Elemental sulfur recommendation for pH reduction in soils from Southern Brazil¹

Recomendação de enxofre elementar para a redução do pH de solos do sul do Brasil

ABSTRACT

The elemental sulfur (S⁰) application may reduce soil pH, benefiting plants adapted to acid conditions and lessening problems of overliming. Nevertheless, there is no official recommendation for its application. The objective of the study was to quantify the S⁰ doses required to reduce the pH of soils from Southern Brazil. The experiment was carried out in the laboratory in a factorial scheme (5 × 5), with a completely randomized design and three replicates. The treatments consisted of five soils, and five doses of S⁰, corresponding to 0, 50, 100, 150, and 200% of the estimated dose need to reach pH 4.0. The applied doses of S⁰ resulted in reduction of pH and base saturation (V%) and increase of potential acidity (H + Al). These effects, however, were reduced due to the low rate of oxidation of the S⁰ applied (0.76-3.36%). The soil variables correlated with S⁰ oxidation were Mg²⁺ (0.86***), Al³⁺ (-0.82***), H + Al (-0.89***), V% (0.68***) and aluminum saturation (m%) (-0.87***). In the evaluated soils the oxidation of 50 kg ha^-1 of S⁰ was required to reduce one unit of pH in H₂O.

Key words:
sulfur oxidation; sulfate; acidity; overliming

RESUMO

A aplicação de enxofre elementar pode reduzir o pH do solo, beneficiando as plantas adaptadas às condições ácidas e diminuindo os problemas de supercalagem. No entanto, não há recomendação oficial para sua aplicação. O objetivo deste estudo foi quantificar doses de S⁰ necessárias para a redução do pH de solos do Sul do Brasil. O experimento foi conduzido em laboratório em um esquema fatorial (5 x 5), com delineamento inteiramente casualizado e três repetições. Os tratamentos foram constituídos por cinco solos e cinco doses de S⁰, correspondente a 0, 50, 100, 150 e 200% da necessidade estimada para atingir pH 4,0. A aplicação de S⁰ resultou na redução do pH e da saturação por bases (V%) e no aumento da acidez potencial (H + Al) esses efeitos, contudo, foram reduzidos em função da baixa taxa de oxidação do S⁰ aplicado (0,76-3,36%). As variáveis de solo correlacionadas com a oxidação de S⁰ foram Mg²⁺ (0,86***), Al³⁺ (-0,82***), H + Al (-0,89***), V% (0,68**) e saturação por alumínio (m%) (-0,87***). Nos solos estudados é necessária a oxidação de 50 kg ha^-1 de S⁰ para redução de uma unidade de pH em H₂O.

Palavras-chave:
oxidação de enxofre; sulfato; acidez; supercalagem

HIGHLIGHTS:

Elemental sulfur application is an option to decrease the pH of southern Brazilian soils.

The soil oxidative potential of elemental sulfur can be estimated by its magnesium concentra-tion, acidity, and base saturation.

Decrease the soil pH by one unity required the oxidation of 25 mg of elemental sulfur by kilo-gram of soil.

Introduction

Some plants of agronomic interest are adapted or benefited from high acidic conditions of the soil. Among those are the blueberry (Vaccinium myrtillus), yerba mate (Ilex paraguariensis), and black-tea (Camellia sinensis). Reducing soil pH for the cultivation of these species may be a recommended practice.

One of the main alternatives for soil acidification is the application of elemental sulfur (S⁰) (Pourbabaee et al., 2020). The oxidation of S⁰ reduce the soil pH, in a reaction derived by microbial activity. Several organisms may oxidize S⁰ (Lucheta & Lambais, 2012; Zhao et al., 2017), as Acidithiobacillus (Malhotra et al., 2002; Mousavi et al., 2006; Tourna et al., 2014; Vitti et al., 2015), Penicillium and Aspergillus (Li et al., 2010). Their population and activity dynamics are strongly influenced by soil factors, consequently impacting the oxidation of S⁰ (Horowitz & Meurer, 2006, 2007; Vitti et al., 2015).

Besides that, in the no-tillage system, in which liming is not incorporated, soil correction is restricted to the surface layers, potentially resulting in the “overliming” effect (Rheinheimer et al., 2018). Therefore, in addition to unnecessary expenses, chemical imbalance detrimental to plant development might occur, as low availability of cationic micronutrients (Saha et al., 2019), ammonia volatilization (Rauber et al., 2017), and formation of calcium phosphate precipitates (Penn & Camberato, 2019).

