproductive traits was performed in the second dekad of June and July, corresponding to key vegetative and reproductive stages. These measures ensured accurate, reproducible data while maintaining treatment integrity throughout the study.

2.4. Crop Establishment and Management

Seeds were sown in early February in 70-cell trays filled with Rekyva Remix 1 peat (pH 5.5–6.5, EC 0.5–1 mS cm⁻¹, NPK ≤ 1 kg m⁻³, fine/medium fraction). At 55–60 days, seedlings were transplanted into 10 L pots containing 2 kg of Rekyva Remix 2 peat (pH 5.5–6.5, EC 1–2 mS cm⁻¹, NPK ≤ 2 kg m⁻³, medium/coarse fraction). Pots were uniformly spaced to avoid competition. Drip irrigation maintained soil moisture near field capacity; frequency averaged 2–3 irrigations per week depending on evapotranspiration demand. Pest and disease control was applied preventively.

2.5. Nutrient Management Regimes and Application Parameters

FMPs were applied according to the manufacturer’s recommendations (

Table 1. Fertilization Strategy and Treatment Details.

Variant	Nutrient Input Design	No of Treatments	Dosage/Concentration	Method of Use	Substance Descriptions	Origin
V1	Biochar	1	10 g plant−1	uniform deposition at soil interface, shallowly incorporated at transplanting	bulk density 276 kg m−3, BET 557.76 m2 g−1, 91.3% C, 0.66% N, 0.25% K, pH 8.76;	Gekka Biochar/Explocom GK SRL—Romania
	Cropmax	2	0.25%	foliar spray at transplanting and 1 month later	pH 7.00; 17 amino acids with reported values (‰, g/L): asparagine 26, glutamine 17, alanine 12, valine 6, isoleucine 4, leucine 5, serine 4, threonine 4, proline 4, glycine 5, phenylalanine 3, tyrosine 3, lysine 3, histidine 1, arginine 1, methionine 1, cystine 1; vitamins and antioxidants including ascorbic acid, tocopherols, and carotenoids (qualitative); macronutrients N 0.20%, P 0.40%, K 0.02%; micronutrients Fe 0.0220%, Mg 0.0550%, Zn 0.0049%, Mn 0.0054%, Cu 0.0035%, B 0.0070%, Ca 0.0010%, Mo 0.0010%, Co 0.0010%, Ni 0.0010%; auxins, cytokinins, and gibberellins (qualitatively confirmed, concentrations proprietary)	Holland Farming B.V.—The Netherlands
V2	Wood Vinegar	2	0.5%	foliar spray twice during growth	14 g L−1 C, 3.37 mg dm−3 N, pH 4.24, contains acetic and pyroligneous acids	Gekka Biochar/Explocom GK SRL—Romania
	Cropmax	2	0.25%	as in V1	as in V1	as in V1
V3	Cropmax	2	0.25%	foliar spray twice during growth	as in V1	as in V1
V4	Untreated (Control)	-	-	-	-	-

). Biochar was administered as a single soil amendment at a rate of 10 g per plant at transplanting, aimed at improving soil structural properties and enhancing nutrient retention. Foliar applications of Cropmax (0.25%) and wood vinegar (0.5%) were delivered twice, first at transplanting and subsequently one month later, with each application standardized to 50 mL per plant. Owing to the differing concentrations of the solutions, the cumulative active compound delivered per plant amounted to 0.25 g for Cropmax (0.125 g per application) and 0.50 g for wood vinegar (0.25 g per application), thereby ensuring precise quantification of nutrient and bioactive inputs. An 8 L Grünman hand-operated sprayer, produced by Zhejiang Menghua Sprayer Co., Ltd. (Zhejiang, China), was used for foliar applications, equipped with an adjustable nozzle, a safety valve, and a locking mechanism to prevent accidental spraying, ensuring precise and uniform distribution of the treatment solutions.

2.6. Metrics

Growth parameters—plant height, collar diameter, leaf and branch number—were recorded in June and July. Pigment indices (anthocyanins, chlorophyll content index) were measured mid-season. At harvest, yield components (fruit number, mean fruit weight, total yield per plant, fruit dimensions, fruit form index—height/width ratio, peduncle weight) and seed traits (seed count, seed weight, seedless pulp weight) were determined. Fruit quality was assessed via dry matter content (oven-dried at 103 ± 2 °C to constant weight), water content, and total soluble solids (°Brix, handheld refractometer, AOAC 932.12).

Chlorophyll and anthocyanin contents

Chlorophyll and anthocyanin contents were non-destructively quantified using two optical chlorophyll meters (CCM-200 Plus and ACM-200 Plus; Opti-Sciences, Hudson, NH, USA). Measurements were performed by gently positioning the sensor clamp on the adaxial surface of fully expanded leaves, avoiding the midrib, to ensure representative sampling of the photosynthetically active tissue. Readings were taken under stable ambient conditions (clear sky, ~25 °C) and at a consistent diurnal time to minimize variation attributable to circadian pigment fluctuations.

The chlorophyll concentration index (CCI) and anthocyanin content index (ACI) generated by the instruments provide dimensionless proxies proportional to the in vivo pigment concentration, derived from dual-wavelength optical absorbance.

Dry matter and water content

Approximately 5.00 ± 0.01 g of fresh, homogenized, seed-free pericarp tissue was oven-dried (forced-air convection, Biobase, Jinan, China) at 103 ± 2 °C for 24 h, or until a constant mass was achieved, in accordance with AOAC Official Method 925.10. Samples were cooled to ambient temperature in a desiccator prior to weighing to avoid moisture reabsorption. Dry matter (DM) was expressed as a percentage of the initial fresh weight. Water content (W) was subsequently calculated as:

W% = 100% − DM%

Total soluble solids (TSS)

Total soluble solids were determined from homogenized juice obtained by gentle pressing of fresh chili pepper fruits, avoiding seed rupture to minimize oil interference. Measurements were conducted using a calibrated, high-precision digital refractometer (±0.1 °Brix accuracy), following AOAC Method 932.12 [31]. The refractometer prism was rinsed with distilled water and dried between readings to prevent carryover effects. Data were expressed in degrees Brix (°Bx) at 20 °C, with automatic temperature compensation applied where available. All determinations were performed in duplicate per sample, with three independent biological replicates per treatment. TSS serves as a proxy for fruit sugar concentration and is closely linked to flavor intensity and consumer acceptance in Capsicum spp.

2.7. Statistical Analysis

The effects of each FMP, genotype, and their interaction were assessed through analysis of variance (ANOVA), followed by Duncan’s multiple range test for post hoc comparisons where appropriate. A significance level of p < 0.05 was applied to evaluate the individual and combined effects of FMPs and genotypes on plant growth, yield, and quality (SPSS v21, IBM Corp., Armonk, NY, USA). This design ensured the independence of experimental units and enhanced the reproducibility of the findings across the growing seasons.

3. Results

3.1. Vegetative Growth Parameters

Both genotype and FMP significantly influenced vegetative growth metrics, such as plant height, stem diameter, leaf number, and branch count, at 30 and 60 days post-transplanting (

Table 2. Growth and Development Metrics of Different Pepper Genotypes and Fertilization Treatments.

