Correction: Song et al. Adaptation of NO₂⁻ Extraction Methods to Different Agricultural Soils: Fine-Tuning Based on Existing Techniques. Agronomy 2024, 14, 331

Text Correction

There were several errors in the original publication [1].

To enhance clarity, the publication title has been revised from “Improved Method for Extracting Nitrites in Soil” to “Adaptation of NO₂⁻ Extraction Methods to Different Agricultural Soils: Fine-Tuning Based on Existing Techniques”.

In the fourth line of the Abstract, the use of the word “optimization” in the original text may lead to inaccurate representation. In order to avoid misunderstanding, a correction has been made to the Abstract and should read as follows:

“In order to reflect the soil NO₂⁻ concentration more accurately, we made minor adjustments on the basis of the existing soil NO₂⁻ extraction method, so that it can be adapted to agricultural soils with different textures and pH values (alkalic fluvo-aquic soil, acidic Mollisol, and Ultisol soils, respectively). Both extractable soil ammonium (NH₄⁺) and nitrate (NO₃⁻) were systematically investigated to refine the simultaneous extraction of soil inorganic nitrogen.”

Given the specific conditions of the samples, the oscillation times were fine-tuned appropriately. A correction has been made to the Abstract, line 17, and should read as follows:

“In conclusion, soil NO₂⁻ extraction was carried out by DIW extraction, shaking for 10 min, and filtering with a 0.45 µm filter, while soil NH₄⁺ and NO₃⁻ were extracted with a KCl solution and shaken for 30 min. The extract should be stored at 4 °C and analyzed within 24 h. We have made minor adjustments to our previously published method for soil NO₂⁻ analysis to make it more adaptable to soils with different textures and pH values. These adjustments make the method more effective in soil geochemical nitrogen cycling studies, especially in the assessment of soil nitrite (HONO) and nitric oxide (NO) emissions.”

To ensure that the work keeps pace with the latest scientific advances, changes have been made to the Introduction, on the first line of the third paragraph, and should read as follows:

“Although DIW has become the recommended extractant for soil NO₂⁻ analysis, the presence of suspended solids in the DIW extract affects the absorbance measurements of NO₂⁻ analyzed spectrophotometrically, thus requiring filtration through a 0.45 μm filter [20].”

Meanwhile, the third sentence of the second paragraph, “During the extraction of NO₂⁻, there are generally no biological or chemical reactions that cause changes in its concentration or isotopic composition [21].” has been deleted. Reference [21] corresponds to [24] in the latest version.

The method published by Homyak et al. (2015) is already a validated and recommended standardized procedure. It is on this solid foundation that our study was conducted, and minor adjustments have been made to ensure the validity and accuracy of the measurements of NO₂⁻ in the soils tested. A correction has been made to the Introduction, on the fourth paragraph, and should read as follows:

“Therefore, this study aims to verify the effectiveness and accuracy of the latest soil NO₂⁻ detection method in soils with different textures and pH values in order to provide a scientific basis for the efficient extraction of NO₂⁻, NO₃⁻ and NH₄⁺.”

In the Discussion section, Section 4.1, line 17, there were some errors in the presentation of the article. The corrected section should read as follows:

“In conclusion, unbuffered KCl solutions considerably reduced NO₂⁻ concentrations, in agreement with previous studies [16,20]. Although more NO₂⁻ can be extracted with DIW, it produces a brown extract that interferes with colorimetric analysis [20]. Homyak et al. (2015) [20] obtained more accurate measurements of NO₂⁻ concentration by filtering through a 0.45 micron filter [20].”

In the first line of the Conclusion, there are some errors in the presentation of the article. To ensure the accuracy of the content, the relevant paragraphs have been revised and should read as follows:

“We have fine-tuned our published soil NO₂⁻ extraction methods to make them applicable to agricultural soils of different textures and pHs.”

Missing Citation

The literature cited in the article [23–25] does reflect the use of soil NO₂⁻ analysis methods prior to 2015 but fails to adequately reflect the latest research advances. To ensure the accuracy and applicability of the content the following changes have been made to the Introduction, on the sixth line of the second paragraph, and should read as follows:

“Subsequently, Homyak et al. (2015) [20] improved the extraction of NO₂⁻ from soil and identified deionized water (DIW) as the preferred extractant as a new method for extracting soil NO₂⁻.”

References

The previously cited references [23–25], as listed below, have been removed.

23. Maynard, D.G.; Kalra, Y.P.; Crumbaugh, J.A. Nitrate and exchangeable ammonium nitrogen. In Soil Sampling and Methods of Analysis, 2nd ed.; Carter, M.R., Gregorich, E.G., Eds.; CRC Press: Boca Raton, FL, USA, 2007; pp. 71–80, ISBN 9780849335860.

24. Pansu, M.; Gautheyrou, J. Handbook of Soil Analysis: Mineralogical, Organic and Inorganic Methods; Springer: Berlin/Heidelberg, Germany; New York, NY, USA, 2006; pp. 767–792, ISBN 978-3-540-31210-9.

25. ISO 14256-2:2005; Soil Quality Determination of Nitrate, Nitrite and Ammonium in Field-Moist Soils by Extraction with Potassium Chloride Solution-Part 2: Automated Method with Segmented Flow Analysis. ISO: Geneva, Switzerland, 2005. Available online: https://www.iso.org/obp/ui/#iso:std:iso:14256:-2:ed-1:v1:en (accessed on 12 December 2023).

As a result of this correction, the order of several references has been adjusted accordingly.

Error in Figure

Since Figure 5 in the article does not contribute additional information, the authors have decided to remove it from the manuscript. Consequently, all references to Figure 5 in the discussion have been removed, and the relevant sentences in the text have been revised. In the Discussion, Section 4.1, line 19, the text should now read as follows:

“Although more NO₂⁻ can be extracted with DIW, it produces a brown extract that interferes with colorimetric analysis [20].”

The authors state that the scientific conclusions are unaffected. This correction was approved by the Academic Editor. The original publication has also been updated.