Production of Panicum maximum cv. Mombaça Under Fertilization Management and Ozonation of Irrigation Water

Abstract

Ozonation of irrigation water is a promising technology that improves the efficiency of irrigation systems. However, it is necessary to investigate the potential adverse effects of the continuous application of this technology on pastures, particularly on Mombaça grass (Panicum maximum cv. Mombaça), to ensure that its benefits are not outweighed by negative impacts. This study aimed to evaluate the impact of ozonated irrigation water on the production of Mombaça grass under different fertilization management practices. The experiment was conducted in a controlled environment using 4.5 L pots, following a completely randomized design with five replications. The experimental setup employed a factorial arrangement, involving two irrigation water sources (with and without ozonation) and two fertilization managements (with and without N and K₂O), resulting in 20 experimental units. A 60-day uniformity cycle and three 30-day cycles were performed, assessing water consumption as well as the morphogenic and agronomic characteristics of Mombaça grass. Fertilization with N and K₂O increased water consumption and improved the agronomic characteristics of Mombaça grass, promoting greater development and growth in line with its morphogenic traits. Regardless of fertilization, ozonation of irrigation water did not cause harm to growth and biomass yield. Therefore, the technique of ozonating irrigation water can be used in the cultivation of Mombaça grass.

1. Introduction

Livestock farming is one of the most important sectors of Brazilian agribusiness. In 2022, Brazil had the largest cattle herd in the world, with approximately 224.6 million head. In the same year, the country was the largest beef producer, with 10.35 million tons of meat, and the largest beef exporter, with 2.90 million tons [1], thus holding a prominent position in the global livestock industry. The use of technologies to increase productivity across the livestock sector is essential to meet the growing demand for animal-based products. However, these technologies must minimize the sector’s impact on the environment and natural resources [2,3].

Forage grasses are the main nutrient sources in traditional dairy cattle production systems in Brazil [4]. The use of pastures is common because it is considered the most economical form of feeding livestock, mainly due to the high cost of concentrated feed [5,6]. According to Vieira et al. [7], grasses also form the foundation of Brazilian beef cattle farming. Therefore, to optimize the productivity of these grasses, especially in extensive pasture systems, it is crucial to investigate efficient management practices, including both fertilization and irrigation water treatment.

The ozonation of irrigation water has emerged as an innovative technology with broad application potential. When used at appropriate concentrations, it can improve the physicochemical properties of the soil, reduce the presence of pathogens, and increase the availability of essential nutrients, contributing to plant health [8]. Moreover, studies have demonstrated that ozone use enhances the activity of antioxidant enzymes and increases plant tolerance to stress conditions [9]. These benefits highlight ozone as a promising tool to sustainably optimize agricultural productivity.

Another notable feature of ozonated water is its effectiveness in protecting irrigation systems against clogging. Research shows that ozonated water can remove and inhibit the growth of biofilms, acting as an anti-clogging agent in drip irrigation systems, including those with smaller emitter nozzles, such as subsurface systems [10,11]. This technology reduces biofilm formation and prevents the growth of microorganisms that impair emitter performance [12]. By keeping emitters clean and operating efficiently, ozonation improves water distribution and the overall efficiency of the irrigation system without negatively impacting the growth of certain agricultural crops [13].

In addition to protecting irrigation systems, ozonation is also widely used in the treatment of domestic wastewater [14] intended for the fertigation of agricultural crops. This process promotes disinfection and the oxidation of dissolved organic compounds, making the water safer for irrigating food and forage crops [15,16]. The reduction in pathogens and chemical contaminants contributes to preserving soil and plant quality, ensuring that the reuse of this water in agriculture occurs sustainably [17]. Thus, ozonation plays a crucial role in water and food security, combining resource reuse with environmental protection.

Given the above, it is essential to investigate whether the continuous use of ozonated water may have adverse effects on pastures, particularly on Mombaça grass. The potential impact of ozonation on plant growth, nutrient uptake, and forage quality must be carefully evaluated. Additional studies are necessary to ensure that the benefits of ozonation in protecting irrigation systems are not outweighed by possible negative effects on pasture health and productivity.

Nitrogen fertilization is a key practice for ensuring robust growth and productivity in pastures [18]. However, the use of nitrogen fertilizers presents some challenges, such as high costs and the need for periodic applications, factors that may limit their widespread adoption [19], especially in contexts with economic or logistical constraints. Studies show that nitrogen fertilization, especially at elevated levels, can improve tiller dynamics, dry matter quality, and nutrient uptake, resulting in a significant increase in forage production [20,21].