Variant	Total Height (cm)		Stem Collar Diameter (mm)		No of Branches·Plant−1		No of Leaves Plant−1		No of Flowers·Plant−1
	30 Days	60 Days	30 Days	60 Days	30 Days	60 Days	30 Days	60 Days	30 Days	60 Days
Cultivar
CR	13.43 ± 1.86 a	44.17 ± 3.66 a	4.53 ± 0.74 a	9.22 ± 1.58 b	-	4.00 ± 1.04 a	15.83 ± 1.70 a	78.50 ± 12.42 a	0.42 ± 0.79 b	70.25 ± 24.60 a
TS	9.40 ± 1.64 b	38.83 ± 6.18 b	3.73 ± 0.64 b	10.27 ± 0.96 a	-	4.17 ± 0.39 a	16.42 ± 1.00 a	84.67 ± 18.41 a	2.00 ± 1.91 a	79.33 ± 14.37 a
HC	12.79 ± 1.27 a	42.92 ± 5.81 ab	4.32 ± 0.80 ab	8.84 ± 0.95 b	-	2.67 ± 0.98 b	13.08 ± 2.15 b	74.17 ± 13.90 a	0.00 b	40.58 ± 15.15 b
Fertilization type
B_C	13.13 ± 1.83 a	46.11 ± 5.81 a	4.37 ± 0.71 a	9.40 ± 1.67 a	-	3.67 ± 1.32 a	15.11 ± 1.27 a	88.22 ± 15.99 a	0.33 ± 0.71 a	59.89 ± 23.48 a
WV_C	12.42 ± 2.66 ab	42.67 ± 3.61 ab	4.19 ± 0.63 a	9.41 ± 1.44 a	-	3.78 ± 0.67 a	15.00 ± 2.50 a	82.11 ± 15.33 ab	0.89 ± 1.62 a	62.00 ± 26.66 a
C	11.37 ± 2.17 ab	40.33 ± 4.90 b	4.70 ± 0.91 a	9.54 ± 0.79 a	-	3.67 ± 1.00 a	14.89 ± 2.52 a	75.78 ± 10.84 ab	1.22 ± 1.99 a	63.11 ± 22.00 a
Unt.	10.57 ± 2.28 b	38.78 ± 5.95 b	3.52 ± 0.39 b	9.44 ± 1.45 a		3.33 ± 1.32 a	15.44 ± 2.60 a	70.33 ± 14.71 b	0.78 ± 1.30 a	68.56 ± 29.52 a

CR—Carolina Reaper; TS—Trinidad Scorpion; HC—Habanero Chocolate; B_C—Biochar + Cropmax; WV_C—WoodVinegar + Cropmax; C—Cropmax; Unt.—Untreated. Within each column and within each experimental factor, different letters mean fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

). Genotypes differed in growth patterns: CR was taller than TS at 30 days and HC at 60 days. However, TS had the largest stem diameter at 60 days. TS also produced more flowers than HC by 60 days. Fertilization also affected growth; at 60 days, plants fertilized with B_C were tallest, outperforming C and Unt. variants. WV_Cropmax resulted in intermediate heights and the most leaves at 60 days. Stem diameter differences due to treatments were mostly insignificant, though the untreated group showed reduced diameter at 30 days. These findings suggest a complex interaction between genetics and environmental factors like nutrient availability in early plant development.

3.1.1. Plant Height

Plant height exhibited pronounced genotype- and treatment-specific responses. In CR, all fertilized treatments surpassed the untreated control (CR4) at both measurement intervals. By 60 days, CR1 reached 45.00 ± 3.61 cm, CR2 45.67 ± 1.50 cm, and CR3 44.67 ± 2.30 cm, compared to 41.33 ± 6.0 cm for CR4, representing increases of 8.9%, 10.4%, and 8.1%, respectively. In TS, TS1 and TS2 attained 43.67 ± 8.3 cm and 42.67 ± 3.2 cm, exceeding TS3 (34.67 ± 2.31 cm) and TS4 (34.33 ± 3.21 cm), corresponding to ~27–28% increases over control. For HC, HC1 displayed the greatest height at 49.67 ± 4.7 cm by 60 days, exceeding the control (40.67 ± 7.0 cm) by ~22%, illustrating the pronounced efficacy of biochar-mediated FMPs in late-stage vegetative growth.

3.1.2. Collar Diameter

Stem collar diameter increased significantly under fertilization, with both genotype and treatment effects evident. In CR, initial diameters at 30 days ranged 3.73–5.08 mm, with final measurements at 60 days spanning 7.92 mm (CR1) to 9.92 mm (CR4, control). This reflects both genotype-specific growth dynamics and treatment-specific modulation, with CR1 exhibiting a 20% reduction relative to the control. In TS, TS1 achieved 11.30 ± 0.26 mm at 60 days, representing a ~22% increase relative to TS3 (9.25 ± 0.42 mm). In HC, HC3 and HC1 attained 9.64 ± 1.09 mm and, respectively, 8.97 ± 1.38 mm, exceeding HC4 (8.20 ± 0.31 mm) by 18 and 9%, whereas HC2 and showed moderate improvements.

3.1.3. Branch Count per Plant

Branching exhibited both treatment- and genotype-specific patterns. In CR, CR3 showed maximal branching, averaging 4.33 ± 0.58 branches per plant, corresponding to ~8% higher than control (CR4, 4.00 ± 1.73). CR1 and CR2 averaged 3.67 ± 1.53 and 4.00 ± 0.00, respectively. TS displayed limited variability in branching, with TS1 exhibiting a marked enhancement (~17%) relative to the remaining variants, which consistently averaged four branches per plant. HC, with inherently lower branching capacity, demonstrated maximal branching under HC2 (3.33 ± 1.15 branches), followed by HC1 and HC3, while HC4 (control) averaged 2.00 ± 0.00 branches, representing a 33% to 67% reduction relative to optimized fertilization.

3.1.4. Leaf Count per Plant

Leaf production exhibited significant genotype- and treatment-dependent variation. In CR, 30-day counts ranged from 15.00 ± 1.15 (CR1) to 16.33 ± 1.53 (CR3 and CR4). By 60 days, CR1 reached 79.00 ± 6.93, CR2 80.67 ± 7.23, CR3 80.67 ± 4.16, and CR4 73.67 ± 26.10, corresponding to ~7–9% increases over control, indicating moderate foliar enhancement with biochar- and wood vinegar-based fertilization. In TS, 30-day counts were similar across treatments (16.00–17.33 leaves). By 60 days, TS1 reached 108.00 ± 9.54 leaves, ~51% above control (TS4), TS2 91.00 ± 7.55 (~28% increase), while TS3 showed a slight reduction (~−4%), demonstrating a pronounced biochar effect on foliar proliferation. For HC, early counts ranged 12.00–14.33 leaves. By 60 days, HC1 reached 77.67 ± 1.53, HC2 74.67 ± 25.01, HC3 78.33 ± 18.25, and HC4 (control) 66.00 ± 7.00, representing ~13–19% increases over control, highlighting the synergistic effect of biochar- and Cropmax-based fertilization on leaf production in genotypes with lower inherent foliar density.

3.1.5. Reproductive Development

Flowering phenology demonstrated clear genotype- and treatment-specific patterns (

Table 3. Morphological Traits of Carolina Reaper, Trinidad Scorpion, and Habanero Chocolate Under Different Fertilization Regimes.

