اثر مصرف گوگرد و محتوای رطوبت خاک بر اکسایش گوگرد و ویژگی‌های شیمیایی خاک‌های آهکی

نوع مقاله : مقاله پژوهشی

نویسندگان

• جلال قادری ¹
• محمد حسین داوودی ²
• ندا محمدی ³
• کریم شهبازی ²
• کمال خلخال ⁴

¹ استادیار پژوهشی بخش تحقیقات خاک و آب، مرکز تحقیقات، آموزش کشاورزی و منابع طبیعی استان کرمانشاه،

² مؤسسه تحقیقات خاک و آب، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرج، ایران

³ بخش تحقیقات خاک و آب، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان آذربایجان شرقی. ایران.

⁴ بخش تحقیقات خاک و آب، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان کرمانشاه، سازمان تحقیقات، آموزش و ترویج کشاورزی، ایران.

چکیده

کلیدواژه‌ها

• اکسایش
• تیوباسیلوس
• رطوبت
• خاک آهکی
• گوگرد

موضوعات

• حاصلخیزی خاک و تغذیه گیاه

عنوان مقاله [English]

Effect of Sulfur Application and Soil Moisture Content on Sulfur Oxidation and Chemical Properties in Calcareous Soils

نویسندگان [English]

• jalal ghaderi ¹
• Mohammad Hossein Davoodi ²
• Neda Mohammadi ³
• Karim Shahbazi ²
• Kamal Khalkhal ⁴

کلیدواژه‌ها [English]

• Calcareous soil
• Moisture
• Oxidation
• Sulfur. Thiobacillus

Introduction

Calcareous soils constitute over 87% of Iran’s agricultural lands and present challenges such as nutrient immobilization due to their alkaline nature and calcium carbonate content. This study aims to investigate the effect of elemental sulfur application at different levels combined with Thiobacillus bacteria, under varying moisture conditions on sulfur oxidation and changes in selected chemical properties of five calcareous and non-calcareous soils with varying calcium carbonate contents.

Methods

A randomized complete block design experiment was conducted with three sulfur application rates (0, 500, and 1000 kg/ha) and two moisture levels (40% and 60% saturation). Soil samples were collected from five different regions in Iran with distinct calcium carbonate contents. Samples were incubated in controlled laboratory conditions at 25°C for one year. Parameters measured included soil pH, electrical conductivity (EC), available phosphorus and sulfate, as well as extractable iron and zinc. The sulfur oxidation rate was determined over specified time intervals. Data were analyzed using analysis of variance (ANOVA) based on a randomized complete block design, and means were compared using Duncan’s multiple range test at the 1% probability level.

Results

Soil analysis results showed that the calcium carbonate content of these soils ranged from less than 1 to 44 percent and were classified into five categories: non-calcareous (less than 1 percent= Balestan soil), low calcareous (1 to 10 percent= Babol soil), moderately calcareous (10 to 25 percent= Qezelr soil), calcareous (25 to 40 percent= Falard soil), and highly calcareous (40 to 60 percent= Sharifabad soil). The results showed that a moisture content of 40% (optimal) and the application of 500 kg sulfur per hectare led to the highest sulfur oxidation rate. This significant increase in oxidation rate was mainly due to the activity of Thiobacillus bacteria as a biological catalyst in the oxidation process, which accelerated sulfuric acid production under optimal moisture conditions combined with sulfur. Increasing moisture to 60% led to a reduction in the oxidation rate due to oxygen limitation and decreased microbial activity. From a soil reclamation perspective, sulfur application, especially at 1000 kg/ha under 40% moisture conditions, had the greatest impact on reducing pH and EC and increasing the availability of nutrients such as phosphorus, sulfate, iron, and zinc. Among the soils, the largest pH reduction was recorded in Qezelr soil (a decrease of 0.87 units), while Babol soil showed the highest increase in EC (1.19 dS/m) and the highest concentrations of available phosphorus (41.1 mg/kg), sulfate (2690 mg/kg), iron (62.9 mg/kg), and zinc (1.25 mg/kg). In contrast, Sharifabad soil, with a 44% calcium carbonate equivalent content, demonstrated the least sensitivity to sulfur oxidation and subsequent pH changes.

Conclusions

Calcium carbonate acts as a determining factor in sulfur oxidation. In soils with low to moderate calcium carbonate content, sulfur was able to effectively reduce pH and increase the solubility of nutrients, but its effect is limited in highly calcareous soils. Therefore, soils with high buffering capacity and calcium carbonate content require larger amounts of sulfur to observe significant changes in sulfur oxidation and pH. This study demonstrated that the application of paste sulfur produced by the Iranian Research Institute of Petroleum Industry, along with Thiobacillus bacteria under optimal moisture conditions (40% saturation moisture), can serve as a practical and effective strategy for reclaiming calcareous soils with calcium carbonate content below 50%. Therefore, high-quality domestically produced sulfur can be utilized in nutrient management and reclamation programs for alkaline soils in Iran. To transfer the results to field conditions, it is recommended to conduct field experiments in soils with calcium carbonate content greater than 50% to determine the critical sulfur dose and optimal moisture level for each soil texture.

Funding

 This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author Contributions

 “Conceptualization. J.Gh. and K.Kh.; methodology, J.Gh.; software, K.Kh.; validation, J.Gh., MH.D. and K.Sh.; formal analysis, J.Gh.; investigation, K.Kh.; resources, J.Gh.; data curation, N.M.; writing—original draft preparation, J.Gh. and K.Kh.; writing—review and editing, J.Gh. and K.Kh.; visualization, J.Gh.; supervision, J.Gh. and MH.D.; project administration, J.Gh.; funding acquisition, J.Gh. All authors have read and agreed to the published version of the manuscript.”

Declaration of Generative AI and AI-assisted technologies in the writing process

During the preparation of this work, the author(s) did not use any generative AI or AI-assisted technologies in the writing process. The author(s) are fully responsible for the originality and content of the publication.

Data Availability statement

Data available on request from the authors.

Acknowledgements

The authors express their appreciation to the experts of the Soil and Water Research Institute laboratory, as well as to the technical team of the Petroleum Industry Research Institute for providing the sulfur prills used in this research.

 Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and other forms of misconduct.

Conflict of interest

 The authors declare no conflicts of interest.