Given the challenges faced by livestock farming, such as high production costs and variable edaphoclimatic conditions [5,22,23], the search for innovative solutions is essential. Panicum maximum cv. Mombaça, due to its potential, offers an opportunity to explore the effectiveness of combining water ozonation and fertilization management to optimize its production. Research on the impact of ozonation and fertilization under different irrigation conditions can provide valuable insights into maximizing the productivity and efficiency of Mombaça grass, contributing to the sustainability and profitability of pasture systems.

Thus, the present study aims to deepen the understanding of the interaction between the ozonation of irrigation water and fertilization practices in the cultivation of Mombaça grass. By analyzing how these practices affect growth, forage quality, and irrigation system efficiency, this work seeks to provide practical and evidence-based recommendations for producers, enhancing pasture productivity and sustainability in Brazil. Therefore, this study aimed to determine the influence and impacts of ozonated irrigation water combined with fertilization management on the water consumption, growth, development, and productivity of Mombaça grass.

2. Materials and Methods

2.1. Study Area and Plant Material

The experiment was conducted in the experimental area of the Hydraulics Laboratory at the Center for Water Resources Reference (CRRH) of the Federal University of Viçosa (UFV), Minas Gerais, Brazil. The region’s climate is classified as Aw (tropical Savanna climate with dry winters), characterized by hot, rainy summers and cold, dry winters [24]. The annual rainfall is 1345 mm, with December being the wettest month and July the driest.

The experiment was carried out in a protected environment to prevent rainfall from affecting the results. The structure covered an area of 30 m² (5 m wide by 6 m long). Its sides were protected with 2 m high polyethylene mesh, leaving open spaces for ventilation. The structure included two openings on opposite sides with removable curtains to allow airflow for natural ventilation. The roof was covered with a 150-micron low-density polyethylene (LDPE) film, treated with ultraviolet radiation inhibitors.

For the experiment, 20 pots were installed, each with dimensions of 20 cm in upper diameter, 16 cm in lower diameter, and 18 cm in height, resulting in a total volume of 4.5 L. The pots were filled with soil collected from a slope on the UFV campus. This same soil was used to fill the pots in the study by Rocha et al. [25], and its physical–hydraulic and chemical characteristics can be found in the cited work.

Based on the soil analysis results, crop requirements, and recommendations by Ribeiro et al. [26], it was not necessary to correct soil acidity, only to adjust fertility. The following fertilizers were used: urea (0.50 g of CO(NH₂)₂ per pot) and potassium chloride (0.30 g of KCl per pot). These amounts corresponded to 100 kg ha⁻¹ of N and 80 kg ha⁻¹ of K₂O per cultivation cycle, respectively. Fertilizer applications were carried out in split doses via fertigation, at three-day intervals.

The forage grass used in the study was Mombaça grass (Panicum maximum cv. Mombaça). For sowing, a circular furrow with a radius of 5 cm and a depth of 2 cm was made in each pot, and 10 seeds were evenly distributed along the furrow. The experimental period lasted from 18 October 2023 to 16 March 2024, with evaluation cycles conducted from December 2023 to March 2024. Four harvests were performed: the first, for standardization, occurred 60 days after sowing, and subsequent harvests were conducted at 30-day intervals, leaving a 15 cm stubble height above the soil surface. The harvest dates were as follows: 17 December 2023, 16 January 2024, 15 February 2024, and 16 March 2024.

The standardization cycle was carried out with the goal of establishing consistency in the forage during the first cycle. This was done to ensure consistent initial conditions and minimize potential variabilities that could interfere with the results. By interrupting the free and disordered growth of the plants, which is common in forage grasses [27,28], a homogeneous starting point was created.

The climatic data recorded during the experimental period are presented in Figure 1. The average values of the meteorological variables for cycles 1, 2, and 3 were as follows: 23.5, 23.3, and 23.8 °C for air temperature; 81.9, 83.2, and 85.4% for relative humidity; and 17.1, 18.9, and 17.6 MJ m⁻² d⁻¹ for solar radiation, respectively. All daily meteorological data recorded during this period can be found in the Supplementary Materials (Table S1).

In the literature, references vary regarding the specific lower and upper basal temperatures for Mombaça grass. Therefore, to calculate the accumulated degree-days (ADD), average values for Mombaça grass were adopted. Thus, the lower and upper basal air temperatures considered were 12 °C and 35 °C, respectively [29,30].

2.2. Experimental Design and Execution

The experiment was conducted in a completely randomized design (CRD) with five replications. The experimental arrangement followed a factorial design with two irrigation water sources and two fertilization managements, resulting in 20 experimental units.

