Agronomic yield of peanuts under mineral and organic fertilization, inoculation, and salt stress

ABSTRACT

The use of brackish water in agriculture reduces plant production. Thus, using mineral or organic fertilization associated with seed inoculation with microorganisms is a promising alternative. In this context, the aim of this study was to evaluate the agronomic performance of peanuts irrigated with brackish water under mineral and organic fertilization and inoculation. The experimental design was entirely randomized, in a 4 × 2 × 2 factorial scheme, with five replications. The first factor corresponded to the forms of fertilization—P0: 0% dose of phosphorus; P50%: 50% of the recommended dose of phosphorus; P100%: 100% of the recommended dose of phosphorus; and Bio: 100% of fertilization with bovine biofertilizer. The second factor corresponded to the two levels of electrical conductivity of the irrigation water (0.3 and 4 dS.m^-1), and the third one represented the presence and absence of the inoculant—WI: with inoculant; and WTI: without inoculant. The use of organic fertilization with bovine biofertilizer combined with inoculation with Bacillus megaterium and Bacillus subtilis mitigates salt stress and enhances both productivity and water use efficiency in peanut cultivation. Fertilization with bovine biofertilizer mitigates the harmful effects of salts in irrigation water and promotes an increase in pod length and mass in peanut crops. Irrigation with saline water at 4 dS.m^-1 reduces the agronomic performance of peanut when neither phosphorus or organic fertilization nor microbial inoculation is applied.

Key words
Arachis hypogaea L.; inoculant; salinity; plant production; water use efficiency

INTRODUCTION

The peanut (Arachis hypogaea L.) is considered one of the most important oil seeds in the world, with an estimated annual production of approximately 46 million tons (Huang et al. 2023). The importance of peanuts is directly related to their nutritional value, being one of the main sources of digestible protein, cooking oil, and vitamins in continents such as Asia, Africa, and America, where they contribute to food security (Arya et al. 2016).

Despite its importance in the global food market, peanut production in developing countries remains low due to production limitations, mainly attributed to abiotic and biotic stresses (Huang et al. 2023, Sousa et al. 2023). In the semi-arid and arid regions of the world, one of the predominant abiotic stresses is water deficit, which leads farmers to use brackish water to alleviate water scarcity and make agricultural production viable (Sousa et al. 2021).

However, the use of brackish water in agriculture causes salt stress, which can potentially reduce crop productivity, including the one of peanuts, which has a threshold salinity of 3.3 dS·m^-1 (Ayers and Westcot 1999). Plant homeostasis can be altered by ionic toxicity, mainly caused by toxic ions such as Na⁺ and Cl^-, which affect photosynthetic processes by damaging photosynthesizing pigments and reducing their activity (Zhang et al. 2022). In addition, the intensification of salt stress causes changes in the partitioning of photoassimilates and biomass production, which results in a reduction in crop production (Guilherme et al. 2021).

To make agricultural production with brackish water viable, one strategy is the use of mineral or organic fertilization associated with the inoculation of seeds with microorganisms via inoculants (Santos et al. 2024). Phosphorus is an essential macronutrient involved in photosynthesis, respiration, and energy metabolism (Shalaby 2024). In saline conditions, it can improve plant metabolism, promoting sugar accumulation, strengthening tolerance mechanisms, and aiding plant acclimatization (Bouras et al. 2021), growth and physiological indices (Ribeiro et al. 2022).

The organic fertilizers based on cattle manure contain essential nutrients such as nitrogen (N), phosphorus (P), potassium (K), and calcium (Ca) in its chemical composition (Freire et al. 2022, Sousa et al. 2023). These elements can promote osmotic adjustment in plants under salt stress and improve K/Na and Ca/Na ionic ratios, contributing to the maintenance of cellular homeostasis and the mitigation of salinity effects (Sousa et al. 2021). In addition, inoculating seeds with microorganisms can intensify the mechanisms that improve plant metabolism in saline environments, by increasing the activity of antioxidant enzymes, increasing the production of plant hormones, producing 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and improving the absorption of water and nutrients (Naing et al. 2021).

