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Article

Technical and Economic Assessment of Tomato Cultivation Through a Macro-Tunnel Production System with the Application of Gluconacetobacter diazotrophicus

by
Nelson Ceballos-Aguirre
1,
Alejandro Hurtado-Salazar
1,*,
Gloria M. Restrepo
2,
Óscar J. Sánchez
3,
María C. Hernández
1 and
Mauricio Montoya
1
1
Faculty of Agricultural Sciences, Universidad de Caldas, Manizales 170004, Colombia
2
Research Institute in Microbiology and Agro-Industrial Biotechnology, Universidad Católica de Manizales, Manizales 170002, Colombia
3
Center for Technological Development—Bioprocess and Agro-Industry Plant, Department of Engineering, Universidad de Caldas, Manizales 170004, Colombia
*
Author to whom correspondence should be addressed.
Horticulturae 2024, 10(10), 1110; https://doi.org/10.3390/horticulturae10101110
Submission received: 11 September 2024 / Revised: 13 October 2024 / Accepted: 17 October 2024 / Published: 18 October 2024
(This article belongs to the Section Vegetable Production Systems)
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Abstract

:
Bacterial inoculants hold promise for enhancing the sustainability and profitability of tomato cultivation in macro-tunnel systems. This study aimed to evaluate the technical and economic viability of applying Gluconacetobacter diazotrophicus to tomato production. The separate addition of native G. diazotrophicus GIBI025 and GIBI029 isolates and a commercial inoculant containing Azotobacter chrococcum and Azospirillium sp. was evaluated at a rate of 1 × 108 CFU·mL−1 without nitrogen addition. Conventional fertilization treatment with no bacteria added and 100%-nitrogen fertilization relative to crop requirements (added as MAP and urea) was also assessed. The treatments were evaluated within the macro-tunnel production system. The experiment utilized a completely randomized block design with four replications per treatment, and each experimental unit consisted of 20 plants. The yield (kg·ha−1) was calculated and economic assessment was performed. The results show that native G. diazotrophicus isolates in tomato cultivation under the macro-tunnel production system improved its economic viability, achieving yields up to 95,501 kg·ha−1 without the addition of nitrogenous fertilizers. This research reveals benefit–cost ratios achieving 1.57 and net incomes reaching 16,707 US dollars per hectare. This work demonstrated that the native isolates assessed may be used in the pursuit of more integrated, sustainable, and competitive cultural practices.

