Agronomic efficiency of different nitrogen sources for banana production and fruit quality

ABSTRACT

To define a suitable N fertilization management strategy to improve the productivity and economic performance of banana (Cavendish subgroup) production, technical criteria are needed to select N sources and establish dose rates. This study aimed to evaluate the effects of different forms of N, specifically amidic (urea and urea + NBPT), ammoniacal (ammonium sulfate), and nitric (calcium nitrate), on the nutritional status of banana plants, the severity of Sigatoka complex, and fruit productivity and quality. Profitability associated with the use of different N sources was also assessed. Treatments were conducted according to the factorial combination (3 × 4 × 2) + 1, considering three N sources (urea treated with NBPT, ammonium sulfate, and calcium nitrate), four N application rates (0, 75, 150, and 225 kg ha^-1), two production cycles (second and third cycles), and a control treatment (plain urea applied at 150 kg ha^-1). Fertilization led to soil acidification in the second cycle, with no increase in foliar N content associated with the N sources or doses, indicating that the N supply was due to the residual effect of previous fertilizations and to the mineralization of organic matter and plant remnants. Urea, urea treated with NBPT, ammonium sulfate, and calcium nitrate did not differ in banana plant nutrition, Sigatoka severity, or fruit production and quality. Higher N doses increased production in the third cycle, indicating that the recommended dose for high productivity was an underestimation. Nitrogen fertilizer that provided the best economic return was urea, followed by urea treated with urease inhibitor (NBPT), ammonium sulfate, and calcium nitrate. Fertilizer cost per unit of N was found to be a major factor determining the expense of fertilization and the profitability of banana production.

Keywords
fruticulture; banana farming; soil conditioner; soil fertility

INTRODUCTION

Banana cultivation is a socially and economically important activity in Brazilian agriculture, where the main producing states are São Paulo, Bahia, Minas Gerais, and Santa Catarina (Goulart Júnior et al., 2023). Despite Brazil being the fourth-largest banana producer globally, the average crop productivity (14.7 Mg ha^-1) is considered low (Goulart Júnior et al., 2023), given the potential for productivity above 50 Mg ha^-1 for the main cultivars planted (Scherer et al., 2023). One of the principal factors contributing to the poor performance of Brazilian banana cultivation is inadequate nutritional management, with a lack of correction of soil acidity, inadequate supply of nutrients for the crop, and underutilization of soil and plant tissue analyses being some of the aspects requiring attention (Deus et al., 2020; Guimarães and Deus, 2021).

Banana plants are fast growing, with rapid production of phytomass composing the plant and the fruits that are exported from the orchard at harvest, so high concentrations of available nutrients in the soil are required to meet the nutritional demand (Teixeira et al., 2008). After potassium, nitrogen (N) is the nutrient most needed by the crop during both plant development and the fruit production phase (Deus et al., 2020). Application rates for N are generally recommended based on the soil organic matter (OM) content and the expected fruit production (CQFS-RS/SC, 2016; Pauletti and Motta, 2017). However, differences in the cultivation environments of the main Brazilian banana production regions result in local recommendations for N applications in banana orchards. For example, in the state of São Paulo, where N doses are recommended solely based on productivity, the range is 120-500 kg ha^-1 (Teixeira et al., 1997). Similarly, in the states of Bahia and Minas Gerais, the recommended N doses range from 160 to 400 kg ha^-1 (Borges and Souza, 2004). In the state of Santa Catarina, a recent update proposes N doses ranging from 35 to 275 kg ha^-1, depending on soil OM content and expected productivity (Guimarães and Deus, 2023). In this case, the N derived from OM mineralization is taken into consideration, which reduces the levels of inputs from fertilizer (Feichtinger et al., 2004; Dorel et al., 2008; Ros et al., 2011).

