Can calcium and boron leaf application increase soybean yield and seed quality?

ABSTRACT

Nutrient leaf application is complementary to soybean nutritional management, mainly at maturity, when plants present high nutritional demand and high nutrients and photoassimilate translocation rates for seed production. The aim of this research was to evaluate the agronomic performance, physiological quality, and nutritional contents of soybean seeds after application of different rates (0, 0.50, 1.0, 1.5, 2.0, and 2.5 kg ha⁻¹) of foliar fertiliser containing calcium (20%) and boron (4%) at the R3 stage (onset of pod formation). This research was carried out in two sites (Guaragi and Floresta) both in Parana State, Brazil, in randomised complete blocks with 4 replicates. Calcium and boron leaf application increased grain sulphur and nitrogen levels (Guaragi) but reduced phosphorus and magnesium (Floresta). Regarding physiological quality, foliar fertilisation increased the index of germination speed. The yield and number of pods increased up to the rate of 0.6 and 1.2 kg ha⁻¹ of leaf fertiliser in Floresta. Foliar fertilisation with calcium and boron showed advantages, however, results depended on the site, indicating different levels of soil fertility and climatic characteristics.

KEYWORDS:

• Glycine max
• leaf fertilisation
• micronutrients
• mineral nutrition
• physiological seed quality

Introduction

Nutritional management combined with seeds with high physiological quality are fundamental for soybeans to express its full productive potential. The physiological quality of soybean seed can be defined as the ability to perform vital functions, such as germination, vigour, and longevity (Popinigis 1985).

To increase soybean yield and obtain high quality seeds, leaf fertilisation emerges as an alternative technique for nutritional management (Domingos et al. 2019). Foliar fertilisation is based on the ability of the leaves to absorb nutrients, avoiding losses through the soil (SBCS/NEPAR 2017). In addition, another aspect that supports the foliar application of nutrients is the high translocation of some nutrients from the leaves to the forming seeds (Borkert et al. 1987). The supply of nutrient elements via foliar fertilisation is a good strategy, with greater efficiency than soil fertilisation, which is more targeted and ecologically correct, as the nutrients can be applied in controlled quantities and in a specific period of plant growth (Niu et al. 2020).

Calcium (Ca) and boron (B) has been widely used in Brazil as a foliar application. The B acts in several metabolic processes, such as the synthesis and transport of photoassimilates, maintenance of cell wall and membrane structures, and synthesis of nucleic acids and proteins (Cakmak and Römheld 1997; Malavolta et al. 1997; Batista et al. 2018). Calcium is an element with structural function, acting on the integrity of the plasma membrane and cell wall and on the activity of enzymes, such as the activation of calmodulin, which is an important secondary messenger for several physiological processes (Malavolta et al. 1997). Like B, Ca is a nutrient essential and fundamental for pollen tube development and pollen grain germination, which is important for fertilisation, uptake, and fruit formation (Faquin 2005).

The nutrient Ca is immobile in the phloem due to the low concentration in the cytoplasm and phloem, ranging from 0.1–10 nM (White and Broadley 2003). Conversely, the mobility of B is influenced by the plant species (Brown and Hu 1998).

Nutrients can be uptaken after foliar application through cuticular penetration and for absorption inside metabolically active cell compartments, followed by the use and translocation of the nutrient absorbed by the plant (Fernández et al. 2013). Although translocation of the nutrient from the application site to other parts of the plant, such as reproductive organs, storage tissues, and roots, increases the probability of success of the foliar fertilisation technique, it must be emphasised that transport from the application site is not essential for the effectiveness of foliar B fertilisation (Fernández et al. 2013), which justifies the study of non-mobile nutrients, such as Ca and B.

The response to foliar application of Ca and B at soybean majority stages are not conclusive. Bevilaqua et al. (2002) and Souza et al. (2009) showed positive results, increasing grain mass per plant and nutritional status, respectively. However, Macedo et al. (2002), and Seidel and Basso (2012) observed that foliar application of Ca and B showed no differences compared to the control. As for physiological quality, Bevilaqua et al. (2002) and Kappes et al. (2008) found no effect after application of Ca and B trough leaf.