1. Introduction

Globally, tomato production reaches approximately 186 million tonnes, with China, India, Turkey, the United States, Egypt, and Italy being the principal producers [1]. In 2022, China was the leading global producer, contributing 68,241,811 t, which represents 36.67% of total production, followed by India with 20,694,000 t or 11.12% of the global output. Colombia produces 508,556 t, accounting for a 0.27% share of the world’s production [1].
Tomato production in Colombia represents a significant opportunity for rural development. This crop is well suited to the tropics, there is extensive knowledge of its cultivation, and a large number of producers are involved, many of whom are smallholders and family businesses [2,3]. The Boyacá region emerged as the dominant producer of greenhouse tomatoes in 2021, accounting for 30.64% of the total greenhouse tomato cultivation area nationwide. It is followed by the Antioquia and Cundinamarca regions, which account for 23.48% and 12.18%, respectively. Over the past 15 years, the area planted under greenhouse conditions in Colombia has increased from 573 ha in 2006 to 7136 ha in 2021 [2,4].
Tomato cultivation is primarily executed in two ways. Field-grown crops are susceptible to a range of biological threats, particularly from mite, thrips, and lepidopteran populations [5]. Abiotic factors, such as excessive precipitation, hail, frost, and strong winds, pose significant challenges due to their adverse climatic impacts. Alternatively, tomato cultivation under semi-controlled or controlled conditions grapples with high infrastructure costs associated with greenhouses and a low cost–benefit ratio. Consequently, many global tomato producers adopt macro-tunnel technology due to its economic viability [6], straightforward installation, adaptability to diverse terrains, and the longevity of certain designs, which can exceed a decade [7]. Using macro-tunnels can minimize fertilizer leaching, reduce the quantity and regularity in the application of fungicides and pesticides, extend production cycles, increase crop quality and yield, reduce pest and disease incidence, and protect against adverse climatic conditions [8,9]. In addition, the use of macro-tunnels creates a microclimate with temperatures 2–5 °C higher than the surrounding environment, hastening crop production and shielding plants from physical damage induced by precipitation and frost [6]. Therefore, additional research is required to investigate the effects of macro-tunnels on tomato cultivation under diverse geographic, varietal, and environmental conditions [10,11]. Furthermore, the integration of diverse agricultural practices, such as plastic mulching and the application of microbial consortia, may provide effective strategies for improving crop sustainability.
The implementation of macro-tunnel production systems and the utilization of alternative ways of fertilization, such as the addition of plant growth-promoting bacteria during agricultural practices, may lead to important increases in the yield during the production of vegetables and fruits. For instance, the interaction of the macro-tunnels combined with plastic mulch and the utilization of bacterial consortia resulted in high gross and net yields of up to 25,041 kg·ha−1 in the case of strawberries. With a favorable cost–benefit ratio of 1.41 in the second year, this approach proves to be a sustainable alternative for growers in the study area. Additionally, using the macro-tunnel production system resulted in a 35.71% reduction in losses when compared to the open-field system [12].
Biofertilizers can serve as a viable alternative to excessive chemical fertilizer use within integrated crop management systems, thereby enhancing nutrient availability for optimal plant growth. Biofertilizers consist of microorganisms capable of atmospheric nitrogen fixation, solubilization of potassium and phosphorus, and decomposition of organic matter. They also produce phytohormones, suppress plant diseases, and enhance soil fertility by providing nutrients and bioactive compounds, such as vitamins and hormones, to promote plant development [13].
One promising organism for the development of these biofertilizers is the Gluconacetobacter diazotrophicus bacterium, which was first isolated by Cavalcante and Döbereiner [14] from sugarcane tissues. Taxonomically, this bacterium is classified within the order Rhodospirillales, belonging to the Proteobacteria class and the Acetobacteraceae family. Originally identified as a nitrogen-fixing bacterium associated with sugarcane, this microorganism has been subsequently detected as an endophyte in a variety of plants, including potato [15], grass [16], coffee [17], African maize [18], and pineapple [19]. Its presence has also been confirmed in the rhizosphere of several plant species, such as coffee, wild rice, and sugarcane [17,18,20].
G. diazotrophicus-sugarcane association exemplifies the symbiotic relationship between monocotyledons and nitrogen-fixing bacteria. Although this relationship is not fully understood, various authors suggest that G. diazotrophicus may enhance plant growth [21,22]. To assess the potential of G. diazotrophicus as a plant growth-promoting bacterium beyond sugarcane, inoculation experiments have been conducted on various plant species. Caballero-Mellado et al. [23] reported the internal colonization of maize by G. diazotrophicus, a finding corroborated by similar observations in tomato [24]. Adriano-Anaya et al. [25] demonstrated that G. diazotrophicus inoculation enhanced sorghum biomass but had no discernible effect on maize growth. Moreover, evidence suggests a synergistic interaction between G. diazotrophicus and arbuscular mycorrhizal fungi in root colonization [15,25]. Thus, G. diazotrophicus possesses significant plant growth-promoting attributes, including the ability to fix atmospheric nitrogen, synthesize phytohormones such as auxins, and solubilize inorganic phosphate, as has been shown in previous work [26]. Considering all these characteristics, this bacterial species is regarded as a plant growth-promoting bacterium (PGPB) [21,27]. Particularly, native G. diazotrophicus isolates GIBI025 and GIBI029, recovered from sugarcane in Colombia’s Central Western region, exhibited phosphate solubilization capabilities comparable to the reference strain G. diazotrophicus ATCC 49037. Furthermore, these isolates demonstrated superior indole compound production and nitrogenase activity [26].
As G. diazotrophicus has the potential to capture and translocate nitrogen and solubilize edaphic phosphorus to make it assimilable, it can increase the availability of these macronutrients for plant assimilation. In fact, these features allow this bacterium to be potentially used as the main biological component for the development of new biofertilizers for improving crop yield and quality. In this sense, the analysis of native strains of G. diazotrophicus may represent a way to exploit the local biodiversity for the production of new bioinputs in the framework of sustainable agriculture. The potential of native G. diazotrophicus isolates as plant growth promoters has been explored in multiple crop systems, such as sugarcane [28], cassava and papaya [29], carrot [22], and tomato plantlets [30]. These works indicate that enhanced growth can facilitate a reduction in chemical fertilizer use. Nevertheless, as far as we know, no published studies have assessed the economic viability of employing G. diazotrophicus as a fertilizer for tomato crops. Therefore, this study aimed to evaluate the impact of applying native G. diazotrophicus isolates GIBI029 and GIBI025 on the yield and economic feasibility of tomato cropping using alternative production systems such as the macro-tunnels.

2. Materials and Methods

2.1. Location

The study was conducted at the Tesorito Farm, a property of the Universidad de Caldas situated at an altitude of 2340 m above sea level (5°01′49″ N, −75°26′13″ W). The site is characterized by an annual precipitation of 1800 mm, relative humidity of 78%, and annual solar radiation of 1215 h. The mean temperature is 17.5 °C, and the soil type is sandy loam [31].

2.2. Bacteria

Native G. diazotrophicus GIBI025 and GIBI029 isolates derived from a Colombian sugarcane plantation [26] were evaluated. A commercial product (Azotobacter chrococcum + Azospirillium sp.) at a concentration of 1 × 108 colony-forming units (CFU) per milliliter was used as the biological commercial control. Both native isolates of G. diazotrophicus used in this study were procured from the Microorganism Collection of the Universidad Católica de Manizales. Their collection and utilization were authorized under Permit No. 1166 for the Collection of Wild Specimens of Biological Diversity for non-commercial scientific research purposes, granted by the Colombian National Authority of Environmental Licenses (ANLA) to the Universidad de Caldas.

2.3. Preparation of Bacterial Suspension

Inocula and bacterial suspensions of G. diazotrophicus GIBI025 and GIBI029 isolates were prepared using modified dextrose-yeast-glutamic acid-salts (DYGS) [32] and Lipman Goodale Ivo-Pernambuco (LGI-P) media [14,33]. The growth media were inoculated and incubated at 30 °C with constant agitation at 150 rpm for a period of 168 h. The commercial bacterial inoculant was prepared according to the technical sheet of the product.
Bacterial cultures were monitored daily until they reached the target concentration of 1 × 108 CFU·mL−1. Bacterial purity, viability, and concentration were monitored throughout the experimental period using colony-forming unit (CFU) counts.