In addition to dose differences, another factor that complicates recommendations for N fertilization is the variety of available sources. Different N fertilizers are available, with typically generalized recommendations for their use in banana farming. However, these fertilizers have different characteristics, including the form and concentration of N, susceptibility to losses, association with other nutrients, and cost per unit of N, which can affect the nutritional status of banana plants (Silva et al., 2012; Fratoni et al., 2017; Islam et al., 2020; Villaseñor-Ortiz et al., 2022), the incidence of diseases such as Sigatoka (Shiyam et al., 2010), productivity and post-harvest quality of banana fruits (Keshavan et al., 2011; Gouda et al., 2021), and the cost and profitability of production (Alves et al., 2010).

Fruit quality is directly related to the ability to meet the nutritional and water requirements of the plants, ensuring an appropriate balance among the nutrient species (Maro et al., 2023). Poor nutrient management can increase the occurrence of physiological disorders due to deficiencies in some nutrients or excesses of others, leading to phytotoxicity (Tyagi et al., 2017). In addition, nutrient imbalance can increase the susceptibility of banana plants to yellow Sigatoka (Freitas et al., 2015).

The most frequently used nitrogen sources in banana farming are urea, ammonium sulfate, and, to a lesser extent, ammonium nitrate and calcium nitrate (Silva and Borges, 2008). Urea [CO(NH₂)₂] is one of the commonest sources, due to its high N content (45 % N, in amidic form). However, the high solubility of urea, followed by its rapid hydrolysis catalyzed by the urease enzyme, results in substantial losses due to ammonia volatilization, reducing its agronomic efficiency (Guimarães and Ribeiro, 2021). To address this, urease inhibitors have been studied to delay urea hydrolysis and, consequently, increase its efficiency (Abalos et al., 2014). Promising results have been obtained using urea treated with the inhibitor NBPT (N-(n-butyl) thiophosphoric triamide), which has been extensively studied (Watson et al., 2008; Dawar et al., 2011; Guimarães et al., 2016).

Ammonium sulfate [(NH₄)₂SO₄] has a low N content (20 %, in ammoniacal form) and a greater capacity to acidify and salinize the soil, compared with urea (Reetz, 2017). However, its use offers the advantages of low N losses due to volatilization and the presence of 24 % sulfur in its composition. Similarly, calcium nitrate [Ca(NO₃)₂] has a low N content (15 %, in nitric form), but presents low losses of N by volatilization. An additional benefit is that it contains 19 % Ca in its composition. However, it has a higher cost per unit of N than the other fertilizers.

Although several studies have investigated the effects of N fertilization in banana cultivation (Silva et al., 2012; Fratoni et al., 2017; Islam et al., 2020; Villaseñor-Ortiz et al., 2022), little is known about the effects of the N source and dose on the severity of Sigatoka complex (black and yellow Sigatoka), fruit quality parameters, and profitability of N fertilization. Strategies for effective N fertilization management must aim to provide high crop yields, good fruit quality, and acceptable economic returns for banana growers.

To define a suitable N fertilization management strategy to improve the productivity and economic performance of banana production, technical criteria are needed to select N sources and establish dose rates. This study aimed to evaluate the effects of different forms of N, specifically amidic (urea and urea + NBPT), ammoniacal (ammonium sulfate), and nitric (calcium nitrate), on the nutritional status of banana plants, the severity of Sigatoka complex, and fruit productivity and quality. The profitability associated with the use of different N sources was also assessed.

MATERIALS AND METHODS

The study was started in September 2019 in a commercial banana (Cavendish subgroup) orchard in the municipality of Corupá in Santa Catarina State, Brazil (26° 30’ 04” S, 49° 16’ 22” W; altitude 300 m a.s.l.). Figure 1 shows the accumulated precipitation and average air temperature in the region for the period from September 2019 to August 2022 (data supplied by Epagri/Ciram). The most frequent soil classes in the region are Acrisols (Argissolos) and Cambisols (Cambissolos) (Potter et al., 2004).

Figure 1
Accumulated precipitation and average air temperature in the study area for the period from September 2019 to August 2022 (data from Epagri/Ciram).

