Comparing the Effect of Chemical and Biol Fertilization on the Fruit Yield and Selected Traits of Greenhouse-Grown Cucumber (Cucumis sativus L.) ^†

Abstract

Cucumber (Cucumis sativus) greenhouse cultivation offers higher yields and quality compared to open-field systems, but success depends on balanced fertilization. This study compared chemical and biol (liquid organic fertilizer) treatments on cucumber yield, fruit number, and size (Centauro 1 variety). Four treatments—Biol30 (3% biol), Biol70 (7% biol), Nitro (urea), and Comp (complete chemical fertilization)—were applied in a randomized design. Results indicated no statistically significant differences in yield among treatments (p = 0.094), yet Biol70 outperformed Nitro and Comp by 1.44× and 1.18×, respectively. Notably, Nitro produced the largest and heaviest fruits but the lowest fruit count, while organic treatments (Biol30 and Biol70) demonstrated comparable fruit quality and higher yields. The Biol70 treatment, in particular, highlighted the potential of biol as a sustainable alternative, achieving yields of 272.59 kg total production and 34.07 kg per bed, with fruit weights averaging 0.4309 kg and lengths of 26.511 cm. These findings underscore the viability of biol, especially at higher concentrations, as an eco-friendly substitute for chemical fertilizers, aligning with global efforts to promote sustainable agricultural practices.

1. Introduction

The greenhouse cultivation of cucumbers (Cucumis sativus L.) has become increasingly popular due to its ability to provide controlled environments that enhance yield and fruit quality compared to open-field systems [1,2]. However, the productivity of greenhouse crops is heavily dependent on balanced fertilization, which directly influences plant growth, fruit development, and overall yield [3].

Conventional fertilization methods often rely on inorganic fertilizers, which, while effective in increasing yields, have raised concerns due to their environmental impact. The excessive use of these inputs has resulted in soil degradation, water contamination, and greenhouse gas emissions [3,4,5]. Additionally, over the past 5 years, the prices of these fertilizers in Mexico have risen drastically due to global inflation and international conflicts in producing countries, like Russia, causing problems in local agricultural systems, such as increased production costs and reduced profitability [6].

In response to these issues, biofertilizers have received increased interest over the past decade [5,7,8]. Derived from natural processes, biofertilizers such as mycorrhizal fungi, nitrifying bacteria, composts, and biols (liquid organic fertilizers) offer multifaceted benefits [9]. Biol, produced through the anaerobic digestion of organic matter, not only enhances soil health and nutrient availability but also mitigates environmental pollution by recycling organic waste [10,11,12,13,14]. Since it can be produced by farmers using local resources, it can help reduce their dependence on imports from other countries while simultaneously improving soil conditions [5]. Field studies have demonstrated its potential to improve crop yields while reducing dependence on synthetic inputs, particularly in smallholder farming systems [15,16]

Recent studies have indicated that liquid organic fertilizers rich in bioactive compounds (e.g., humic acids and beneficial microbes) can stimulate root development, increasing nutrient uptake efficiency [17]. Liquid organic fertilizer can improve crop yield by increasing soil nutrient concentrations, reducing soil pH and salinity, and optimizing rhizosphere microbial community structure and co-occurrence patterns [18]. When compared to chemical fertilization, results vary. For instance, Gámez et al. [15] reported lower yields with biol, whereas Callizaya Huanca [16] observed improved fruit diameter with increased biol application. The application of liquid biogas digestate in greenhouses increased cucumber yields by up to 29% compared to controls, with optimal doses varying by digestate source and application rate [19]. Yields with organic liquid fertilizers approached those of conventional fertilizers; however, the yield response was not always linear with the increasing dose [19,20]. Additionally, the implementation of biol as a fertilizer in any agricultural system requires continuous monitoring and adjustment to prevent negative effects. Over-application, insufficient dilution, or excessive fertilization can reduce beneficial soil organisms and cause phytotoxicity, leading to lower yields due to salinity or a heavy metal presence [18,21,22].

This study aims to evaluate the effects of chemical and biol fertilization on the fruit yield and selected traits (size and weight) of greenhouse-grown cucumbers. Conducted as a collaborative study, the experiment compares four fertilization treatments, testing biol made by smallholder farmers against standard chemical fertilizer doses. The findings will provide valuable insights into the potential of biol production by smallholder farmers as a sustainable alternative to chemical fertilizers in greenhouse cucumber production.