The application of Bacillus megaterium as a biofertilizer, in combination with phosphorus doses of 60 and 80 kg·ha^-1, has shown potential not only to mitigate the deleterious effects of salinity but also to enhance the uptake of essential nutrients such as N, P, K, and Ca. Compared to plants that did not receive B. megaterium, those inoculated with the bacterium exhibited improved nutritional status, thereby contributing to better agronomic performance of cauliflower (Shalaby 2024).

The interaction of these factors can enable the production of crops irrigated with brackish water. We hypothesized that the integration of mineral and organic fertilization with microbial inoculation can mitigate the detrimental effects of salt stress and improve the agronomic performance of peanuts irrigated with brackish water. In this context, the objective of this study was to evaluate the agronomic performance of peanuts irrigated with brackish water under mineral and organic fertilization and inoculation.

MATERIALS AND METHODS

Experimental conditions

The study was conducted from February to May 2023 at the Auroras Production Unit, located in the municipality of Redenção, Ceará, Brazil. The geographic coordinates of the experimental area are latitude 4°13’05.3’’S, longitude 38°42’46.1’’W, and altitude 207 meters.

The region’s climate is characterized as tropical rainy, very hot and with rainfall predominating in the summer and autumn seasons, which classifies this climate as tropical savanna with a dry winter (Aw) (Alvares et al. 2013). The meteorological conditions during the experimental period are shown in Fig. 1. Daily measurements of maximum and minimum air temperatures, as well as average relative humidity, were recorded using a data logger (HOBO^® U12-012 Temp/RH/Light/Ext).

Figure 1
Minimum and maximum air temperatures and relative air humidity during the experimental period.

Experimental design

The experimental design used was entirely randomized, in a 4 × 2 × 2 factorial scheme, with five replications. The first factor corresponded to the forms of fertilization—P0: 0% dose of phosphorus; P50%: 50% of the recommended dose of phosphorus; P100%: 100% of the recommended dose of phosphorus; and Bio: 100% of fertilization with bovine biofertilizer. The second factor corresponded to the two levels of electrical conductivity of the irrigation water (0.3 and 4 dS·m^-1), and the third factor represented the presence and absence of the inoculant BiomaPhos^®—bacteria strains BRM 119 (B. megaterium) and BRM 2084 (Bacillus subtilis)—, i.e., WI: with inoculant; and WTI: without inoculant (Fig. 2).

Figure 2
Graphical summary of the treatments used in the experiment.

Setup and conduct of the experiment

Five peanut seeds of the BR-1 cultivar were sown at a depth of 2 cm in polyethylene pots with capacity of 11 dm³. The substrate used to fill the pots consisted of a mixture of arisco (a light-textured sandy material normally used in constructions in the north-east of Brazil), sand, and cattle manure, in a ratio of 7:2:1 (v/v), respectively. The chemical characteristics of this mixture are shown in Table 1.

Table 1
Chemical characteristics of the substrate used before the treatments were applied.

OM	N	P	K	Ca	Mg	Na	pH H2O	ESP (%)	ECse dS·m-1
g·kg-1
0.8	0.21	0.06	0.28	0.07	0.03	0.11	6.5	3.4	0.37

• OM: organic matter; ESP: exchangeable sodium percentage; ECse: electrical conductivity of the soil saturation extract.

Before sowing, the peanut seeds intended for the treatments that included inoculation were treated with the commercial product BiomaPhosSymbol following the manufacturer’s recommendation (100 mL of the product for every 60,000 seeds). This product is made up of a mixture of the bacterial strains BRM 119 (B. megaterium) and BRM 2084 (B. subtilis).

The mineral fertilization of the plants was based on the chemical analysis of the substrate (Table 1) and the recommendations of Fernandes (1993), which correspond to 15 kg·ha^-1 of N, 62.5 kg·ha^-1 of P₂O₅, and 50 kg·ha^-1 of K₂O. With a stand of 10,000 plants, the maximum dosage per plant^-1 in the cycle was: 1.5 g of N, 6.25 g of P₂O₅, and 5 g of K₂O.

The phosphorus doses were therefore equivalent to the treatments adopted—P0%: 0; P50%: 3.12 g, and P100%: 6.25 g. Fertilization was carried out as the study progressed, with total N applied at the foundation, P and K, 50% at the foundation and 50% at the top dressing (20 days after sowing—DAS). The sources used in this experiment were urea, potassium chloride, and simple superphosphate, respectively.