The experiment was set up in a young banana plantation with banana plants in the formation phase, arranged in double rows, with a 4 m spacing between the double rows, 1.5 m between the simple rows, and 2 m spacing between the plants in the same row, resulting in a density of 1,818 plants per hectare. Table 1 shows the results for chemical characterization of the soil at the time that the banana plantation was renewed and after the second production cycle. Soil acidity corrective and nutrient doses were as recommended in the liming and fertilization manual for the states of Santa Catarina and Rio Grande do Sul (CQFS RS/SC, 2016). Liming was performed after sapling transplanting, with a surface application over the entire area to increase base saturation to 70 % prior to starting the experiment.

Table 1
Chemical analysis of the soils (0.00-0.20 m layer) collected before the start of the experiment (2019) and after the second production cycle (2021)

Collection	Clay	pH(1)	P	K	S	OM	Al3+	Ca2+	Mg2+	H+Al	CEC(2)	m(3)	V(4)
	g kg-1		––––– mg dm-3 –––––			%	––––– cmolc dm-3 –––––					––––– % –––––
2019	380	5.1	33.8	248.7	32.0	1.3	0.2	3.7	1.7	3.5	9.5	3.1	63.7
2021	380	4.9	23.4	224.0	25.0	2.7	1.0	3.6	1.2	4.9	10.2	15.8	52.2

• ⁽¹⁾
  Determination of pH in H₂O;
• ⁽²⁾
  Cation exchange capacity at pH 7;
• ⁽³⁾
  Aluminum saturation;
• ⁽⁴⁾
  Base saturation.

Treatments were established using a randomized block design with three replicates, employing the factorial combination (3 × 4 × 2) + 1, consisting of three N sources [urea treated with NBPT (33 % N), ammonium sulfate (21 % N), and calcium nitrate (15.5 % N)], four N doses (0, 75, 150, and 225 kg ha^-1), two production cycles (second and third cycles), and a control treatment with plain urea (45 % N) at a dose of 150 kg ha^-1.

Each plot comprised ten families, with only the eight central plants evaluated, since the two plants at the ends of the double row (the plot boundaries) were treated as borders. Given the arrangement of the plants in double rows with a spacing of 4 m, the border plants between the double rows were not considered. Doses of N, P₂O₅, and K₂O were estimated for banana production of 50 Mg ha^-1 in the second and third cycles, based on analysis of the 0.00-0.20 m soil layer. The standard N dose was 150 kg ha^-1, with the variations described above. Phosphate and K applications were the same for all plots, using 120 kg ha^-1 of P₂O₅, in the form of simple superphosphate, and 520 kg ha^-1 of K₂O, in the form of potassium chloride. Fertilizer doses were divided into four applications during the period of greatest soil water availability and plant growth, with equal amounts applied in October, December, February, and April. Nitrogen sources were applied to the soil surface, in front of the plants (~0.40 m in front of the daughter plant, in a half-moon line with curvature of ~1.00 m), during each production cycle (2020/2021 and 2021/2022). After the second cycle, liming was performed to correct acidity, based on soil analysis (Table 1), in accordance with CQFS RS/SC (2016). Banana plant management and Sigatoka control were according to technical recommendations for this crop (Guimarães et al., 2023).

The bunches produced by the eight central families of each plot in the two consecutive cycles were weighed. The severity of the Sigatoka complex in the banana leaves was monitored periodically throughout the experimental period, as described by Pérez-Vicente et al. (2021). Nutrient availability in the soil (0.00-0.20 m layer) was assessed after the second production cycle. Nutrient contents of the banana leaves and fruits (pulp) were determined in the second and third production cycles, according to the methodology described by Malavolta et al. (1997). Samples of soil and leaves used for chemical analysis were collected as described previously (Guimarães and Deus, 2023). The second and third hands of two bunches harvested in each plot in the two cycles were also sampled. The second hand was acclimatized as described by Maro et al. (2023), followed by determinations of weight, number of fingers, and length, diameter, and weight of the central fruit. Destructive analyses were used to quantify total soluble solids content by refractometry, total titratable acidity according to the methodology described in the Adolfo Lutz Institute Analysis Manual (2008), and fruit firmness with peel using a benchtop digital penetrometer with an 8 mm tip. Color parameters of the peel were obtained using a spectrometer (model CM-2300d, Minolta). To assess the nutrient content in the fruit pulp, flour was prepared from green bananas from the third hand, as described by Reis et al. (2018).