The irrigation water sources used were redistributed water and ozonized water. The ozonation of the irrigation water was performed at the Post-Harvest Laboratory of DEA-UFV. Ozone gas was generated using an M10I generator model (myOZONE, Jaguariúna, São Paulo, Brazil), which produces ozone through the corona discharge effect. This generator was supplied by an EverFlo oxygen concentrator (Philips Respironics, Murrysville, PA, USA), delivering oxygen with 90% purity at a volumetric flow rate of 5 L min⁻¹ (Figure 2).

The incorporation of ozone gas into the water was conducted in a jacketed tank with temperature control (2–40 °C). In this tank, ozone was incorporated via a superventuri injector. During the ozonization process, the water temperature was maintained between 15 °C and 17 °C, and the ozone concentration ranged from 3.5 to 5.0 mg L⁻¹. The ozone concentration in the water was determined using the iodometric method [31].

To prevent significant variations in soil water storage and maintain soil moisture near field capacity, Mombaça grass was irrigated every three days. Irrigation management was carried out by measuring the difference in mass between two irrigation events. The pots functioned similarly to weighing lysimeters, enabling the measurement of crop evapotranspiration (ETc). Equation (1) was used to calculate ETc and determine the amount of water applied to the soil-filled pots.

$$\mathrm{ETc}={\mathrm{M}}_{\mathrm{pot} \mathrm{i}}-{\mathrm{M}}_{\mathrm{pot} \mathrm{i}+1}-\mathrm{D}$$

(1)

where ETc—crop evapotranspiration, L; M_{pot i}—pot mass on day i, kg; and D—drained water, L.

With the ETc value, it was possible to apply an amount of water sufficient to raise the soil moisture to field capacity at each irrigation event. It is worth noting that the pots were irrigated manually and superficially, and all drained water from each pot was reintroduced with the irrigation water into the same pot, ensuring the balance of salts and nutrients in the soil. The irrigation water, collected from the redistribution network near the greenhouse, was analyzed. The maximum redox potential (${\mathrm{E}}_{\max }^{ 1+}$) was measured, and the recorded pH ranged from 7.2 to 7.9. Furthermore, the electrical conductivity was monitored during irrigation, with an average value of 106.9 ± 12.7 µS cm⁻¹ at 25 °C.

Regarding fertilization, treatments were divided into fertilized and non-fertilized groups. The fertilized treatment received N and K₂O fertilization starting from the uniformity cut. Urea and potassium chloride were applied at rates equivalent to 100 kg ha⁻¹ of N and 80 kg ha⁻¹ of K₂O per cycle, respectively. Fertilizers were applied in split doses of 50 mL via fertigation, with fertilizers diluted in common water, at three-day intervals.

2.3. Experimental Evaluations

2.3.1. Morphogenic Characteristics

After the uniformity cycle, two tillers were randomly selected from each pot for the morphogenesis evaluation of Mombaça grass. Measurements included the total length of expanded and emerging leaves, as well as the length of the pseudostem, measuring from the last exposed ligule to the base of the tiller. Data collection occurred in the morning, three times per week (Monday, Wednesday, and Friday).

From the growth data obtained, the following variables were calculated according to Gomide and Gomide [27]:

-

Number of emerging leaves (NEmL): Obtained at the end of the growth period, considering as emerging or expanding leaves those without an exposed ligule.

-

Number of expanded leaves (NExL): Obtained at the end of the growth period, representing the number of fully expanded leaves on each tiller, i.e., with an exposed ligule.

-

Number of live leaves (NLL): Obtained at the end of the growth period by summing the number of expanding and expanded leaves per tiller.

-

Leaf appearance rate (LAR, leaves tiller⁻¹ day⁻¹): Calculated by subtracting the number of leaves that emerged per tiller from the initial number of leaves, divided by the number of days in the evaluation period.

-

Leaf elongation rate (LER, cm tiller⁻¹ day⁻¹): Calculated by subtracting the initial from the final lengths of the leaves and dividing the result by the number of days in the evaluation, then multiplying by the number of tillers considered.

-

Stem elongation rate (SER, cm tiller⁻¹ day⁻¹): Calculated by subtracting the initial from the final lengths of the stems and dividing the result by the number of days in the evaluation, then multiplying by the number of tillers considered.

2.3.2. Agronomic Characteristics

Agronomic characteristics such as fresh shoot biomass (FSB) and dry shoot biomass (DSB) were evaluated at the end of each cultivation cycle of Mombaça grass. FSB corresponded to the entire aerial part (leaves and stems) of the plant above a height of 15 cm, which was weighed using a precision digital scale (0.01 g). Subsequently, the leaves and stems from each pot were stored in paper bags and dried in a forced-air oven at 65 °C for 72 h, then weighed again using a precision digital scale (0.01 g) to determine the DSB.