To determine the amount of fertilizer to be applied, the amount of nutrients in the substrate was calculated by multiplying the density of the substrate (1.3 g·dm^-3) by the volume of the substrate placed in each pot (11 L). Subsequently, the value found (14.3 kg^-1) was multiplied by the amounts of N, P, and K obtained from the substrate analysis (Table 2). Fertilization began at eight DAS and was performed manually once a week, according to the treatments—P0%, P50%, and P100%—of the recommended phosphorus dose as a chemical source and in the treatment with bovine biofertilizer as an organic source, applying 6 L·plant^-1.

Table 2
Chemical analysis of the aerobically fermented bovine biofertilizer.

Chemical characteristics
Biofertilizer	N	P	K	Ca	Mg		Fe	Cu	Zn	Mn
	g·L-1						mg·L-1
	0.82	1.4	1.0	2.5	0.75		141.6	1.92	68.2	14.72

The organic fertilizer used in this study was prepared through a 30-day fermentation process, in a ratio of 1:1 (v/v) between bovine manure and water, enriched with bone meal containing 23% P₂O₅. The mixture was stored in a plastic container with capacity of 100 L. The chemical characteristics of this mixture are shown in Table 2.

To prepare the water with electrical conductivity of 4 dS·m^-1, the soluble salts NaCl, CaCl₂·2H₂O, and MgCl₂·6H₂O were used in a ratio of 7:2:1 (Rhoades et al. 2000) between Na, Ca, and Mg, respectively, following the relationship between the electrical conductivity of the water (ECw) and its molar concentration (mmol_c·L^-1 = ECw × 10).

Irrigation with water with the highest electrical conductivity began at 10 DAS and continued until harvest at 80 DAS. Irrigation was carried out daily and was calculated according to the drainage lysimeter principle (Bernardo et al. 2019), keeping the soil at field capacity. The volume of water applied to the plants was determined using a 15% leaching rate (Eq. 1).

$\mathrm{VI}=\frac{(\mathrm{Vp} - \mathrm{Vd})}{(1 - \mathrm{LF})}$ (1)

where: VI: volume of water to be applied during irrigation (mL); Vp: volume of water applied in the previous irrigation (mL); Vd: volume of water drained (mL); LF: leaching fraction of 0.15.

At the end of the experimental cycle of 80 DAS, the pods were harvested and dried for around 75 hours until they reached a constant mass. After drying the pods, the following variables were determined:

• Total number of pods per plant;

• Pod length (PL, mm) and diameter (PD, mm), measured with a digital caliper;

• Pod mass in grams (PM, g);

• Yield (Y, g·pots^-1): estimated by the mass of the grains on an analytical balance with precision of 0.0001 g.

Water use efficiency (WUE, g·L^-1) was obtained by dividing the yield values by the total amount of water applied during the experimental cycle (28 L).

Statistical analysis

The data were subjected to analysis of variance assumptions, with normality being analyzed using the Shapiro-Wilk test, homogeneity of variance using the Bartlett’s test, and independence of errors using the Durbin-Watson test. Data that did not meet the assumptions were transformed using the Box-Cox family (Box and Cox 1964). The variables PL, PD, Y, and WUE did not follow a normal distribution and were adjusted using the Box-Cox transformation. The transformation is defined by Eq. 2:

$y\left(\mathrm{\lambda }\right)=\left\{\begin{array}{cc}\frac{y^{\mathit{\lambda }}-1}{\lambda }& \mathrm{if} \lambda =0\\ \ln \left(y\right)& \mathrm{if} \lambda \ne 0\end{array}\right.$ (2)

where: y: the original data (with y > 0); λ: the transformation parameter; y (λ): the transformed data.

The optimal value of λ was determined to maximize the log-likelihood function, ensuring the transformed data approximates a normal distribution.

Analysis of variance (ANOVA) was then carried out, and, when significant, the means were compared by the Tukey’s test (p ≤ 0.05) using the AgroR package. Transformations, statistical analyses, and Pearson correlation were carried out using RStudio (R Core Team 2022), while graphs were generated using Sigmaplot [version 14, (SYSTAT Software, Inc.)].