Only the results for the second cycle onwards are presented here to minimize possible interference from fertilizations performed before renewing the banana plantation or during sapling planting.

Statistical analyses were conducted in R (R Development Core Team, 2020) using the ExpDes.pt and easyreg packages. The distributions of the variables were evaluated using the Shapiro-Wilk and Bartlett tests for normality and homoscedasticity, respectively. The effects of the different N sources and doses were evaluated using analysis of variance (ANOVA), without including the urea control treatment. When significant effects of the experimental factors were identified, the averages for the treatments were submitted to the Tukey multiple comparisons test (5 % significance level), for the source factor, and to regression analysis, for the dose factor. The regression analyses were performed with fitting by linear and quadratic models, with ANOVA used to evaluate the improvement obtained by inserting the curvature parameter, when significant.

RESULTS AND DISCUSSION

Chemical characterization of the soil after the second cycle showed that the liming performed after transplanting the saplings in 2019 did not increase the soil pH to 6 and the base saturation to 70 %, levels which would be desirable in banana cultivation (CQFS RS/SC, 2016). Furthermore, fertilization may have led to acidification during the first two cycles, as observed by Guimarães et al. (2020) for three cycles in commercial banana plantations. Mineral fertilizers, especially nitrogenous compounds such as urea and ammonium sulfate, contribute to acidification by reactions that occur in the soil after application (Tian and Niu, 2015).

Despite the reductions observed in the concentrations of P, K, S, and Ca during the study period, the values were still be classified as high, very high, very high, and medium, respectively (Guimarães and Deus, 2023), which could be attributed to the fertilizer applications in the banana plantation before renewal and in the first months after transplanting the seedlings, prior to installation of the experiment. Excesses of P and K are frequently observed in the soils of banana plantations in Santa Catarina, attributed to fertilizations carried out without adhering to technical criteria (Guimarães and Deus, 2021). It was also observed that OM concentration increased, which could be attributed to the deposition of banana plant remains (leaves, pseudostems, rhizomes, and roots) in the soil during the first two cycles. These features reinforce the importance of periodic soil analysis in orchards to monitor acidity and fertility parameters and ensure application of appropriate doses of lime and fertilizer.

Table 2 summarizes the ANOVA results, highlighting the variables that presented at least one significant effect for the parameters of the statistical model. No significant effects were observed for the number of fingers per bunch; length, diameter, and weight of the fruit; color of the peel; total titratable acidity; and total soluble solids content of the fruit pulp.

Table 2
Summary of analysis of variance (ANOVA) for the parameters evaluated, as a function of the sources and doses of N fertilizers in two production cycles. Effects with p<0.05 were considered significant

Effect	Sigatoka(1)	Ca (leaf)	S (leaf)	N (leaf)	Weight (bunch)	Weight (hand)	Firmness	N (flour)	Ca (flour)	S (flour)
Cycle	<0.001	<0.001	<0.001	0.011	<0.001	0.029	0.008	<0.001	<0.001	<0.001
Source	0.998	0.412	0.011	0.539	0.597	0.606	0.672	0.867	0.819	0.854
Dose	0.622	0.420	0.032	0.165	<0.001	0.037	0.443	0.058	0.289	0.225
Block	<0.001	0.749	0.009	0.117	0.182	0.351	0.227	0.084	0.002	0.199
Source:cycle	0.628	0.637	0.423	0.958	0.263	0.781	0.715	0.720	0.191	0.905
Dose:cycle	0.635	0.548	<0.001	0.005	<0.001	0.991	0.166	0.211	0.035	0.089
Source:dose	0.829	0.964	0.334	0.855	0.083	0.244	0.260	0.563	0.039	0.614
Source:dose:cycle	0.798	0.781	0.278	0.012	0.813	0.257	0.695	0.879	0.424	0.598

• ⁽¹⁾
  Only considering the parameters that showed at least one significant effect in the ANOVA. The p-values in bold type were used in the regression analysis.

