SJA_39_s2_153-163

Introduction

Pepper (C. annuum) is one of the most important vegetables for nutrition of millions of people and is also considered the second most consumed vegetable worldwide (Reyes Pérez et al., 2017). According to FAO (2018) six countries are responsible for 76.6% of world pepper production, with China as the first producing country with 50.1% while Mexico, Turkey, Spain, the United States and Nigeria produce the other 26.5%. In Ecuador, approximately 2,300 ha are cultivated with a production of approximately 8,500 tons with an average yield of 37 t h-1 (FAO, 2018).

The production of pepper in Ecuador is favored by a variation of agro-climatic conditions. Currently, it is grown from the Coastal region (Guayas, Santa Elena, Manabí and El Oro provinces) to part of the Andean region in the highlands (Imbabura, Chimborazo and, Loja provinces) with a vegetative cycle of 4 to 6 months (from sowing to harvest). One of the main national production areas, the province of Manabí, has approximately 485 ha planted with this crop, with a harvested area of 461 ha and a production of 4442 t (INEC, 2021).

Pepper cropping is demanding in Nitrogen and Phosphorus from transplanting to the beginning of flowering; however, during the time of fruit-filling the demand for nutrients increases. Therefore, farmers use an intensive model with excessive applications of chemical synthesized fertilizers (Reyes and Cortés, 2017) whose objective is to maximize yields and generate optimal plant growth (Correa et al., 2001; Armendáriz et al., 2012; Lee et al., 2014; Albaugh et al., 2015); even though, this model produces some collateral negative effects such as the release of reactive Nitrogen to the ecosystem, change the chemical composition of the soil over time or alter the floristic composition in natural systems (Galloway et al., 2003; Villarreal et al., 2012; Hedwall et al., 2013).

The growing concern over agrochemical use’s environmental and economic impacts has led to an increasing interest in organic agriculture as a sustainable alternative (Gomiero, 2018; Nicholls and Altieri, 2019). Organic farming promotes more environmentally friendly production and marketing systems, reducing dependency on synthetic inputs while enhancing soil health and biodiversity. One of the key benefits of organic agriculture is applying organic matter to agricultural soils, which improves water retention capacity, enhances soil structure, and stimulates microbiological activity (Rivera and Dallatore, 2018).

Manure is widely used as an organic fertilization option due to its high nitrogen and organic matter content. Another promising alternative is vermicompost leachate, a dark, odorless liquid rich in soluble nutrients and beneficial microorganisms derived from the vermicomposting process (Delgado-Moreno and Peña, 2009). These organic amendments improve soil fertility and help farmers reduce production costs by decreasing reliance on external inputs (Arellano et al., 2014).

Vermicomposting is a bio-oxidation and stabilization process in which earthworms and microorganisms transform organic matter into a nutrient-rich, homogeneous, and fine-grained product (Ramírez-Ibarra et al., 2017). This natural process plays a vital role in closing the organic matter cycle, mimicking biological decomposition occurring in ecosystems (Delgado-Moreno and Peña, 2009). Vermicompost is known for its high biological activity, even at low concentrations, promoting root development, enhancing stem and leaf growth, and increasing flowering and fruit production. Consequently, plants exhibit greater vigor and higher yields per cultivated area (Reyes Pérez et al., 2017).

The rising costs of chemical fertilizers and the need to preserve soil organic matter highlight the relevance of organic fertilization in modern agriculture (Nicholls and Altieri, 2019). However, comparative studies are still needed to evaluate the effectiveness of organic and chemical fertilizers in crop productivity.

This study assesses the effects of bovine manure and vermicompost as organic fertilizers and compares them with conventional chemical fertilization (N, P, K) in pepper cultivation. By providing insights into different plant nutrition strategies, this research aims to contribute to developing more sustainable and cost-effective fertilization practices.

