Feasibility of Organic Fertilization for Reducing Greenhouse Gas Emissions Compared to Mineral Fertilization

Abstract

The objective of this study was to evaluate the impact of different nitrogen sources (urea, compost, and digestate) on N₂O and CH₄ emissions and the forage production of Piatã grass in tropical pastures, with the aim of identifying the fertilization practices that can balance productivity with environmental mitigation. The experiment included 10 forage cuts over a period of 14 months, from January 2017 to February 2018. The CH₄ and N₂O emissions were monitored using closed chambers and analyzed by gas chromatography. The forage production was assessed by weighing and drying the material. The emission intensity was calculated based on the global warming potential of the gases. The data were analyzed using ANOVA and compared by Tukey’s test (p ≤ 0.05). Fertilizer application increased the N₂O emissions, with the highest flux (79.56 mg N-N₂O/m²/day) observed for the digestate treatment (p < 0.01). The N₂O consumption was the most significant for the control treatment (−5.90 mg N-N₂O/m²/day) in July. The CH₄ oxidation was prevalent across all the treatments, with the highest oxidation for the urea treatment (−49.80 µg C-CH₄/m²/day) two days after fertilization. The dry matter production (DMP) was the highest with urea during the summer (16.9 t/ha; p < 0.01). The emission intensity values were 243.41 kg CO₂eq/t DM for urea, 103.44 kg CO₂eq/t DM for digestate, and 27.35 kg CO₂eq/t DM for compost (p < 0.01). The compost application stimulated CH₄ oxidation. In conclusion, compost can be considered an important alternative for fertilizing pasture areas, both from a productive and environmental perspective.

1. Introduction

Beef cattle production in Brazil is based on grazing systems, with the forage species of the Urochloa genus being the most commonly used. A key characteristic of this plant is its ability to grow in low-fertility soils, particularly with low nitrogen (N) levels.

For N₂O emissions to occur, the denitrification of nitrate (NO₃⁻) must take place, especially in fertilized soils that become waterlogged during warmer periods. This happens because such environmental conditions favor the microbial activity responsible for this process [1,2]. Previous studies have indicated that organic nitrogen sources may help reduce N₂O emissions due to their slow decomposition, which provides the soil with a gradual nitrogen release. Organic fertilizers, such as compost and digestates (products of anaerobic digestion), contain nitrogen in organic forms, meaning that not all of the nitrogen present in these fertilizers is immediately available for N₂O production [3,4]. Another advantage of organic fertilization is the recycling of nutrients derived from animal production waste, returning them to the productive system [5]. The ammonium ion (NH₄⁺), an inorganic form of nitrogen, plays a fundamental role in the nitrogen cycle and in plant nutrition, as it provides a primary source of assimilable nitrogen for plants. In this context, the adoption of organic fertilization practices could help reduce the need for external inputs, promoting greater economic and environmental sustainability in forage production.

However, a lack of nitrogen replenishment can lead to pasture degradation [6]. Therefore, proper fertilization is essential to promote grass growth and development, improve nutritional quality, maintain canopy persistence, and prevent degradation issues [2]. Despite its benefits, nitrogen fertilization raises environmental concerns, due to the emission of greenhouse gases, such as nitrous oxide (N₂O). This gas has a global warming potential 265 times greater than that of carbon dioxide (CO₂) [7]. Given the significant warming potential of N₂O, it is necessary to study alternative nitrogen sources for pasture fertilization in order to mitigate greenhouse gas emissions.

Like any nitrogen source used for pasture fertilization, organic fertilization also influences methane (CH₄) emissions from and/or oxidation in soils [7]. However, information is still limited regarding the magnitude of these emissions, their timing, and the persistence of greenhouse gas (GHG) emissions in response to the type of fertilization (organic or mineral) used in pastures. It is also important to note that comparisons of emissions intensities (the ratio of GHG emissions to forage production) among the different nitrogen sources are scarce, as simply comparing the total GHG emissions may not provide an adequate assessment of the sustainability of a fertilization management practice.

The objective of this study was to evaluate the impact of different nitrogen sources (urea, compost, and digestate) on N₂O and CH₄ emissions and on the forage production of Piatã grass in tropical pastures, with the aim of identifying the fertilization practices that can balance productivity and environmental mitigation. The hypotheses tested were as follows: (I) whether organic fertilizers, due to their slower nitrogen release, would result in lower N₂O emissions compared to synthetic urea; (II) whether N₂O emissions would be higher during the autumn and winter due to lower forage production; and (III) whether urea would result in a higher forage production and emission intensity compared to organic fertilizers.