2. Materials and Methods

This study was conducted through a transdisciplinary collaboration between researchers from the Faculty of Higher Studies Cuautitlán, part of the National Autonomous University of Mexico (FESC-UNAM), the National Polytechnic Institute, and smallholder farmers affiliated with the La Laguna field school in Apan, Hidalgo, Mexico. The biol used in the experiment was produced locally by farmers trained under the Producción para el Bienestar program, ensuring that the organic fertilizer reflected real-world, smallholder practices. Farmers contributed empirical knowledge on biol production (e.g., feedstock selection, anaerobic digestion techniques), while academic partners designed the randomized trial, performed the soil analyses, and standardized the application protocols, bridging gaps between scientific rigor and on-farm applicability.

The experiment was conducted during 2024 in a greenhouse located at the FESC-UNAM, using the Centauro 1 cucumber variety. A completely randomized design was employed, with four fertilization treatments replicated three times. Each replication consisted of a 25 m² cultivation bed, with 120 cucumber seedlings planted per bed. Two irrigation drip lines (2 L per hour) were placed in each bed. The incidence of pests, diseases, and weeds was monitored and dealt with according to the best practices. Shoots that grew in the axils and leaves in the lower sections of the plants were removed manually. The experiment lasted 94 days: seedlings were transplanted on April 24, and the harvest was conducted between May 23 and July 8. Fruits were harvested every four days, and a total of 11 cuts were made during the experiment.

Prior to establishing the experiment, a comprehensive soil fertility analysis was conducted. The results indicated an alkaline soil with pH 8.31, an organic matter content of 3.74%, phosphorus of 472 ppm (P-Bray), and potassium of 1225 ppm. Macronutrient concentrations were measured at 81.1 ppm N-NO₃, 3575 ppm Ca, and 1103 ppm Mg. The micronutrient analysis revealed the availability of essential elements: Fe (10.1 ppm), Zn (11.9 ppm), Mn (9.15 ppm), Cu (3.31 ppm), B (2.72 ppm), and S (83.7 ppm).

The treatments were as follows:

• Biol30: 3% biol applied every 30 days;
• Biol70: 7% biol applied every 30 days;
• Nitro: Nitrogen adjusted fertilization 1.9 kg urea applied in three split applications;
• Comp: Complete fertilization with 2 kg Ca(NO₃)₂, 1.6 kg MgSO₄, 0.8 kg (NH₄)₂HPO₄, 1.6 kg KNO₃, and 1.6 kg urea.

The nutrient composition of each treatment can be seen in

Table 1. Nutrient contents of experimental treatments.

Treatment	Composition (N–P–K)
Comp	425–125–310
Biol30	0.125–1.57–52.32
Biol70	0.292–3.5–122.08
Nitro	155–00–00

. For the Comp treatment, phosphorus and potassium were applied 14 days after planting (dap), while the remaining nutrients were split into three applications at 14, 42, and 63 dap. For the biol treatments, liquid biofertilizer (biol) was diluted to 100 L with water according to each formulation (Biol30: 3 L of biol/100 L; Biol70: 7 L of biol/100 L) and sprayed via drench. Meanwhile, Nitro was designed considering soil nutrient contributions, where urea was applied at planting, 15 dap, and 8 days after the first harvest.

The four treatments evaluated in this study were chosen to reflect locally recommended practices for greenhouse cucumber production in central Mexico, as part of a preliminary trial. The chemical treatments (Nitro and Comp) followed guidelines from [23], a manual edited by the Secretariate of Agriculture and Rural Development, which prescribes split nutrient applications. The biol concentrations were selected according to practical manuals for bioinput production from the Producción para el Bienestar program, which recommend doses of 3–5% for vegetables and 5–10% for other crops. The 7% biol treatment (Biol70) was included to evaluate potential adverse effects at higher doses while remaining within the program’s upper threshold for diversified crops.

2.1. Data Collection

Fifteen plants per bed were randomly selected for data collection. Fruits were harvested manually once they reached adequate maturity. The weight and dimensions of the fruits were recorded separately for each treatment. Fruit size (length and diameter), yield, and weight were measured starting at 50 dap. Yield was calculated as the total number of fruits harvested per plant, while fruit weight was measured using a digital scale. Fruit length and diameter were measured using a caliper.

2.2. Statistical Analysis

Data were analyzed using a one-way ANOVA, and means were compared using Tukey’s HSD test at a 5% significance level. All statistical analyses were performed using Minitab 17 (Minitab Inc., State College, PA, USA).