Materials and Methods

Location

The present study was carried out in the Experimental Campus “La Teodomira”, in the Faculty of Agronomic Engineering of the Technical University of Manabí, located in the Lodana parish, Santa Ana canton, Manabí Province, Ecuador. The experiment was carried out under a semi-protected system (which consists of planting in shadow houses, using a transparent plastic roof (AGROCLEAR X) with a thickness of 6 thousandths of an inch, with UV light transmission at 380 nm, and anti-aphids mesh on the sides).

Plant material

The plant material used in this test was the Odin variety pepper (Odin Holland CV). A germination test was carried out with a temperature of 27ºC and luminosity of 660 nm, resulting in 95% of germination.

Management of the experiment

First a soil analysis on the experimental site was carried out, which consisted of taking soil samples to later be sent to AGROCALIDAD (Agency for Regulation and Control of Phytosanitary and Zoosanitary) laboratory for analysis.

The substrate for the seedlings in the germinating tray was composed of completely mineralized organic matter of bovine origin and fluffy peanut shell in a 2: 1 (v/v) ratio; while the soil of the semi-protected system corresponds to the Clay Loam textural class which was prepared with plows and rotavator crossing. Transplantation from the seedbed to the semi-protected system was carried out when the seedlings developed 4 to 6 pairs of leaves (20 to 25 days after sowing). The provision of water to the seedbed was carried out with a watering can on alternate days and the irrigation during the experiment in the semi-protected system, was carried out through a drip system for 15 to 20 minutes every two to three days, guaranteeing humidity between 70 and 80% of field capacity.

Application of treatments

Chemical fertilizer: The application of 30% of the chemical fertilizer (NPK) was carried out 15 days after transplantation (DAT) and the remaining 70% at 60 DAT. The complete fertilizer used was YaraMila COMPLEX (10 g/plant according to the manufacturer’s recommendations) as a complex fertilizer containing Nitrogen, Phosphorus and Potassium (12% N - 11% P2O5 -18% K2O).

Organic fertilizer: The used manure was stored for 35 days with a relative humidity of 45%. The application of the bovine manure was carried out after two weeks of transplantation, frequently every ten days.

Bovine vermicompost (LVCEB): The bovine vermicompost leachate (LVCEB) was applied 15 days after transplantation and then every ten days. The applications in the doses 1: 20 V/V and 1:30 V/V, were made with a 2-liter sprayer to the foliar area of the plants in each plot according to the experiment scheme. An analysis of the chemical composition of the vermicompost leachate was carried out also at the laboratory of AGROCALIDAD.

Phytosanitary controls: As part of the phytosanitary management strategy, preventive applications were carried out to control Cercospora capsici. A copper-based fungicide (e.g., Copper Hydroxide 77% WP) was applied at a rate of 2.0 g/L every 10 to 14 days, depending on weather conditions. Additionally, neem extract (Azadirachta indica) was used as a complementary treatment at 3 mL/L every 10 days to reduce fungal pressure. These applications were combined with cultural practices, such as the removal of infected plant debris, to further minimize disease incidence.

Harvest: This activity was developed manually when the plants produced fruits that have reached their physiological maturity. Fruit collections were made considering their adequate quality for commercialization (color, flavor, aroma, texture, internal composition and, hardness). The harvest was carried out four months after transplantation with a duration of approximately two months.

Experimental design and statistical analysis

Table 1 presents the structure of the applied treatments: they were represented by two organic inputs with two doses each and a chemical treatment for comparison. For the analyzes, the last data recorded minus the first one (increment) was calculated.

Table 1: Treatments under study to evaluate the effects of organic and chemical fertilization on pepper (C. annuum) in a semi-protected cropping system.