2.4. Experimental Design

A randomized complete block experimental design was employed, comprising four replications with 20 plants per experimental unit. Each replication is equivalent to a block, and within each block, 20 plants per treatment were arranged for a total of 80 plants per treatment and 320 useful plants per plot within a macro-tunnel. The study plot contained 600 plants in total. The following four separate treatments were evaluated: G. diazotrophicus GIBI025 isolate, G. diazotrophicus GIBI029 isolate, commercial microbial inoculant (Azotobacter chrococcum + Azospirillium sp.) as a commercial control, and conventional fertilization (farmer’s standard) as a negative control. The production system evaluated corresponded to the macro-tunnel system. Bacterial concentrations for GIBI025 and GIBI029 isolates were set at 1 × 108 CFU·mL−1 [26], and the commercial inoculant treatment was similarly administered at 1 × 108 CFU·mL−1.
The plants were directly sown into the soil at a density of 20,833 plants per hectare. A planting arrangement of 40 cm within-row spacing and 120 cm between-row spacing was employed. Each GIBI isolate was supplied to the crop through the addition of 75 mL per plant of a liquid mixture prepared, in turn, by diluting 5 mL of the isolate’s bacterial suspension with water until 1 L. Each isolate suspension had a concentration of 18 × 108 CFU·mL−1, as well as the commercial inoculant. The bacterial suspensions were inoculated 20 days after transplanting.
The conventional farmer-type fertilization treatment, which represents the conventional fertilization of the farmer when biofertilization is not applied (negative control), involved applying 100% of the nitrogen required by the crop to the soil; this was equivalent to 280 kg N·ha−1, applied as 200 kg·ha−1 mono ammonium phosphate (12-61-0, i.e., 12% NH4+ and 61% P2O5; Haifa Negev technologies Co. Ltd., Matam-Haifa, Israel) and 500 kg·ha−1 urea (BASF Co. Ltd., Limburgerhof, Germany). Gluconacetobacter treatments did not include nitrogen but were supplemented with the following nutrients necessary for balanced fertilization, based on soil analysis: K2SO4 (Tianda Chemical Co. Ltd., Liaocheng, China), MgSO4 (IFFCO Kisan Suvidha Ltd., New Delhi, India), and KCl (Lvfeng Fertilizer Co., Ltd., Zibo, China).
For this analysis, the collected soil was homogenized to obtain a 1-kg analytical sample in pre-labeled plastic bags, and physicochemical soil characterization was performed by determining: texture (using the Bouyoucos hydrometer technique), pH with a potentiometer and considering a soil:water suspension with a 1:2 ratio; organic matter content by wet oxidation and colorimetric quantification [34], total nitrogen by the Kjeldahl method [35], available phosphorus by Bray II extraction and colorimetric quantification [36], exchangeable cations (calcium, magnesium, sodium, and potassium) by ammonium acetate (1 N pH 7) extraction and atomic absorption [37], microelements (iron, copper, manganese, and zinc) by EDTA extraction and atomic absorption [38], sulfur by monocalcium phosphate turbidimetric extraction, and boron by calcium monobasic phosphate Azometine-H colorimetric extraction [39]. The results of the soil analysis are shown in Table 1.
Once the interpretation of the soil analysis was accomplished, the fertilization requirements for the following elements were found: nitrogen—280 kg·ha−1, potassium—250 kg·ha−1, magnesium—30 kg·ha−1, and sulfur—60 kg·ha−1. The remaining elements assessed were found at high levels in the soil. The fertilization plan was defined for each one of the treatments, as presented in Table 2. This table also provides an overview of the treatment combinations and their corresponding codes.
The macro-tunnel production system was specified with dimensions of 5.55 m in width and 45.70 m in length (see Figure 1). The climatic conditions were monitored using a data logger. The average temperature within the macro-tunnel was 3.67 °C higher than the ambient temperature, and the relative humidity was 6.11% lower than the ambient relative humidity. A self-compensating drip irrigation system with 15 cm drip emitters was employed to meet the plant’s water requirements. The irrigation duration was adjusted according to the plant’s phenological stage. Thus, for the first stage (between 0 and 30 days, corresponding to the beginning of flowering), 500 mL·plant−1·day−1 of water were added; for the second stage (between 30 and 60 days, corresponding to the beginning of fruit filling), 1000 mL·plant−1·day−1 of water were applied; and during the third stage (after 60 days until 15 days before the end of the crop cycle, corresponding to the full fruit filling), 1500 mL·plant−1·day−1 of water were added.
The response variables measured during the experiment setup were total yield per hectare (in kg·ha−1), production per plant (in g), and fruits per plant. Data were analyzed through analysis of variance (ANOVA), followed by Duncan’s multiple range test to determine significant differences among treatments. Statistical significance was set at p < 0.05. All statistical analyses were performed using SAS version 9.1 (SAS Institute, Inc., Cary, NC, USA).

2.5. Economic Viability Assessment

Economic viability was assessed through individual calculations using the methodological approach of Herrera et al. [40]; their cost structure model for tomato production served as a framework for our individual calculations. G. diazotrophicus suspension cost was estimated at 754.67 United States dollars (USD) per hectare, equivalent to the cost of the application of a commercial preparation in one-liter presentation of a bacterial inoculant, including the price of the acquisition of a commercial strain of this bacterium [41]. Costs for various fertilization types according to established treatments were considered as well. The average price of tomatoes over the last ten years (2014–2024) was estimated at 0.48 USD·kg−1 [42]. A financial analysis was conducted to assess net revenue and gross income. The main techno-economic parameters used to accomplish this analysis are presented in Table 3.
Gross income was calculated by multiplying the total yield per hectare (kg·ha−1) obtained in each treatment by the average market price of 0.48 USD·kg−1. Direct and indirect production costs were estimated using the reference format outlined in Section 3.2. The total cost of production per hectare was determined by summing these costs across all treatments. Net income was calculated by subtracting the total production cost from the corresponding gross income. The benefit–cost ratio (B/C) was calculated by dividing the gross income by the net income for each treatment. The unit production margin (UPM) was determined by dividing the total production cost by the total production in kg·ha−1. Additionally, the construction and annual operational costs of the macro-tunnel system corresponded to an area of 540 m2.