RESULTS AND DISCUSSION

The analysis of variance (Table 3) revealed that only the variables PD, productivity, and WUE of the peanut plants showed a significant interaction between the fertilization methods, electrical conductivity of the irrigation water, and inoculation (p < 0.05). On the other hand, the PL variable was significantly influenced by the interactions between forms of fertilization and electrical conductivity of the irrigation water, as well as between forms of fertilization and inoculation (p < 0.01). Moreover, the number of pods produced by the peanut plants showed a significant effect only for the forms of fertilization (p < 0.01).

Table 3
Summary of the analysis of variance (ANOVA) for number of pods (NP), pod diameter (PD), pod length (PL), pod mass (PM), yield (Y), and water use efficiency (WUE) in peanut plants under different forms of fertilization, levels of electrical conductivity of irrigation water, and inoculation.

SV	Medium square
	DF	NP	PD	PL	PM	Y	WUE
FF	3	27.76**	1.22ns	7.84ns	21.12***	31,821.75**	40.59**
ECw	1	14.87ns	0.88ns	9.71ns	0.46ns	19,739.69**	25.18**
IN	1	3.0ns	0.003ns	0.47ns	0.001ns	20.76ns	0.03ns
FF x ECw	3	12.14ns	2.52*	23.98*	6.37*	9,257.70**	11.81**
FF x IN	3	1.16ns	1.30ns	58.65***	1.30ns	2,266.74**	2.89**
IN x ECw	1	3.82ns	4.40*	4.54ns	1.25ns	632.73ns	0.81ns
FF x ECw x IN	3	4.96ns	2.51*	4.88ns	4.00ns	4,629.17**	5.90**
Residual	64	5.32	0.72	6.69	2.2	213.26	0.09
CV (%)		4.34	8.12	10.36	27.4	8.77	8.77

• SV: source of variation; DF: degree of freedom; FF: forms of fertilization; ECw: levels of electrical conductivity of the irrigation water; IN: inoculation; CV: coefficient of variation;
• ^***
  significant at the 0.1% probability level (p ≤ 0.001);
• ^**
  significant at the 1% probability level (p < 0.01);
• ^*
  significant at the 5% probability level (p ≤ 0.05);
• ^ns
  not significant.

For the number of pods in the peanut crop as a function of the different forms of fertilization (Fig. 3a), the treatment with the application of bovine biofertilizer was statistically superior to the P0% and P50% treatments. However, there was no statistical difference in relation to the P100% fertilizer treatment. The plants that received organic fertilization produced an average of 6.90 pods, while those that received P100% fertilization produced an average of 5.10 pods.

Figure 3
Mean comparison test showing the effect of different forms of fertilization, inoculation, and electrical conductivities of irrigation water on the agronomic performance of peanut (Arachis hypogaea L. cv. BR-1) cultivated for 80 DAS: (a) Pod mass of peanut plants under different forms of fertilization and different electrical conductivities of irrigation water; (b) productivity; and (c) water use efficiency of peanut plants under different forms of fertilization and presence and absence and different electrical conductivities of irrigation water.

The greater efficiency of bovine biofertilizer in increasing the number of pods, compared to phosphate fertilization, can be attributed to the presence and more efficient availability of essential nutrients such as N, P, K, and Ca (Table 2). These elements are fundamental for cell development, enzyme regulation, and induction of photosynthetic processes (Gao et al. 2020). Furthermore, the biofertilizer used in this study was enriched with bone meal, which likely contributed to the increased Ca content. In peanut cultivation, pod formation is dependent on an adequate supply of Ca, which is essential for pod formation (Kadirimangalam et al. 2022). Thus, the observed increase in pod number suggests that Ca enrichment played a key role in promoting more efficient pod formation.

In addition, these essential nutrients can contribute to improving soil fertility by enhancing the soil microbial community, strengthening its conservation capacity and increasing nitrogen use efficiency (Zhang et al. 2022), as well as increasing soil water availability and improving soil structure and root development.

Results similar to those of this study were found by Sousa et al. (2023), who used biofertilizer of animal origin as an organic source in peanut cultivation. Similarly, Santos et al. (2024) reported an increase in the number of pods in soybean plants that received exclusively bovine biofertilizer or organomineral fertilization, with superior performance to the mineral treatment.

