Brazilian beef production is predominantly pasture-based with very low nutrient replacement, which results in low productivity indices (Boddey et al., 2004; Martha et al., 2012). This results in a scenario where a large percentage of Brazilian pastures are in some stage of degradation (Santos et al., 2024). Therefore, to sustain the same cattle herd, clearing new areas has been required to compensate for the increasing pasture deficit caused by degradation and to accommodate herd growth (Santos et al., 2024). In view of this situation, Brazil is committed to recovering these degraded pasture areas by 2030 through its Nationally Determined Contribution (NDC), aiming for sustainable livestock farming (Silva et al., 2018). Thus, soil correction, adequate soil preparation, and the use of quality seeds are important steps in pasture recovery. However, discussions often focus on these initial actions as one-time measures, with little attention given to long-term nutrient replacement strategies necessary to maintain pasture persistence and productivity over time. Evidence from previous studies suggests that, without nutrients inputs, pasture productivity may decline significantly within a few years after recovery, highlighting the need for sustained nutrient management to ensure long-term success (Monaghan et al., 2005; Thomas et al., 2021; Carneiro et al., 2022).

Among the various nutrients, nitrogen (N) is particularly important due to its high demand by forage plants (Delevatti et al., 2019). In grass monocultures pastures, the only feasible way to supply N and to avoid further degradation is through the application of N fertilizers (Cassim et al., 2024). Nitrogen fertilizer is produced using the Haber-Bosch process, which combines N₂ from the atmosphere with hydrogen, typically derived from natural gas (Galloway et al., 2017; Cassim et al., 2024). This process is energy-intensive and contributes significantly to the greenhouse gas (GHG) emissions (Robertson and Grace, 2004). As the demand for fertilizers increases, this may lead to competition within agriculture and rising prices for these inputs, all while contributing to greater GHG emissions associated with livestock production (Godde et al., 2021; Homem et al., 2024; Vos et al., 2025).

Legumes in pastures are a technology that is being reborn in Brazil, focusing on sustainable animal production since legumes deliver greater ecosystem services (Boddey et al., 2020; Dubeux Jr et al., 2024). Recent studies have demonstrated the viability of this technology in tropical regions, focusing on compatibility between grasses and legumes (Tamele et al., 2018), grazing management (Gomes et al., 2018; Rodrigues da Cruz et al., 2024), N balance in the soil-plant-animal system (Homem et al., 2021c), animal productivity (Homem et al., 2021a), fatty acid profile of meat (Schmitz et al., 2023) and environmental sustainability (Homem et al., 2024). However, there is still limited information in the literature regarding pasture and animal productivity in mixed grass-legume systems evaluated over time.

Therefore, we hypothesize that introducing forage peanut into pastures is a viable strategy to supply N and maintain forage and animal productivity at levels similar to those achieved with N fertilization. Thus, the objective of this study was to investigate the influence of N input via fertilizer or biological N fixation on canopy structural characteristics, forage production, and the stocking rate.

The grazing cycles varied among treatments due to differences in forage growth. On average, the rest periods were 40 d for the N-fertilized pasture, 47 d for the Mixed pasture, and 68 d for the Unfertilized pasture. There were no differences between PTs for the canopy height in the pre- and post-grazing conditions (P = 0.115 and P = 0.370, respectively; Figure 2) and the averages were 26.4 and 17.6 cm, respectively. In the pre-grazing condition, the PTs did not influence the total herbage mass (P = 0.111; mean of 7,234 kg ha¹), but PT treatments promoted changes in the morphological composition of the forage (Table 1). The greatest green grass mass in the pre-grazing condition was recorded for the N-fertilized pasture, followed by the Unfertilized pasture and the lowest values in the Mixed pasture. The leaf mass was greater in the N-fertilized pasture compared with the other pastures, while stem and dead material mass did not differ among PTs under pre-grazing conditions. Concerning the seasons evaluated, the greatest total herbage mass (P = 0.039) and dead material mass (P = 0.078) were obtained in the summer (means of 7816 and 3064 kg ha¹, respectively). There was no season’s effect for the green grass, leaf, and stem mass in the pre-grazing condition (P≥0.108; Table 1).