Variant	Total Height (cm)		Stem Collar Diameter (mm)		No of Branches·Plant−1		No of Leaves·Plant−1		No of Flowers·Plant−1
	30 Days	60 Days	30 Days	60 Days	30 Days	60 Days	30 Days	60 Days	30 Days	60 Days
CR1	14.50 ± 0.87 a	45.00 ± 3.61 ab	4.78 ± 0.52 ab	7.92 ± 0.35 c	-	3.67 ± 1.53 abc	15.00 ± 1.15 abcd	79.00 ± 6.93 b	0.67 ± 1.15 b	52.67 ± 9.87 ab
CR2	14.87 ± 0.23 a	45.67 ± 1.5 ab	4.53 ± 0.64 abc	9.33 ± 2.33 abc	-	4.00 ± 0.00 ab	15.67 ± 2.89 abc	80.67 ± 7.23 b	0.33 ± 0.58 b	64.33 ± 27.10 ab
CR3	12.67 ± 1.53 ab	44.67 ± 2.3 ab	5.08 ± 0.77 a	9.72 ± 0.96 abc	-	4.33 ± 0.58 ab	16.33 ± 1.53 ab	80.67 ± 4.16 b	0.67 ± 1.15 b	80.00 ± 24.98 a
CR4	11.67 ± 2.36 b	41.33 ± 6.0 abc	3.73 ± 0.50 bc	9.92 ± 1.89 abc	-	4.00 ± 1.73 ab	16.33 ± 1.53 ab	73.67 ± 26.10 b	0.00 b	84.00 ± 30.51 a
TS1	11.23 ± 1.66 bc	43.67 ± 8.3 ab	3.88 ± 0.81 abc	11.30 ± 0.26 a	-	4.67 ± 0.58 a	16.00 ± 1.00 abc	108.00 ± 9.54 a	0.33 ± 0.58 b	83.00 ± 17.58 a
TS2	9.10 ± 0.95 cd	42.67 ± 3.2 abc	3.74 ± 0.46 bc	10.33 ± 0.63 ab	-	4.00 ± 0.00 ab	16.00 ± 1.00 abc	91.00 ± 7.55 ab	2.33 ± 2.31 ab	86.33 ± 7.02 a
TS3	8.97 ± 1.53 cd	34.67 ± 2.31 c	3.98 ± 0.97 abc	9.25 ± 0.42 abc	-	4.00 ± 0.00 ab	16.33 ± 1.15 ab	68.33 ± 9.07 b	3.00 ± 2.65 a	65.33 ± 14.57 ab
TS4	8.30 ± 1.27 d	34.33 ± 3.21 c	3.33 ± 0.25 c	10.21 ± 1.12 ab	-	4.00 ± 0.00 ab	17.33 ± 0.58 a	71.33 ± 9.45 b	2.33 ± 1.15 ab	82.67 ± 12.70 a
HC1	13.67 ± 1.15 ab	49.67 ± 4.7 a	4.45 ± 0.70 abc	8.97 ± 1.38 bc	-	2.67 ± 1.15 bc	14.33 ± 1.53 abcd	77.67 ± 1.53 b	0.00 b	44.00 ± 23.26 b
HC2	13.30 ± 0.82 ab	39.67 ± 3.5 bc	4.30 ± 0.68 abc	8.56 ± 0.26 bc	-	3.33 ± 1.15 abc	13.33 ± 3.06 bcd	74.67 ± 25.01 b	0.00 b	35.33 ± 9.87 b
HC3	12.47 ± 1.08 ab	41.67 ± 2.5 abc	5.04 ± 0.78 a	9.64 ± 1.09 abc	-	2.67 ± 1.15 bc	12.00 ± 1.73 d	78.33 ± 18.25 b	0.00 b	44.00 ± 10.82 b
HC4	11.73 ± 1.50 b	40.67 ± 7.0 bc	3.50 ± 0.40 c	8.20 ± 0.31 bc	-	2.00 ± 0.00 c	12.67 ± 2.52 cd	66.00 ± 7.00 b	0.00 b	39.00 ± 20.66 b

CR1—Carolina Reaper × Biochar + Cropmax; CR2—Carolina Reaper × WoodVinegar + Cropmax; CR3—Carolina Reaper × Cropmax; CR4—Carolina Reaper (Untreated); TS1—Trinidad Scorpion × Biochar × Cropmax; TS2—Trinidad Scorpion + WoodVinegar × Cropmax; TS3—Trinidad Scorpion + Cropmax; TS3—Trinidad Scorpion (Untreated); HC1—Habanero Chocolate × Biochar + Cropmax; HC2—Habanero Chocolate × WoodVinegar + Cropmax; HC3—Habanero Chocolate × Cropmax; HC4—Habanero Chocolate (Untreated). Within each column and within each experimental factor, different letters mean genotype and fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

). In CR variants at 60 days, CR1 produced 52.67 ± 9.87 flowers per plant, CR2 64.33 ± 27.10, CR3 80.00 ± 24.98, and CR4 84.00 ± 30.51. Relative to the control (CR4), CR1 and CR2 were ~59% and 31% lower, respectively, whereas CR3 was slightly lower (5%), indicating that while fertilization promoted reproductive development, absolute flower production was largely genotype-driven. For TS, TS1 reached 83.00 ± 17.58 flowers per plant, TS2 86.33 ± 7.02, TS3 65.33 ± 14.57, and TS4 (control) 82.67 ± 12.70. TS1 and TS2 exhibited ~0.4% increase and 4.4% increase, respectively, relative to the control, whereas TS3 was ~21% lower, highlighting the pronounced effect of biochar and wood vinegar amendments in sustaining flowering in this genotype. In HC, HC1 and HC3 produced 44.00 ± 23.26 and 44.00 ± 10.82 flowers per plant, HC2 35.33 ± 9.87, and HC4 (control) 39.00 ± 20.66. Relative to the control, HC1 and HC3 were ~12.8% higher, and HC2 was ~10% lower, indicating that biochar-enhanced fertilization yielded the most pronounced reproductive stimulation in this genotype. These results demonstrate that flowering at 60 days is genotype-dependent, with biochar- and wood vinegar-based FMPs generally maintaining or slightly enhancing flower production relative to controls, whereas C variants produced intermediate effects.

3.2. Anthocyanin and Chlorophyll Pigment Content

3.2.1. Anthocyanin Pigment Content

Anthocyanin Concentration Index (ACI) varied significantly among C. chinense Jacq. cultivars at both 30 and 60 days after planting. At 30 days, TS exhibited the highest ACI, whereas at 60 days, HC surpassed CR in anthocyanin accumulation (Figure 3).

FMPs influenced ACI, with the B_C treatment producing the greatest increase by 60 days (Figure 4). In contrast, WV_C and C variants resulted in lower ACI levels, while untreated plants showed moderate anthocyanin content. No significant differences among fertilization treatments were observed at 30 days, indicating that early anthocyanin accumulation was largely cultivar-dependent.

Both cultivar and fertilization exerted significant effects on ACI, with biochar-based treatments consistently enhancing anthocyanin accumulation, suggesting a synergistic interaction between organic amendments and foliar fertilizers.

Within CR genotype, mid-June measurements showed the highest ACI in CR3 (C variant), followed by CR2 (WV_C), while unfertilized plants recorded an ACI of 5.12. By mid-July, all treatments exhibited increases, with CR1 (B_C) showing the most pronounced enhancement.

TS generally had higher baseline ACI than CR. TS1 (B_C) achieved the highest mid-June values. By late July, the TS1 variant reached an ACI of 8.70, representing a 29% increase, highlighting biochar’s effectiveness. TS2 (WV_C) increased moderately from 6.03 to 7.10, whereas TS3 (C variant) decreased from 6.38 to 5.93, indicating a comparatively lower response. The control variant (TS4) increased from 6.02 to 7.37, reflecting TS’s inherent anthocyanin potential.