In the analysis of the interaction between factors for pod diameter (Fig. 3b), the plants irrigated with brackish water, which did not receive phosphate fertilization and were not inoculated, had pods with the smallest diameter, with an average value of 8.63 mm, differing statistically from the other treatments. The results indicated that, except for the plants grown in saline environments, without phosphate fertilization and not inoculated, the other fertilization and inoculation strategies mitigated salt stress in this variable.

In response to the osmotic and toxic effects of salt stress, plants adopt mechanisms to complete their cycle (Liao et al. 2022). These mechanisms include a reduction in the partitioning and translocation of photoassimilates and an increase in energy expenditure to maintain essential metabolic activities. Although these processes allow plants to produce fruit in saline environments, there are adverse consequences for fruit quality, which was observed in this study. In other words, plants irrigated with higher salinity water without the presence of fertilization and inoculation produced pods with a smaller diameter (Ali et al. 2023, Santos et al. 2024).

Similar to the results of the present study, Sousa et al. (2023) also reported a decrease in pod diameter in peanut crops as electrical conductivity increased. The authors explained that, under saline stress conditions, plants prioritize the maintenance of essential metabolic activities.

Analysis of PL (Fig. 3c) revealed significant differences between treatments. Analysis of the inoculated plants showed that those that were not fertilized (P0%) had significantly longer pods (26.7 mm) and differed only from the treatment that received 100% phosphate fertilization. On the other hand, non-inoculated plants fertilized with 100% phosphorus produced significantly larger pods (27.9 mm) and differed from plants that did not receive fertilization.

The results obtained in this study may be associated with the bacteria’s ability to solubilize phosphorus (P) through the production of phosphatases, enzymes that release phosphate ions (orthophosphates) into the soil solution (Shalaby 2024). However, it is possible that the bacteria were unable to convert this phosphorus into labile forms, even under conditions of high concentration in the soil. This phenomenon can be explained by the inverse relationship between the availability of phosphorus in the soil and the activity of phosphatases, as described by Basílio et al. (2022), who highlight a reduction in enzyme activity as phosphorus availability increases.

This dynamic is consistent with the results observed in the present study, in which the largest peanut pods were achieved in plants inoculated with bacteria but not subjected to phosphate fertilization or fertilized but not inoculated. This finding suggests that the bacteria are more active under conditions of low phosphorus availability in the soil.

In a study by Preetham et al. (2020), fertilization with 100% of the recommended dose for maize in the presence of B. megaterium and Azospirillum resulted in greater ear lengths compared to plants that did not receive fertilization and inoculation, although this did not differ from plants that only received 100% mineral fertilization in the absence of bacteria.

When analyzing the effects of irrigation with water of different electrical conductivities and forms of fertilization on PL (Fig. 3d), the plants irrigated with water of 0.3 dS·m^-1 and receiving 100% phosphorus had an average PL of 26.8 mm, but did not differ significantly from the other treatments. On the other hand, plants irrigated with brackish water and fertilized with bovine biofertilizer had a longer PL (26.5 mm), but did not differ from the other treatments, showing differences of 11.57, 9.48, and 8.61% in relation to the P0%, P50% and P100% treatments, respectively.

The application of organic fertilizer contributes to an increase in organic matter in the soil, promoting the proliferation of beneficial microorganisms that can act to accelerate the decomposition of organic matter, resulting in the release of essential nutrients for plants. Furthermore, in saline conditions, the organic acids released during the decomposition of organic matter can act to reduce the pH of the soil, thus mitigating the adverse effects of the high pH associated with the use of brackish water in irrigation (Zhang et al. 2022). These benefits attributed to the use of organic fertilizers probably explain the results observed in this study, in which peanut plants irrigated with brackish water and fertilized with biofertilizer produced pods with similar lengths to plants irrigated with water of lower salinity.

Freire et al. (2022) observed results contrary to the present study. They found that maize plants irrigated with low salinity water and fertilized with bovine biofertilizer produced the longest ears (12.34 cm). In contrast, plants irrigated with brackish water produced the longest ears when they did not receive any type of fertilizer (9.47 cm).

When analyzing the interaction between forms of fertilization and irrigation with water of different electrical conductivities for PM (Fig. 4a), in the plants irrigated with water of lower salinity, the treatments without phosphate fertilization, with 100% phosphate fertilization and with biofertilizer differed from the plants that received 50% fertilization, showing differences of 38.28, 41.07, and 62.69%, respectively. Regarding the plants irrigated with brackish water, it was found that the use of biofertilizer mitigated the salt stress, resulting in plants that produced pods with a greater weight, reaching 5.35 g.