In addition, B fertilisation must be careful, as there is a narrow line between deficiency and toxicity, when compared to other nutrients (Dechen and Nachtigall 2006). Boron is absorbed in its totality by mass flow (Malavolta et al. 1997), but in conditions of hydric deficit and high temperature, plants can show difficulty in absorbing this nutrient, due to low transpiration, with foliar addiction as an alternative for nutritional supplementation, even on soil with adequate levels. However, a series of variables can interfere with the efficiency of foliar fertilisation, for example, light, temperature, humidity, nutritional status, and hydraulic status of the plant. Therefore, the environment affects all aspects of foliar fertilisation, including physical and chemical reactions of the applied sources, plant architecture, cuticular composition of the leaf, and destination of nutrients (Fernández et al. 2013), and can be unsuccessful for the success of the technique. Therefore, more studies are needed to understand the factors that interfere in the crop response to this nutritional management technique (Besen et al. 2019).

The hypothesis of the present study is that foliar fertilisation based on Ca and B in the reproductive phase of soybean can increase grain yield and the physiological quality of seeds, with a different response between locations. However, high doses can be detrimental to soybean. The aim was to evaluate agronomic performance, physiological quality, and nutritional levels (macro and micronutrients) of soybean seeds after Ca and B foliar application at the reproductive phase.

Material and methods

Site characterisation

Two experiments were carried out in 2014, both in the state of Paraná, Brazil. One was the municipality of Floresta, located in the northwest region of the State at a latitude of 23°39′09″ south and longitude of 52°05′42″ and an average altitude of 340 m. The other site was Guaragi, district of Ponta Grossa municipality, located in the Campos Gerais region of the State at a latitude of 25°16′70′'south and longitude of 50°11′12′’ to the west with an altitude of 820 m.

The soil of the experimental area of Floresta was classified as a Ferralsol with 67% clay, and in Guaragi, as a dystrophic Cambisol with 34% clay. The soil chemical characterisation is shown in Table 1.

Table 1. Soil chemical characterisation of the two experiment sites at 0.00–0.20 m depth.

Site	pH	Al^3+	Ca^2+	Mg^2+	K^+	ECEC	P	B	V	C
	(CaCl2)	------------cmolc dm^−3--------------					--mg dm^−3--		%	g dm^−3
Floresta	5.21	0.00	5.64	2.23	0.33	12.3	3.69	0.24	66.6	17.7
Guaragi	4.80	0.15	2.20	1.10	0.17	7.2	12.69	0.25	48.0	28.0

Al³⁺, Ca²⁺, and Mg²⁺: extractor KCl 1M; P e K⁺: extractor Melich-1; Boron (B): hot water extractor; Carbon (C): Walkey Black; ECEC: effective cation exchange capacity; base saturation (V).

The climate of the municipality of Floresta is classified in Cfa and Guaragi as Cfb, according to the Köppen classification. Data for the maximum and minimum temperature and daily precipitation for the experimental coverage period can be seen in Figure 1.

Figure 1. Climatic daily data of rainfall (solid bat) and maximum (dotted line) and minimum (solid line) temperature during the experimental time in Floresta (A) and Guaragi (B).

The experimental design was completely randomised blocks, with six rates of foliar fertiliser application Fortgreen CaB Dry® (20% Ca and 4% B, applied at 0, 0.50, 1.0, 1.5, 2.0, and 2.5 kg ha⁻¹) at the R3 stage (onset of pod formation). The applications were carried out with a crop sprayer and carbon dioxide gas pump at a flow rate of 150 L ha⁻¹, with a four-point application bar (Teejet XR 110 02).