Nomenclature	Denomination	Dose
NPK	Chemical fertilization (NPK)	Required by the crop
EB1tha	Bovine manure	1 t ha
EB3tha	Bovine manure	3 t ha
LVCEB 1:20	Bovine manure, Vermicompost leachate	1:20 V/V
LCVEB 1:30	Bovine manure, Vermicompost leachate	1:30 V/V

A completely randomized experimental design with 5 treatments and 3 replications was used. The statistics included an analysis of variance and Tukey’s mean comparison test with an alpha of 0.05. For the comparative analysis, the data was standardized by using the natural logarithm in order to obtain results that could be comparable and as a complement, MANOVA-Biplot was used to obtain groups of variables and determine their correlation with each of the treatments by using the Multiplot software (Vicente-Villardón, 2017).

Description of variables and data record

Sampling was carried out on 6 plants of each experimental unit to record the following variables: plant height (cm), number of leaves (it was counted before the appearance of the first flower bud), stem diameter (mm) and photosynthetic pigments (Spad units: indirect determination of chlorophyll) registered at 15 and 45 days after transplantation. For the photosynthetic pigments variable, leaves of the middle third of the plant were taken, these tissues must be in an intermediate phase (not too young, not too old). Three (3) measurements were made in the same plant to obtain an average value per plant. For this, climatic conditions such as temperature and relative humidity should be considered as a reference.

The analysis of these variables was carried out subtracting values from the last record minus the first one (increment). In addition to these variables, others were also considered at harvest time (65 DAT): number of fruits per plant, weight of fruit per plant (g), length of fruit per plant (cm), diameter of fruit per plant (cm) and yield (t ha-1).

Results and Discussion

Soil and vermicompost leachates analysis

Table 2 presents the results of the chemical analysis of the experimental site’s soil. The soil exhibited high concentrations of macroelements, including nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca), which are essential for plant growth and development. Additionally, magnesium (Mg) and manganese (Mn) were found at optimal levels, suggesting that the soil has adequate nutrient availability to support plant metabolism and physiological functions. However, other essential components, such as organic matter, were detected in low quantities. Organic matter is crucial in soil fertility by enhancing microbial activity, improving soil structure, and increasing water retention capacity (Molina and Meléndez, 2007).

Previous fertilization practices or the soil’s natural composition in the region may have contributed to the high macroelement content. Nevertheless, despite the apparent nutrient richness, nutrient availability imbalances and soil organic matter deficiency could impact crop productivity and plant health in the long term.

Table 2: Chemical properties of the soil where the experiment was carried out to evaluate the effects of organic and chemical fertilization on pepper (C. annuum) in a semi-protected cropping system.

Parameter	Value
pH	6.75
Organic matter (%)	2.12
Nitrogen (%)	2.12
Phosphorous (mg kg-1)	57.20
Potassium (cmol kg-1)	1.78
Calcium (cmol kg-1)	18.40
Magnesium (cmol kg-1)	4.16
Iron (ppm)	<15.00
Manganese (ppm)	14.56
Copper (ppm)	1.92
Zinc (ppm)	1.64

Table 3: Chemical composition of vermicompost leachates used to evaluate the effects of organic and chemical fertilization on pepper (C. annuum) in a semi-protected cropping system.

Parameter	%
Nitrogen	0.1800
Phosphorous	0.0015
Potassium	0.2780
Calcium	0.0180
Magnesium	0.0503
Iron	0.0003
Zinc	0.0019

Table 3 details the chemical composition of the vermicompost leachates. The analysis revealed that potassium (K) and nitrogen (N) were the most abundant elements in the leachates, confirming their potential as valuable sources of essential nutrients for plant growth. Potassium plays a vital role in plant water regulation, enzyme activation, and overall stress tolerance (Johnson et al., 2022; Mostofa et al., 2022), while nitrogen is fundamental for vegetative growth, chlorophyll synthesis, and protein formation (Muhammad et al., 2022).

Table 4: Effect of organic and chemical fertilization on the agronomic performance of pepper (C. annuum) in a semi-protected cropping system. Values represent mean ± standard deviation. Different letters in the same column indicate significant differences according to Tukey’s test (p ≤ 0.05). CV: Coefficient of variation.