HC displayed a distinctive response, with HC1 (B_C) increasing from 4.57 in June to 9.90 in July, the highest recorded ACI, demonstrating strong synergy between biochar and foliar fertilization, through enhanced nutrient assimilation and metabolic activation [32]. Other treatments also showed notable gains: HC2 (WV_C) increased from 4.38 to 8.07, HC3 (C variant) from 5.06 to 7.83, and the control (HC4) from 4.73 to 8.17, indicating an inherently strong anthocyanin accumulation capacity in this genotype.

Overall, biochar-based FMPs consistently promoted anthocyanin accumulation across all genotypes, with the magnitude of response being genotype-specific, highlighting the potential for targeted nutrient and organic amendment strategies to enhance secondary metabolite production in C. chinense Jacq. (Figure 5).

3.2.2. Chlorophyll Pigment Content

The Chlorophyll Concentration Index (CCI) varied significantly among cultivars (Figure 6) and fertilization treatments (Figure 7) at both 30 and 60 days after application. TS consistently exhibited the highest CCI values, surpassing CR and HC, suggesting this cultivar has a greater capacity for chlorophyll retention or synthesis under the experimental conditions.

Fertilization treatments significantly influenced CCI. At 30 days, no significant differences were observed among B_C, WV_C, C, or the untreated control. By 60 days, B_C significantly increased CCI compared to WV_C, C, and the control, highlighting its superior efficacy in enhancing chlorophyll during later growth stages (Figure 7).

In CR, CCI at 30 days ranged from 10.94 to 15.27. The CR2 variant, treated with WV_C, showed higher CCI, suggesting improved chlorophyll synthesis due to the combined effect of wood vinegar and foliar fertilization, while CR1 exhibited lower initial values. By the second measurement, CCI increased across all variants, with CR1 (B_C) reaching 31.37, demonstrating a stronger response to biochar over time (Figure 8).

TS variants had substantially higher CCI values. TS1 (B_C) reached 49.82 at 60 days, indicating biochar’s potential to enhance chlorophyll content and photosynthetic efficiency. TS2 and TS3 recorded 36.58 and 32.02, respectively, showing positive fertilization effects, though the magnitude varied among variants.

HC exhibited the lowest CCI values, with HC1 recording 10.42 at 30 days. Fertilization treatments were less effective for this cultivar, possibly due to genetic limitations in chlorophyll synthesis or lower responsiveness to applied amendments. By 60 days, HC1 increased to 35.24 but remained below TS levels, suggesting the need for optimized fertilization strategies for this genotype.

Overall, both genotype and fertilization significantly influenced chlorophyll content. The observed CCI differences among cultivars highlight the importance of customized fertilization strategies to optimize chlorophyll synthesis and photosynthetic performance. Further investigation into genotype–fertilizer interactions is recommended to enhance growth and productivity in these C. chinense Jacq. varieties.

3.3. Fruit Yield and Morphometrics

Table 4. Comparative Analysis of Fruit Morphological Traits, Yield Components, and Peduncle Characteristics Across Pepper Genotypes and Fertilization Regimens.

Variant	No of Fruits/Plant	Average Fruit Weight (g)	Yield/Plant (g)	Fruit Width (mm)	Fruit Height (mm)	Fruit Form Index (H/W)	Peduncle Weight (g)
Cultivar
CR	16.25 ± 2.26 b	4.72 ± 1.77 c	77.85 ± 33.86 b	25.15 ± 6.10 b	40.52 ± 7.82 a	1.68 ± 0.43 a	0.12 ± 0.05 a
TS	20.33 ± 7.34 a	8.31 ± 1.46 a	174.34 ± 87.68 a	30.28 ± 2.84 a	36.88 ± 4.24 a	1.22 ± 0.11 b	0.16 ± 0.05 a
HC	15.00 ± 3.51 b	6.86 ± 1.32 b	104.12 ± 34.1 b	29.46 ± 5.08 a	42.42 ± 6.76 a	1.46 ± 0.22 a	0.11 ± 0.05 a
Fertilization type
B_C	22.22 ± 7.12 a	7.92 ± 2.13 a	183.22 ± 98.0 a	32.88 ± 5.00 a	43.43 ± 5.27 a	1.34 ± 0.21 a	0.17 ± 0.04 a
WV_C	17.56 ± 2.74 b	6.61 ± 2.40 ab	117.33 ± 49.64 b	26.63 ± 5.14 b	36.37 ± 4.75 b	1.42 ± 0.40a	0.14 ± 0.05 ab
C	15.22 ± 1.99 b	6.34 ± 1.73 ab	96.03 ± 26.98 b	27.12 ± 4.37 b	41.29 ± 8.91 ab	1.56 ± 0.43 a	0.13 ± 0.04 ab
Unt.	13.78 ± 3.63 b	5.67 ± 1.76 b	78.48 ± 35.77 b	26.56 ± 4.28 b	38.64 ± 5.80 ab	1.48 ± 0.28 a	0.09 ± 0.05 b

CR—Carolina Reaper; TS—Trinidad Scorpion; HC—Habanero Chocolate; B_C—Biochar + Cropmax; WV_C—WoodVinegar + Cropmax; C—Cropmax; Unt.—Untreated. Within each column and within each experimental factor, different letters mean fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

summarizes the effects of genotype and fertilization treatments on fruit characteristics and yield. TS produced the highest fruit yield, averaging 174.34 ± 87.68 g per plant, exceeding both CR and HC in total yield, fruit count, and average fruit weight. CR produced fewer fruits with lower weight and overall yield, while HC showed intermediate values. Notably, CR and HC exhibited higher fruit form index values, indicating more elongated fruits compared to TS.

Fertilization significantly influenced fruit yield and quality. B_C was the most effective treatment, achieving 183.22 ± 98.60 g per plant, the highest fruit count, and larger fruit dimensions. WV_C produced moderate improvements, while the C variant and untreated plants showed progressively lower performance. Untreated plants consistently had the lowest fruit weight and total yield, highlighting the importance of optimized fertilization.

Marked genotypic and treatment-dependent differences were observed across all yield- and fruit-associated traits (

Table 5. Genotypic and Fertilization-Induced Variations in Fruit Productivity, Morphological Parameters, and Peduncle Biomass Among Capsicum Cultivars.