Each plot was composed of six lines of soybean, 6 m long, 0.45 m apart, totalling 16.2 m² of total area. The useful area corresponded to the four central lines and 4 m in length, with 1 m being excluded at the ends (borders), corresponding to a useful area of 7.2 m².

The soybean genotype used was ‘BMX Potência RR’. For sowing fertilisation in Floresta, 200 kg ha⁻¹ of the organomineral fertiliser NPK 2-10-10 was applied (farm pattern). In Guaragi, sowing fertilisation was 330 kg ha⁻¹ of the mineral fertiliser NPK 00-20-20 and a coverage with 230 kg ha⁻¹ of potassium chloride at stage V2. In both locations, 22 seeds per metre were sown (due sowing will be later), with inoculation with bacteria of the genus Bradyrhizobium.

Variable responses

The following traits were evaluated in the R6 soybean stage: final stand (FS), height of plants (HP), height of insertion of the first pod (HIFP), number of branches (NB), and number of pods per plant (NPP). After harvest, the mass of a thousand seeds (TMS) and yield (YIE) were also measured.

FS was obtained by averaging the number of plants counted in two lines per plot. HP and HIFP were obtained with a millimetre ruler by measuring five plants per plot, and the results were expressed in centimetres (cm). NPP and NB were determined by counting these items in five plants randomly chosen per plot. YIE was determined by harvesting the useful area per plot (7.2 m²) and extrapolating the results to kilograms per hectare. TMS was determined by weighing eight subsamples of 100 seeds per plot on an analytical balance. The average values obtained were multiplied by ten and expressed in g (Brasil 2009).

The physiological quality of the seeds was determined by the standard germination (SG), first germination (FG), accelerated aging test (AAT), modified cold (MC), emergency speed index (ESI), and electrical conductivity (EC). SG was performed with four subsamples of 50 seeds for each plot. The seeds were placed between three sheets of paper towels moistened with distilled water, with an amount of water equivalent to 2.5 times the mass of the dry paper being used. Rolls were prepared, which were taken to a Mangelsdorf germinator, which was regulated to maintain a constant temperature of 25°C, where the rolls were kept for a period of eight days. The results were expressed as the percentage of normal seedlings (Brasil 2009). FG measured together with SG was used to compute the percentage of normal seedlings obtained on the fifth day after the onset of SG (Brasil 2009). EC was performed using four subsamples of 50 seeds for each plot. Initially, the seeds were placed in plastic cups (200 mL) and weighed to an accuracy of 0.01 g. After the seeds had been weighed, 75 mL deionised water was added to the plastic cups.

These cups were kept in a germination chamber (BOD) at 25°C for 24 hours (Loeffler et al. 1988). Afterwards, electrical conductivity was measured in the solution using a digital microprocessor conductivity metre (model TEC-4MP), and the result was expressed μS cm⁻¹ g⁻¹ (Vieira and Krzyzanowski 1999). MC was performed using germination paper as the substrate, with water applied at a ratio 2.5 times the dry weight of the paper, the same as with SG, and with four replicates of 50 seeds evenly distributed throughout the substrate, which was used to form the rolls. The rolls were placed in plastic bags and then sealed with crepe tape. These were kept in a pre-adjusted BOD chamber at 10°C, where they remained for five days. Then, the bags were opened, and the rolls were placed in a Mangelsdorf-type germinator set at 25°C for five days. The results were expressed as the percentage of normal seedlings.

The AAT was conducted with four subsamples of 50 seeds per plot, which were arranged on a stainless-steel screen inserted in plastic boxes (gerboxes) containing 40 mL of deionised water. Subsequently, the boxes were taken to a germinating chamber (BOD) at 42°C for 48 hours. After this period, the seeds were submitted to the germination test, as previously described. Evaluation was performed on the fifth day after the start of the test, with the seedlings considered normal being counted (Marcos Filho 2005). The results were expressed as a percentage.

ESI was performed using four subsamples per plot. The seeds were sown 3 cm deep in plastic boxes containing moist washed sand. The test was conducted in a drying oven with no light and temperature control. The normal seedlings that emerged were counted until emergency stabilisation. ESI was calculated according to Vieira and Krzyzanowski (1999).