Figure 2

Table 1

Variable	Pasture types (PT)			Seasons (S)		SEM	P-value
	N-fertilized	Mixed	Unfertilized	Summer	Autumn		PT	S	PT × S
Total herbage mass (kg ha−1)	7963	6750	6989	7816A	6754B	591	0.111	0.039	0.595
Botanical composition
Green grass mass (kg ha−1)	5131a	3059c	3935b	4222	3861	257	<0.001	0.205	0.450
Legume mass (kg ha−1)	-	1371	-	1434	1308	200	-	-	-
		Morphological composition
Leaf mass (kg ha−1)	2837a	1915b	2026b	2437	2082	208	0.004	0.108	0.691
Stem mass (kg ha−1)	2293	2515	1933	2272	2223	207	0.144	0.827	0.525
Dead material mass (kg ha−1)	2833	2319	3052	3064A	2405B	406	0.247	0.078	0.100

SEM - standard error of the mean.

The herbage mass (green grass mass + legume mass), in both pre- and post-grazing conditions ranged according to the PTs (P = 0.051 and P = 0.012, respectively; Figure 3). In pre-grazing conditions, the greatest and lowest herbage mass were recorded for the N-fertilized and Unfertilized pastures, (5131 and 3282 kg ha¹ respectively), but these values did not differ from the Mixed pasture (4430 kg ha¹; Figure 3). This occurred because the legume mass in the pre-grazing condition for the Mixed pasture was 1371 ± 200 kg ha¹ (Table 1), which corresponded to a legume proportion of 30.5% of the herbage mass. In the post-grazing condition, the N-fertilized and Mixed pastures had the greatest herbage mass (Figure 3). In general, the legume proportion corresponded to approximately 30% of the herbage mass for the pre- and post-grazing conditions (Table 1).

Figure 3

Herbage and grass accumulation rates ranged depending on PTs and seasons (P<0.100). The greatest grass accumulation rate was recorded for the N-fertilized pasture (42.1 kg ha¹ day¹) and the lowest rates were observed in the other PTs (23.5 kg ha¹ day¹), which, in turn, corresponded to a rate approximately 43% lower than that obtained in the N-fertilized pasture (Figure 4). Although the grass accumulation rate in the Mixed pasture was lower, the herbage accumulation rate (37.0 kg ha⁻¹ day⁻¹) was similar to that of the N-fertilized pasture, as forage peanut contributed with 37.8% of the total herbage accumulated. The total herbage and grass accumulation rates increased 66.8 and 71.6% in the summer, respectively, when compared with the rates in the autumn (P≤0.023).

Figure 4 Light green bars represent the accumulation rate of Marandu palisadegrass, dark green bars represent forage peanut, and the gray line indicates the average stocking rate. Vertical bars denote the standard error of the mean.

The stocking rate varied among PT treatments (P<0.001) and across seasons (P = 0.008). The greatest and lowest stocking rates were recorded in the N-fertilized (4.2 AU ha¹) and Unfertilized pastures (0.9 AU ha¹), respectively, with an intermediate value for the Mixed pasture (2.7 AU ha¹; Figure 4). In relation to the N-fertilized pasture, the stocking rate reduced by 35.7 and 78.5% in the Mixed and Unfertilized pastures, respectively. The greatest stocking rate was obtained in the summer, which was 26.7% greater than in the autumn.

There has been much discussion in Brazil concerning the recovery of degraded pastures to increase animal production in a sustainable manner (Feltran-Barbieri and Féres, 2021). Undoubtedly, the recovery of degraded pastures in Brazil is a win-win strategy that could boost livestock husbandry and avoid deforestation in Brazil. It must be a priority strategy of the agribusiness sector (Gianetti and Filho, 2024). However, a major aspect of maintaining productive pasture still needs to be addressed: nutrient replacement, especially nitrogen (N).

Pasture recovery, as an isolated strategy, cannot sustain increased production over the years (Homem et al., 2021c). In the present study, the pasture was established in the 2014/2015 during the rainy season, and the applied treatments began in the following year. Pastures were managed under continuous stocking with variable stocking rate during the rainy period from 2016/2017 to 2018/2019, with similar canopy height targets (Homem et al., 2021a). Thus, Homem et al. (2021a) reported the lowest stocking rate in the Unfertilized pasture, which was 2.3 AU ha¹ on average, compared with the Mixed pasture, with 2.8 AU ha¹, and the N-fertilized pasture, with 3.8 AU ha¹. The stocking rate in the Unfertilized pasture was approximately twice the average for Brazilian pastures, indicating that recovery of degraded pastures can increase forage and animal production (Latawiec et al., 2014; Arantes et al., 2018). However, the present study shows data from the following year, in which the stocking rate of the Unfertilized pasture decreased to 0.9 AU ha¹. This demonstrates that five years after the grass establishment, pasture productivity declined considerably, approaching the average Brazilian stocking rate.