Treatments	Plant height (cm)	Leaf number		Stem diameter (mm)	Chlorophyll content (SPAD)	Fruit number	Fruit weight (g)	Fruit length (cm)	Fruit diameter (cm)	Yield (t ha-1)
NPK	64.94±9.12	132.83±26.56	a	6.99 ± 1.29	8.63 ± 4.42	22.22 ± 9.08	100.55 ± 18.87	17.55 ± 0.52	14.29 ± 0.38	36.12 ± 5.77
EB3tha	64.19±13.10	130.06±20.64	ab	6.96 ± 1.03	8.49 ± 2.60	21.89 ± 2.70	95.06 ± 12.07	17.53 ± 0.69	14.04 ± 0.39	36.03 ± 8.59
LVCEB 1:30	63.19±7.18	108.00±17.80	bc	6.91 ± 1.33	8.42 ± 4.60	21.22 ± 4.26	92.99 ± 8.05	16.58 ± 1.56	13.82 ± 1.30	32.85 ± 10.02
EB1tha	63.17±11.41	105.39±17.18	c	6.56 ± 1.03	7.47 ± 4.05	19.06 ± 4.28	92.47 ± 10.39	16.42 ± 1.89	13.56 ± 1.42	31.85 ± 8.02
LVCEB 1:20	58.75±11.73	101.06±34.82	c	6.26 ± 1.12	6.71 ± 2.98	18.22 ± 3.72	86.19 ± 22.04	16.33 ± 1.99	13.40 ± 1.51	31.75 ± 6.76
p-value	0.4614	0.0003		0.2679	0.4980	0.0963	0.0916	0.0199	0.1262	0.2527
C.V: %	17.05	22.58		17.29	48.01	25.80	16.30	8.66	8.10	23.64

These key nutrients suggest that the application of vermicompost leachates could serve as an effective alternative or complementary fertilization strategy, particularly in soils with low organic matter content (Velecela et al., 2019; Manzoor et al., 2024). Additionally, vermicompost leachates contain beneficial microorganisms and bioactive compounds that enhance nutrient uptake efficiency and promote soil microbial activity (Loera-Muro et al., 2021; Torres-García et al., 2024).

Given these results, vermicompost leachates can serve as a valuable complement to the soil’s existing nutrient profile, particularly by enhancing nitrogen availability and improving soil organic matter content. This supplementation could benefit pepper (C. annuum) cultivation, as it provides a more balanced nutrient supply, promotes microbial activity, and enhances overall soil health. Integrating vermicompost leachates with the soil’s existing nutrients may optimize plant nutrition, reducing the need for synthetic fertilizers while maintaining sustainable crop productivity (Oyege and Balaji-Bhaskar, 2023; Hajam et al., 2023).

Plant variables

Table 4 presents the mean values for the increase in plant height, leaf number, stem diameter, chlorophyll content, fruit number, fruit weight, fruit length, fruit diameter, and yield in C. annuum plants throughout the crop cycle.

Vegetative growth parameters

The analysis revealed no statistically significant differences (p > 0.05) among treatments for plant height, stem diameter, and chlorophyll content. However, a slight numerical increase in plant height was observed with NPK, EB3tha, and LVCEB 1:30, aligning with findings from García et al. (2019), who reported improved plant growth and yield in C. annuum (var. Savior) following the application of vermicompost. Similarly, while stem diameter did not differ significantly among treatments, LVCEB 1:30, LVCEB 1:20, and EB1tha resulted in slightly larger diameters (6.99, 6.96, and 6.91 mm, respectively) compared to NPK.