Water use productivity (WP) was calculated using Equation (2) as the ratio between DSB and the volume of water applied to the pots cultivated with Mombaça grass.

$$\mathrm{WP}={\displaystyle \frac{\mathrm{DSB}}{\mathrm{Vw}}}$$

(2)

where WP—water use productivity, g L⁻³; DSB—dry shoot biomass, g pot⁻¹; Vw—total volume of water applied, L pot⁻¹.

2.4. Statistical Analysis

The data were submitted to analysis of variance (ANAVA) with a significance level of 0.05 in the F-test. Regardless of the significance of the interaction between factors, it was decided to break it down, considering the interest in the study. The assumptions of variance homogeneity and normality were checked using Bartlett and Shapiro–Wilk tests, respectively, with a significance level of 0.05 for both. Means were compared using the Tukey test at a 0.05 significance level. The statistical analyses were performed using the Experimental Designs package in the “R” software version 4.4.2 [32].

3. Results and Discussion

3.1. Water Consumption

Figure 3 shows the evolution of reference evapotranspiration (ETo) and crop evapotranspiration (ETc), calculated according to Allen et al. [33], in the different treatments, over three cultivation cycles of Mombaça grass. The accumulated ETo values for cycles 1, 2, and 3 were 102, 102, and 99 mm, respectively. The accumulated ETo values were similar because the meteorological variables also exhibited similar behavior across the different cultivation cycles, particularly solar radiation, air temperature, and relative humidity (Figure 1). All data used to generate Figure 3 can also be found in the Supplementary Materials (Table S2).

In Figure 3, it can be observed that the water consumption (ETc) of the different treatments decreased throughout the experimental cycles. This reduction may be associated with the loss of vigor of the plants as the cycles progressed, possibly due to root confinement in a limited soil volume, which restricts the grass’s ability to efficiently absorb water. Although fertilization was performed with nitrogen and potassium, the reduction in other macronutrients and micronutrients over time may have limited plant growth and physiological activity. These combined factors could have reduced the physiological capacity of Mombaça grass, leading to an overall decrease in ETc. However, this decrease was observed in all treatments, which does not compromise the objectives of the present study.

3.2. Morphogenetic Analyses

All raw data on morphogenic characteristics can be found in the Supplementary Materials (Table S3). The variable number of emergent leaves (NEmL) of Mombaça grass was affected by fertilization only in the second cultivation cycle (

Table 1. Mean squares, F-test significance (ANAVA), and mean values of morphogenetic characteristics: number of emergent leaves (NEmL), number of expanded leaves (NExL), number of live leaves (NLL), leaf appearance rate (LAR), leaf elongation rate (LER), and stem elongation rate (SER) in different cycles of Mombaça grass under fertilization (Fert.) and ozonized (O₃) irrigation water treatments. Viçosa-MG, DEA-UFV, 2023–2024.