Although the mechanisms involved in the S⁰ oxidation is known, there are no recommendations regarding the amount that needs to be applied to obtain the predetermined pH values. Thus, the objective of the study was to quantify the S⁰ doses required to reduce the pH of soils from Southern Brazil.

Material and Methods

Soil samples were collected from the 0.00-0.20 m layer in five sites, at regions that represent the area of expansion of the blueberry crop over previously limed commercial orchards and crops in southern Brazil (Figure 1). The soil samples collected corresponded to three Ultisols (Bento Gonçalves - RS, Farroupilha - RS and Pinto Bandeira - RS), one Oxisol (Vacaria -RS) and one Inceptisol (Itá - SC), according to Soil Survey Staff (2014).

Figure 1
Geographic location of the municipalities in the southern region of Brazil with expansion of the blueberry cultivation area, where soil samples were collected

After being collected, soil samples were dried in an oven with forced circulation of air at 65 °C and then sieved in 2 mm mesh. Subsequently, their chemical attributes were characterized according to the methodologies proposed by Tedesco et al. (1995). The soils of Bento Gonçalves and Vacaria, which presented the lowest pH values, were incubated with doses of limestone to raise the pH to 6.0, as recommended by the CQFS RS/SC (2016). The soils chemical characteristics after pH corrections, if needed, are presented in Table 1.

Table 1
Chemical characterization of the 0.00-0.20 m layer of the subtropical soils used in the study

Soil	pH	Al3+	K+	Ca2+	Mg2+	H + Al	CEC	T(1)	BS(2)	m(3)	P	S-SO4-	S.O.M.(4)	Clay
	(cmolc kg-1)								(%)		(mg kg-1)		(g kg-1)
Farropilha	6.3	0.0	0.4	8.3	3.3	2.1	14.1	42.0	85.0	0.3	47.4	3.1	25	180
Itá	5.9	0.1	0.2	6.9	3.2	3.7	14.1	7.1	73.6	0.7	3.3	9.6	40	510
Pinto Bandeira	6.7	0.1	2.3	9.6	3.4	2.3	17.5	17.6	87.1	0.5	173.1	11.0	36	460
Bento Gonçalves	6.3	0.0	0.3	6.6	6.4	1.9	15.2	18.4	87.3	0.2	9.7	13.6	25	470
Vacaria	6.3	0.1	0.3	7.6	6.3	1.5	15.7	26.2	90.2	0.3	52.2	28.2	42	180

• ⁽¹⁾T - Clay activity corrected for carbon concentration; ⁽²⁾BS - Percentual of base saturation; ⁽³⁾m - Percentual of aluminum saturation; ⁽⁴⁾S.O.M. - Soil organic matter

The experimental design was completely randomized with three repetitions, with the treatments disposed in a 5 × 5 factorial arrangement, being five soils and five doses of S⁰, corresponding to 0, 50, 100, 150, and 200% of the estimated dose need to reach pH 4.0.

The need for S⁰ was calculated by estimating the amount of lime to be neutralized in the soil in order to reach the desired pH, and this in turn was estimated by base saturation. In subtropical soils, base saturation of 20% corresponds to pH in H₂O 4.0 (Predebon et al., 2018), a value used as a reference in Eq. 1, which calculates the need for limestone (CQFS RS/SC, 2016).

$$LR=\left[\frac{\left(V1-V2\right)}{100}\right]E{C}_{pH7.0}$$ (1)

where:

LR - limestone requirement in Mg ha^-1;

V1 and V2 - the desired and initial base saturation values, respectively, in percent; and,

EC pH 7.0 - soil cations exchange capacity estimated at pH 7.0 in cmolc kg^-1.

The negative results obtained by Eq. 1 represent the amount of limestone to be neutralized in the soil in order to reach the desired pH.

Based on the reactions presented in Eqs. 2 and 3, it is possible to observe that there is a need for oxidation of one mol of S⁰ to neutralize one mol of CaCO₃, that is, for the neutralization of 1000 kg of CaCO₃ are theoretically required the oxidation of 321 kg of S⁰.

$$S^0+1_2^1{O}_2+H_{2}O\to 2H^{+}+S{O}_4^{-}$$ (2)

$$CaC{O}_3+H_{2}O\to C{a}^{2+}+2O{H}^{-}+C{O}_2$$ (3)

Based on the above assumptions, the S⁰ doses applied to each treatment were calculated, as detailed in Table 2.