2. Materials and Methods

2.1. Site, Climate, and Soil

The trial was carried out in a greenhouse at the experimental area Embrapa Agropecuária West in Dourados, MS, Brazil (22°16′ S, 54°49′ W; at an altitude of 408 m a.s.l). The climate in the region, according to the Köppen classification, is type Cwa (humid mesothermal, hot summers, and dry winters). The data on maximum, minimum, and mean temperatures collected at the experimental area during the research can be seen in Figure 1. The soil used was Oxisol of clay texture with the following characteristics: sand, 128g/kg; silt, 107 g/kg; clay, 765 g/kg; organic matter, 27.24 g/kg; pH of CaCI₂, 4.78; P, 5.14 mg/dm³; K, 1.00 cmolc/dm³; Ca⁺², 2.86 cmolc/dm³; Mg⁺², 1.29 cmolc/dm³; Al⁺³, 0.15 cmolc/dm³; H+Al, 6.08 cmolc/dm³; and cation exchange capacity, 11.22 cmolc/dm³.

2.2. Treatments and Preparation

The treatments in this study were designed to ensure balanced nitrogen (N) application across different fertilizer sources. Four treatments were evaluated: (1) control (no fertilization), (2) urea, (3) compost, and (4) digestate. The N application rate was standardized at 400 kg N/ha/year for all fertilized treatments to allow for a direct comparison of their effects on greenhouse gas (GHG) emissions and forage production. A block split-plot- in-time (seasons) design was used, with four treatments and six repetitions, totaling 24 experimental units (40 L pots Figure S1 in Supplementary Materials).

Urea, a synthetic nitrogen fertilizer with 46% N content, was applied at 909 kg/ha to supply the required 400 kg N/ha/year. The compost was derived from laying hen manure composted for 70 days, with a C:N ratio of 10:1 and a total N content of 2.13%. The digestate was obtained from anaerobic digestion of laying hen manure with a 25-day hydraulic retention time, resulting in a C:N ratio of 9:1 and a total N content of 0.23%. Due to the lower N concentration in compost and digestate, higher application rates were required to match the N target, with 18,779 kg/ha of compost and 173,913 kg/ha of digestate. These values corresponded to pot-scale applications of 18 g urea, 370 g compost, and 3430 g digestate per 40 L pot, split into ten applications throughout the experimental period (

Table 1. Doses of the N fertilizers used in the experiment.

Doses	Urea	Compost	Digestate
kg N/ha †	400	400	400
kg fertilizer/ha	909	18,779	173,913
g fertilizer/pot ‡	18	370	3430
g fertilizer/pot/cut	1.8	37	343

† Hectare = 2000.000 dm³; ‡ pot = 40 dm³.

).

Soil moisture was maintained at 70% of field capacity using an irrigation system. On December 6th, 2016, Urochloa brizantha cv. Piatã (Piatã grass) was sown with 30 seeds per pot, and seven days after emergence, the number of plants was reduced to nine per pot. The experimental period began after a standardization cut 50 days after sowing, at 20 cm from the soil. Evaluations were conducted every 35 days, with fertilization applied after each cut, initiating a new data collection cycle. A total of ten cuts were performed from February 2017 to February 2018.

2.3. Greenhouse Gas Emissions Assessment

CH₄ and N₂O fluxes were measured by the static closed-chamber technique using a static 32.2 L opaque round chamber. A trough was attached to the pot with the chamber (Figure S1) fitted over the pot to create a closed system with water in the trough.

GHG emissions were monitored on days 1, 2, 3, 5, 8, 11, 15, 22, and 28 after fertilizer application. When emissions remained higher than the control treatment after the 28th day, sampling continued every seven days until the next forage cut.

On each collection day, the sampling chamber was coupled to the pot for 30 to 60 min depending on the emissions. At regular intervals during this time (0, 15, and 30 min), three 20 mL samples were collected from inside each chamber using a polypropylene syringe. Before collection, the air inside the chamber was homogenized with an internal fan for 30 s and the temperature was measured with digital thermometers coupled to each chamber. The collections always started at 9 a.m. for the mean representativeness of the daily N₂O and CH₄ emissions from the soil.