For determination of their nutritional contents, the seeds were washed with deionised water and then placed in a drying oven with forced air circulation at 65°C until reaching a constant mass. After this process, the samples were milled with a Wiley-type mill. To determine nitrogen content (N), the Kjeldahl method (Embrapa 2009) was used, based on distillation-titration. An analytical balance was used to weigh samples (0.100 g) previously ground in 90 mL digestion tubes. The reagents used in the digestion consisted of a catalytic mixture composed of potassium sulfate (K₂SO₄) and copper sulfate (CuSO₄) 10:1, added directly to samples, as well as concentrated sulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂). For the distillation titration, 10 mol L⁻¹ sodium hydroxide (NaOH), 10 g L⁻¹ boric acid (H₃BO₃), and 0.02 mol L⁻¹ sulfuric acid (H₂SO₄) were used.

For determination of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), Zinc (Zn), manganese (Mn), and boron (B), the samples were weighed (0.250 g), added to Teflon tubes in which 6 mL of HNO₃ was added, and allowed to stand for 30 min. Then, the samples were digested on a wet basis in a microwave oven at a temperature of 230°C and 25 bar pressure. After digestion, the samples were diluted and prepared for analysis by the inductively coupled plasma atomic emission spectrometry (ICP-OES) technique. This method is based on the principles for analysis of the dissolved metals in the solution (acid extraction) (Giné-Rosias 1998).

Statistical analyses

All data of the variables were subjected to an analysis of basic statistic assumptions using the Shapiro–Wilk (error normality) and Bartlett (homogeneity of variances) tests (p > 0.01). Quantitative data, referred to as ‘rates’, were analysed by means of regression, and beta coefficients subjected to the t-test.

Results and discussion

The results showed that the response to foliar fertilisation may vary depending on the location, with different responses between Floresta and Guragi. The highest plant height and first pod insertion height were observed in Floresta (9 and 26%, respectively). However, FS was 16% higher in Guaragi (Table 2). Variables FS and HP were not influenced by the application of leaf fertiliser (LF). Despite this, Kappes et al. (2008), after working with applications of a B-based product in soybean plants, found an increase in plant height, varying according to the dose and time of application.

Table 2. Agronomic components, physiological and nutritional quality of soybean: height of insertion of the first pod (HIFP); electrical conductivity (EC).

Variable	Site
	Guaragi	Floresta
Final stand (FS)	19.62	16.49
Height of plants (HP)	47.34	52.19
HIFP	5.18	6.87
Number of branches	2.41	2.23
Standard germination	1.42	1.54
First germination	1.42	1.53
Modified cold (%)	96.64	98.39
Accelerated aging test (%)	93.05	94.83
EC (µS cm^−1)	23.63	30.85
K (g kg^−1) Ca (g kg^−1)	16.79 1.07	16.96 2.52
Fe (mg kg^−1)	73.18	79.53
Mn (mg kg^−1)	22.83	37.67

The applied LF doses revealed that in Guaragi, the number of pods were adjusted to the linear plateau model, with a linear increase from 0.6 kg to 1.0 kg ha⁻¹, however in Floresta, there was not a significant effect for this variable (Figure 2A). Musskopf and Bier (2010) also reported the R1 and R3 application of Ca and B doses increased the number of pods per plant, being at a dose of 1.4 kg ha⁻¹, corresponding to 180 g of Ca e 112 g of B. In a study by Varanda et al. (2018), leaf application of B at different majority stages increased the number of pods per plant in a quadratic way. The results obtained are relevant, since the number of pods is an important component of soybean yield.

Figure 2. Effects of foliar fertilisation with application of calcium and boron on the number of pods per plant (A), mass of a thousand seeds (B), and soybean yield (C).