Variant	No of Fruits/Plant	Average Fruit Weight (g)	Yield/Plant (g)	Fruit Width (mm)	Fruit Height (mm)	Fruit Form Index (H/W)	Peduncle Weight (g)
CR1	17.67 ± 0.58 bc	6.21 ± 1.52 bc	109.72 ± 29.93 bcde	31.04 ± 8.14 ab	39.28 ± 3.38 b	1.34 ± 0.39 bcd	0.16 ± 0.03 ab
CR2	17.33 ± 2.52 bc	3.61 ± 1.49 d	64.019 ± 33.84 de	20.97 ± 4.26 c	36.11 ± 7.42 b	1.78 ± 0.52 ab	0.07 ± 0.05 cd
CR3	16.33 ± 2.52 bc	5.46 ± 1.82 cd	88.53 ± 28.15 cde	24.29 ± 6.51 bc	49.50 ± 10.22 a	2.07 ± 0.26 a	0.16 ± 0.06 ab
CR4	13.67 ± 0.58 bc	3.62 ± 1.26 d	49.12 ± 15.86 e	24.28 ± 2.99 bc	37.19 ± 5.33 b	1.53 ± 0.27 bcd	0.10 ± 0.03 bcd
TS1	29.33 ± 9.02 a	10.29 ± 1.39 a	298.08 ± 86.19 a	31.95 ± 3.33 ab	41.05 ± 4.89 ab	1.29 ± 0.08 cd	0.20 ± 0.06 a
TS2	20.00 ± 1.00 b	8.23 ± 1.38 ab	164.87 ± 19.35 b	28.69 ± 4.92 ab	36.07 ± 4.10 b	1.27 ± 0.14 d	0.17 ± 0.06 ab
TS3	15.67 ± 1.53 bc	7.55 ± 1.18 bc	118.14 ± 16.17 bcd	29.37 ± 4.40 ab	33.39 ± 3.07 b	1.14 ± 0.06 d	0.13 ± 0.04 abc
TS4	16.33 ± 5.77 bc	7.08 ± 2.58 bc	116.25 ± 36.35 bcd	31.13 ± 3.04 ab	37.01 ± 7.51 b	1.18 ± 0.13 d	0.13 ± 0.05 abc
HC1	19.67 ± 2.08 b	7.25 ± 1.42 bc	141.88 ± 10.48 bc	35.65 ± 3.81 a	49.97 ± 4.82 a	1.40 ± 0.01 bcd	0.14 ± 0.06 abc
HC2	15.33 ± 2.52 bc	8.00 ± 0.43 b	123.12 ± 25.18 bcd	30.23 ± 2.41 ab	36.92 ± 7.99 b	1.22 ± 0.21 d	0.17 ± 0.01 ab
HC3	13.67 ± 1.15 bc	6.01 ± 2.22 bc	81.42 ± 26.85 cde	27.71 ± 4.98 bc	40.99 ± 6.68 ab	1.48 ± 0.06 bcd	0.11 ± 0.05 bcd
HC4	11.33 ± 0.58 c	6.19 ± 0.04 bc	70.05 ± 2.29 de	24.28 ± 3.04 bc	41.74 ± 2.41 ab	1.73 ± 0.09 abc	0.04 ± 0.03 d

CR1—Carolina Reaper × Biochar + Cropmax; CR2—Carolina Reaper × WoodVinegar + Cropmax; CR3—Carolina Reaper × Cropmax; CR4—Carolina Reaper (Untreated); TS1—Trinidad Scorpion × Biochar + Cropmax; TS2—Trinidad Scorpion × WoodVinegar + Cropmax; TS3—Trinidad Scorpion × Cropmax; TS3—Trinidad Scorpion (Untreated); HC1—Habanero Chocolate × Biochar + Cropmax; HC2—Habanero Chocolate × WoodVinegar + Cropmax; HC3—Habanero Chocolate × Cropmax; HC4—Habanero Chocolate (Untreated). Within each column and within each experimental factor, different letters mean genotype and fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

). Among the CR variants, fruit number per plant ranged from 13.67 (CR4) to 17.67 (CR1). Despite a relatively stable fruit set, marked differences in fruit biomass emerged: CR1 attained the highest mean fruit weight within this genotype (6.21 g), translating into a per-plant yield of 109.72 g, whereas CR4 exhibited the lowest productive output (49.12 g), attributable to both reduced fruit number and size. Notably, CR3 expressed an intermediate profile, with larger fruit dimensions (49.50 mm in height) and a fruit form index exceeding 2.0, suggestive of elongated fruit morphology.

In contrast, the TS genotype demonstrated markedly higher productivity. TS1 was particularly outstanding, achieving the maximum fruit number (29.33 fruits per plant) and average fruit weight (10.29 g), which jointly conferred the highest yield across all treatments (298.08 g per plant). The other TS treatments showed reduced performance but nonetheless maintained yields exceeding 110 g, supported by balanced fruit dimensions and consistent peduncle biomass.

The HC variants displayed a more moderate productive potential. HC1 achieved the most favorable outcome within this group, with 19.67 fruits per plant and a corresponding yield of 141.88 g. This variant also produced the largest fruit height values (49.97 mm), comparable to CR3. Conversely, HC4 registered the lowest yield in this genotype (70.05 g per plant), despite relatively high fruit width (41.74 mm), indicating that fruit number was the limiting factor.

Across genotypes, peduncle weight followed yield trends, peaking in TS1 (0.20 g) and remaining lowest in HC4 (0.04 g). Morphological variation was also reflected in the fruit form index, with elongated phenotypes in CR3 (2.07) and more spherical forms in TS3 and TS2 (1.14–1.27).

Collectively, these results highlight TS1 as the most productive genotype-treatment combination, while CR4 and HC4 represented the least efficient. The data underscore genotype-specific responses to the applied fertilization regimes, with implications for targeted optimization in greenhouse chili pepper production.

3.4. Seed Metrics and Fruit Pulp Biomass

Seed and fruit pulp characteristics were significantly influenced by both genotype and fertilization regime (

Table 6. Comparative Evaluation of Seed Traits and Seedless Fruit Pulp Yield Across Distinct Capsicum Genotypes and Fertilization Regimens.

Variant	No. of Seeds/Fruit	Total Seed Weight (g)	Seedless Fruit Pulp Weight (g)
Cultivar
CR	19.00 ± 7.51 c	0.16 ± 0.05 c	4.70 ± 1.46 b
TS	47.08 ± 9.88 a	0.41 ± 0.12 a	7.61 ± 1.37 a
HC	30.33 ± 12.35 b	0.28 ± 0.14 b	4.58 ± 1.44 b
Fertilization type
B_C	38.33 ± 18.33 a	0.35 ± 0.21 a	7.07 ± 1.99 a
WV_C	28.78 ± 13.12 a	0.27 ± 0.13 a	5.62 ± 1.58 ab
C	31.56 ± 13.80 a	0.28 ± 0.12 a	5.54 ± 1.36 ab
Unt.	29.89 ± 16.10 a	0.23 ± 0.13 a	4.31 ± 2.15 b

CR—Carolina Reaper; TS—Trinidad Scorpion; HC—Habanero Chocolate; B_C—Biochar + Cropmax; WV_C—WoodVinegar + Cropmax; C—Cropmax; Unt.—Untreated. Within each column and within each experimental factor, different letters mean fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

).

TS consistently exhibited the highest seed number, total seed weight, and seedless pulp weight, reflecting its strong inherent reproductive capacity, whereas CR displayed comparatively lower values, indicative of its distinct reproductive pattern. Fertilization further modulated these traits, with B_C consistently enhancing seed and pulp parameters across all genotypes. WV_C and C variants showed moderate improvements, while untreated controls produced the lowest values.

In CR variants, B_C yielded 20 seeds per fruit, total seed weight of 0.142 g, and pulp weight of 6.284 g—the highest pulp value recorded—demonstrating a synergistic effect of biochar and Cropmax on fruit flesh development. WV_C produced comparable seed numbers and weight but lower pulp mass, whereas the C variant slightly increased seed number (≥20) but with moderate pulp weight (4.840 g). The untreated control exhibited 15.8 seeds, 0.125 g seed weight, and 3.254 g pulp, highlighting the crucial role of fertilization.

