Conceptually Simple - Easy to Use - Easy to Analyze
Interpreting and Understanding IRIS Data
1. Principles
2. General Guidance
2. General Guidance
a. Removal/stripping of the coating shows areas of reduction.
b. The more coating is removed, the greater the degree of reduction within the soil.
2. General Guidance
2. General Guidance
2. General Guidance
a. Identify the zone of interest.
b. The NTCHS suggests that the focus should be on the 30 cm nearest the soil surface as the "upper part" of the soil.
c. In some cases, documenting what goes on below 30 cm may also be important.
3. NTCHS Criteria
2. General Guidance
4. Suggested Criteria of Castenson and Rabenhorst, 2006.
a. For each film, identify the 15 cm contiguous zone (within the upper 30 cm) showing the maximum coating removal.
b. Quantify the percentage of coating removed within those zones.
c. The NTCHS Technical Standard states that if 3 or more (out of 5) have >30% removal of the coating, the soil is considered to be reducing.
4. Suggested Criteria of Castenson and Rabenhorst, 2006.
4. Suggested Criteria of Castenson and Rabenhorst, 2006.
4. Suggested Criteria of Castenson and Rabenhorst, 2006.
a. For each film, identify the 10 cm contiguous zone (within the upper 30 cm) showing the maximum coating removal.
b. Quantify the percentage of coating removed within those zones.
c. The suggested criteria of Castenson and Rabenhorst (2006) states that if 3 or more (out of 5) have >=25% removal of the coating, the soil should be considered to be reducing.
d. Note: Focusing on a 10 cm zone (C&R), rather than a 15 cm zone (NTCHS) typically results in a slightly greater amount of paint removed.
Castenson, K. L., and M. C. Rabenhorst. 2006. Indicator of Reduction in Soil (IRIS): Evaluation of a New Approach for Assessing Reduced Conditions in Soil. Soil Sci. Soc. Am. J. 70: 1222-1226. https://dl.sciencesocieties.org/publications/sssaj/abstracts/70/4/1222
5. What about Mn-Coated Films
4. Suggested Criteria of Castenson and Rabenhorst, 2006.
5. What about Mn-Coated Films
Mn oxide coatings are solubilized under moderately reducing conditions that are closer to environmentally important reactions such as denitrification. Thus, Mn oxides are removed more easily and faster than Fe oxide coatings. Although, at present, no formal standard has been approved for interpreting Mn-coated IRIS devices, advances have been made in understanding how to interpret Mn-coated IRIS. Mn IRIS may be particularly useful early in the growing season when soil temperatures are lower and microbial activity is slower. This is explained in detail in this article:
Rabenhorst, M. C., P. J. Drohan, J. M. Galbraith, C. Moorberg, L. Spokas, M. H. Stolt, J. A. Thompson, J. Turk, B. L. Vasilas, K. L. Vaughan. 2021. Mn-Coated IRIS to Document Reducing Soil Conditions. Soil Sci. Soc. Am. J. 85:2201-2209. https://acsess.onlinelibrary.wiley.com/doi/full/10.1002/saj2.20301
Other Considerations
4. Suggested Criteria of Castenson and Rabenhorst, 2006.
5. What about Mn-Coated Films
More to come.