However, the severity of the Sigatoka complex and the N content of leaves and green banana flour differed between the production cycles, with higher values in the second cycle compared to the third. On the other hand, the variables bunch weight, hand weight, and the Ca and S contents of the leaves and green banana flour were higher in the third cycle than in the second cycle.

The more severe Sigatoka complex in the second cycle could have been due to greater inoculum amounts of the phytopathogens (Pseudocercospora fijiensis and Pseudocercospora musae), more favorable climatic conditions for development of the disease, and/or poorer control of the disease, compared to the third cycle. However, these effects were not evaluated. Although no significant effects of N fertilization management on Sigatoka complex dynamics were observed in this study, effects of the nutritional status of banana plants have been reported in the literature, with lower severity of the disease in banana plants that were adequately fertilized (Shiyam et al., 2010). Freitas et al. (2015) found that banana seedlings grown in a nutrient solution lacking K, N, P, S, Mg, Ca, and B showed more severe yellow Sigatoka symptoms than those grown in a nutrient solution containing a complete range of nutrients. The absence of a significant effect of N dose (Table 2) on the severity of Sigatoka in the leaves could be attributed to the adequate nutritional status in the experimental units, with no deficiency being observed in the banana leaves during the experiment, including for the plants that did not receive nitrogen fertilizer (Figure 4).

Figure 2
Foliar S concentrations in banana plants in the second (a) and third (b) production cycles, as a function of the different doses of N from calcium nitrate (C. Nitrate), ammonium sulfate (A. Sulfate), or urea treated with urease inhibitor (U+NBPT). Plain urea fertilizer was only used at a dose of 150 kg ha^-1. The error bars show the standard deviations.

Figure 3
Foliar S concentrations in banana plants obtained with the different N fertilizer sources. The plain urea fertilizer was only used at a dose of 150 kg ha^-1. The same letters indicate no difference between the means (Tukey’s test, 5 % significance level).

Figure 4
Foliar N concentrations in banana plant in the second (a) and third (b) production cycles, as a function of different doses of N from calcium nitrate (C. Nitrate), ammonium sulfate (A. Sulfate), or urea treated with urease inhibitor (U+NBPT). Plain urea fertilizer was only used at a dose of 150 kg ha^-1. Error bars show the standard deviations.

The higher N contents in the leaves and the green banana flour in the second cycle reflected greater availability of N in the soil, relative to the demand of the banana plants. The higher bunch and hand weights in the third cycle were expected, given that the banana plants had completed their development and presented their full productive potential (UPOV, 2010). Hence, the higher rates of growth and fruit production in the third cycle may have acted to reduce the N concentration in the plants, indicating a dilution effect, relative to the second cycle. This was suggested by Deus et al. (2020), who found that the accumulation of N in banana leaves was inversely proportional to increase of productivity and decreased from 27.4 to 19.6 % for plants that produced less than 30 Mg ha^-1 and more than 45 Mg ha^-1, respectively. These results indicated that under conditions of high productivity, N was redistributed from the leaves to the fruits, due to its high mobility in the phloem (Marschner, 2012).

On the other hand, the higher leaf concentrations of Ca and S in the third cycle suggested that the plants were able to more efficiently absorb these nutrients from the soil in this cycle, since soil concentrations did not increase during this period (Table 1). This could be attributed to the same mechanism described previously, with the higher rates of growth and production in the third cycle resulting in a greater demand for these nutrients. However, different to N, the compartmentalization of Ca resulted in higher concentrations in the pseudostem and leaves, but lower concentrations in the fruits (Deus et al., 2020). The lower accumulation in the fruits could be explained by the low mobility of Ca and its limited redistribution from the leaves to the fruits (Marschner, 2012).