In the TS variants, B_C achieved 49.67 seeds per fruit, 0.48 g seed weight, and 9.39 g pulp, representing the maximal enhancement of pulp mass, likely via improved nutrient cycling and water retention. WV_C produced 43.00 seeds, 0.41 g seed weight, and 7.46 g pulp, whereas the C variant (46.33 seeds, 0.38 g seed weight, 6.81 g pulp) and the untreated control (49.33 seeds, 6.80 g pulp) indicated that foliar fertilization alone increases seed production but has limited impact on pulp development without organic amendments.

For HC, B_C also maximized all traits (45.33 seeds, 0.45 g seed weight, 5.52 g pulp), while WV_C offered moderate improvements (27.00 seeds, 0.25 g seed weight, 4.97 g pulp). The C and Unt. variants recorded the lowest reproductive outputs, with seed counts of 24 and 25, seed masses of 0.23 g and 0.19 g, and corresponding pulp biomasses of 4.97 g and 2.87 g, respectively.

Overall, these findings confirm that genotype establishes inherent reproductive potential, whereas fertilization—particularly biochar combined with Cropmax—optimizes seed production and fruit flesh development, demonstrating the efficacy of integrated organic and biostimulant strategies for maximizing fruit quality in C. chinense genotypes (

Table 7. Genotypic and Fertilization-Driven Variations in Seed Phenotypes and Seedless Fruit Pulp Yield Across Capsicum Cultivars.

Variant	No of Seeds/Fruit	Total Seed Weight (g)	Seedless Fruit Pulp Weight (g)
CR1	20.00 ± 5.00 c	0.14 ± 0.07 e	6.28 ± 1.34 bcd
CR2	16.33 ± 7.81 c	0.15 ± 0.11 e	4.43 ± 0.47 def
CR3	24.33 ± 14.94 c	0.22 ± 0.18 cde	4.84 ± 1.46 cde
CR4	15.33 ± 10.89 c	0.13 ± 0.10 e	3.25 ± 1.36 ef
TS1	49.67 ± 19.03 a	0.48 ± 0.20 a	9.39 ± 1.18 a
TS2	43.00 ± 10.84 ab	0.41 ± 0.13 abc	7.46 ± 1.25 b
TS3	46.33 ± 8.77 a	0.38 ± 0.10 abcd	6.81 ± 1.08 bc
TS4	49.33 ± 14.69 a	0.38 ± 0.14 abcd	6.80 ± 1.87 bc
HC1	45.33 ± 15.56 a	0.45 ± 0.18 ab	5.52 ± 1.12 bcd
HC2	27.00 ± 16.11 bc	0.25 ± 0.15 bcde	4.97 ± 1.45 cde
HC3	24.00 ± 13.89 c	0.23 ± 0.18 cde	4.97 ± 1.54 cde
HC4	25.00 ± 2.83 c	0.19 ± 0.09 de	2.87 ± 0.95 f

CR1—Carolina Reaper × Biochar + Cropmax; CR2—Carolina Reaper × WoodVinegar + Cropmax; CR3—Carolina Reaper × Cropmax; CR4—Carolina Reaper (Untreated); TS1—Trinidad Scorpion × Biochar + Cropmax; TS2—Trinidad Scorpion × WoodVinegar + Cropmax; TS3—Trinidad Scorpion × Cropmax; TS3—Trinidad Scorpion (Untreated); HC1—Habanero Chocolate × Biochar + Cropmax; HC2—Habanero Chocolate × WoodVinegar + Cropmax; HC3—Habanero Chocolate × Cropmax; HC4—Habanero Chocolate (Untreated). Within each column and within each experimental factor, different letters mean genotype and fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

).

3.5. Total Dry Matter, Water Content, and Soluble Solids in Chili Pepper Fruits

Analysis of total dry matter (DM), water content, and soluble solids content (SSC, °Brix) revealed significant influences of genotype and fertilization (

Table 8. Comparative Evaluation of Total Dry Matter, Water Content, and Soluble Solids (°Brix) in Pepper Fruits in Relation to Genotype and Fertilization Regimens.

Variant	Total Dry Matter Content (%)	Water Content (%)	Soluble Solids Content (°Brix)
Cultivar
CR	7.70 ± 0.69 a	92.30 ± 0.69 a	6.50 ± 0.52 b
TS	8.46 ± 2.25 a	91.54 ± 2.25 a	7.67 ± 0.94 a
HC	8.23 ± 1.48 a	91.77 ± 1.48 a	7.25 ± 0.94 a
Fertilization type
B_C	9.57 ± 0.80 a	90.43 ± 0.80 b	8.08 ± 0.74 a
WV_C	9.50 ± 1.26 a	90.50 ± 1.26 b	6.32 ± 0.44 c
C	6.71 ± 0.52 b	93.29 ± 0.52 a	6.89 ± 0.47 bc
Unt.	6.75 ± 0.60 b	93.25 ± 0.60 a	7.27 ± 1.03 b

CR—Carolina Reaper; TS—Trinidad Scorpion; HC—Habanero Chocolate; B_C—Biochar + Cropmax; WV_C—WoodVinegar + Cropmax; C—Cropmax; Unt.—Untreated. Within each column and within each experimental factor, different letters mean fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

).

At the genotypic level, TS exhibited the highest DM (8.46 ± 2.25%) and SSC (7.67 ± 0.94 °Brix), significantly surpassing CR (7.70 ± 0.69% DM; 6.50 ± 0.52 °Brix), while HC displayed intermediate values (8.23 ± 1.48% DM; 7.25 ± 0.94 °Brix). Water content remained uniform across genotypes (91.54–92.30%).

Fertilization markedly altered fruit composition. B_C consistently produced the highest DM (9.57 ± 0.80%) and elevated SSC (8.08 ± 0.74 °Brix), whereas WV_C resulted in the lowest SSC (6.32 ± 0.44 °Brix). Water content was maximized in the unfertilized control (93.25 ± 0.60%), surpassing all fertilized treatments, except for the C variant, which exhibited a comparable value.

Within CR, B_C (CR1) achieved the greatest DM (8.62%), with 91.38% water and SSC of 7.18 °Brix. WV_C (CR2) yielded slightly lower DM (8.12%) and SSC (5.98 °Brix). Cropmax alone (CR3) and the control (CR4) recorded the lowest DM (7.02% and 7.04%), with comparable water content and SSC, confirming biochar’s superiority in enhancing fruit density and sweetness.

In TS, B_C (TS1) reached the highest DM across all genotype × treatment combinations (10.32%), with 89.69% water and SSC of 8.35 °Brix. WV_C (TS2) produced the highest DM overall (10.84%) with reduced SSC (6.35 °Brix), suggesting a dilution of sugars despite improved structural quality. Cropmax (TS3) and control (TS4) exhibited lower DM (6.04% and 6.67%) and higher water (>93%), though TS4 reached the highest SSC within TS (8.55 °Brix).

In HC, B_C (HC1) achieved high DM (9.79%), low water content (90.21%), and the highest SSC across all treatments and genotypes (8.73 °Brix). WV_C (HC2) produced slightly lower DM (9.54%), with SSC of 6.62 °Brix. Cropmax (HC3) reduced DM (7.06%) and increased water (92.94%), with SSC of 6.70 °Brix. The control (HC4) exhibited the lowest DM (6.53%), highest water (93.47%), and SSC of 6.97 °Brix.