Figure 4
Mean comparison test showing the effect of different forms of fertilization, inoculation, and electrical conductivities of irrigation water on the agronomic performance of peanut (Arachis hypogaea L. cv. BR-1) cultivated for 80 DAS: (a) Pod mass of peanut plants under different forms of fertilization and different electrical conductivities of irrigation water; (b) productivity; and (c) water use efficiency of peanut plants under different forms of fertilization and presence and absence and different electrical conductivities of irrigation water.

The superior effect observed with the addition of organic fertilizers on the mass of pods produced by the peanut plants can be attributed to their potential to induce a greater osmotic adjustment in the plants, through the accumulation of organic solutes, which aids plant metabolism and by the presence of humic substances, helping to improve the absorption of water and nutrients by the plants (Gao et al. 2020). This may have allowed the plants to maintain water balance and greater nutrient absorption, mainly Ca, even under conditions of saline stress.

Ca is an essential nutrient for pod formation in peanut crops. Its deficiency in soil compromises gynophore development and the pod filling phase, resulting in aborted seeds and the production of empty pods (Kadirimangalam et al. 2022). In this study, the biofertilizer was enriched with bone meal, a known source of calcium, which likely increased the availability of this nutrient. The results indicated that this calcium enrichment contributed to the formation of pods with higher average weights, even under saline stress conditions.

Similar to the results of this study, Sousa et al. (2023), when analyzing the agronomic performance of peanuts under saline stress and different forms of fertilization, found that bovine biofertilizer provided a greater mass of pods compared to mineral fertilization with NPK, in plants under saline stress. Guilherme et al. (2021) observed a decrease in the mass of peanut pods when the plants were subjected to salt stress and fertilized with only 50% of the recommended dose of phosphorus.

In the analysis of the interaction between the factors for peanut productivity (Fig. 4b), in the plants irrigated with water of lower electrical conductivity, the treatments with 50% phosphate fertilization with and without inoculation and with bovine biofertilizer without inoculation did not differ statistically and showed higher productivity. Among these, the plants that received bovine biofertilizer without inoculation showed the highest productivity, with 194-g pots, followed by the P50% WI treatment (184-g pots) and P50% WTI (177-g pots). However, the plants irrigated with brackish water and fertilized with biofertilizer and inoculation showed significantly higher yields compared to the other treatments, reaching 261-g pots.

The higher productivity observed in the peanut plants can be attributed to the synergism between the salt stress mitigation strategies used (biofertilizer and inoculation). This is due to the ability of plant growth-promoting bacteria to act as an ethylene sink through the enzyme ACC deaminase. This action reduces the levels of ethylene, a hormone associated with stress, and consequently stimulates the action of auxin (IAA) produced by these microorganisms (Naing et al. 2021).

The IAA produced by microorganisms can act on root differentiation and cell division, possibly increasing root hair growth and favoring greater absorption of water and nutrients. This effect resulted in plant growth and, consequently, an increase in the productivity of peanut plants irrigated with brackish water (Chen et al. 2024). This process may have been stimulated by the presence of bovine biofertilizer, an organic fertilizer whose microorganisms can increase the production of metabolites that regulate the osmotic activity of the medium, favoring their action in the decomposition of organic compounds and release to plants (Zhang et al. 2022).

Ali et al. (2023) studied different rhizobial inoculants in the productivity of Vigna radiata L. under saline stress and found that mung bean plants at 6 dS·m^-1 failed to develop grains, but plants that were inoculated with the Mg³ strain (Rhizobium) produced the maximum number of grains (1.60 g per plant).

Masrahi et al. (2023) studied the effect of arbuscular mycorrhizal fungi, phosphate-solubilizing bacteria (PSB), and phosphorus doses on barley yield in saline soils and found that the use of PSB + 100% phosphorus dose showed a significant increase in grain yield of 38.61 and 38.73% more than the control in the two seasons, respectively. This result found by the previous authors differed from the results found in the present study.