The analyses to determine gas concentrations were made right after collection or, on some occasions, after a maximum of 15 days of storage [8] in properly sealed and evacuated 12 mL chromatography vials. Gas samples were analyzed for CH₄ by gas chromatograph (GC) (Shimadzu Green House Gas Analyzer GC-2014; Kyoto, Japan)–flame ionization detector with methanizer and for N₂O concentrations by GC–electron capture detector. Before each analysis batch, standards with known concentrations of gases were injected, whose results were used to determine the analytical curves to calculate gas concentrations of each sample.

Air samples were quantified for CH₄ and N₂O concentrations and corrected with the temperature measured at the moment of collection for concentrations at 25 °C (standard temperature and pressure conditions). Gas fluxes were calculated from the differences in concentrations over the evaluation period for each chamber according to the equation below, described by [9].

FGHG = δC/δt (V/A) M/Vm,

where:

• δC/δt is the change in gas concentration in a chamber during the incubation period;
• V and A are, respectively, chamber volume and area of soil covered by a chamber;
• M is the molecular weight of the gas;
• Vm is the molecular volume corrected for standard conditions of temperature and pressure: Vm = 0.02241 × (273.15 + temp/273.15) c p0/p1, where 0.02241 m³ is 22.41 L mol volume, temp is the chamber temperature at the moment of sampling (in °C), p0 is sea level air pressure, and p1 is the air temperature of the experimental field. Air pressure at the study site was estimated using the barometric equation that takes altitude into account.

CH₄ and N₂O emissions during the evaluation period were determined by the accumulated emissions during the evaluation period calculated by the integration of daily emissions across the period assessed. The GHG emissions attributed to the application of organic or mineral fertilizers were estimated by subtracting the calculated emissions of the control treatment (without fertilization).

Based on the total N₂O emissions of each treatment and the dose of N applied, the emission factor (EF) of N-N₂O (N as N₂O) was calculated. This factor expresses how much N, applied as fertilizer, was transformed into N₂O. EF was calculated using the following equation: EF = (total N-N₂O emitted − total N-N₂O emitted by control)/total N applied by the fertilizer.

2.4. Forage Characteristic Evaluation

The mass of green forage (aerial part) was measured from the total weight of green forage contained in the pots after a cut at 20 cm from the soil. The material collected was taken to the laboratory and placed in a forced-air oven at 65 °C for at least 72 h to determine the dry matter content according to the methodology described by [10].

2.5. Emission Intensity Calculation

GHG emission intensity was calculated using the emission factors obtained in the present study for N₂O and CH₄, and the global warming potential of each gas was extracted from [7,11], i.e., 28 for CH₄ and 265 for N₂O. The functional unit adopted was kg CO₂eq/t DM.

2.6. Data Analysis

The accumulated GHG emissions and productive characteristics of Piatã grass were subjected to analysis of variance using the split-plot-in-time scheme (using the PROC MIXED procedure) to assess the effect of the main treatments (fertilization types), secondary treatments (seasons), and their interaction (fertilization x season). The means of the treatments were compared by Tukey’s test at 5% probability. The statistical analysis was performed using the software SAS 6.1.

3. Results

3.1. Greenhouse Gas Emissions

The fertilizer application stimulated N₂O production. The mean flux of the treatment without N addition was 0.1 mg N-N₂O/m²/day, which increased to 0.33, 0.61, and 1.39 mg N-N₂O/m²/day in the compost, urea, and digestate treatments, respectively. The highest N₂O flux (79.56 mg N-N₂O/m²/day) was observed seven months after the beginning of the trial for the digestate treatment (Figure 2). N₂O consumption was observed in all the treatments, with the highest daily value found for the control treatment (−5.90 mg N-N₂O/m²/day) in July. The lowest N₂O fluxes were −3.77, −2.95, and −2.79 mg N-N₂O/m²/day in the compost, urea, and digestate treatments, respectively. The highest N₂O fluxes were observed during the autumn and winter, which had the lowest temperatures (Figure 2).

The largest fraction of N lost as N₂O was observed for the digestate treatment. The emission factors observed were 1.28, 0.50, and 0.23% for the digestate, urea, and compost, respectively. The accumulated N₂O emissions were statistically different among the treatments, with the highest values observed in the soils treated with digestate (

Table 2. Herbage mass, N₂O and CH₄ emissions per area, emission factor (EF), and emission intensity (EI) for soil cultivated with Piatã grass and fertilized with different types of fertilizer during different seasons.

