Potassium Concentration In Soil Solution Research Articles

Metrological assessment of TDR performance for measurement of potassium concentration in soil solution

ABSTRACT Despite the growing use of the time domain reflectometry (TDR) technique to monitoring ions in the soil solution, there are few studies that provide insight into measurement error. To overcome this lack of information, a methodology, based on the central limit theorem error, was used to quantify the uncertainty associated with using the technique to estimate potassium ion concentration in two soil types. Mathematical models based on electrical conductivity and soil moisture derived from TDR readings were used to estimate potassium concentration, and the results were compared to potassium concentration determined by flame spectrophotometry. It was possible to correct for random and systematic errors associated with TDR readings, significantly increasing the accuracy of the potassium estimation methodology. However, a single TDR reading can lead to an error of up to ± 18.84 mg L-1 K+ in soil solution (0 to 3 dS m-1), with a 95.42% degree of confidence, for a loamy sand soil; and an error of up to ± 12.50 mg L-1 of K+ (0 to 2.5 dS m-1) in soil solution, with a 95.06% degree of confidence, for a sandy clay soil.

Variability of the soil-to-plant radiocaesium transfer factor for Japanese soils predicted with soil and plant properties

Food chain contamination with radiocaesium (RCs) in the aftermath of the Fukushima accident calls for an analysis of the specific factors that control the RCs transfer. Here, soil-to-plant transfer factors (TF) of RCs for grass were predicted from the potassium concentration in soil solution (mK) and the Radiocaesium Interception Potential (RIP) of the soil using existing mechanistic models. The mK and RIP were (a) either measured for 37 topsoils collected from the Fukushima accident affected area or (b) predicted from the soil clay content and the soil exchangeable potassium content using the models that had been calibrated for European soils. An average ammonium concentration was used throughout in the prediction. The measured RIP ranged 14-fold and measured mK varied 37-fold among the soils. The measured RIP was lower than the RIP predicted from the soil clay content likely due to the lower content of weathered micas in the clay fraction of Japanese soils. Also the measured mK was lower than that predicted. As a result, the predicted TFs relying on the measured RIP and mK were, on average, about 22-fold larger than the TFs predicted using the European calibrated models. The geometric mean of the measured TFs for grass in the affected area (N = 82) was in the middle of both. The TFs were poorly related to soil classification classes, likely because soil fertility (mK) was obscuring the effects of the soil classification related to the soil mineralogy (RIP). This study suggests that, on average, Japanese soils are more vulnerable than European soils at equal soil clay and exchangeable K content. The affected regions will be targeted for refined model validation.

Migration and bioavailability of 137Cs in forest soil of southern Germany

To give a quantitative description of the radiocaesium soil–plant transfer for fern ( Dryopteris carthusiana) and blackberry ( Rubus fruticosus), physical and chemical properties of soils in spruce and mixed forest stands were investigated. Of special interest was the selective sorption of radiocaesium, which was determined by measuring the Radiocaesium Interception Potential (RIP). Forest soil and plants were taken at 10 locations of the Altdorfer Wald (5 sites in spruce forest and 5 sites in mixed forest). It was found that the bioavailability of radiocaesium in spruce forest was on average seven times higher than in mixed forest. It was shown that important factors determining the bioavailability of radiocaesium in forest soil were its exchangeability and the radiocaesium interception potential (RIP) of the soil. Low potassium concentration in soil solution of forest soils favors radiocaesium soil–plant transfer. Ammonium in forest soils plays an even more important role than potassium as a mobilizer of radiocaesium. The availability factor – a function of RIP, exchangeability and cationic composition of soil solution – characterized reliably the soil–plant transfer in both spruce and mixed forest. For highly organic soils in coniferous forest, radiocaesium sorption at regular exchange sites should be taken into account when its bioavailability is considered.

Extratores de cápsulas porosas para o monitoramento da condutividade elétrica e do teor de potássio na solução de um solo

Este trabalho teve como objetivo avaliar a utilização de extratores de cápsulas porosas no monitoramento da condutividade elétrica e da concentração de potássio na solução do solo, em uma área cultivada com tomates e fertirrigada com três níveis de potássio e frequências de aplicação de um e três dias. Os valores de condutividade elétrica e concentração de potássio encontrados na solução do solo foram corrigidos para a umidade da pasta saturada, em função das diferentes umidades do solo no momento da extração. Os valores de condutividade elétrica obtidos com os extratores de cápsulas porosas e corrigidos para a umidade da pasta subestimaram os medidos no extrato da pasta saturada em torno de 16%. Para as concentrações de potássio, a mesma tendência foi observada, sendo a magnitude cerca de 10%. Os coeficientes de determinação (R²) foram superiores a 0,7 para as duas variáveis analisadas. A condutividade elétrica e a concentração de potássio podem ser avaliadas utilizando-se extratores de solução, com precisão razoável.

Potassium-calcium exchange in five Ap soils from paddy fields and its effect on potassium concentration in soil solution

Abstract We measured the selectivity coefficient (K V) for K-Ca exchange equilibrium as a function of K-saturation on two smectitic soils, two halloysitic soils and a soil dominated by noncrystalline aluminum silicates. The selectivity coefficients for all the soils decreased as K-saturation increased. Among the five soils, the halloysitic soils exhibited higher K V values than the smectitic soils, while the K V values for the soils dominated by noncrystalline aluminum silicates were comparable with those of the halloysitic soils at low K-saturation but the K V values were even lower than those for the smectitic soils at higher K-saturation. Numerical simulations showed that the K concentration in the soil solution after addition of a K-salt differed significantly among the soils, depending on the exchangeable K status and K-selectivity of the soils.