Figure 2 shows the S contents of the banana leaves in the second and third production cycles, as a function of N dose. In the second cycle, the S content of the leaves showed no influence of N dose, irrespective of the type of N source. Average S content in this cycle was below the range considered appropriate for banana plants (1.5 to 2.0 g kg^-1) (Guimarães and Deus, 2023). In the third cycle, the S content increased as a function of N dose, with values above the sufficiency range. The increase was similar for the three sources and presented quadratic behavior, with a maximum S content of 4 g kg^-1 for the N dose corresponding to 132 kg ha^-1. The use of urea resulted in a similar leaf S content to the values obtained with the other N sources at the same dose.

Evaluation of the effects of the different N sources used in the two cycles showed that the foliar S contents of the banana plants fertilized with ammonium sulfate were generally close to those of the plants fertilized with urea+NBPT, and higher than those of the plants fertilized with calcium nitrate (Figure 3). It was expected that the use of ammonium sulfate would provide more S to the banana plants, since the compound contains 24 % S. However, the high concentration of S in the soil (Table 1) reduced the effect of applying this nutrient in the form of fertilizer, since the foliar S contents were above 2 g kg^-1 for all the N sources.

Chemical analysis of the leaves collected during the second cycle evidenced no increase in the N content with the different N sources and doses (Figure 4a). Nitrogen concentrations in the leaves, including those from unfertilized plants, were within the recommended range of 21 to 24 g kg^-1 (Guimarães and Deus, 2023), showing that, irrespective of the N sources and doses, all the banana plants received an adequate supply of N. These results indicated that the residual N from fertilization prior to the experiment, together with the N derived from the mineralization of OM and plant remnants from the first cycle (leaves, pseudostems, and rhizomes), was able to meet the demand of the banana plants (including the unfertilized plants) for this nutrient during the second production cycle.

Foliar N contents were also similar in the third cycle, except for the U+NBPT source, where there was an increase at the highest dose (Figure 4b). Leaf N contents classified as adequate were even observed for the unfertilized banana plants (control), starting from the development phase of the plants in the first cycle. This finding corroborated the important contribution of mineralization of OM and biomass residues in supplying the plants with N, as discussed above. However, it was expected that the capacity of these sources to supply N would decrease over the cycles, due to the successive nutrient exports as the fruits were harvested, especially when there was high production (Dorel et al., 2008). This reduction would then tend to limit banana production, as evidenced by the lower weights of the bunches collected in the third cycle from the plants that were not fertilized with N (Figure 5b).

Figure 5
Weights of banana bunches harvested in the second (a) and third (v) production cycles, as a function of different doses of N from calcium nitrate (C. Nitrate), ammonium sulfate (A. Sulfate), or urea treated with urease inhibitor (U+NBPT). Plain urea fertilizer was only used at a dose of 150 kg ha^-1. Error bars show the standard deviations.

There were no increases in the weights of the bunches harvested in the second cycle, for any of the N sources and doses evaluated, compared to the plants that did not receive N fertilizer (Figure 5a). This corroborated the adequate N supply indicated by the foliar analysis of the unfertilized and fertilized banana plants. Other studies have also found no increase in banana productivity in the initial cycles, according to increasing N dose (Sousa et al., 2004; Santos et al., 2009; Fratoni et al., 2017), or even a decrease of productivity with increase of the N dose (Silva et al., 2003, 2012). In these studies, the absence of a response to N fertilization was attributed to OM mineralization as a source of N, high return of nutrients by mineralization of residues from the banana plant itself (Hoffmann et al., 2010), and residual fertilizer from applications prior to the experiment. The cases of reduced productivity were attributed to nutritional imbalance caused by high availability of N from mineralization and the application of high doses of fertilizer. Nutritional imbalance is one of the main causes of low banana productivity (Guimarães and Deus, 2021).

In the third cycle, although foliar N levels were similar for the fertilized and unfertilized banana plants, the bunch weight increased linearly with the N dose (Figure 5b). The results suggested that for the N sources used in this study, the dose for maximum banana productivity was higher than 225 kg ha^-1 of N, which could provide bunch weights higher than 31.6 kg. Villaseñor-Ortiz et al. (2022) reported maximum banana (Cavendish subgroup cv. Williams) productivity corresponding to 58 Mg ha^-1, with average bunch weight of 21.6 kg, for an N dose equivalent to 358 kg ha^-1 in the form of ammonium nitrate.