Chlorophyll content also showed no significant differences among treatments, though higher mean values were recorded for LVCEB 1:30 (8.63), NPK (8.49), and LVCEB 1:20 (8.42). These results are consistent with those García et al. (2019) reported, who found that vermicompost leachates contributed to higher chlorophyll index values in a semi-protected system for C. annuum hybrid Salvador. The presence of humic substances and bioactive compounds in vermicompost may enhance chlorophyll synthesis and photosynthetic efficiency (Domínguez et al., 2010). Several studies (Wang et al., 2018; Sharma et al., 2019; Kumara et al., 2020) have emphasized the role of humic substances in plant growth regulation, though conflicting findings in the literature highlight the need for further research to clarify their mechanisms of action.

In contrast, the number of leaves per plant exhibited significant differences (p < 0.05) among treatments, with the highest values recorded for NPK (132.83 leaves) and bovine manure at 1 t ha-1 (130 leaves). This fact suggests that these treatments provided favorable conditions for vegetative growth, likely due to their nitrogen contribution, which is essential for foliar development. López et al. (2013) similarly observed enhanced leaf production in chili plants cultivated with vermicompost-based substrates, reinforcing the beneficial effects of organic inputs on canopy development.

Yield and fruit development parameters

For the variables fruit number per plant, fruit weight per plant, fruit length per plant, fruit diameter per plant, and total yield (t ha-¹), no significant differences (p > 0.05) were found among treatments. However, organic inputs, particularly vermicompost leachates, showed a slight numerical advantage over chemical fertilization. When comparing total yield, LVCEB 1:30 and LVCEB 1:20 exceeded NPK by 9.05% and 8.83%, respectively. These results align with studies by Cruz et al. (2017) and García et al. (2019), who highlighted the effectiveness of vermicompost in promoting higher biomass production, reducing foliar damage, and enhancing overall plant performance under shaded conditions.

From an economic perspective, the numerical yield difference of 3.27 t ha-1 between LVCEB 1:30 and NPK and 3.18 t ha-¹ between LVCEB 1:20 and NPK could be significant when assessing profitability in commercial production. Organic amendments maintain comparable productivity levels and offer additional long-term benefits, such as improved soil fertility, reduced dependency on synthetic fertilizers, and lower production costs (Hajam et al., 2023; Aytenew and Bore, 2020; Cesarano et al., 2017).

Comparative analysis

The MANOVA-Biplot (Figure 1) shows the groups or circles clustered in the center, therefore, it can be concluded that there are no significant differences between the treatments under study. These circles are multivariate of confidence in such a way that, when

projecting them on each one of the variables of this biplot a confidence interval is obtained for each one of the means. It is important to indicate that there are differences in some variables in this study that cannot be observed in the figure, since their greatest representativeness is found in the third axis, which has not been represented in the figure. These two axes explained 81.64% of the total variability of the regarding the type of fertilization, when chemical fertilization was used, there was a greater increase in the number of leaves as with the increase in plant height; however, these two variables have negative or null correlation with yield (r= -0.11 and 0.07, respectively). On the other hand, six of the nine variables under study obtained the highest results, highlighting the performance of LVCEB 1:30 and with less variability the increase in photosynthetic pigments, both strongly correlated (r= 0.97). For EB3th the weight of the fruit is negatively correlated to the diameter of the stem (r= -0.05).

Other significant correlations that could be highlighted in this analysis are: the diameter of the fruit with the length of the fruit (r = 0.84); the increase in stem diameter with the number of fruit (r = 0.30); the increase in height with the weight of the fruit (r = 0.49). It should be noted that all the variables that were related to the fruit had a correlation (on a greater or lesser scale) with the yield.

Other benefits of organic farming. Reyes-Pérez et al. (2017) indicate that organic fertilizers constitute one of the alternatives in the group of products used in sustainable agriculture, fundamentally those obtained from recyclable organic sources such as compost and vermicompost. This study could not establish statistical differences between chemical and organic treatments similarly to Álvarez-Hernández et al. (2011) in Mexico, after testing the effects of various levels and sources of fertilization on the phenological, productive responses and physical-chemical characteristics of the onion crop. However, other favorable results have been published by Rodríguez et al. (2008), De la Cruz et al. (2009) and Márquez et al. (2013) in crop production with the use of vermicompost leachates. It is important to mention that the benefits of organic fertilization can be best reflected over time once the availability of nutrients depends on some biotic factors in the soil, decomposition, among other factors, while in the case of chemical fertilization the nutrients are immediately available.