Overall, both genotype and fertilization significantly influenced fruit DM and SSC, with Biochar + Cropmax consistently delivering superior structural and compositional quality across all C. chinense genotypes (

Table 9. Genotypic and Fertilization-Induced Variations in Total Dry Matter, Water Content, and Soluble Solids (°Brix) in Pepper Fruits Across Capsicum Cultivars.

Variant	Total Dry Matter Content (%)	Water Content (%)	Soluble Solids Content (°Brix)
CR1	8.62 ± 0.02 d	91.38 ± 0.02 c	7.18 ± 0.30 bc
CR2	8.12 ± 0.03 d	91.88 ± 0.03 c	5.98 ± 0.30 f
CR3	7.02 ± 0.05 e	92.98 ± 0.05 b	6.53 ± 0.25 de
CR4	7.04 ± 1.04 e	92.95 ± 1.04 b	6.28 ± 0.30 ef
TS1	10.32 ± 0.03 b	89.69 ± 0.03 e	8.35 ± 0.25 a
TS2	10.84 ± 0.02 a	89.16 ± 0.02 f	6.35 ± 0.41 ef
TS3	6.04 ± 0.02 f	93.96 ± 0.02 a	7.43 ± 0.26 b
TS4	6.67 ± 0.02 e	93.33 ± 0.02 b	8.55 ± 0.25 a
HC1	9.79 ± 0.01 c	90.21 ± 0.01 d	8.73 ± 0.25 a
HC2	9.54 ± 0.01 c	90.46 ± 0.01 d	6.62 ± 0.46 de
HC3	7.06 ± 0.02 e	92.94 ± 0.02 b	6.70 ± 0.26 cde
HC4	6.53 ± 0.09 ef	93.47 ± 0.09 ab	6.97 ± 0.21 bcd

CR1—Carolina Reaper × Biochar + Cropmax; CR2—Carolina Reaper × WoodVinegar + Cropmax; CR3—Carolina Reaper × Cropmax; CR4—Carolina Reaper (Untreated); TS1—Trinidad Scorpion × Biochar + Cropmax; TS2—Trinidad Scorpion × WoodVinegar + Cropmax; TS3—Trinidad Scorpion × Cropmax; TS3—Trinidad Scorpion (Untreated); HC1—Habanero Chocolate × Biochar + Cropmax; HC2—Habanero Chocolate × WoodVinegar + Cropmax; HC3—Habanero Chocolate × Cropmax; HC4—Habanero Chocolate (Untreated). Within each column and within each experimental factor, different letters mean genotype and fertilization treatments differ significantly according to Duncan’s test at p ≤ 0.05.

).

4. Discussion

This study exploratorily examines the responses of three C. chinense Jacq. genotypes—Carolina Reaper, Trinidad Scorpion, and Habanero Chocolate—to distinct fertilization regimes, namely biochar, wood vinegar, and Cropmax. Variations in vegetative and reproductive parameters, including plant height, stem collar diameter, leaf number, branching, and flowering, underscore the combined influence of genetic determinants and nutrient management strategies on growth. Results indicate that tailored fertilization can enhance yield stability, particularly under variable environmental conditions.

All genotypes exhibited significant height responses to fertilization, with CR attaining the greatest vertical growth, while TS excelled in flowering. Biochar application proved most effective for height enhancement, reaffirming its role in sustainable agriculture. CR notably benefitted from the combined use of wood vinegar and Cropmax, suggesting a synergistic interaction potentially arising from wood vinegar–mediated nutrient absorption improvement [33,34] and Cropmax-induced physiological efficiency [35]. In TS, the TS2 variant (WV_C) displayed a delayed but marked height recovery, possibly linked to wood vinegar’s capacity to mitigate heat stress, consistent with prior reports on its role in enhancing abiotic stress tolerance [36,37] via organic acids and phenolic compounds that improve water retention and stimulate growth hormones [38,39].

Collar diameter, a proxy for structural robustness, showed significant inter-genotypic and treatment-related variation during June and July. Biochar, wood vinegar, and Cropmax consistently enhanced structural development across cultivars. CR exhibited pronounced collar diameter expansion even in the untreated control, indicating intrinsic structural adaptability, while biochar-treated TS demonstrated superior stem thickening—likely due to biochar’s high porosity and nutrient-retentive capacity [40,41]. Stable collar diameter in HC indicates sequential growth promotion by biochar and wood vinegar, though species-specific nutrition may be required [42]. Preliminary results further indicate that Cropmax, when applied alone, may enhance collar diameter through improved nutrient uptake efficiency. The TS1 variant highlighted the efficacy of Biochar + Cropmax, whereas the limited growth of HC4 suggests potential susceptibility to environmental stress or nutrient deficiency, underscoring the necessity for genotype-tailored fertilization.

Overall, the trends in collar diameter and plant height reveal a complex interplay between genotype, environmental factors, and fertilization methodology. The adaptability of unfertilized CR and biochar-treated TS contrasts with the variable performance of HC, warranting further research into optimized nutrient regimes. These findings hold critical implications for sustainable, high-yield C. chinense Jacq. production under diverse climatic conditions.

Leaf count, a key determinant of photosynthetic capacity and vigor, varied significantly among genotypes in response to the FMPs. CR and TS exhibited notable increases under wood vinegar and biochar, paralleling gains in height and collar diameter. The TS1 variant’s superior leaf count under B_C supports the hypothesis that biochar ensures prolonged nutrient availability, sustaining leaf production and photosynthetic efficiency [43]. In contrast, HC showed consistently limited leaf expansion, suggesting slower leaf development or reduced responsiveness to the tested inputs, potentially reflecting an adaptive genotype trait aimed at conserving resources under nutrient constraints. These findings reinforce the necessity of genotype-specific nutrient regimes to optimize photosynthetic productivity.

Reproductive growth, as reflected in flowering, was strongly influenced by fertilization. CR’s high flowering rate even in the absence of fertilization indicates an intrinsic reproductive capacity, further enhanced by Cropmax—likely through stimulation of flower induction pathways [44]. In TS, the TS2 variant displayed marked increases, suggesting hormonal and stress tolerance modulation by wood vinegar [45,46]. HC exhibited modest flowering irrespective of treatment, implying a slower reproductive phase or reduced sensitivity to nutrient inputs [47]. The results highlight distinct genotype-specific flowering phenologies, with biochar, wood vinegar, and their combinations with Cropmax offering the greatest potential to enhance reproductive output, albeit within the limits imposed by genetic and environmental factors.

Branching responses further illustrated genotype-dependent patterns. CR’s pronounced branching under sole Cropmax suggests cytokinin-mediated axillary bud activation [48]. TS exhibited stable branching with modest increases under B_C, consistent with biochar’s nutrient supply benefits [49,50,51]. HC demonstrated minimal branching across treatments, with WV providing only a slight advantage. These patterns indicate that branching in CR is most responsive to Cropmax, while TS benefits moderately from biochar-based inputs. The minimal response in HC underscores its limited architectural plasticity and highlights the importance of targeted fertilization to optimize vegetative structure for each genotype.

B_C applications notably enhanced anthocyanin content, particularly in HC and TS, underscoring biochar’s role as a soil conditioner and nutrient facilitator [52]. Its high porosity and surface area likely improve soil microenvironments, nutrient availability, and water retention, thereby supporting anthocyanin biosynthesis [53]. The pronounced synergy in B_C treatments suggests activation of secondary metabolite pathways, consistent with reports of biochar increasing root biomass and microbial activity, amplifying foliar fertilizer efficacy [54,55]. The marked anthocyanin increase from June to July across all genotypes reflects biochar’s capacity for nutrient stabilization and gradual release. TS’s consistently higher baseline [56,57,58] and strong biochar responsiveness suggest genotype-specific potential, while HC’s elevated anthocyanin under B_C highlights treatment–genotype specificity [59]. CR also showed progressive increases, reinforcing biochar’s sustained stimulatory effect.