However, there was no increase in the weight of the second hand of the bunches (Figure 6). Irrespective of the sources and doses of N applied to the plantations, the average weight of the hands was 2.97 kg, suggesting that the increased weight of the bunches harvested in the third cycle may have been due to an increase in the number of fingers, or increased weight of the lower hands, which are usually smaller when there is limitation of N and K (Islam et al., 2020).

Figure 6
Weights of the second hand of banana, according to the doses of N from calcium nitrate (C. Nitrate), ammonium sulfate (A. Sulfate), or urea treated with urease inhibitor (U+NBPT). Plain urea fertilizer was only used at a dose of 150 kg ha^-1. Error bars show the standard deviations.

These results suggested that the recommended dose of 150 kg ha^-1 of N, for an estimated productivity of 50 Mg ha^-1, was overestimated in the second cycle (average productivity of 36.7 Mg ha^-1), but was underestimated in the third cycle (average productivity of 45.6 Mg ha^-1). The banana plants fertilized with plain urea also showed a higher average bunch weight in the third cycle, compared to the second cycle, with a value close to those for the other sources at the same dose.

As observed for N and S (Table 2), the Ca content of the green banana flour showed no effect of the dose or source of N (Figure 7). Even the banana plants fertilized with calcium nitrate showed no increase of Ca in the pulp. Hence, the Ca present in the soil could adequately meet the demand of the banana plants, as evidenced by average foliar Ca contents of 6 and 10 mg kg^-1 in the second and third cycles, respectively, so the additional Ca supplied in the fertilizer did not lead to any increase.

Figure 7
Calcium content in the green banana flour, according to the dose of N from calcium nitrate (C. Nitrate), ammonium sulfate (A. Sulfate), or urea treated with urease inhibitor (U+NBPT). Plain urea fertilizer was only used at a dose of 150 kg ha^-1 of N. Error bars show the standard deviations.

Although the ANOVA results indicated a significant effect for the N Dose*Cycle interaction, Ca content in the pulp showed no increase with increasing N dose, regardless of the cycle evaluated (Figure 8). However, the Ca content increased in the third cycle relative to the second. This was consistent with the foliar nutrient content, which also showed higher values in the third cycle. Since the Ca concentrations in the soil did not vary during this period (Table 1), the observed increase suggested that the banana plants were more efficient at absorbing soil-available Ca. This could be attributed to the greater root density in the third production cycle, thereby enhancing the absorption of water and nutrients from the soil (Bassoi et al., 2004).

Figure 8
Calcium contents in the green banana flour in the second (a) and third (b) production cycles, as a function of different doses of N from calcium nitrate (C. Nitrate), ammonium sulfate (A. Sulfate), or urea treated with urease inhibitor (U+NBPT). Plain urea fertilizer was only used at a dose of 150 kg ha^-1. Error bars show the standard deviations.

The increase in bunch weight with N dose in the third cycle highlighted the importance of N fertilization in increasing banana plantation productivity during full production. The application of N at 225 kg ha^-1 resulted in an estimated productivity increase of over 16 Mg ha^-1 relative to unfertilized banana plants (Table 3), irrespective of the N source used. The efficiency of N fertilization was constant during the period evaluated, as indicated by the linear relationship between productivity and N dose, with an average increase of 74 kg of fruit per kg of N applied. Therefore, the results suggested that, in the third cycle, N fertilization was underestimated and that productivity could have been higher than 51 Mg ha^-1 if the banana plants had been fertilized with N doses above 225 kg ha^-1.