TMS was negatively influenced by the application of the LF in Guaragi, with adjustment to the quadratic model with the minimum point estimated at a dose of 1.21 kg ha⁻¹ but with no effect in Floresta (Figure 2B). Varanda et al. (2018) also observed a negative effect, with adjustment of the quadratic model (with minimum point), for TMS with the increase of B doses when the application was carried out at the R2 stage.

In our study, the highest doses of B may have been responsible for adjusting the statistical models, with a maximum point and for the linear reduction in TMS. High doses of B can promote toxicity (Çelik et al. 2019; Pawlowski et al. 2019), and consequently, there may be a reduction in the photosynthetic rates of the plant (Reid et al. 2004; Viçosi et al. 2020). The decrease in photosynthesis can be attributed to injuries in the structure of thylakoids, which affect electron transmission, decrease Fv/Fm (Rostami et al. 2017), and can change the leaf temperature, stomatal conductance, and transpiration (Viçosi et al. 2020). Notably, climatic conditions at the time of application and the metabolic state of the plants can cause a different response to occur between locations.

Yield was influenced by LF only in Floresta, with adjustment of the quadratic model, with the maximum point at 1.23 kg ha⁻¹ of LF (Figure 2C). These results revealed favourable effects of leaf fertilisation, even under conditions of adequate fertility, since the levels of Ca and B in the soil were classified as high and medium, respectively (SBCS/NEPAR 2017). Souza et al. (2009) observed an interaction between doses of foliar fertiliser based on Ca and B and the cultivars studied, whose dose was 1.5 L ha⁻¹ of LF; the cultivar BRS 705S was higher than the others. However, according to the authors, application at the R3 soybean stage increased the grain yield when compared to the application carried out in R1. Like beneficial effects of Ca and B, LF observed in Floresta. Dos Santos (2013), after Ca and B application doses in two soybean stages (R1 and R3), showed higher yield when the application was carried out at the soybean R3 stage.

The results suggested an environmental effect on leaf fertiliser since it was the same soybean cultivar in both locations. According to Fernández et al. (2013), the environment influences the efficiency of foliar fertilisation through direct effects on the physicochemical properties. Thus, the environment can alter the plant metabolic activity, interfering on the availability of substrate and energy for absorption and assimilation of nutrients. In association with this, hydration of the cuticle and opening of stomata in conditions of non-limiting relative humidity can contribute to the efficiency of foliar fertilisation. Additionally, the metabolic state of the plant is altered by the conditions of light, temperature, and humidity at the time of application. Therefore, these factors influence the absorption process on the entire leaf surface, as well as in the internal spaces (Fernández et al. 2013), which explains the different responses at each site.

Accordingly, in the study sites, there were adverse climatic conditions, including water deficit (Figure 1). Guaragi is in a region of higher altitude with mild and constant temperatures. There was a short period of drought in the first ten days of March, the beginning of the majority stage and leaf application, which caused flower abortion and probably contributed to the lack of response to foliar fertilisation in these conditions. According to Mocellin (2004), leaf absorption is favoured by high atmospheric humidity because it keeps the cuticle hydrated and prevents the applied solution from evaporating, maintaining it longer on the leaf surface.

In Floresta, higher temperatures were observed through the crop life cycle, decreasing as harvest approached. The ideal temperature to maximise the absorption of leaf mineral nutrients ranges between 22°C and 30°C. It is recommended that spraying be carried out during periods of less sunlight (Mocellin 2004), although higher temperatures increase the drying speed (Fernández et al. 2013). Reed and Tukey (1982) reported that under continuous periods of high temperature, the components of superficial wax adopt a vertical configuration, culminating in an increase in nutrient absorption through the leaf. Moreover, this could justify the results observed in Floresta. This difference may also be explained by environment effects on leaf surface characteristics, such as canopy composition and size, plant morphology, and physiology (Fernández et al. 2013), which can favour the efficiency of foliar fertilisation, although these variables have not been evaluated in the present study.