In pastures with N fertilizer application, the stocking rate was maintained over time, with the N-fertilized pasture supporting 4.2 AU ha⁻¹, compared with 0.9 AU ha⁻¹ in the Unfertilized pasture. This difference is further supported by the forage accumulation rate, which was lowest in the absence of additional N. Although different stocking methods were used before this study, comparisons between the years studied may be valid, as similar canopy height targets were maintained across treatments (Homem et al., 2021a). It is also important to note that without proper management, a decline in productivity may occur shortly after recovery of degraded pastures.

A study conducted at the same experimental site by Homem et al. (2021c). assessed the N balance in the soil-plant-animal system, considering N inputs (e.g., fertilizer application and biological N fixation) and outputs (e.g., product and N-losses). Their findings support the present results, showing that the Unfertilized pasture had a negative N balance, with higher outputs than inputs. In contrast, both the N-fertilized and Mixed pastures exhibited positive N balances, indicating greater N input into the ecosystem than losses. This indicates that the beneficial effects of recovering degraded pastures are limited without N replacement (Feltran-Barbieri and Féres, 2021; Homem et al., 2021c). After a few years, the pasture is likely to revert to low productivity and re-enter the degradation process, even with good grazing management, as observed in the present study.

The Brazilian National Determined Contribution (NDC) has set a target to recover 30 million hectares of degraded pasture by 2030, aiming to mitigate greenhouse gas emissions (Silva et al., 2018; Feltran-Barbieri and Féres, 2021). If Brazil achieves this target, it will require an annual consumption of over 10 million tons of N fertilizer to supply 150 kg N ha⁻¹ yr⁻¹, according to this study. This amount is equivalent to approximately 75% of the N fertilizer used in the country for all crops (FAO, 2023). Even with a minimum application rate of 50 kg N ha⁻¹ yr⁻¹ for the recovery of degraded pastures, N fertilizer consumption would need to increase by 25%. This would impact input costs economically, which could be reflected in food prices. Therefore, it is evident that incorporating legumes into pastures should be adopted as public policy. Legumes can fix N through their association with rhizobia, reducing or eliminating the pasture’s N requirements (Homem et al., 2021c). This promotes increased forage accumulation, higher stocking rates, and extended pasture persistence (Homem et al., 2021a), resulting in positive economic and environmental impacts. Furthermore, Brazil stands out for its successful use of biological nitrogen fixation in agriculture, particularly in soybean production (Rezende et al., 2021; Telles et al., 2023). However, this sustainable approach has not been widely adopted in pasture systems. The present study highlights the viability of using grass-legume mixed pastures to positively impact forage productivity and carrying capacity positively.

The PTs studied minimally affected the canopy structure. Despite differences in forage accumulation rates, the similar target canopy heights between treatments resulted in comparable canopy structures. The only notable difference was the increased percentage of leaf mass in the N-fertilized pasture. Similar results were observed in previous studies conducted in the same area (Homem et al., 2021b). Using canopy height targets to control forage regrowth and defoliation is highly effective. This study set the target height based on achieving 95% light interception (LI) for palisadegrass monoculture pastures (Trindade et al., 2007) and mixed pastures with forage peanut (Gomes et al., 2018). Managing mixed pastures with forage peanut at the same canopy height as monoculture pastures can facilitate the adoption of this technology by farmers.

In Brazil, farmers traditionally use grass pastures in monoculture and sometimes manage these pastures effectively. Therefore, if legumes are adopted as a public policy to promote sustainable livestock farming, farmers should find it relatively easy to assimilate the management practices. This is because the same management recommendations used for monoculture grass pastures can be applied to mixed pastures with forage peanut (Gomes et al., 2018; Tamele et al., 2018). Based on the results presented, forage peanut is a valuable tool for many regions of Brazil. Although this study was conducted in the Atlantic Forest Biome, other research suggests that the benefits of forage peanut may also be observed in the Amazon Biome (Andrade et al., 2021). It is also important to note that, while this study presents data from a single year, the experimental systems have been maintained over several years, supporting the reliability and consistency of the observed responses.

Our findings support the hypothesis that introducing forage peanut into pastures is an efficient strategy to maintain forage and animal productivity at levels comparable to nitrogen fertilization. The introduction of forage peanut into grazing systems presents a viable alternative to meeting nitrogen needs while reducing economic costs and environmental impacts. In Brazil, efficient nitrogen utilization is crucial for livestock sustainability. To enable this strategy, future research should prioritize the development and availability of seeds or seedlings for farmers, as well as the improvement of techniques for mixed pasture establishment and the incorporation of forage peanut into existing pastures. These efforts can contribute to the sustainable intensification of livestock production, promoting environmental and productive benefits.