3. Results

3.1. Effects of Biofertilization on Production per Plant, Total Yield, and Fruits per Plant

The yield data revealed no statistically significant differences among treatments (Figure 2). In all cases, the application of the native bacterial suspensions at a concentration of 1 × 108 showed yields of 87,718 kg·ha−1 for the isolate GIBI025 and 95,501 kg·ha−1 for GIBI029. The commercial treatment, consisting of Azotobacter chrococcum and Azospirillium sp., resulted in a lower yield of 83,509 kg·ha−1 compared to the farmer’s control (100% nitrogen fertilization), which produced 93,458 kg·ha−1. Both treatments yielded less than the GIBI029 treatment. These figures demonstrate that both native and commercial nitrogen-solubilizing bacteria have a good performance without the addition of nitrogen fertilization.
No significant differences were observed in production per plant or fruit per plant among the treatments (Figure 2), evaluated over a crop cycle. While the commercial treatment yielded 4009 g and 48.45 fruits per plant, these differences were not statistically significant. The application of native bacterial suspensions GIBI029 and GIBI025 resulted in production per plant of 4584 g and 4211 g, respectively, and fruit per plant of 51.02 and 47.27, respectively.

3.2. Impact of Biofertilization on Cost Structure and Economic Analysis of the Tomato Crop

Table 4 presents the direct and indirect cost estimates for the tomato production system. These costs were calculated for each treatment evaluated, using the reference format provided [40]. By comparing the costs across treatments, we determined the total cost of production per hectare. Regarding the production costs per hectare of tomato cultivation under the conditions of Caldas, Colombia, an investment over a 240-day crop cycle was estimated (Table 4). Costs were calculated over the investment period. The inoculations with G. diazotrophicus GIBI029 and GIBI025 native isolates without nitrogen fertilization showed the least participation in the total cost of inputs at 6798 USD. Conversely, the Farmer-100N control with 100% nitrogen fertilization had an input cost of 7830 USD because of the high current fertilizer costs.
A comparative analysis of production costs revealed that the farmer control treatment with 100% complete technical fertilization based on soil analysis and corresponding crop extraction incurred the highest total costs. The primary driver of this difference was the cost of the treatments, mostly depending on the cost of the fertilizers applied (input B.6 in Table 4), which amounted to 1786 USD for the conventional farmer-type fertilization (negative control, coded as Farmer-100N) compared to 755 USD for the native and commercial bacterial treatments, representing an average difference of 1031 USD.
Labor costs (labor A.3 in Table 4) for harvest and post-harvest activities also contributed to the variation in total costs. The GIBI029-0N treatment, which yielded 95,501 kg·ha−1, required $2022 for labor, while the Farmer-100N treatment, with a yield of 93,458 kg·ha−1, required $1984. Treatments with lower yields correspondingly had lower labor costs.
While the bacterial treatments achieved cost reductions of up to $1275 ha−1, lower production costs alone do not guarantee economic viability. The gross and net revenues generated by the crop yields must also be considered. As demonstrated, the GIBI025-0N and the commercial treatment without nitrogen fertilization (Commercial-0N) exhibited lower costs but only the bacterial GIBI029-0N treatment showed both low costs and the highest revenues, indicating superior economic performance (see Table 5).
The production costs per hectare for each treatment differed up to the start of harvesting due to the differential costs associated with cultural practices and inputs, such as labor and fertilization. Variations were most substantial within the labor category, specifically related to harvesting tasks, due to fluctuations in productivity observed across the evaluated treatments. Additionally, fluctuations in input costs were noted, due to the cost of synthetic fertilizers (Table 4). In estimating total costs per hectare, parameters such as labor costs, input costs, and the cost of bacterial suspensions were considered. The cost of the construction and installation of macro-tunnels is also considered in Table 4 (see Appendix A). The highest production cost, amounting to USD$30,469 per hectare, was associated with conventional fertilization. In this treatment (negative control), the share of input costs was high relative to total costs (25.70%) and based on the yield achieved (93,458 kg·ha−1). Labor costs accounted for the most significant proportion of production costs across all evaluated treatments (including the control), ranging from 52.18% to 54.26% of the total production cost (Table 4). Within the labor category, harvesting and post-harvesting tasks were the most significant.
Although the analysis of variance reported no statistically significant differences, the economic analysis highlighted the order of treatments in terms of economic viability. The most economically viable was GIBI029-0N with a B/C of 1.57, followed by Farmer-100N with a B/C of 1.48, and GIBI025-0N with a B/C of 1.45 (see Table 5). Additionally, the integrated management of nutrition was emphasized, ensuring yield and profitability while maintaining soil biological balance by avoiding unnecessary additions of nitrogenous sources.