Again, although there are no statistical differences between the treatments under study, numerical values of the response variables may be significantly associated with the potential economic benefit for the producer. In this regard, Moreno and García (2016) indicate that at present there is a great preference among consumers for fresh foods, free of agrochemicals, innocuous and with high nutritional value, which with adequate marketing can benefit the small farmers of our study.

Additionally, the use of organic over the chemical fertilization presents notable benefits to the environment which have been widely documented (Bengtsson et al., 2005; Martínez-Torres, 2008; Batáry et al., 2010; Gabriel et al., 2010; Tuck et al., 2014; Zamilpa et al., 2016; Koelsch et al., 2020; Kumara et al., 2020: Mupambwa et al., 2020). Although we did not include any measurement of this effect on our study.

Conclusions and Recommendations

Our findings indicate that organic fertilization strategies, particularly those incorporating vermicompost leachates and bovine manure, represent a promising alternative to conventional NPK fertilization in C. annuum cultivation. While plant height, stem diameter, chlorophyll content, and yield variables did not show statistically significant differences among treatments, the numerical advantages observed with organic inputs suggest potential benefits for both soil health and plant physiological processes. The ability of organic fertilizers to enhance microbial activity, improve soil structure, and contribute to nutrient availability highlights their role in sustainable agricultural practices.

Despite the comparable performance of organic and chemical fertilization in this study, further research is required to evaluate the long-term impact of organic amendments on soil fertility, crop productivity, and overall ecosystem stability. Future studies should focus on the influence of organic fertilizers on microbial diversity, nutrient cycling, and water retention, as well as their effectiveness under different environmental and soil conditions. Additionally, integrating organic and chemical fertilization approaches could provide insights into optimizing nutrient management strategies that balance productivity with sustainability. Understanding these interactions will be essential for developing fertilization programs that support resilient and high-yielding C. annuum production systems while reducing reliance on synthetic inputs and mitigating environmental impact.

Acknowledgements

We sincerely thank the Faculty of Agronomic Engineering and the Graduate Institute of the Universidad Técnica de Manabí for their invaluable support and collaboration in conducting this research. We also extend our gratitude to the research groups “Biostimulants in Plant Production” and FAGROCLIM for their contributions and insights, which were essential to the development of this work.

Novelty Statement

Our manuscript presents relevant information about use of bovine manure and vermicompost as organic fertilizers and compares them with the effects of complete fertilization of chemical origin (N, P, K) in the pepper cropping; considering that it is currently necessary to count with information on the effects of different plant nutrition schemes, our data about organic fertilizers as an alternative to chemistry, can contribute to the new paradigm of plant nutrition.

Author’s Contribution

Mayra Falcones-Vélez, Robinson Pachay-Santana and Caridad A. Torres-García: Collect the data and make the original draft writing.

Silvia Velecela-Abambari: Collect the data and write initial results.

Álvaro Monteros-Altamirano and Liliana Corozo-Quiñonez: Contributed data or analysis tools, review and editing.

Francisco J. Arteaga-Alcívar: Contributed data or analysis tools and wrote the paper.

Karime Montes-Escobar: Conceived and designed the analysis and performed the analysis.

Carlos A. Salas-Macías: Conceived and designed the analysis, performed the analysis, wrote the paper, review and editing

Conflict of interest

We confirm that this manuscript has not been published else where and is not under consideration by another journal. All authors have approved the manuscript and agree with submission to Sarhad Journal of Agriculture (SJA). We have read and have abided by the statement ethical standards for manuscripts submitted to Sarhad Journal of Agriculture (SJA). The authors have no conflict to interested to declare.

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