Spectrophotometric methods for the measurement of soil pH: A reappraisal

Fornasier, Emanuele; Fornasier, Flavio; Marco, Valerio Di

doi:10.1016/j.saa.2018.06.029

Cited by 11 publications

(3 citation statements)

References 28 publications

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“…The "suspension effect" has long been observed (Gorham, 1960;Jenny et al, 1950;Oman et al, 2007;Ponnamperuma et al, 1966), and describes the apparent decrease in pH when a pH probe is moved between the supernatant and sediment of a settled suspension, although the precise explanation for the problem is somewhat unresolved (Feldman, 1956;Fornasier et al, 2018). Sacchi et al (2001) have recommended preparing fresh samples using the centrifugation method of extracting solutions from claywater systems, pertaining to most unsaturated soils, with a risk of incomplete water extraction at extreme dry conditions.…”

Section: Soil Solution Extractionmentioning

confidence: 99%

Standard and Non-Standard Measurements of Acidity and the Bacterial Ecology of Northern Temperate Mineral Soils

Braus

Whitman

2020

Preprint

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Databases of soil pH values today guide the decisions of land managers and the experimental designs of microbiologists and biogeochemists. Soil acidity underpins fundamental properties and functions in the soil, such as the solubilities of exchangeable ions and nutrients, or bacterial use of gradients of internal and external acidity to generate ATP and turn flagellar motors. Therefore, it is perhaps unsurprising that soil pH has emerged as the strongest predictor of soil bacterial community composition. However, the measurement of these particular values today does not address whether soil pH accurately represents the in situ acidity of soil microhabitats where microorganisms survive and reproduce. This study analyzes and compares soils of a large-scale natural soil pH gradient and a long-term experimental soil pH gradient for the purposes of testing new methods of measuring and interpreting soil acidity when applied to soil ecology. We extracted and prepared soil solutions using laboratory simulation of levels of carbon dioxide and soil moisture more typical of soil conditions while also miniaturizing extraction methods using a centrifuge for extractions. The simulation of in situ soil conditions resulted in significantly different estimates of soil pH. Furthermore, for soils from the long-term experimental soil pH gradient trial, the simulated soil pH values substantially improved predictions of bacterial community composition (from R2 = 0.09 to R2 = 0.16). We offer suggestions and cautions for researchers considering how to better represent soil pH as it exists in situ.

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Section: Soil Solution Extractionmentioning

confidence: 99%

Standard and Non-Standard Measurements of Acidity and the Bacterial Ecology of Northern Temperate Mineral Soils

Braus

Whitman

2020

Preprint

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“…Depending on the intensity of the fire, burnt soil samples could have portions of ashes, unburnt particles, and colloidal material, sometimes in the range of nanoparticles. However, in most of the studies involving burnt soils [11][12][13], there is no standard or consensus on pH analysis method for this specific scenario. In recently burnt soils submitted to low-intensity fires, high amounts of vegetal debris are commonly mixed in the first soil horizons.…”

Section: Introductionmentioning

confidence: 99%

“…Despite this variety of methods, the most used protocols are based on potentiometric measurement performed by glass or reference electrode. Moreover, the electrode measurement is considered precise and relatively inexpensive [13].…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Analytical Methods for the Determination of Soil pH: Case Study on Burned Soils in Northern Portugal

Faria

Bertocco

Barroso

et al. 2023

Fire

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Wildfires can cause serious imbalances in ecosystems, primarily at the soil level, making it vulnerable to degradation processes such as erosion. During and after a fire, changes occur in soil properties, including pH, which affects the solubility and availability of nutrients. Currently, there is a great diversity of protocols, some involving normalized standards, to determine soil pH, but there is no consensual or universal analytical method for this parameter, especially in burned soils, in which mineral and organic fractions could have been modified. Therefore, the objective of the present work is to evaluate the effect that variations in these analytical protocols may have on pH results. For this, five methods commonly found in the international bibliography for the analysis of pH of soil in water (pHH2O) were selected and compared to propose the most precise procedure. The analytical methods were applied to 43 soil samples, collected in a plot subjected to prescribed burning in the Parque Natural de Montesinho (Northern Portugal). The studied methods differ in the following protocol items: water suspension ratio (1:2.5 or 1:5), mechanical stirring time in the suspension (10 min or 1 h), and in the resting time for the solid particles to settle (15 min or 8 h). The obtained results point to the suitability of the five methods used for soil pH analysis, indicating that there are no statistically significant differences. However, results also allow suggesting a more appropriate method concerning practical reasons, such as labor in a lab. Thus, to make the analysis process more profitable, M2 is a good option because it uses a small amount of sample (5 g), short agitation (10 min) and settling time (15 min). In turn, M1 and M5, which use a lower proportion of soil (1:2.5) show lower pH variation in the measurements. This fact may be explained by a smaller dilution effect. Considering that these two methods differ in the settling time, it is suggested to apply M1, because only 15 min are required. Therefore, the main conclusion reached with this work is that the measurement of soil pH using M1, i.e., a soil:water ratio of 1:2.5, with agitation of 10 min and settling time of 15 min, is a robust and more expeditious protocol to be applied to soil samples after a fire.

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Determination of Physical Properties of Environmental Samples

2020

Environmental Analysis Laboratory Handbook

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Spectrophotometric methods for the measurement of soil pH: A reappraisal

Cited by 11 publications

References 28 publications

Standard and Non-Standard Measurements of Acidity and the Bacterial Ecology of Northern Temperate Mineral Soils

Standard and Non-Standard Measurements of Acidity and the Bacterial Ecology of Northern Temperate Mineral Soils

A Comparison of Analytical Methods for the Determination of Soil pH: Case Study on Burned Soils in Northern Portugal

Determination of Physical Properties of Environmental Samples

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