4. Discussion

The results obtained indicate that the yields exceeded the national average for macro-tunnel tomato production (84,580 kg·ha−1) and the average yield under field conditions in Caldas province (44,210 kg·ha−1) for the year 2022 [4]. These values indicate a minimum added value of approximately 3500 kg·ha−1 above the national average.
This study was conducted without the addition of chemically synthesized nitrogen in G. diazotrophicus treatments, compared to the farmer’s control where 100% of the nitrogen required by the plant was added. Rodríguez-Andrade et al. [46] reported a decline in G. diazotrophicus populations within plants under nitrogen fertilization conditions. This reduction is potentially attributed to plant physiological alterations directly impacting bacterial numbers. Nevertheless, in the rhizosphere, the release of metabolites may initially be required to induce environmental changes. The decline in G. diazotrophicus populations might also be attributed to pleomorphic changes occurring when the bacteria are cultivated under conditions of elevated nitrogen levels [20]. Physiological changes in plants subjected to high nitrogen fertilization levels have been suggested as a potential cause for reduced G. diazotrophicus populations [47]. Nitrogen is an essential element for plant growth and development, contributing to the synthesis of key molecules that promote plant biomass accumulation and metabolism [48,49]. Nitrogen fertilization can significantly influence the population of rhizospheric bacterial communities. For instance, ammonium-based fertilization has been shown to enhance root colonization by Pseudomonas fluorescens 2-79RLI, particularly in root tip and lateral root regions, when the pH is allowed to fluctuate with nitrogen form [50]. Conversely, nitrogen fertilization, irrespective of its form, has been reported to reduce Gluconacetobacter diazotrophicus populations in sugarcane [51,52]. This decline might be attributed to morphological alterations observed in G. diazotrophicus cells exposed to elevated concentrations of NH4NO3 (25 mM).
While statistical analyses of production per plant, total yield, and fruits per plant did not reveal significant differences among the treatments (see Figure 2), the GIBI029 isolate of G. diazotrophicus demonstrated superior economic performance compared to both the commercial control and the negative control, i.e., the conventional 100% nitrogen fertilization practice (Table 5). This advantage can be attributed to the isolate’s ability to effectively supply nitrogen to tomato plants, eliminating the need for supplemental nitrogen fertilizer. Consequently, the use of environmentally harmful chemical nitrogen fertilizers was significantly reduced. These findings enable the development of innovative production systems that integrate biotechnological inputs, including microbial inoculants to enhance plant growth. According to Wu et al. [53], to optimize tomato yields, reduce the use of inorganic fertilizers, and thus mitigate soil pollution and agroecological degradation, it is necessary to manage practices that enhance the availability and accessibility of nutrient sources for the plant. Furthermore, Fernández-Delgado et al. [54] report that inoculation with G. diazotrophicus can reduce the nitrogen fertilization recommended for tomato cultivation in typical Red Ferralitic soil conditions by 30%, without affecting the external quality of the fruits, thus offering a nutritionally, ecologically, and economically viable management alternative. In the case of carrot cultivation, the use of G. diazotrophicus (reference strain and native isolation) at concentrations of 18 × 107 CFU·mL−1 achieved a yield of up to 37,417 kg·ha−1 without the addition of nitrogen and phosphorus fertilizers, provided that the soil has reserves of these nutrients [55].
The potential benefits of this bacterium to plants include nitrogen fixation, phytohormone production, biocontrol against pathogens, and enhanced mineral nutrient availability through solubilization [27,56]. Additionally, Srebot et al. [57] reported that G. diazotrophicus inoculation enhances tomato plant tolerance to environmental stress through physiological and anatomical modifications. These authors observed thickened cell walls in root vascular cylinders and stem vascular bundles of inoculated plants, along with the development of contact cells containing dense cellular material.
Luna et al. [24] inoculated tomato seedlings with G. diazotrophicus to assess the bacterium’s ability to colonize the plants and its subsequent effect on fruit yield. Their findings suggest that inoculated tomatoes can benefit from effective plant colonization. The same authors observed an increase in fruit number for plants inoculated with G. diazotrophicus, yielding 53.45 fruits compared to 49.8 in non-inoculated plants. Similarly, the weight of fruits per inoculated and non-inoculated plant was 8.45 kg and 7.45 kg respectively. Suárez et al. [58] assessed the number of clusters in an indeterminate variety of tomatoes and achieved a maximum yield of 6.8 kg·plant−1.
These results indicate that endophytic plant growth-promoting bacteria have greater nutrient availability within plant tissues and minimal competition with other bacterial genera, as occurs in the rhizosphere and soil. One characteristic of G. diazotrophicus is its ability to invade the vascular system within the root system, where carbohydrates and organic acids produced by photosynthesis serve as a food source; these bacteria colonize and circulate in the xylem of a wide variety of domestic and wild plants [46]. Further investigation is required to elucidate the precise mechanism by which bacterial application enhances tomato fruit yield. Potential explanations include bacterial colonization, hormone production, or other growth-promoting factors.
The application of biofertilizers to economically important crops beyond tomatoes has been explored. Studies have demonstrated the potential of biofertilizers to enhance crop productivity, reduce input costs, and improve soil health, thereby contributing to sustainable agriculture. For instance, Rajula Shanthy and Venkatesaperumal [59] conducted a social and economic study on the use of biofertilizers in sugarcane cultivation. They found that biofertilizers increased sugarcane yields, reduced fertilizer costs, and improved soil health, resulting in higher profits. Despite challenges such as labor availability and cost, and lack of timely availability of good quality biofertilizers, farmers expressed a positive attitude toward adopting biofertilizer technology. On the other hand, Aechra et al. [60] investigated the effects of biofertilizers and vermicompost on wheat productivity. Their results indicated that the combination of Azotobacter sp. and vermicompost applied in two stages (50% at sowing and 50% at tillering) yielded the highest net yield and benefit–cost ratio. These findings underscore the potential of biofertilizers to offer environmentally friendly and economically viable solutions for sustainable agricultural production systems.
The results of this investigation highlight the significance of G. diazotrophicus in enhancing crop yield, particularly when used in conjunction with appropriate fertilization levels.
These findings emphasize the need for comprehensive assessments of soil physical, chemical, and biological properties to promote the long-term sustainability of agricultural systems. The use of soil reserve levels of nitrogen (0.36%) and suitable phosphorus levels (203 mg·kg−1) reported in the initial laboratory soil analysis (Table 1) achieved the highest yields in the crop cycle evaluated. Nevertheless, sustaining this condition over time would necessitate a return of nutrients to the system equivalent to those removed by the crop. On the other hand, the evaluation of intermediate levels of nitrogen fertilization in conjunction with the application of diazotrophic bacteria should be evaluated in depth. Previous research on tomatoes [3] examined the interaction between varying nitrogen levels (0, 50%, and 100%) and the addition of Azospyrillum brasilense and Bradyrhizobium japonicum on tomato yield and economic viability. That study demonstrated that a mixture of these nitrogen-fixing bacteria, applied at a rate of 100 mL·ha−1, significantly increased tomato yield and fruits per plant when nitrogen (urea) was either omitted or applied at intermediate levels. A similar previous study conducted on carrots [22] explored the impact of different G. diazotrophicus initial concentrations and various combinations of chemical nitrogen and phosphorus fertilizers. Future research should focus on determining the optimal combinations of chemical fertilizers and bacterial suspensions at varying initial concentrations, considering the specific soil chemical characteristics, not only for tomato crops but also for other vegetables. Hence, strategies for integrated crop nutrition management should be promoted, combining the use of nitrogen-fixing bacteria like G. diazotrophicus with the addition of organic amendments and smaller proportions of fertilizing sources.