Variable	Cycle	Mean Square			CV	Fert.	O3
		O3	Fert.	O3 × Fert.	(%)		No	Yes
NEmL	1	1.13 × 10−1 ns	1.25 × 10−2 ns	1.25 × 10−2 ns	20.12	No	2.200 Aa	2.400 Aa
						Yes	2.300 Aa	2.400 Aa
	2	1.25 × 10−2 ns	6.13 × 10−1 **	1.25 × 10−2 ns	11.23	No	1.600 Ab	1.500 Ab
						Yes	1.900 Aa	1.900 Aa
	3	1.25 × 10−2 ns	1.13 × 10−1 ns	1.13 × 10−1 ns	23.12	No	1.700 Aa	1.500 Aa
						Yes	1.700 Aa	1.800 Aa
NExL	1	1.13 × 10−1 *	1.01 × 100 ns	1.13 × 10−1 *	15.97	No	2.100 Ba	2.400 Aa
						Yes	2.700 Aa	2.700 Aa
	2	8.00 × 10−1 **	1.85 × 10−5 ns	2.00 × 10−1 **	14.55	No	1.600 Ba	2.200 Aa
						Yes	1.800 Aa	2.000 Aa
	3	4.00 × 10−5 ns	8.00 × 10−1 *	2.00 × 10−1 *	23.57	No	1.200 Ab	1.400 Aa
						Yes	1.800 Aa	1.600 Aa
NLL	1	4.50 × 10−1 *	1.25 × 100 ns	2.00 × 10−1 *	10.80	No	4.300 Ba	4.800 Aa
						Yes	5.000 Aa	5.100 Aa
	2	6.13 × 10−1 *	6.13 × 10−1 *	1.13 × 10−1 *	8.72	No	3.200 Bb	3.700 Aa
						Yes	3.700 Aa	3.900 Aa
	3	1.25 × 10−2 ns	1.25 × 10−2 **	1.51 × 100 ns	8.26	No	2.900 Ab	2.900 Ab
						Yes	3.500 Aa	3.400 Aa
LAR (leaves tiller−1 day−1)	1	6.49 × 10−4 ns	2.34 × 10−4 ns	2.34 × 10−4 ns	11.03	No	0.136 Aa	0.141 Aa
						Yes	0.136 Aa	0.155 Aa
	2	3.14 × 10−4 ns	3.14 × 10−4 ns	3.14 × 10−5 ns	20.39	No	0.105 Aa	0.111 Aa
						Yes	0.111 Aa	0.121 Aa
	3	1.10 × 10−4 ns	2.83 × 10−3 **	6.51 × 10−5 **	11.98	No	0.090 Ab	0.086 Ab
						Yes	0.114 Aa	0.110 Aa
LER (cm tiller−1 day−1)	1	3.49 × 10−1 ns	6.10 × 100 **	4.09 × 10−2 ns	17.68	No	3.203 Ab	3.030 Ab
						Yes	4.398 Aa	4.044 Aa
	2	2.44 × 10−1 ns	1.78 × 100 **	6.37 × 10−4 ns	16.09	No	2.211 Ab	2.443 Ab
						Yes	2.819 Aa	3.028 Aa
	3	3.07 × 10−3 ns	1.41 × 100 **	4.50 × 10−1 *	19.47	No	1.562 Ab	1.887 Aa
						Yes	2.393 Aa	2.118 Aa
SER (cm tiller−1 day−1)	1	3.01 × 10−3 ns	2.55 × 10−2 **	3.48 × 10−3 *	19.91	No	0.162 Aa	0.170 Ab
						Yes	0.227 Aa	0.268 Aa
	2	1.80 × 10−4 ns	1.32 × 10−2 *	3.26 × 10−3 *	27.01	No	0.166 Aa	0.134 Ab
						Yes	0.192 Aa	0.211 Aa
	3	2.58 × 10−5 ns	1.02 × 10−3 ns	2.58 × 10−5 ns	17.23	No	0.148 Aa	0.148 Aa
						Yes	0.160 Aa	0.164 Aa

O₃ × Fert.: Interaction between irrigation water and fertilization of Mombaça grass; CV: coefficient of variation; * and **: significance at 5% and 1% probability, respectively, by the F-test; ^ns: not significant; means followed by the same uppercase letters in the row and lowercase letters in the column do not differ from each other by the Tukey test (p < 0.01).

), where the fertilized treatment resulted in significantly higher values. This effect can be explained by the increased availability of essential nutrients, promoted by fertilization, which stimulated leaf growth during this specific cycle. However, in earlier and later cycles, other factors, such as nutrient depletion in the soil or climatic variations, may have altered the efficiency of the fertilization effect on NEmL. Additionally, the ozonation of the irrigation water may have indirectly influenced leaf development by improving nutrient availability in the soil, creating a more favorable environment for plant growth, particularly in cycles with higher nutritional demand.

Regardless of the cultivation cycle or fertilization treatment, the ozonation of the water had no significant effect on the NEmL of Mombaça grass (Table 1). This result suggests that, although ozone can influence other aspects of plant physiology, its application in irrigation water did not alter the dynamics of leaf growth. A possible explanation for this lack of effect may be that ozone, despite its antimicrobial properties and potential to improve water quality [34,35], does not have a direct or sufficient impact on the metabolic processes that regulate leaf emergence. Furthermore, the effects of ozonation may be more evident under stress conditions or when applied at higher concentrations, which were not achieved in this experiment.

For the variable number of expanded leaves (NExL), an interaction between fertilization and the ozonation of the irrigation water was observed in all cultivation cycles of Mombaça grass (Table 1). In the fertilized treatments, the increase in NExL was more evident only in cycle 3, when the irrigation water was not ozonized. In the other cycles, fertilization did not have a significant impact on the variable. On the other hand, the ozonation of the irrigation water favored NExL in cycles 1 and 2, but only in the non-fertilized treatments. This effect can be attributed to the improvement in water quality provided by ozonation, which, in turn, increased nutrient availability in the soil, enhancing absorption by the roots. This more favorable environment for leaf growth may have optimized NExL, particularly in the absence of fertilization. Thus, while fertilization with N and K₂O did not directly influence NExL when combined with ozone, the interaction between both factors suggests an increase in nutritional efficiency due to the improved water quality.