Table 2
Elemental sulfur doses applied to the five soils from Southern Brazil used in the study, as a function of the percentage empirically estimated to reach pH 4.0

Soil	0	50	100	150	200
	%
	S applied (g kg-1)
Bento Gonçalves	0.00	1.52	3.04	4.56	6.07
Vacaria	0.00	1.52	3.04	4.56	6.07
Itá	0.00	0.94	1.87	2.80	3.74
Farroupilha	0.00	1.26	2.50	3.77	5.02
Pinto Bandeira	0.00	1.61	3.22	4.83	6.44

Each experimental unit consisted of 2 L plastic bag containing 250 g of soil. After the application of the treatments, the soil packages were closed, sealing the air inside. The soil was incubated for 90 days at room temperature (25 °C ± 5) and 80% moisture of the field capacity. The moisture was corrected in periods no longer than three days by weighing, with the packages being opened and the soil homogenized, allowing gas exchange with the external environment. After the incubation period, the soil was again dried in an oven with forced circulation of air at 65 °C, sieved in a 2 mm mesh, and characterized regarding its chemical attributes, according to the methodologies proposed by Tedesco et al. (1995).

The obtained data were checked regarding the assumptions of normality and homoscedasticity by the Shapiro Wilk and Levene tests. Once these assumptions were met, the data were submitted to the analysis of variance and regression for doses, or Tukey test for the soils. Additionally, linear correlations were performed by the Spearman test between the oxidation potential of S⁰ and the chemical attributes of the soil. In order to predict the oxidation potential of the soils studied, a multiple linear regression model with the backward stepwise method was used between the significantly correlated variables, treated as independent, and the oxidation potential of S⁰, a dependent variable. In addition, the variation of pH data as a function of S⁰ oxidation was submitted to simple linear regression analysis. For all tests p ≤ 0.05 was assumed using the SigmaPlot12.5 software.

Results and Discussion

There was significant effect of the interaction between S⁰ doses and soils, for all the variables tested (Table 3). The soil of Bento Gonçalves presented the highest reduction in pH, in the order of 0.01 units per percentage of S⁰ applied, which corresponded to 0.03 g kg^-1 of S⁰ for this soil (Figure 2A). The soils of Vacaria and Farroupilha presented exponential decay of pH with the increase of the S⁰ dose. This reduction was more expressive with the lower dose and later there was a tendency to stabilize at low values. For the Itá soil there was an opposite effect, with small increase in pH caused by the lowest dose and gradual reduction with the others, however, no proper adjustment was possible (y = 5.93 + 10^-4x - 1.61^-5**x²; R² = 0.52). The Pinto Bandeira soil has not presented significant pH change according to the S⁰ doses.

Table 3
Summary of the analysis of variance and error probability (p-valor) by the F test to the variables evaluated

Source of variation	Degree of freedom	Variable evaluated
		pH	V%	H + Al	S-SO4-2	S-Oxidized
Soil	4	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001
Dose of S0	4	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001
Soil x Dose of S0	16	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001	p ≤ 0.001
Error	50	-	-	-	-	-
CV%		2.7	1.7	12.5	12.7	13.8

Figure 2
Water pH (A), H + Al (B), and base saturation (C) in function of S⁰ doses in five soils from Southern Brazil

The application of S⁰ proved to be effective in modifying the potential acidity, with different behavior in the soils tested (Figure 2B). Related to the pH result, the Bento Gonçalves soil presented the highest increase of H + Al, varying from 1.67 to 4.19 cmolc kg^-1 between the lowest and highest S⁰ dose, respectively. For the Vacaria soil, the H + Al increase behaved in a similar way, but in a lower magnitude, however, no proper adjustment was possible (y = 1.52 + 5.7 10^-3**x; R²: 0.56). The Itá and Pinto Bandeira soils presented a similar behavior, with reduction of H + Al with the lowest S⁰ dose and gradual increase with the other ones. For the Farroupilha soil there was no effect of the doses upon this variable.