5. Conclusions

The use of native GIBI029 isolate of the diazotrophic bacterium G. diazotrophicus in suspensions at concentrations of 1 × 108 UFC·mL−1 in tomato cultivation under the macro-tunnel production system improved its economic viability, achieving yields up to 95,501 kg·ha−1 without the addition of nitrogenous fertilizers and ensuring appropriate levels of the other nutrients according to the soil analysis performed. Findings from this research reveal benefit–cost ratios reaching 1.57 and net incomes reaching as high as 16,707 US dollars per hectare. Specifically, this work demonstrated the potential for economically efficient use of the native Colombian isolates of G. diazotrophicus in the pursuit of more integrated, sustainable, and competitive cultural practices.

Author Contributions

Conceptualization, N.C.-A. and A.H.-S.; methodology, M.C.H. and M.M.; software, N.C.-A. and A.H.-S.; validation, G.M.R., N.C.-A. and A.H.-S.; formal analysis, G.M.R., N.C.-A., A.H.-S. and Ó.J.S.; investigation, M.C.H. and M.M.; resources, G.M.R., N.C.-A. and Ó.J.S.; data curation, N.C.-A. and G.M.R.; writing—original draft preparation, A.H.-S., G.M.R., M.C.H. and M.M.; writing—review and editing, A.H.-S. and Ó.J.S.; visualization, M.C.H. and M.M.; supervision, N.C.-A. and G.M.R.; project administration, G.M.R.; funding acquisition, G.M.R. and Ó.J.S. All authors have read and agreed to the published version of the manuscript.

Funding

This article is derived from the program “Biofactories: An Opportunity for Bioeconomic Development for Caldas through Biotechnology, code 1235-903-8697”, funded by the Colombian Ministry of Science, Technology and Innovation through the Francisco José de Caldas fund, contingent recovery contract No. 80740-503-2021, executed by the Universidad de Manizales in partnership with the Universidad de Caldas, Universidad Católica de Manizales, Universidad Católica Luis Amigó, Universidad Autónoma de Manizales, Gobernación de Caldas, Fundación Centro Internacional de Educación y Desarrollo Humano (CINDE), and Centro de Bioinformática y Biología Computacional de Colombia (BIOS). This research was also funded by the Universidad de Caldas and the Universidad Católica de Manizales through the research initiative “Production of a biofertilizer based on Gluconacetobacter diazotrophicus on the pilot scale and its evaluation in promoting the growth of vegetable crops”. The APC was funded by the above-mentioned research program.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

The authors thank the technical support of the Tesorito Farm at the Universidad de Caldas and the Research Institute in Microbiology and Agro-industrial Biotechnology at the Universidad Católica de Manizales. The administrative support of the Universidad de Manizales is acknowledged as well.

Conflicts of Interest

The authors declare no conflicts of interest.

Appendix A

Table A1. Cost structure for the construction and installation of a macro-tunnel for tomato cultivation in Manizales, Caldas, Colombia.
Table A1. Cost structure for the construction and installation of a macro-tunnel for tomato cultivation in Manizales, Caldas, Colombia.
Construction and Installation CostsUnitTotal QuantityUnit Value
(USD)		Total Value
(USD)		Annual Value
(USD)		Cycle Value
(USD)		%
Structure—Inputs (A)
Galvanized pipe 1″ × 6 m C 2 mmUnit66717.6311,759.21587.96293.986.82
1 1/2″ × 6 m galvanized pipeUnit4002.771108.0055.4027.700.64
3/4″ × 6 m black pipeUnit679.47634.4931.7215.860.37
1/8″ steel cablem44440.17755.4837.7718.890.44
Welding reference 6013 × 1/8kg674.14277.3813.876.930.16
Staples 50–19Box222.9464.6821.5610.780.25
Tamping rope roll × 800Roll116.9476.3425,4512.720.30
3/8″ galvanized threaded rodm671.82121.946.103.050.07
3/8″ galvanized nutUnit11110.0444.442.221.110.03
3/8″ galvanized washerUnit11110.19211.0910.555.280.12
Agroclear 7 × 7 × 50kg26674.2311,281.413760.471880.2443.63
Agroclear 1 × 8 × 50kg2894.231222.47407.49203.754.73
Anticorrosive paintGallon68.7952.7417.588.790.20
Total (A) 27,609.674978.152489.0757.75%
Construction work (B)
Plastic construction and installationWage17812.722264754.52377.268.75
Total (B) 2264754.52377.268.75
Irrigation (C)
Hose 2″ 40 gaugem14580.771122.66224.53112.272.60
Suction hose 2″ water inletm20832.755728.251145.65572.8313.29
Tank 2000 LUnit21132.072773.47554.69277.356.44
Dripline 16 mm dripline 40 cm drippersm83330.322666.56533.31266.666.19
Motor pump 0.75 HPUnit2192.461941.66194.1797.082.25
Accessories 2″ motor pumpUnit219.61201.8120.1810.090.23
Total (C) 14,434.412886.881443.4431.01%
Total (A + B + C) 44,307.418619.554309.77100.00%