Parameters	Control	Urea	Compost	Digestate	† SEM	p Value
DMP ‡, t/ha	7.7C	16.9A	11.7B	13.1B	1.48	<0.01
N2O, kg/ha	0.4C	2.2B	1.2C	5.0A	0.46	<0.01
CH4, g/ha	0.1A	−0.5B	−0.3AB	0.1A	0.15	<0.01
EF, %	-	0.5B	0.2C	1.3A	0.06	<0.01
N2O, kg CO2eq/ha	104D	596B	322C	1345A	71.1	<0.01
CH4, kg CO2eq/ha	0.0028A	−0.0131B	−0.0089AB	0.0023A	−0.00121	<0.01
Total, kg CO2eq/ha	104.4D	596.4B	322.0C	1345.9A	59.21	<0.01
EI, kg CO2eq/t DM	13D	35B	27C	103A	11.6	<0.01

‡ DMP = dry matter production; † SEM = standard error of the mean; means with different uppercase letters differ by Tukey’s test (p < 0.05).

).

The prevalence (over 60% of the evaluations) of CH₄ oxidation by the soil was observed in all the treatments. The mean fluxes were −6.0, −20.3, −11.7, and −34.0 µg C-CH₄/m²/day for the control, digestate, compost, and urea treatments, respectively. The highest emissions occurred in September, approximately seven months after the beginning of the trial. The highest CH₄ production was observed for the control treatment (25.58 µg C-CH₄/m²/day). The highest methane oxidation occurred two days after fertilizer application (−49.80 µg C-CH₄/m²/day) for the treatment with the urea application. The cumulative CH₄ emissions differed among the treatments (p < 0.001), with the highest values observed for the control and digestate treatments (Figure 3).

3.2. Forage Production and Emissions Intensities

An interaction (p < 0.05) was found between the seasons and type of fertilization on the dry matter production (DMP). The highest DMP was observed for the treatment fertilized with urea during the summer, followed by the digestate, compost, and control treatments in the same season. Summer was the most productive season; followed by spring in second; and autumn and winter, which did not differ from each other, in third place for DMP. The only exception was observed for the digestate treatment, in which the DMP did not differ (p > 0.05) between spring and autumn (Figure 4).

The emissions intensities were hugely affected by the treatments (Table 2) and were as follows: 243.41 kg CO₂eq/t DM, 103.44 kg CO₂eq/t DM, and 27.35 kg CO₂eq/t DM, for the urea, digestate, and compost, respectively.

4. Discussion

4.1. Greenhouse Gas Emissions

A large portion of nitrous oxide (N₂O) emissions is associated with the use of synthetic fertilizers and manure in agricultural systems [12]. This mainly occurs when these inputs are applied during stages in which crops do not yet require the full amount of nitrogen provided, resulting in nitrogen accumulation in the soil [13]. The excess nitrogen not absorbed by plants reduces nitrogen use efficiency [6,7,8]. As a consequence of the intensification of agricultural practices worldwide, N₂O emissions have been increasing at an estimated annual rate of 0.25%.

N₂O emissions from agricultural soils primarily result from the microbial processes of nitrification and denitrification [14], and are influenced by factors such as inorganic nitrogen availability, soil moisture, and temperature [1,15]. The functional amoA gene is responsible for encoding the enzyme ammonia monooxygenase, which acts in the first step of the nitrification process by promoting the oxidation of ammonia (NH₃) to hydroxylamine (NH₂OH) [4,16]. The abundance of amoA gene copies in the soil has been positively correlated with higher emissions of nitrous oxide (N₂O) [4]. This occurs because high nitrification rates lead to increased production of reactive intermediates such as NH₂OH, nitric oxide (NO), and nitrate (NO₃⁻), which are substrates directly involved in the formation of N₂O [17].

Moreover, the increased nitrifying activity also intensifies oxygen consumption in the soil, creating more reducing (anaerobic) conditions, which can favor the occurrence of denitrification—another microbial process responsible for generating N₂O as a byproduct [16]. Thus, the combination of a greater availability of nitrogenous substrates and anaerobic conditions strongly stimulates N₂O emissions.