The interaction of processes acting in opposite directions may explain the heterogeneous response of the Itá and Pinto Bandeira soils, regarding the change in pH and H + Al as a function of the S⁰ dose. An explanation for the initial increase of soil pH values may be due to the S⁰ reaction that produces thiosulfate which, when reacting with H⁺, forms sulfites, raising the pH (Germida & Jansen, 1993). This reaction, however, is followed by the formation of sulfuric acid and its dissolution in SO₄ ^2- and 2H⁺, reducing the soil pH to values below the early ones. Additionally, the specific adsorption of SO₄ ^2- to oxides present in the soil culminates with the consumption of H⁺ in solution, resulting in an increase in the pH of the medium (Kitadai et al., 2018). This process is favored in clay soils with low activity (Kitadai et al., 2018), as in the case of the Itá soil, the most clayey one and with less clay activity among the evaluated soils, and the Pinto Bandeira soil, which presents the second lowest clay activity (Table 1).

The V% of the Bento Gonçalves soil decreased linearly with the increase of the S⁰ dose, at 0.07 percentage points per percentage unit of S⁰ (Figure 2C). The V% reduction as a function of S⁰ doses was less expressive in the Vacaria soils, and zero for the Pinto Bandeira and Farroupilha soils. Emphasis may be placed on the behavior observed in the Itá soil which, similarly to what is observed for the pH in H₂O and H + Al, presented a quadratic effect as a function of the S⁰ doses: while the lowest dose increases V%, the higher doses decrease its value. The increase in a soil pH, resulting from the addition of limestone, is followed by increase in base saturation (Predebon et al., 2018) and, conversely, the reduction in base saturation is one of the factors related to soil acidification.

In this context, the non-removal of bases, since it is an incubation study in a system without free drainage, might have contributed to a low pH reduction and base saturation of the soils. A secondary effect observed by the application of S⁰ is the increase of electrical conductivity (Boaro et al., 2014). This increase is the result of the release of exchangeable cations into the soil solution, due to the increase of H⁺ ions in the exchange complex. The non-leaching of these elements may result in their accumulation in the soil, leading to toxic effects to the microorganisms involved in the S⁰ oxidation, impairing the maintenance of the process. This effect will be more expressive according to the increase of the S⁰ dose (Horowitz & Meurer, 2006).

The application of S⁰ is an effective practice for reducing soil pH and modifying other acidity variables, such as H + Al and V% for most soils evaluated and is a potential source of S for plants (Lucheta & Lambais, 2012), by increasing the sulfate concentration (SO₄ ^2-) available in the soil (Figure 3B) (Pias et al., 2019; Pourbabaee et al., 2020). The efficiency of S⁰ as a soil acidifier and source of S to plants is, however, dependent on its oxidation rate to SO₄ ^2-. As observed in Figure 3A, the percentage of S⁰ oxidized, in comparison to the total applied, varied between 0.75 and 3.35%. Similar to this, the SO₄ ^2- concentrations presented decreasing increments with increasing doses applied S⁰ (Figure 3B). These results indicate the occurrence of limiting factors to the oxidation of S⁰, which will be further discussed.

Figure 3
Percentage of S⁰ oxidized to the sulfate form (A) and concentration of sulfate in the soil (B), in function of S⁰ doses in five soils from Southern Brazil

Aerobic soil microorganisms, especially of the genus Acidithiobacillus, are responsible for the oxidation of S⁰ (Li et al., 2010; Tourna et al., 2014; Pourbabaee et al., 2020; Kulczycki, 2021). These, in turn, are influenced by soil chemical variables, such as initial soil pH, organic matter concentration and adequate nutrient availability (Horowitz & Meurer, 2006; Zhao et al., 2017), associated with physical variables such as particle size, temperature, moisture, and aeration (Germida & Janzen, 1993).

In this study, there was no significant correlation between S⁰ oxidation and soil initial pH, probably due to the very close pH values of the soil group studied, ranging from 5.9 to 6.7. According to Horowitz & Meurer (2007), the oxidation rate of elemental S itself is not correlated with pH values, but with the presence or absence of exchangeable Al. The presence of this element may directly impair the oxidation of the elemental S by reducing the microbial activity due to its bacteriostatic effects (Horowitz & Meurer, 2007; Herisson et al., 2014). This factor is corroborated in this study since there was a negative correlation between the potential for S⁰ oxidation and the content of exchangeable Al (-0.82***).

In general, pH may have an ambiguous effect on the S⁰ oxidation, favoring the process in low pH conditions, due to the preference of the major microorganisms involved (Malhotra et al., 2002; Mousavi et al., 2006; Tourna et al., 2014; Zhao et al., 2017), or disfavoring it, due to the presence of Al (Horowitz & Meurer, 2007; Herisson et al., 2014). Kulczycki (2021) studying the effect of S⁰ doses over various types of soils, concluded that lowering soil pH impairs its oxidation rate.