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Horticulturae 10 01110 g001
Figure 1. Macro-tunnel production system: (A) Schematic diagram illustrating the dimensions and layout; (B) detailed view of the system with a data logger installed to continuously record daily temperature and humidity within the tunnel.
Figure 1. Macro-tunnel production system: (A) Schematic diagram illustrating the dimensions and layout; (B) detailed view of the system with a data logger installed to continuously record daily temperature and humidity within the tunnel.
Horticulturae 10 01110 g001
Horticulturae 10 01110 g002
Figure 2. Production per plant, total yield, and fruits per plant of tomato fruits depending on the fertilization treatment. The values of tomato fruits per plant are multiplied by 100 in the figure. Means with the same letter are not significantly different (p > 0.05) based on Duncan’s multiple range test. The treatment codes are deciphered in Table 2. GIBI025-0N; addition of a suspension of G. diazotrophicus GIBI025 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; GIBI029-0N; addition of a suspension of G. diazotrophicus GIBI029 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Commercial-0N: addition of a commercial inoculant containing Azotobacter chrococcum and Azospirillium sp. at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Farmer-100N (negative control): conventional full nitrogen fertilization through the addition of 200 kg·ha−1 mono ammonium phosphate (12-61-0) and 500 kg·ha−1 urea, with no bacterial addition. Other nutrients were added for all the treatments as specified in Table 2.
Figure 2. Production per plant, total yield, and fruits per plant of tomato fruits depending on the fertilization treatment. The values of tomato fruits per plant are multiplied by 100 in the figure. Means with the same letter are not significantly different (p > 0.05) based on Duncan’s multiple range test. The treatment codes are deciphered in Table 2. GIBI025-0N; addition of a suspension of G. diazotrophicus GIBI025 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; GIBI029-0N; addition of a suspension of G. diazotrophicus GIBI029 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Commercial-0N: addition of a commercial inoculant containing Azotobacter chrococcum and Azospirillium sp. at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Farmer-100N (negative control): conventional full nitrogen fertilization through the addition of 200 kg·ha−1 mono ammonium phosphate (12-61-0) and 500 kg·ha−1 urea, with no bacterial addition. Other nutrients were added for all the treatments as specified in Table 2.
Horticulturae 10 01110 g002
Table 1. Chemical and physical characteristics of the soil in Tesorito Farm at the Universidad de Caldas (Manizales, Colombia).
Table 1. Chemical and physical characteristics of the soil in Tesorito Farm at the Universidad de Caldas (Manizales, Colombia).
pHNitrogen
(%)		Organic Matter
(%)		Phosphorus
(mg·kg−1)		Potassium
(cmol·kg−1)		Calcium
(cmol·kg−1)		Magnesium
(cmol·kg−1)		Sodium
(cmol·kg−1)		Iron
(mg·kg−1)
5.80.368.592030.606.371.650.231272
Manganese
(mg·kg−1)		Zinc
(mg·kg−1)		Copper
(mg·kg−1)		Sulfur
(mg·kg−1)		Boron
(mg·kg−1)		Sand
(%)		Silt
(%)		Clay
(%)		Texture
16.3926.276.4022.791.24602317Sandy loam
Table 2. Treatment combinations of the experimental setup.
Table 2. Treatment combinations of the experimental setup.
MicroorganismConcentration
(CFU·mL−1)		Nitrogen
Fertilization
(%)		Other NutrientsCode
GIBI0251 × 1080For all the treatments: 200 kg·ha−1 K2SO4 (18% S + 50% K2O), 200 kg·ha−1 MgSO4 (16% S + 50% MgO), and 250 kg·ha−1 KCl (60% K2O) GIBI025-0N
GIBI0291 × 1080GIBI029-0N
Azotobacter chrococcum + Azospirillium sp.1 × 1080Commercial-0N
No addition of bacteria0100Farmer-100N
Table 3. Techno-economic parameters used to assess the economic viability of the tomato production system using macro-tunnels.
Table 3. Techno-economic parameters used to assess the economic viability of the tomato production system using macro-tunnels.
ParameterValueReference
Year of analysis2024
Year construction starts2023
Construction period (months)18
Start-up period (months)7
Project life (years)15
Depreciation period (years)10
Depreciation methodStraight–line method
Salvage cost0
Inflation (%)6.86[43]
Opportunity interest rate (year 2024) (%)9.09[44]
Income tax (year 2024) (%)35[45]
Table 4. Production cost structure per hectare of the tomato crop for four types of fertilization.
Table 4. Production cost structure per hectare of the tomato crop for four types of fertilization.
Treatment 1GIBI029-0NGIBI025-0NCommercial-0NFarmer-100N
Total Value (USD·ha−1)%Total Value (USD·ha−1)%Total Value (USD·ha−1)%Total Value (USD·ha−1)%
A. Labor (1 + 2 + 3)15,93854.2615,77354.0315,68453.9015,90052.18
(1) Adequacy of land18956.4518956.4918956.5118956.22
Preparation16155.5016155.5316155.5516155.30
Sowing2800.952800.962800.962800.92
(2) Crop maintenance12,02140.9212,02141.1812,02141.3212,02139.45
Crop cultivation975833.22975833.42975833.54975832.03
Application of inputs19076.4919076.5319076.5619076.26
Application of treatments3561.213561.223561.223561.17
(3) Harvest and post-harvest20226.8818576.3617686.0719846.51
B. Inputs (4 + 5 + 6 + 7 + 8 + 9 + 10)679823.14679823.29679823.37783025.70
(4) Seed23257.9123257.9623257.9923257.63
(5) Edaphic fertilizer23758.0823758.1323758.1623757.79
(6) Treatments7552.577552.587552.5917865.86
(7) Fungicide920.31920.32920.32920.30
(8) Insecticide1330.451330.461330.461330.44
(9) Pita cord, 13 gauge wire, cushioned10423.5510423.5710423.5810423.42
(10) Tutoring (amortization)760.26760.26760.26760.25
Direct cost (A + B)22,73777.4022,57177.3122,48277.2723,73077.88
C. Indirect Cost (11 + 12 + 13)24368.2924208.2924118.2925368.32
(11) Lease1480.501480.511480.511480.49
(12) Administration11443.9011363.8911323.8911943.92
(13) Technical assistance11443.9011363.8911323.8911943.92
D. Macro-tunnel cost per cycle 24309.7714.314309.7714.404309.7714.454309.7713.80
TOTAL (A + B + C + D)29,376100.0029,194100.0029,097100.0030,469100.00
1 The treatment codes are deciphered in Table 2. GIBI025-0N; addition of a suspension of G. diazotrophicus GIBI025 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; GIBI029-0N; addition of a suspension of G. diazotrophicus GIBI029 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Commercial-0N: addition of a commercial inoculant containing Azotobacter chrococcum and Azospirillium sp. at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Farmer-100N (negative control): conventional full nitrogen fertilization through the addition of 200 kg·ha−1 mono ammonium phosphate (12-61-0) and 500 kg·ha−1 urea, with no bacterial addition. Other nutrients were added for all the treatments as specified in Table 2. 2 See Appendix A.
Table 5. Economic analysis of the tomato crop depending on the type of fertilization.
Table 5. Economic analysis of the tomato crop depending on the type of fertilization.
Treatment 1Gross Income
(USD·ha−1)		Total Cost 2
(USD·ha−1)		Net Income
(USD·ha−1)		Unit Value of Production (USD·ha−1)B/CRate of Return
(%)
GIBI025-0N42,32729,19413,1330.331.4544.98
GIBI029-0N46,08329,37616,7070.311.5756.87
Commercial-0N40,29629,09711,2000.351.3838.49
Farmer-100N45,09730,46914,6280.331.4848.01
1 The treatment codes are deciphered in Table 2. 2 Total costs are broken down by treatment taken from Table 4. B/C: benefit/cost ratio; GIBI025-0N: addition of a suspension of G. diazotrophicus GIBI025 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; GIBI029-0N; addition of a suspension of G. diazotrophicus GIBI029 isolate at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Commercial-0N: addition of a commercial inoculant containing Azotobacter chrococcum and Azospirillium sp. at an initial concentration of 1 × 108 CFU·mL−1, with no addition of nitrogen fertilizer; Farmer-100N (negative control): conventional full nitrogen fertilization through the addition of 200 kg·ha−1 mono ammonium phosphate (12-61-0) and 500 kg·ha−1 urea, with no bacterial addition. Other nutrients were added for all the treatments as specified in Table 2. 2 See Appendix A.
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Ceballos-Aguirre, N.; Hurtado-Salazar, A.; Restrepo, G.M.; Sánchez, Ó.J.; Hernández, M.C.; Montoya, M. Technical and Economic Assessment of Tomato Cultivation Through a Macro-Tunnel Production System with the Application of Gluconacetobacter diazotrophicus. Horticulturae 2024, 10, 1110. https://doi.org/10.3390/horticulturae10101110