Several studies in the scientific literature support this association, having shown that repeated applications of raw manure to the soil not only increase denitrification rates but also lead to a higher abundance of the genes encoding the enzymes involved in this process, such as nirK, nirS, and nosZ [18].

In this study, the highest N₂O emissions were observed in the plots treated with digestate. This can be attributed to the liquid form of the digestate and its lower nitrogen content, requiring higher doses to provide the same amount of nitrogen as the other treatments (Table 1).

In agreement with this, elevated levels of ammonium (NH₄⁺), combined with the commonly high pH of digestates, have been shown to enhance the risk of ammonia volatilization, representing a major concern about nitrogen losses and potential impacts on human health [19]. Liquid fertilizers, when applied in large quantities, can penetrate deeper soil layers, creating a prolonged anaerobic environment, which favors N₂O emissions (Figure S2). This may be explained by the increased activity of denitrifying microorganisms, which is stimulated by greater soil carbon availability, higher soil respiration rates, and soil pore clogging from the effluent, reducing aeration [20].

Another important factor is the nitrogen availability of organic fertilizers. This may help explain why the compost was more effective at reducing N₂O emissions compared to the urea and digestate [2]. Similarly, ref. [19] observed lower N₂O emissions from green compost compared to other liquid organic fertilizers, such as food-based digestate and livestock slurry.

The N₂O emissions from pasture systems are largely influenced by various factors, such as soil characteristics, regional climate, nitrogen input levels, the forage species composition, and grazing management practices. Among these, the air temperature and soil moisture play a critical role, as they directly affect the microbial activity and gas diffusion within the soil [21]. The soil moisture has a direct impact on the biological processes of nitrification and denitrification carried out by soil microorganisms. The highest N₂O fluxes recorded during the autumn and winter contrast with the findings from [22], who reported lower N₂O emissions at cooler temperatures. However, it should be noted that in many tropical regions, colder periods are often followed by dry winters with low rainfall, which may explain the lower emissions observed by those authors.

Additionally, ref. [14] reported similar results in a controlled environment, where high nitrogen doses and soil temperatures around 18 °C led to peak N₂O fluxes, after which a negative correlation between the temperature and N₂O emissions was observed. Based on these findings, it can be concluded that the average temperatures in this study had a minimal impact on the N₂O emissions (which were either close to or above 18 °C).

However, N₂O emissions can vary with temperature, as the proportion of nitrification and denitrification as sources of the gas tends to decrease with increasing temperature. Another important factor is that N₂O emissions, in relation to temperature and soil moisture, follow an inverted parabolic pattern, with the highest fluxes observed at moisture levels between 50% and 60% [23].

The form of the fertilizer (liquid or solid) and available nitrogen were the primary factors influencing the N₂O emissions. The correlation analysis of the physicochemical conditions and microbial succession in the system indicates that the moisture content and NO³⁻ levels during the composting process provided suitable conditions for the growth of the bacteria that contributed to the reductions in the NH₃ and N₂O emissions. Therefore, the compost drying process is a way to minimize NH₃ and N₂O emissions [22].

Typically, the highest N₂O fluxes occur between three and fifteen days following fertilizer application [11,15]. However, in this study, the peak fluxes were observed five months after fertilizer application. This could be due to the cumulative effect of fertilizer application, which was applied after each cutting (totaling ten applications), and/or the reduced ability of tropical grasses to assimilate nitrogen under low-temperature and short-day conditions.

The N₂O emission factor (EF) default value for fertilizers is 1% of the total nitrogen applied, as per [10]. The N fraction lost with the digestate application (1.16%) was in line with IPCC guidelines, while the emissions from the urea were only half of the recommended EF values, as indicated by [24]. Ref. [11] also observed lower EF values for green compost compared to liquid organic fertilizers, although these values were still lower than those observed in the current study.

Soil moisture plays a crucial role in the production or oxidation of methane (CH₄), as long as organic material is available [25]. In this study, the moisture was consistent across the treatments, and the fertilizer applications promoted CH₄ oxidation (Figure 2 and Figure 3). Nitrogen fertilizers may either stimulate the production [26] or consumption [27] of CH₄, or, in some cases, have no effect on CH₄ fluxes [28]. The increased CH₄ oxidation observed after fertilizer application may have been due to the stimulation of methanotrophic microorganisms in the soil. The highest CH₄ oxidation occurred two days after fertilizer application. Initially, the methanotrophic population present in the soil when it was collected dominated, and their growth was stimulated by the added carbon and nitrogen. According to [29], both carbon and nitrogen are vital for the growth of these microorganisms. In terms of the nitrogen source, the lowest CH₄ oxidation occurred in the urea treatment because organic nitrogen sources provide available carbon, which leads to CO₂ production during oxidation rather than CH₄ [30].