Additionally, the high pH may favor the S⁰ oxidation process by consuming the excess of sulfuric acid formed in the reaction, which is detrimental to the continuation of the process (Germida & Janzen, 1993) or by favoring other groups of microorganisms, other than Acidithiobacillus, capable of oxidizing S⁰ (Zhao et al., 2017). However, the Pinto Bandeira soil, which presented the highest initial pH value among the soils evaluated, 6.7, was also the one with the lowest effect as a function of the S⁰ doses, for all the variables assessed.

Besides the initial pH, soil organic matter has been pointed out as an important conditioning factor of the S⁰ oxidation (Horowitz & Meurer, 2007; Zhao et al., 2017), due to the dependence of microorganisms on the energy contained in organic compounds (Di Lonardo et al., 2019). In this study, however, there was no correlation between organic matter concentration and S⁰ oxidation, possibly due to the organic matter concentration, higher than 25 g kg^-1 not being limited to microbial development. Studies that reveal a relationship between organic matter and S⁰ oxidation (Horowitz & Meurer, 2007; Zhao et al., 2017) present lower organic matter values, possibly limiting microbial development.

The SO₄ ^2- concentration present in the soil may interfere with the S⁰ oxidation. Under high concentration, the SO₄ ^2- content may limit S⁰ oxidation, since it is one of the products of this reaction (Horowitz & Meurer, 2007) and because it has an inhibitory effect on microbial activity (Souza et al., 2015; Garg et al., 2019). This effect might be minimized with the vertical displacement of part of the oxidized S, favoring the maintenance of the oxidation process (Souza et al., 2015), which does not occur in incubation assays, as in the present study. It should be noted that, except for the Farroupilha soil, all soils presented initial S-SO₄ ^2- values above 7,5 mg kg^-1, considered adequate by Pias et al. (2019). With the application of S⁰ doses, all soils presented values above 100 mg kg^-1 (Figure 3B), ten folds higher than the critical level for sulfur demanding plants as soybeans, (CQFS RS/SC, 2016) and yerba mate (Ilex paraguariensis) (Schmitt et al., 2018). Besides that, S-SO₄ ^2- values above 100 mg kg^-1 are considered inhibitory for some microorganisms (Garg et al., 2019).

The granulometric composition of the soil may also influence the amount of oxidized S⁰ (Horowitz & Meurer, 2006). However, there was no correlation between S⁰ oxidation and the clay concentration of soils in this study. Most likely, one of the effects of granulometry, besides allowing a larger contact area between S⁰ and soil, is in the buffering of soil acidity, generally higher in clay soils (Motta & Melo, 2019). Horowitz & Meurer (2006), comparing the effect of S⁰ doses in sandy and clay soils, observed that the highest oxidized content occurred in sandy soils, which is attributed to the higher fertility of this soil, especially higher pH and availability of P. However, in the study of these authors, the sandy soil was also the one with the lowest buffering of acidity. This was similar in this study, in which the soils of Bento Gonçalves and Vacaria, with the highest rates of S⁰ oxidation and reduction of pH as a function of the doses of S⁰, are also the soils with the lowest buffering capacity, expressed by their initial H + Al concentration (Table 1).

As already shown, there are many factors that influence the effectiveness of S⁰ as a soil conditioner, largely due to its impacts on the microbial activity involved in its oxidation. Understanding these factors in isolation and their interactions is necessary for an adequate estimate of the S⁰ dose required with the aim of reducing the pH in H₂O of the soil.

Regardless of the soil and dose, it was not possible to reduce the pH to the pre-defined value (4.0). Similarly, base saturation was also reduced below the expect 20% (Figure 2C). These results are directly related to the reduced oxidation rate of the applied S⁰, whose variables involved were discussed previously.

As observed in Figure 3B, which shows the amount of S⁰ applied in mg kg^-1 of soil, to practically demonstrate its conversion to sulfate, all the soils tend to present a maximum SO₄ ^2- concentration. For the Bento Gonçalves and Vacaria soils, the maximum concentration is 237 and 221 mg kg^-1 of SO₄ ^2-, respectively; for the Farroupilha and Pinto Bandeira soils, are 178 and 148 mg kg^-1 of SO₄ ^2-, respectively; and for the Itá soil is 121 mg kg^-1 of SO₄ ^2-. Based on this it is possible to define, for the set of soils studied, the S⁰ oxidation potential. This is represented by the amount of S present in the anion SO₄ ^2- and its maximum concentration found for these soils. The oxidation potential of S⁰ estimated for these soils, according to the equations of Figure 3B, is 79, 73, 40, 60, and 50 mg kg^-1 for the Bento Gonçalves, Vacaria, Itá, Farroupilha, and Pinto Bandeira soils, respectively.

