Evaluation of nonexchangeable potassium content of agricultural soils in Japan by the boiling HNO₃ extraction method in comparison with exchangeable potassium

Abstract

The nonexchangeable potassium (neK) content of 178 agricultural soils in Japan was determined by subtracting the amount of K extracted with 1 mol L −1 ammonium acetate, i.e., exchangeable K (exK) from that extracted with boiling 1 mol L −1 HNO 3. The statistical relationships between the neK content and physico-chemical properties of the soils were examined to investigate the factors controlling neK content. The neK content of agricultural soils in Japan ranged from 0 to 1120 mg kg −1 with an arithmetic mean and median of 303 and 255 mg kg −1 , respectively. It showed a significant positive correlation with the total K content, fixed ammonium content, and silt content (p < 0.01) and a significant negative correlation with Alo+1/2 Feo content and total carbon content (p < 0.01). These results suggest that the controlling factors of neK are mainly the total K content and 2:1 type phyllosilicates such as mica and vermiculite, with the indirect negative influence of organic matter and amorphous materials. Terrestrial Regosols, Brown Lowland soils, and Dark Red soils had relatively high neK contents. In contrast, Andosols, Wet Andosols, and Volcanogenous Regosols had relatively low neK contents. The neK content showed no significant correlation with exK content, suggesting that neK is a moderately to slowly available fraction of soil K, which is independent of exK. In conclusion, evaluation of nonexchangeable K in combination with exchangeable K would enhance the rational management of agricultural soils in terms of K fertility by taking account of longer term K-supplying power of soils.

Potassium fractions in soil and simple K balance in long-term fertilising experiments

“…The significantly positive correlation with the fixed ammonium ions supports the hypothesis that K ne is mainly bound at the boundaries of clay minerals of the 2 : 1 types, mica and vermiculite (Brouder 2011). Kitagawa et al (2018) stated that the clay mineral type is more important than the total content of the clay particles. Madaras et al (2010), in their model for determining K-SAR, use the values obtained by the aqua regia extraction.…”

“…Furthermore, Kitagawa et al (2018) recommend determining the exchangeable potassium (K ex ), completed by the content of the non-exchangeable potassium K ne (using extraction at 1 mol/L boiling HNO 3 ). The method of determining K ne is not complicated, and its results do not significantly change over the years; it is, therefore, possible to recommend this method as a supplementary one, mainly for longterm unbalanced results.…”

The Dynamics of Radio-Cesium in Soils and Mechanism of Cesium Uptake Into Higher Plants: Newly Elucidated Mechanism of Cesium Uptake Into Rice Plants

“…The concentration of exchangeable K + is an indicator of plant available K + . The exchangeable K + concentration in 178 agricultural soils (95 paddy fields and 83 upland fields in Japan) ranged from 43 to 1304 mg kg −1 , with a median of 209 mg kg −1 (Kitagawa et al, 2017). The concentration of K + in soil solution is less than 10% of exchangeable K + concentration.…”

“…In contrast to radio Cs + , potassium is an environmentally abundant element supplied from soil clay minerals, at concentrations of 5000-13,000 mg/kg soil (Tsukada et al, 2002). The exchangeable K + available to plants is approximately 200 mg/kg soil, while 10-100 µM K + is retained in soil solution (Sparks and Huang, 1985;Gomez-Porras et al, 2012;Kitagawa et al, 2017). The actual K/Cs ratio is approximately 10 3 in the soil solution.…”

Evaluation of mungbean [Vigna radiata (L.) Wilczek] varieties under water deficit stress

“…The following soil properties were determined: Electrical conductivity (EC) of the soil suspension was determined with an EC meter; pH of suspension with soil: water at the ratio of 2:5 (w/v) was measured by using a p H meter; organic carbon was determined by Walkley and Black's wet oxidation method (1934), nitrogen (N) by Kjeldahl method, phosphorus (P) through molybdate-ascorbic acid procedure, available iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn) content determined using atomic absorption spectrophotometer (AAS). Available Sulphur in soil was determined by turbidometric method (18) and cation such as potassium (K) was also determined (19). The available Boron was estimated by spectrophotometric method (20).…”