Regarding physiological quality, the only change for Ca and B doses occurred for the emergency speed index. Soybean characteristics were higher at Floresta for the standard germination test, first germination count, modified cold test, accelerated aging test, and electrical conductivity (Table 2). The best results were obtained at Floresta (Table 2) for the physiological quality variables, which are possibly associated with climatic conditions (Figure 1) and the best fertility conditions, exemplified by pH and base saturation (Table 1).

For the emergency speed index, there was an adjustment of a linear plateau model only in Floresta up to 1.06 kg ha⁻¹ of the LF (Figure 3). Domingos et al. (2019) also observed that foliar fertilisation only changed the emergency speed index in one of the evaluated sites. Bevilaqua et al. (2002) also did not observe changes in the physiological quality of soybean seeds evaluated by the germination and vigour tests after foliar application of Ca and B. Our results demonstrated that foliar fertilisation has little influence on the physiological quality of soybean seeds. Future studies with foliar fertilisation should investigate under what conditions foliar fertilisation can be beneficial to the physiological quality of the seeds.

Figure 3. Emergence speed index (ESI) of soybean after foliar application of different doses of calcium (Ca) and boron (B).

In relation to the nutritional content in the grains, Ca content in the seeds was not altered by dose. Ca is immobile in the phloem, so translocation from the leaf to other organs is not frequently observed (Faquin 2005). Furthermore, higher availability of Ca in the soil in Floresta (Table 1), with 3.4 cmolc dm⁻³ more than in Guaragi, was crucial for the highest values, as observed in Floresta.

For N levels, in Floresta, there was no effect of LF doses; in Guaragi, there was an increase in N levels in the seed, (angular coefficient of 1.19) (Figure 4A) corresponding to an average increase of 1.3% in crude protein in the seeds, for each 0.1 kg ha⁻¹ of the applied product. Bellaloui (2011) found that the foliar application of B changed the composition of soybean seeds, with an increase in protein content, and the supply of B in flowering or in grain filling induces the assimilation of N. This shows the close relationship between the metabolism of these two nutrients. These results are promising, as according to Henning et al. (2010), high vigour seeds have higher levels of soluble proteins, to the detriment of low vigour seeds.

Figure 4. Nitrogen (A), phosphorus (B), sulfur (C), and magnesium (D) content in soybean seeds after foliar application of calcium and boron.

In Floresta, when applying LF, there was a reduction of P and Mg seed content, with slope −0.069 and −0.036, respectively. However, there was no effect at Guaragi (Figure 4B and 4D). The level of S increased with the application of LF in both locations, with linear adjustment in Floresta and quadratic with a maximum point estimated at 0.94 kg ha⁻¹ of the LF in Guaragi (Figure 4C).

Souza et al. (2009) studying doses (0, 0.5, 1, 1.5, and 2 L ha⁻¹) of LF based on Ca and B applied at the R1 and R3 stages in four soybean cultivars observed that at a dose of 1 L ha⁻¹ applied in R3, Mg content was reduced, however, it was the time that favoured the S content in the seeds. Regarding P content in the seeds, Souza et al. (2009) also observed a linear reduction for the cultivar BRS MG 705S RR and did not observe the effect of dose and application times on K levels, similar to our study.

Regarding micronutrients, for Zn and Fe, it was not possible to adjust any polynomial model. For B, only in Guaragi, a linear plateau response was adjusted, with an increase in B levels up to 0.54 kg ha⁻¹ of the LF (Figure 5C). In contrast, the increase in LF doses reduced the Cu levels (Figure 5B) in Guaragi. The data showed that application of LF influenced the nutritional content of soybean seeds, with variations according to the nutrient and location. In a study by Esper Neto et al. (2018), in climate and soil conditions like the Floresta site, the foliar application of elemental S did not interfere in the concentration of macro and micronutrients in soybeans. The effect of foliar applied nutrients on the absorption or translocation of other nutrients is still poorly understood in the literature. However, our findings show nutritional changes in the grains (Figures 4 and 5), due to the doses of Ca and B. In a review work, Niu et al. (2020) observed many studies have suggested that the nutrient elements and other constituents of foliar fertiliser formulations may stimulate the uptake of soil-applied fertilisers. Although the effect of foliar spraying is sometimes inferior to that of soil fertilisation, leaf nutrients can be transported to the roots, improving root activity and preventing premature senescence of roots, therefore, enhancing the root absorption capacity (Niu et al. 2020).