An interaction between fertilization and the ozonation of the irrigation water was observed in the number of living leaves (NLL) of Mombaça grass in the first two cultivation cycles (Table 1). Fertilization increased NLL values in cycle 3, regardless of ozonation, and also in cycle 2, when the water was not ozonized. On the other hand, ozonation increased NLL values only in cycles 1 and 2, when Mombaça grass was not fertilized, a similar effect to that observed for the number of expanded leaves (NExL). The interaction between these factors suggests that, when fertilization was not applied, ozonation played a relevant role in improving leaf growth, possibly through the improvement in water quality and nutrient availability in the soil. It is worth noting that NLL, being the sum of NExL and NEmL, is highly correlated with forage productivity [36,37], highlighting the importance of these factors in the overall performance of Mombaça grass.

The characteristics associated with the number of leaves, whether emergent, expanded, or total, are significantly influenced by water conditions and soil fertility [38,39,40]. On the other hand, there is no information in the literature regarding the effect of ozonation of irrigation water on these leaf number characteristics. The results found in the present study did not fully support the idea that ozonation improves characteristics related to the number of leaves. However, it is important to emphasize that the results obtained are sufficient to agree that the ozonation of irrigation water does not compromise these aforementioned characteristics.

For the leaf appearance rate (LAR), an isolated effect of fertilization was observed only in cycle 3, where values were higher when Mombaça grass was fertilized, regardless of the ozonation of the irrigation water (Table 1). In contrast, ozonation did not have a significant impact on the leaf appearance rate. Possibly, ozonation of the water influences only the water quality and not the physiological processes related to the emergence of new leaves. The lack of effect of ozonation may reflect that, although it can improve water quality and irrigation efficiency, it is not sufficient to alter leaf appearance compared to the direct impact of fertilization, which provides essential nutrients for growth.

It can be observed in Table 1 that fertilization provided higher leaf elongation rates (LERs) in Mombaça grass. This effect can be attributed to the increased availability of essential nutrients for protein synthesis and the formation of new cells. Nitrogen, for example, is a crucial component of chlorophyll and structural proteins of cells, stimulating cell division and, consequently, promoting faster leaf elongation.

On the other hand, ozonation of the irrigation water had no impact on the LER of Mombaça grass (Table 1), as observed for other morphogenetic characteristics. Although ozonation showed positive effects on leaf growth in other variables, such as the number of leaves, in this case, the improvement in water quality does not seem to have directly influenced the LER. The LER, as an essential component for the biomass flow of plants, is directly related to photosynthetic capacity, impacting forage production [41]. Together with the leaf accumulation rate (LAR), the LER contributes to the increase in the number of leaves in the forage crop [42].

Fertilization resulted in higher values of stem elongation rate (SER) in cycles 1 and 2, but only in treatments with ozonated irrigation water (Table 1). Abreu et al. [43] reported that, to intensify tillering in a given forage species, factors related to plant development (water and nutrients) must be in favorable conditions. When one of these factors is restricted, one of the adaptation mechanisms triggered by the plant is the reduction in stem elongation.

The SER was also not influenced by the ozonation of the irrigation water (Table 1), showing a pattern similar to that observed for other morphogenetic variables. Although ozonation did not significantly alter SER, its effects may be intertwined with the benefits provided by fertilization with N and K₂O. Fertilization favored the increase in LER by improving the availability of essential nutrients, such as nitrogen, which is crucial for cell growth and the formation of new structures. In this sense, the ozonation of the water may have indirectly contributed to a more favorable environment for the absorption of these nutrients without hindering the processes of organogenesis. Mombaça grass maintained its leaf and structural development, with fertilization and ozonation functioning complementarily, without negatively interfering with the processes of leaf growth and elongation.

3.3. Agronomic Characteristics

All raw data on agronomic characteristics can be found in the Supplementary Materials (Table S4). Regardless of the cultivation cycle of Mombaça grass, it was observed that fertilized treatments generally had higher water consumption compared to non-fertilized treatments (Figure 3), a trend that can be more clearly seen in

Table 2. Mean squares, F-test significance (ANAVA), and average values of agronomic characteristics: water consumption (WC), fresh shoot biomass (FSB), dry shoot biomass (DSB), and water use productivity (WP) across different Mombaça grass cycles under fertilization and ozonation of irrigation water. Viçosa-MG, DEA-UFV, 2023–2024.