AMA Style

Ceballos-Aguirre N, Hurtado-Salazar A, Restrepo GM, Sánchez ÓJ, Hernández MC, Montoya M. Technical and Economic Assessment of Tomato Cultivation Through a Macro-Tunnel Production System with the Application of Gluconacetobacter diazotrophicus. Horticulturae. 2024; 10(10):1110. https://doi.org/10.3390/horticulturae10101110

Chicago/Turabian Style

Ceballos-Aguirre, Nelson, Alejandro Hurtado-Salazar, Gloria M. Restrepo, Óscar J. Sánchez, María C. Hernández, and Mauricio Montoya. 2024. "Technical and Economic Assessment of Tomato Cultivation Through a Macro-Tunnel Production System with the Application of Gluconacetobacter diazotrophicus" Horticulturae 10, no. 10: 1110. https://doi.org/10.3390/horticulturae10101110

APA Style

Ceballos-Aguirre, N., Hurtado-Salazar, A., Restrepo, G. M., Sánchez, Ó. J., Hernández, M. C., & Montoya, M. (2024). Technical and Economic Assessment of Tomato Cultivation Through a Macro-Tunnel Production System with the Application of Gluconacetobacter diazotrophicus. Horticulturae, 10(10), 1110. https://doi.org/10.3390/horticulturae10101110

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