Table 3
Estimated banana productivity in the third production cycle, agronomic efficiency of N fertilization, and increase in revenue according to dose and source of N

Dose	Productivity(1)	FE(2)	Urea	Urea+NBPT	Ammonium sulfate	Calcium nitrate
––– kg ha-1 –––		kg kg-1	–––––––––––––––––––– R$ ha-1 ––––––––––––––––––––
0	34,441	-	-	-	-	-
75	40,030	74.52	-	5,595(3)	5,539	4,624
150	45,619	74.52	11,703	11,191	11,078	9,248
225	51,208	74.52	-	16,786	16,616	13,873

• ⁽¹⁾
  Productivity estimated using the equation: ŷ = 0.046x + 21.26 (Figure 5b).
• ⁽²⁾
  Nitrogen fertilization efficiency estimated using the equation: FE = (production with N fertilization – production without N fertilization) / quantity of N applied.
• ⁽³⁾
  Increase observed (for urea with observed productivity of 45.846 Mg ha^-1) or estimated (for the other sources), based on the production difference between the fertilized and unfertilized banana plants, considering the average price of the fruit paid to producers in Santa Catarina between 2020 and 2021 (R$ 1.09 kg^-1) and the average price paid (in the region of Corupá in Santa Catarina, in the same period) per kg of N from the different sources (urea: R$ 4.86; urea+NBPT: R$ 6.62; ammonium sulfate: R$ 7.3; calcium nitrate: R$ 19.57).

Since the different N sources had similar effects on productivity, any increase in revenue from N fertilization would be influenced solely by the cost of the fertilizer. In this case, for the N dose of 150 kg ha^-1, the source that provided the greatest revenue increase was urea, followed by (in decreasing order) urea treated with NBPT, ammonium sulfate, and calcium nitrate. The increase in revenue for plants fertilized with urea was R$ 2,454 ha^-1, higher than for fertilization with calcium nitrate, considering that during the period of the study, the average costs per kg of N from the urea and calcium nitrate sources were R$ 4.86 and R$ 19.27, respectively. Alves et al. (2010) also found no differences between the effects of urea and calcium nitrate in the production of the ‘Grande Naine’ banana variety, concluding that the use of calcium nitrate offered no advantage, since it increased the cost of banana production, compared to the use of urea as fertilizer.

Nitrogen fertilization strategies should consider the contributions of N from mineralization of soil OM and the cycling of banana plant residues. It was also evident that applying N fertilizer was important to enable banana plants to reach their full potential, resulting in a productivity increase of up to 16 Mg ha^-1. The findings revealed that the N doses and sources evaluated had no effect on the severity of Sigatoka disease, and did not alter fruit quality parameters. Finally, since the agronomic efficiencies of the sources evaluated were similar, the cost per N unit of fertilizers should be evaluated, enabling the cost of fertilization to be reduced and making banana production more profitable.

CONCLUSIONS

Evaluation of the N sources urea, urea treated with NBPT, ammonium sulfate, and calcium nitrate showed that they did not differ in terms of banana nutrition, Sigatoka severity, and fruit production and quality. Higher N doses increased productivity in the third cycle, suggesting the currently recommended dose for high productivity may be an underestimation. Nitrogen fertilizer that provided the greatest economic return was urea, followed by urea treated with urease inhibitor (NBPT), ammonium sulfate, and calcium nitrate. Fertilizer cost per unit of N was found to be a major factor determining the expense of fertilization and the profitability of banana production.

ACKNOWLEDGEMENTS

The authors thank ASBACO for collaboration in conceptualization and data acquisition; thank the Brazilian agencies CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), and FAPESC (Fundação de Amparo à Pesquisa e Inovação de Santa Catarina) for funding this study.

• How to cite:
  Guimarães GGF, Beltrame AB, Maro LAC, Vale MLC, Segatto M, Trevisan L. Agronomic efficiency of different nitrogen sources for banana production and fruit quality. Rev Bras Cienc Solo. 2026;50:e0250023. https://doi.org/10.36783/18069657rbcs20250023

DATA AVAILABILITY

The data will be provided upon request.

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Edited by

• Editors:
  José Miguel Reicher https://orcid.org/0000-0001-9943-2898 and Adelson Paulo de Araújo https://orcid.org/0000-0002-4106-6175

Publication Dates

• Publication in this collection
  23 Mar 2026
• Date of issue
  2026

History

• Received
  28 Jan 2025
• Accepted
  17 July 2025