Concerning the analysis of the interaction of factors for efficiency and water use in the peanut crop (Fig. 4c), it was observed that the plants subjected to fertilization with biofertilizer, both with and without inoculation, and irrigated with brackish water showed the highest average WUE values, reaching 9.36 and 8.89 g·L^-1, respectively. These values were not statistically superior compared to the treatments in which the plants were irrigated with low salinity water, in which the average WUE values were 6.58 and 6.32 g·L^-1, respectively, for the conditions with and without inoculation and fertilized with P50%.

Possibly, the higher WUE values observed under the interaction between the factors biofertilizer, inoculation, and irrigation with brackish water can be attributed to the greater photosynthetic efficiency shown by the peanut plants. This efficiency resulted in a more effective conversion of biomass per unit of water used, even in adverse environmental conditions influenced by the factors analyzed in this study (Liao et al. 2022). The possible carbon gain stimulated by the aforementioned factors hypothetically increased the WUE and productivity of peanuts and minimized salt stress (Leakey et al. 2019).

Another factor that presumably justifies this result is the greater availability of P provided by these inputs, combined with the potential absorption of other essential nutrients such as Ca²⁺, K⁺, Mo, Zn, and Fe, which may have optimized photosynthetic processes (Bouras et al., 2022). At the same time, the reduction in toxicity caused by the presence of sodium ions Na⁺ and Cl^- in the irrigation water, mediated by the treatments, may have contributed to the maintenance of photosynthesis. The combination of these factors resulted in greater biomass gain per unit of water used, indicating better acclimatization by the plants to the salinity conditions.

When analyzing the Pearson correlation for the variables evaluated in this study (Fig. 5), there was a highly significant and positive correlation between WUE and yield, as well as between PM and number of pods. In addition, there was a significant and moderately positive correlation between yield and number of pods, as well as PM, and between WUE and PM and number of pods. Low and positive correlations were identified between PL and diameter, as well as between PD and mass.

Figure 5
Pearson’s correlation between the variables analyzed in this study. The color gradient scale corresponds to Pearson’s correlation coefficient.

Notably, it was observed that PL was a variable that correlated negatively with yield, WUE and pod number (Fig. 5).

The results found in the correlation suggested that an increase in water use efficiency is directly linked to a greater number and weight of pods, contributing to the increased productivity. This fact corroborates what Blankenagel et al. (2018) describe: the search for greater WUE in crops is important in areas with water scarcity. These same authors emphasize that increasing water efficiency is only advantageous when it does not compromise plant growth and production.

CONCLUSION

The use of organic fertilization with bovine biofertilizer combined with inoculation with B. megaterium and B. subtilis mitigates salt stress and enhances both productivity and WUE in peanut cultivation.

Fertilization with bovine biofertilizer mitigated the harmful effects of salts in irrigation water and promoted an increase in PL and PM in peanut crops.

Irrigation with saline water at 4 dS·m^-1 reduced the agronomic performance of peanut when neither phosphorus or organic fertilization nor microbial inoculation is applied.

ACKNOWLEDGMENTS

To Instituto Nacional de Ciência e Tecnologia em Agricultura Sustentável no Semiárido Tropical for their support.

• How to cite: Oliveira, G. S., Viana, T. V. A., Sousa, G. G., Sousa, J. T. M., Santos, G. M., Barbosa, A. S., Leite, K. N., Simplício, A. A. F. and Pinheiro Neto, L. G. (2026). Agronomic yield of peanuts under mineral and organic fertilization, inoculation, and salt stress. Bragantia, 85, e20250025. https://doi.org/10.1590/1678-4499.20250025
• FUNDING
  Instituto Nacional de Ciência e Tecnologia em Agricultura Sustentável no Semiárido Tropical
  Grant No.: 406570/2022-1
  Conselho Nacional de Desenvolvimento Científico e Tecnológico
  Grant No.: 311828/2022-1
  Coordenação de Aperfeicoamento de Pessoal de Nível Superior
  Finance code 001

DATA AVAILABILITY STATEMENT

The data will be available from the corresponding author upon request.

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Edited by

• Section Editor:
  Aline Renée Coscione https://orcid.org/0000-0002-8331-603X

Publication Dates

• Publication in this collection
  09 Jan 2026
• Date of issue
  2026

History

• Received
  02 Feb 2025
• Accepted
  21 Oct 2025