The relationship between soil pH measurements in calcium chloride and water suspensions

Little, IP

doi:10.1071/sr9920587

Cited by 28 publications

(14 citation statements)

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“…Subsequently, Little (1992) also demonstrated a curvilinear relationship between pHw and pHca for a larger data set from New South Wales with a wider pHw range (4. 6-8.85).…”

Section: Introductionmentioning

confidence: 78%

“…Linear relationships with slopes not significantly different from one have been obtained for some data sets with a limited pH range (Bruce et al, 1989;Little, 1992) implying a constant difference between pHw and pHca. Equation (1) has a slope significantly less than unity, indicating that for this data set the difference between pHw and pHca decreases with decreasing pH.…”

Section: =0018 )mentioning

confidence: 87%

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Models for relating pH measurements in water and calcium chloride for a wide range of pH, soil types and depths

1995

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Soil pH is commonly measured in water (pHw) or 0.01 M CaC12 (pHca). The need to convert between these methods has led to the publication of linear, quadratic and cubic polynomial relationships for limited suites of soils. Concerns over the applicability of such relationships when mapping a wide range of soils and pH led to the establishment of a database of pHw and pHca values on each of 7894 samples from soil survey and field experimental sites in Queensland. The relationship between pHw and pHca across all soils was investigated and preliminary results examining the effect of soil depth and soil type on the relationship are presented.For all soils and depths, a linear regression accounted for 93.2% of the variation but did not predict pHca well at very high or low pHw values. The inclusion of second and third powers of pHw accounted for significantly more of the variation (R 2 = 0.94) in pHca and the resultant curve matched the data better at high and low pH.Analysis of surface, sub-surface and subsoil groupings did not reveal any appreciable differences in the relationship between pHw and pHca attributable to depth. In contrast, differences in the relationship were evident between soil types. Generally, the mildly leached soils had linear relationships, while the weathered soils were distinctly curvilinear at low pH.

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“…Subsequently, Little (1992) also demonstrated a curvilinear relationship between pHw and pHca for a larger data set from New South Wales with a wider pHw range (4. 6-8.85).…”

Section: Introductionmentioning

confidence: 78%

Section: =0018 )mentioning

confidence: 87%

Models for relating pH measurements in water and calcium chloride for a wide range of pH, soil types and depths

1995

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“…The black dotted line shows the 1:1 relationship and the red dotted line (2) is the regression model of [56]. …”

Section: Figurementioning

confidence: 99%

Soil pH Mapping with an On-The-Go Sensor

Schirrmann

Gebbers

Krämer

et al. 2011

Sensors

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Soil pH is a key parameter for crop productivity, therefore, its spatial variation should be adequately addressed to improve precision management decisions. Recently, the Veris pH Manager™, a sensor for high-resolution mapping of soil pH at the field scale, has been made commercially available in the US. While driving over the field, soil pH is measured on-the-go directly within the soil by ion selective antimony electrodes. The aim of this study was to evaluate the Veris pH Manager™ under farming conditions in Germany. Sensor readings were compared with data obtained by standard protocols of soil pH assessment. Experiments took place under different scenarios: (a) controlled tests in the lab, (b) semicontrolled test on transects in a stop-and-go mode, and (c) tests under practical conditions in the field with the sensor working in its typical on-the-go mode. Accuracy issues, problems, options, and potential benefits of the Veris pH Manager™ were addressed. The tests demonstrated a high degree of linearity between standard laboratory values and sensor readings. Under practical conditions in the field (scenario c), the measure of fit (r2) for the regression between the on-the-go measurements and the reference data was 0.71, 0.63, and 0.84, respectively. Field-specific calibration was necessary to reduce systematic errors. Accuracy of the on-the-go maps was considerably higher compared with the pH maps obtained by following the standard protocols, and the error in calculating lime requirements was reduced by about one half. However, the system showed some weaknesses due to blockage by residual straw and weed roots. If these problems were solved, the on-the-go sensor investigated here could be an efficient alternative to standard sampling protocols as a basis for liming in Germany.

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“…They found that in soil suspensions receiving controlled applied potentials similar to those measured in SP12 (248 to 2260 mV), pH values "increased as the applied potentials became more negative." As has been observed by others (8,12,13,38), achieving an absolute value for pH is improbable at best. Given, in the present case, agreement between both methods of pH measurement (when employed simultaneously for a given sample) in pH trends over time, it must be considered that the variations in pH values (since they move up and down in synchrony with ambient GEM values) are real.…”

Section: Discussionmentioning

confidence: 67%

Global synchrony in biospheric variations and influence on soil pH

Mullenax

Baumann

Kihn

et al. 2001

Communications in Soil Science and Plant Analysis

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Data collected from 1968 through 1997 showed a globally synchronous annual increase in soil acidity during the period June through August which was highly correlated with progressively decreasing geomagnetic field strength despite periodic local alterations in electromagnetic activity at the planetary boundary layer. Monthly determinations of soil pH for periods of one or more years at sites in Australia, South America, North America, Scotland, and Germany showed pH values to be consistently and significantly correlated with the monthly average geomagnetic field strength and the auroral electrojet values recorded during the time period covered by the data. Unweighed simple and multiple 2631 ORDER REPRINTS least squares linear regressions of soil pH on geomagnetic D, H, and Z, and the auroral electrojet gave r 2 and p values as high as r 2 ¼ 0:9997; p ¼ 0:0000: These relationships were subject to modifications in soil pH by telluric currents and electromagnetic events, such as thunderstorms and accompanying acid rain, occurring at the planetary boundary layer. Short-term variations in electrical conductivity of soil, in situ plant-available soil moisture, availability of soil mineral nutrient elements for plant uptake, soil pH, and the pH of fresh and stored samples of soil diluted 1:5 in water, rainwater, and other solutions, and Rn levels in soil and air were highly correlated with ambient telluric currents and with atmospheric electrical discharges. Decreasing soil pH values were consistently associated with decreased availability of soil mineral nutrients for plant uptake, lower foliar mineral element content in growing plants, and reduced health status, fertility, and productivity of herbivores. Rising pH values were accompanied by increases in available soil mineral nutrient elements and improvements in plant and animal health and productivity.

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The relationship between soil pH measurements in calcium chloride and water suspensions

Cited by 28 publications

References 0 publications

Models for relating pH measurements in water and calcium chloride for a wide range of pH, soil types and depths

Models for relating pH measurements in water and calcium chloride for a wide range of pH, soil types and depths

Soil pH Mapping with an On-The-Go Sensor

Global synchrony in biospheric variations and influence on soil pH

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