The chemical characteristics that influenced soil oxidation potential of S⁰ were Mg²⁺ (0.86***), Al³⁺ (-0.82***), H + Al (-0.89***), V% (0.68***), and m% (-0.87***). Based on some of these variables, the equation below presents the oxidation potential of the studied soils:

$${\psi }_s=276.44+5.70Mg-25.13\left(H+Al\right)-2.17V\%$$ (4)

where:

Ψs - S⁰ oxidation potential of the soil in mg kg^-1;

Mg and H + Al - values of exchangeable magnesium and potential acidity, both in cmol_c kg^-1; and,

V% - base saturation in percentage.

All coefficients of the equation were significant (p ≤ 0.05) and presented R² = 0.95.

The relation between the oxidative potential of S⁰ and V% and H + Al, as well as to the concentration of exchangeable Al, is known and has been discussed previously. It draws attention, however, to the positive relation between the concentration of exchangeable content of Mg²⁺ with the oxidation rate of S⁰. This close relationship may be related to the essentiality of this chemical element in the oxidation process performed by microorganisms. Based on the results of Malhotra et al. (2002) and Mousavi et al. (2006), Mg²⁺ is defined as fundamental in the bioxidation of iron sulphate, a process performed by bacteria of the genus Acidithiobacillus, which are also involved in the oxidation of S⁰ (Germida & Janzen, 1993; Vitti et al., 2015). Studying the factors affecting S⁰ oxidation in Brazilian soils, Horowitz & Meurer (2007) found no significant correlation between the oxidation potential and the exchangeable Mg²⁺ concentrations. However, the soils grouped as having the highest and lowest oxidation rate by these authors are, respectively, those with the highest and lowest average Mg²⁺ concentration.

Considering the pH variation observed for the set of evaluated soils, given the difference between the initial and final pH, and the amount of oxidized S⁰, it is possible to establish a linear relationship between these variables (Figure 4). Through this, it is possible to determine that, to reduce the pH in H₂O in one unit, it is necessary to apply 25 mg kg^-1 of S⁰ to the soil. In practical terms and extrapolating the experimental situation tested to field conditions, for the reduction of a pH unit in the arable layer, 0-20 cm deep, it would be necessary to apply 50 kg ha^-1 of S⁰. The success of this practice, however, is conditioned to the oxidation of 100% of the amount of S⁰ applied. Corroborating the results of the present study, in a study developed in the United States, on alkaline soils cultivated with blueberry (Vaccinium corymbosum L.), Almutairi et al. (2017) obtained reduction of 0.8 units of pH just one month after the application of 100 kg ha^-1 of S⁰.

Figure 4
Variation of soil pH according to the total amount of oxidized S

Finally, knowing the amount of S⁰ required to reduce the pH in one unit and the oxidation potential of the soil, it is possible to estimate in an accurate way the amount of S⁰ required to reach the desired pH. Thus, technicians and producers who need to adapt the acidity conditions in areas where overliming has occurred, or even for the conversion of orchards and crops for the cultivation of species benefited by higher soil acidic conditions, gain an important ally with the application of S⁰. However, it is worth to mention the limitations of this work, such as the limited number of soils and the conditions of the incubation environment, such as the absence of drainage. Even so, this preliminary work should be used as a stimulus for future research projects to focus on the understanding of the factors involved in the oxidation of S⁰, and the calibration of this product in more comprehensive conditions, for its use as a soil acidity conditioner.

Conclusions

1. The application of elemental S reduces soil pH.

2. For the evaluated soils from Southern Brazil, the application of 50 kg of elemental S per hectare is required to reduce one unit of pH in H₂O, conditioned to the oxidation of all the elemental S applied.

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• ¹ Research developed at Departamento de Solos e Recursos Naturais, Universidade do Estado de Santa Catarina, Lages, SC, Brazil

Edited by

Editors: Geovani Soares de Lima & Walter Esfrain Pereira

Publication Dates

• Publication in this collection
  14 Jan 2022
• Date of issue
  Mar 2022

History

• Received
  17 May 2021
• Accepted
  21 Sept 2021
• Published
  28 Sept 2021