Figure 5. Content of micronutrients, zinc (A), copper (B), and boron (C) in soybean seeds after foliar application of calcium and boron.

Of all the variables analysed, only S content in the grains in Floresta and N in Guaragi showed linear behaviour, with a predominant adjustment of the quadratic and plateau model. Our findings reveal that high doses of leaf Ca and B were harmful, and benefits are usually obtained at the lowest doses tested. In a study by Gomes et al. (2020), deleterious effects were observed on the leaf cuticle with the use of leaf fertilisers. Thus, the authors highlighted the importance of developing foliar fertilisers capable of fulfilling the task of supplying nutrients, avoiding damage to the leaf cuticle.

Notably, foliar fertilisation with Ca and B carried out at the R3 soybean stage influence crop development, however, the magnitude of the effects differed between the doses applied and the sites where the experiments were carried out. Conversely, there is a clear need for advances in research seeking to understand the factors that maximise the efficiency of foliar fertilisation.

In conclusion, the application of foliar fertiliser based on calcium and boron increased the number of pods and soybean yield only at Floresta, showing the influence of environmental factors, such as light, temperature, and humidity, as well as levels soil fertility.

Foliar fertilisation alters the nutritional levels in soybean seeds, increasing the levels of sulphur, nitrogen, and boron, as observed in Guaragi, and a reduction in the levels of phosphorus and magnesium as seen in Floresta, in addition to copper in Guaragi.

The physiological quality of soybean seeds was not influenced by the application of leaf fertiliser, apart from the emergence speed index in the municipality of Floresta.

The positive effects of leaf fertilisation were obtained between 0.54 and 1.23 kg ha⁻¹ of leaf fertiliser. In conclusion, leaf fertilisation improved yield and production components of the soybean crop.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Cleyton da Silva Domingos

Cleyton da Silva Domingos, Agronomist, Fortgreen. Technical development manager, Interest: Plant Nutrition and Physiology. E-mail: [email protected]

Marcos Renan Besen

Marcos Renan Besen, PhD candidate, Agronomy Department. Soil Science and Plant Nutrition. Research interests: Soil Fertility and Plan Nutrition. E-mail: [email protected]

Michel Esper Neto

Michel Esper Neto, PhD, Agronomy Department (UEM). Soil Science and Plant Nutrition. Research interests: Nanofertilizer and Soil Fertility. E-mail: [email protected]

Eunápio José Oliveira Costa

Eunápio José Oliveira Costa, Agronomits. Master in Agronomy (UEM). Soil Science and Plant Nutrition. Research interests: Plan Nutrition. E-mail: [email protected]

Carlos Alberto Scapim

Carlos Alberto Scapim, PhD, Agronomy Department Professor (UEM). Experience in Agronomy, with an emphasis on Vegetable Breeding in corn. E-mail: [email protected]

Tadeu Takeyoshi Inoue

Tadeu Takeyoshi Inoue, PhD, Agronomy Department Professor (UEM). Soil Science and Plant Nutrition. Research interests: Plant Nutrition. E-mail: [email protected]

Marcelo Augusto Batista

Marcelo Augusto Batista, PhD, Agronomy Department Professor (UEM). Soil Science and Plant Nutrition. Research interests: Soil Chemistry and Fertility. E-mail: [email protected]

Alessandro Lucca Braccini

Alessandro Lucca Braccini, PhD, Agronomy Department Professor (UEM). Experience in Agronomy, with an emphasis on Seed Production and Processing. E-mail: [email protected]