Variable	Cycle	Mean Square			CV	Fert.	O3
		O3	Fert.	O3 × Fert.	(%)		No	Yes
WC (L pot−1)	1	2.21 × 10−4 *	4.29 × 100 **	4.53 × 10−1 **	3.92	No	4.330 Bb	4.624 Ab
						Yes	5.557 Aa	5.249 Ba
	2	5.09 × 10−2 ns	2.40 × 100 **	3.49 × 10−2 ns	6.38	No	3.364 Ab	3.179 Ab
						Yes	3.972 Aa	3.955 Aa
	3	9.18 × 10−2 ns	3.01 × 10−1 *	4.56 × 10−2 *	5.20	No	2.499 Ab	2.730 Aa
						Yes	2.840 Aa	2.880 Aa
FSB (g pot−1)	1	9.83 × 100 ns	1.27 × 103 **	1.77 × 101 ns	9.54	No	38.993 Ab	39.475 Ab
						Yes	56.841 Aa	53.555 Aa
	2	1.71 × 100 ns	3.32 × 103 **	6.53 × 100 ns	6.96	No	16.079 Ab	16.637 Ab
						Yes	42.994 Aa	41.265 Aa
	3	2.89 × 100 *	2.25 × 103 **	8.66 × 100 *	5.68	No	9.025 Bb	11.102 Ab
						Yes	31.558 Aa	31.003 Aa
DSB (g pot−1)	1	8.59 × 10−1 ns	7.54 × 101 **	6.60 × 10−1 ns	7.40	No	9.692 Ab	9.641 Ab
						Yes	13.939 Aa	13.161 Aa
	2	8.98 × 10−3 ns	1.68 × 102 **	7.96 × 10−1 ns	7.79	No	3.593 Ab	3.950 Ab
						Yes	9.784 Aa	9.343 Aa
	3	1.84 × 10−1 *	1.00 × 102 **	5.26 × 10−1 **	5.51	No	1.749 Bb	2.265 Ab
						Yes	6.545 Aa	6.412 Aa
WP (g L−1)	1	3.06 × 10−2 ns	6.17 × 10−1 **	2.71 × 10−2 ns	7.72	No	2.237 Ab	2.085 Ab
						Yes	2.514 Aa	2.510 Aa
	2	1.06 × 10−2 ns	7.85 × 100 **	9.78 × 10−2 ns	12.21	No	1.074 Ab	1.259 Ab
						Yes	2.466 Aa	2.372 Aa
	3	4.01 × 10−3 ns	1.14 × 101 **	5.02 × 10−2 ns	10.59	No	0.704 Ab	0.832 Ab
						Yes	2.313 Aa	2.241 Aa

O₃ × Fert.: Interaction between irrigation water and fertilization of Mombaça grass; CV: coefficient of variation; * and **: significance at 5% and 1% probability, respectively, by the F-test; ^ns: not significant; means followed by the same uppercase letters in the row and lowercase letters in the column do not differ from each other by the Tukey test (p < 0.01).

. An analysis of these data reveals an interaction between fertilization and the ozonation of the irrigation water in cycles 1 and 3. However, in cycle 3, it was noted that the ozonation of the water did not alter water consumption in the fertilized treatments, contrasting with the other cycles, where fertilization led to an increase in water consumption. This behavior is expected, as fertilization with N and K₂O promotes more vigorous plant growth, increasing biomass and leaf area, which consequently elevates the transpiration rate [44]. Additionally, fertilization improves soil structure, facilitating root growth, which requires more water to sustain the plant’s development [45].

Table 2 also reveals that in cycle 1, the ozonation of the water had a distinct effect on water consumption depending on whether fertilization was applied or not: in the non-fertilized treatment, water consumption increased, while in the fertilized treatment, consumption was lower. This result may suggest that, although ozonation improves the quality of irrigation water and enhances nutrient availability in the soil, its effect on water consumption by Mombaça grass may be more pronounced in the absence of fertilization. Ozonation may have created a more favorable environment for nutrient absorption and more efficient root growth, which, without fertilization, led to increased water uptake. On the other hand, fertilization may have resulted in sufficient growth to increase water demand, making the effect of ozonation less significant. In subsequent cycles, ozonation did not have a relevant impact on water consumption, which could be attributed to stable environmental conditions and water availability in the soil, which maintained moisture up to field capacity, such that ozonation did not cause significant differences in water absorption and transpiration of Mombaça grass.

The fresh shoot biomass (FSB) and dry shoot biomass (DSB) of Mombaça grass were significantly higher in the fertilized treatments, as shown in Table 2. This result can be explained by the direct influence of the nutrients provided by fertilization on plant growth and development. Nitrogen, in particular, is essential for protein and chlorophyll synthesis, plays a key role in regulating cell growth, activates enzymes involved in carbohydrate metabolism, and modulates stomatal opening, which favors photosynthesis and promotes plant growth [46,47]. These physiological responses enhance the plant’s ability to produce biomass, as the energy generated by photosynthesis is more efficiently used in the formation and growth of aerial parts.

