Chemistry of soil potassium in Atlantic coastal plain soils: A review

Abstract

Literature dealing with general properties of soil K and with K relationships in Atlantic Coastal Plain Soils was discussed.Potassium, among major and secondary nutrient elements, is the most abundant in soils. It, among mineral cations required by plants, is largest in non-hydrated size. Potassium has a polarizability equal to .88 Å 3 and a low hydration energy of 34 kcal g -1 ion -1 . The major K forms in soils are water soluble, exchangeable, nonexchangeable, and mineral. Various dynamic interrelationships exist between these forms with the reaction kinetics between the various phases determining the fate of applied K.Many Atlantic Coastal Plain soils contain high levels of total K. Most of the total K in these soils is contained in mineral forms such as micas and K-feldspars. These K forms are slowly released to solution and exchangeable forms that are available to plants. Many researchers have noted a lack of crop response to K fertilization on Atlantic Coastal Plain soils. This lack of response has been ascribed to the high indigenous levels 435

Potassium Dynamics in Soils

“…The reaction rate between soil solution and exchangeable phases of K is strongly dependent on the type of clay minerals present (Sivasubramaniam and Talibudeen, 1972;Sparks, 1980;Sparks et al, 1980b,c;Jardine, 1981, 1984;Sparks and Rcchcigl, 1982;Jardine and Sparks, 1984a) and the method employed to measure the kinetics of K exchange (Sparks and Rechcigl, 1982;Sparks, 1985a,b;Sparks and Huang, 1985;Ogwada and Sparks, 1986a,b). Vermiculite, montmorillonite, kaolinite, and hydrous mica vary drastically in their ionic preferences, ion-binding affinities, and types of ion-exchange reactions.…”

“…Potassium has a polarizability equal to 0.088 nm 3 , which is higher than for Ca 2 +, Li +, Mg2 + , and Na + ions but lower than for Ba 2 +, Cs+, [NH4r, and Rb+ (Rich, 1968(Rich, , 1972Sparks, 1980;Sparks and Huang, 1985). Ions with higher polarizability are preferred in ion-exchange reactions.…”

“…All of these forms may be quantified as shown in Table 2. Soil solution K is the form taken up directly by plants and microbes and is also subject to leaching (Sparks, 1980). It is usually found in low quantities.…”

Formas de potássio em solos de várzea e sua disponibilidade para o feijoeiro

“…Considerando sua disponibilidade para as plantas, o K do solo pode ser classificado em quatro categorias, que seguem uma ordem crescente de disponibilidade: estrutural (mineral), não-trocável ou dificilmente disponível, trocável e em solução, que, somadas, fornecem o K total (Tisdale & Nelson, 1993). Como essas frações encontram-se em equilíbrio dinâmico (Sparks, 1980), extratores químicos específicos têm sido utilizados nas suas quantificações, tendo como vantagem permitir a comparação das formas de K sob diferentes condições.…”

Formas, relação quantidade/intensidade e biodisponibilidade de potássio em diferentes Latossolos

“…Estas formas, quando somadas, fornecem o K total (Tisdale et al, 1993). Essas frações encontram-se em equilíbrio dinâmico (Sparks, 1980), e extratores químicos específicos têm sido utilizados na sua quantificação, tendo como vantagem permitir a comparação das formas de K em estudos conduzidos sob diferentes condições.…”