3. Results

The results showed no significant differences between the organic and chemical treatments regarding yield (p = 0.094), as shown in

Table 2. Total production and yields of the different fertilization treatments.

Treatment	Total Production (kg)	Yield (kg/Bed)	Fruit Weight (kg)	Fruit Length (cm)
Comp	269.35	33.67 a	0.4036 b	25.418 b
Biol30	235.08	29.38 a	0.4424 ab	27.171 a
Biol70	272.59	34.07 a	0.4309 ab	26.511 ab
Nitro	247.55	30.94 a	0.45327 a	27.387 a
Pooled Standard Deviation	N.A.	3.994	0.0458	1.378

Biol30 and Biol70: 3% and 7% liquid biofertilizer, respectively. Nitro: nitrogen-adjusted fertilization; Comp: complete fertilization. Letters indicate differences between treatment means (p < 0.05); means that do not share a letter are significantly different (Tukey method, α = 0.05).

. Biol70 (7% biol) produced the highest numerical yield at 272.59 kg total production (34.07 kg/bed), representing a 1.44-fold increase over Nitro (30.94 kg/bed) and 1.18-fold over Comp (33.67 kg/bed).

The Nitro treatment yielded the heaviest (0.453 kg) and longest (27.39 cm) fruits but the lowest number of fruits per plant (p = 0.046). Fruit weight varied significantly between treatments (p ≤ 0.029), with Nitro producing the heaviest fruits, followed by Biol30 (442 g), Biol70 (431 g), and Comp (404 g).

Fruit length measurements showed Nitro and Biol30 producing significantly longer fruits (27.39 cm and 27.17 cm, respectively) compared to Comp (25.42 cm). In general, it was seen that the diameter of the fruits was not affected by organic fertilization (Figure 1), but this measure showed great variation in the Nitro treatment, which was also the highest numerically.

As shown in Figure 1, the application of 7% biol improved the total number of fruits per plant (149 fruits), while the least favorable results were observed in the treatment with nitrogen-adjusted fertilization (Nitro: 98 fruits, p = 0.046).

4. Discussion

The results of this study demonstrate that organic fertilization using biol can achieve yields comparable to, or even higher than, conventional chemical fertilization. The lack of significant yield differences contrasts with Gámez et al. [15] (2013) where lower yields were obtained even with higher doses of biol. This discrepancy could be associated with the quality of the biofertilizer, as the aforementioned study did not report the nutrient content percentages.

The higher yield observed in the Biol70 treatment may be attributed to the improved nutrient availability and soil health associated with organic fertilizers [4,11,24,25]. These findings are consistent with previous studies that have reported the benefits of organic fertilizers in enhancing crop yield and soil quality [10,25,26]. It is possible that the soil’s moderate phosphorus availability and high baseline nutrient levels could explain why the lower-nutrient biol treatments performed competitively against complete chemical fertilization.

The Nitro treatment yielded the largest and heaviest fruits. This may be due to the high nitrogen content in urea, which promotes vegetative growth and fruit size [3,27]. However, the lower number of fruits harvested in this treatment suggests that excessive nitrogen application may reduce the fruit set [1,27,28].

The comparable fruit size observed in the organic treatments highlights the potential of biol as a sustainable alternative to chemical fertilizers. These findings align with the growing body of evidence supporting the use of organic fertilizers in production systems [10,27,29,30,31,32]. While the short-term yield results are promising, future research should investigate long-term soil health impacts and economic viability across multiple growing seasons.

While this study provides comparisons of yield and fruit morphology under different fertilization regimes, it did not assess additional quality traits such as biochemical composition (e.g., soluble solids, acidity) or postharvest characteristics (e.g., firmness, shelf life). These metrics are valuable for fully evaluating marketability and consumer preference. Future research should integrate standardized quality assessments, including nutritional content (e.g., vitamin C, phenolic compounds) and sensory attributes, to comprehensively quantify the advantages of biol beyond productivity. Such work would further validate its potential as a sustainable alternative for commercial greenhouse production.

5. Conclusions

This study showed that organic fertilization using biol can produce cucumber yields and fruit quality comparable to conventional chemical fertilization. The Biol70 treatment, in particular, showed superior yield performance, suggesting that higher concentrations of biol may enhance nutrient availability and crop productivity. Therefore, substituting inorganic fertilization for one with Biol from the La Laguna Field School can be considered a sustainable and accessible alternative for the fertilization of cucumber by producers. These findings support the use of biofertilizers in greenhouse cucumber production, offering a viable solution to reduce the environmental impact of conventional fertilization practices.