Additionally, fertilization improves soil properties, increasing water availability and nutrient absorption efficiency by the roots. This effect is likely mediated by stimulating microbial activity in the soil, which facilitates nutrient mineralization and improves soil structure, creating a more favorable environment for plant growth [48,49]. The positive interaction between nutrients and soil microbiota thus optimizes the plants’ physiological processes, resulting in substantial increases in FSB and DSB production.

Regarding the ozonation of irrigation water, the data presented in Table 2 show that it led to higher FSB and DSB production only in the third cycle, when Mombaça grass was fertilized. In other cycles and cultivation combinations without fertilization, ozonation did not have a significant impact on biomass production, similar to what was observed in the morphogenic characteristics. This effect can be explained by the interaction between ozonation and growth parameters, as biomass production is closely linked to the morphogenic performance of the plants. In cycles where no fertilization was applied, ozonation did not show noticeable effects on plant growth. Therefore, the combination of fertilization with ozonated irrigation water seems to be more effective in promoting higher biomass production, with fertilization being the predominant factor in maximizing FSB and DSB production. Ozonation, although beneficial, appears to act synergistically with fertilization, amplifying its positive effects on biomass production [50,51].

Water use productivity (WP), calculated as the ratio between DSB and water consumption by Mombaça grass, varied between 0.704 and 2.514 g L⁻¹, as shown in Table 2. The average WP value was 1.884 g L⁻¹, meaning that to produce 1 kg of dry matter of forage, 531 L of water is needed. The analysis reveals isolated effects of fertilization on WP across all cultivation cycles, indicating that fertilized Mombaça grass had higher WP values. This suggests that fertilization increased the plant’s efficiency in converting consumed water into biomass, possibly due to improved regulation of CO₂ and leaf temperature, as well as reduced water loss through adjustments in stomatal opening [52].

In addition to benefiting plant growth, fertilization contributes to water resource conservation, as higher water use efficiency promotes sustainable water use. Water use efficiency is a crucial factor for agricultural adaptation to climate change, as it enhances crop resilience [53,54]. This approach not only results in more efficient and sustainable forage production but also ensures greater water and food security in the face of growing global demands. On the other hand, ozonation of irrigation water did not have as significant an impact on WP, but when combined with fertilization, it may have indirectly influenced water use efficiency by reflecting the improved growth conditions provided by the available nutrients.

Although this study has provided important evidence on the effects of fertigation with ozonated water on Mombaça grass growth, some limitations should be considered. The experiment was conducted under controlled conditions using pots, which may not fully represent the complexity of agricultural systems in the field. Factors such as soil variability, climatic conditions, and ecological interactions may influence the results differently in open environments. Additionally, the long-term effects of continuous exposure to ozonated water on soil microbiota, plant physiology, and nutrient availability were not evaluated. Therefore, further field studies are essential to validate these findings and provide more robust recommendations for the practical application of this technology in forage production.

4. Conclusions

The application of fertilization with N and K₂O promoted greater development and growth of Mombaça grass, as observed through the evaluated morphogenetic characteristics. As a result, fertilization also increased biomass production and improved various agronomic traits of the forage plant, which consequently led to higher water consumption. These findings highlight the importance of an adequate nutrient supply to optimize forage productivity and resource use efficiency in irrigated systems.

The application of ozonated irrigation water did not negatively affect the growth of Mombaça grass and, although it did not independently lead to significant improvements in the morphogenetic or agronomic characteristics of the forage, its interaction with fertilization in the third cycle resulted in increased biomass. This suggests that ozonation may play an indirect role in optimizing nutrient availability in the soil, enhancing the effects of fertilization. Additionally, its use in irrigation can provide further benefits, such as improving water quality and reducing microbial load, making it a promising strategy for sustainable crop management, especially in systems with limited access to high-quality water sources.

Although this study provides valuable insights into the effects of fertigation with ozonated irrigation water on Mombaça grass, further research is needed to address certain limitations. Future studies should investigate the long-term effects of irrigation water ozonation on soil physical properties, microbial communities, and nutrient dynamics. Moreover, field experiments under different environmental conditions are essential to validate these findings and assess the practical feasibility of implementing ozonation technology in large-scale agricultural systems. By expanding the scope of research, it will be possible to gain a deeper understanding of the broader implications of ozonated irrigation water on crop productivity and sustainable forage management.