The soil CH₄ uptake, in turn, showed a positive correlation with the temperature and a negative correlation with the soil moisture content. Some studies have also suggested that both low and high soil moisture levels can inhibit CH₄ uptake, either by reducing the activity of methanotrophic microorganisms or by limiting the diffusion and transport of CH₄ and O₂ within the soil [23].

Contrary to expectations, the application of compost did not stimulate CH₄ production, which differs from findings of [22], who reported increased CH₄ production in soils with pasture fertilized with organic fertilizers in both tropical and temperate climates.

4.2. Relationship Between GHG Emissions and Forage Production

Numerous studies have demonstrated a positive correlation between soil nitrogen (N) availability and the dry matter (DM) production of tropical grasses [6]. This is because N significantly enhances enzymatic reactions and metabolic processes in plants, leading to increased chlorophyll content in the leaves and promoting the supply of photoassimilates, which directly impacts biomass production [24].

According to [25], organic fertilizers tend to result in lower forage growth compared to synthetic fertilizers, due to the more diverse nutrient availability in organic fertilizers. This explains the superior production of Piatã grass observed with the urea treatment in this study.

Digestates, resulting from anaerobic processes, offer a higher N availability (with increased NH₄⁺-N concentrations in the effluents) compared to compost [25]. Consequently, higher quantities of compost are required to achieve the same DM production as liquid digestates. For example, ref. [31] found that the DM production of Piatã grass with compost was similar to that obtained with digestate, though the compost dose was 4.8 times higher.

Tropical grass production is influenced by the water regime, temperature, and photoperiod, especially during autumn and winter when production tends to decrease [8]. In the present study, however, only the temperature (Figure 1) and photoperiod affected plant development, as the soil moisture was consistently controlled.

When comparing the grass production data with the N₂O emissions data, it appears that the reduced plant growth during autumn and winter may have contributed to increased soil N availability, which, in turn, enhanced N₂O emissions. The tropical soil temperature and moisture conditions (via irrigation) were optimal for N₂O production [14].

Therefore, this study serves as a cautionary note for producers, advising against the use of high digestate doses during seasons with reduced grass production. Fertigation is a common practice in Brazil, as digestate is produced year-round (due to daily waste production by animals) and is frequently used for fertilization throughout the year.

Among the various parameters examined in this study, emission intensity may be the most crucial, as it allows for the comparison of greenhouse gas (GHG) emissions (N₂O + CH₄) on a consistent basis (CO₂ equivalents) relative to the final product (tons of dry matter). Of the organic fertilizers tested, the compost exhibited the lowest emission intensity values (similar to the control treatment), making it a viable alternative both for forage production and reducing GHG emissions. While there is limited literature on emission intensity [32], no studies have specifically examined emissions relative to forage DM production. Therefore, further research is needed in this area, as emission intensity may be a more appropriate metric for comparing treatments than simply quantifying the GHG emissions from pastures.

In a field experiment conducted by [18] to evaluate the impact of organic soil amendments derived from animal waste on N₂O, CH₄, and heterotrophic CO₂ emissions, as well as the net greenhouse gas (GHG) balance in ryegrass and forage maize pastures, it was found that both compost and digestate helped mitigate GHG emissions into the atmosphere when compared to chemical fertilizer treatments.

Furthermore, the use of mixed pastures that include forage legumes has been identified as a promising strategy to enhance sustainability. These legumes contribute to a more continuous and synchronized nitrogen supply that better matches plant demand, thereby helping to reduce the intensity of N₂O emissions [21].

5. Conclusions

The hypothesis that organic fertilizers result in lower N₂O emissions compared to urea was only partially supported. While the compost resulted in lower N₂O emissions, liquid fertilizers like digestates required more caution due to their higher emissions. Fertilization during the colder months, particularly autumn and winter, led to increased N₂O emissions, suggesting that the practice of applying large quantities of organic fertilizers during these seasons should be reconsidered. Although the urea fertilization resulted in the highest forage production, the compost exhibited a lower emission intensity, making it a more environmentally sustainable option for pasture fertilization.