Chlorophyll content (CCI) similarly showed genotype-specific responses. TS exhibited the highest CCI, indicating superior photosynthetic efficiency and utilization of biochar-mediated nutrient availability. Lower CCI in HC suggests genotype-dependent regulation of chlorophyll synthesis [60,61], possibly linked to inherent nutrient uptake and enzyme activity differences. In CR, WV_C yielded moderate CCI increases, likely through biostimulant-induced enhancement of chlorophyll biosynthesis [62].

Biochar, especially when combined with Cropmax, consistently delivered the highest yields, fruit weights, and dimensions across genotypes, corroborating previous findings on its capacity to improve soil structure, nutrient retention, and microbial activity [63,64,65]. In CR, the B_C treatment (CR1) achieved maximum productivity, most likely due to biochar’s ability to enhance moisture retention and cation exchange capacity in conjunction with the foliar nutrient supply from Cropmax [22,66]. By contrast, WV_C (CR2) provided only moderate yield improvements, indicating beneficial but weaker effects and lacking the synergistic impact observed with biochar [67].

Among the tested genotypes, TS exhibited the most robust response, with B_C (TS1) resulting in the highest yields and morphometric traits. This outcome reflects the genotype’s high nutrient demand and its strong affinity for biochar-mediated fertility enhancements [68,69,70]. While WV (TS2) also improved yields, its effect was consistently less pronounced, suggesting that WV may play a supplementary rather than a primary role in yield improvement.

HC also responded positively to B_C (HC1), although the yield gains were comparatively smaller, possibly due to this genotype’s lower nutrient uptake efficiency. Here, biochar’s primary benefits likely stemmed from improved root growth and enhanced soil moisture retention [71]. Interestingly, WV (HC2) produced notable improvements in this genotype, potentially attributable to its organic acids and micronutrient content [72]. Conversely, Cropmax applied alone (HC3) resulted in the lowest outputs, emphasizing that foliar fertilizers achieve maximum effectiveness only when integrated with soil amendments such as biochar or wood vinegar [73].

Overall, biochar—particularly with foliar fertilization—proved highly effective in enhancing seed count, seed mass, and pulp weight, with genotype-specific metabolic and physiological traits governing responses to FMPs [74,75].

In CR, B_C (CR1) achieved an optimal balance of seed and pulp biomass, highlighting biochar’s role in enhancing fruit flesh development alongside seed formation [76,77]. While biochar improved pulp weight, sole Cropmax (CR3) produced more seeds, suggesting foliar fertilization alone can stimulate reproductive organogenesis [78]. Control plants (CR4) showed markedly reduced reproductive traits, indicating strong fertilization benefits.

TS responded most strongly to B_C (TS1), achieving the highest seed count, seed weight, and pulp biomass, reflecting compatibility between its nutrient demands and biochar’s ability to improve nutrient cycling and water retention [79,80]. WV_C (TS2) performed moderately, likely due to its organic acids but absence of biochar’s structural and microbial benefits [81]. The control (TS4) showed unexpectedly high pulp weight, suggesting strong intrinsic yield potential, but biochar remained essential for maximum productivity [82].

HC displayed moderate gains under B_C treatment (HC1), with biochar enhancing pulp mass despite genetic limitations in nutrient uptake [83]. WV_C (HC2) yielded fewer seeds but moderate pulp weight, indicating greater responsiveness to wood vinegar’s bioactive compounds.

Across genotypes, biochar with foliar fertilization proved most effective for enhancing seed and pulp traits. Biochar’s long-term nutrient release and microbial stimulation [84] complemented Cropmax’s immediate nutrient delivery [85], resulting in significant improvements—particularly in TS, where TS1 reached peak values.

B_C also consistently improved fruit quality, increasing dry matter and soluble solids content (SSC), traits critical for market and culinary value [86]. Biochar’s high porosity and cation exchange capacity enhanced rhizosphere nutrient and water availability [87], while foliar inputs boosted metabolic activity and photosynthate allocation to fruit [88], synergistically improving compositional attributes [89].

TS achieved the highest DM and SSC under B_C, enhancing density and sweetness. HC also showed elevated SSC, reinforcing the potential of biochar-based regimes to simultaneously optimize yield and quality in high-value C. chinense Jacq. cultivars.

The application of WVS demonstrated a moderate capacity to enhance plant growth and yield-related traits, an effect frequently attributed to its organic acids and phenolic compounds, which improve soil pH buffering, enhance nutrient solubility, and promote stress tolerance mechanisms. Such effects are consistent with earlier findings where wood vinegar facilitated abiotic stress mitigation and improved plant performance under suboptimal growing conditions [23,37,90,91]

When applied as a foliar fertilizer, Cropmax alone promoted reproductive development and structural robustness, particularly by stimulating flower induction pathways and enhancing collar diameter expansion. These effects can be explained by Cropmax’s composition of micronutrients, amino acids, and growth stimulators that augment metabolic efficiency and photosynthetic performance, in line with previous reports on biostimulant-driven physiological enhancement [73,92].

The evidence suggests that wood vinegar is best utilized as a complementary input, enhancing nutrient availability and stress tolerance [33,93,94] while Cropmax alone provides a more direct stimulation of physiological and reproductive processes [95,96]. When combined, these inputs can act in concert to improve both vegetative and reproductive performance, but their effectiveness remains contingent on genotype-specific responses and environmental conditions.

Limitations of the Study

Although this study provides novel insights into the response of C. chinense Jacq. to pyrolysis-derived amendments and sustainable fertilizers in controlled containerized systems, certain limitations must be considered. The relatively short duration of the trial may have constrained the full expression of long-term physiological and yield responses. Moreover, the greenhouse environment, while enabling precise control of temperature, humidity, and photoperiod, may not fully capture the complexity of field conditions, including interactions with soil microbiota, variable weather patterns, and other environmental stressors. Consequently, while the results demonstrate the potential of these amendments, further validation under extended and field-based conditions is warranted to establish their broader agronomic relevance.

5. Conclusions

The present investigation supports the view that fertilization strategies influence growth, pigment composition, and yield traits in Capsicum chinense Jacq. in a genotype-dependent manner. Among the cultivars tested, Carolina Reaper exhibited consistently high vegetative and reproductive performance under both nutrient-rich and control conditions, whereas Trinidad Scorpion and Habanero Chocolate showed differential responses influenced by the applied amendments.

The combined application of biochar and the biostimulant Cropmax consistently enhanced total fruit yield and selected fruit quality parameters across genotypes, likely due to biochar’s role in improving nutrient retention and soil structure, and Cropmax’s effect on promoting vegetative vigor and reproductive development. In contrast, wood vinegar produced variable, genotype-specific outcomes, indicating that its use may require more targeted application strategies.

These findings suggest that integrating biochar with Cropmax provides a practical and sustainable approach to increasing yield and fruit quality in greenhouse chili pepper production. Implementation of such genotype-tailored fertilization programs can improve economic returns and support soil health. Future research should evaluate long-term effects under varying greenhouse conditions and optimize application rates and timing to maximize benefits.