Models for potassium release kinetics of four Humic Gleysols high in clay by electro-ultrafiltration

Abstract

Ziadi, N., Simard, R. R. and Tran, T. S. 2001. Models for potassium release kinetics of four Humic Gleysols high in clay by electro-ultrafiltration. Can. J. Soil Sci. 81: 603-611. The rate of K release from the soil solid phase to its solution, especially from its rapidly and slowly exchangeable forms, can affect plant K uptake. The electro-ultrafiltration (EUF) technique was used to kinetically characterize the K release from four soils (Humic Gleysols) from Abitibi-Temiscaming, Quebec, Canada. Potassium was desorbed from soils that received over 166 kg K ha -1 yr -1 from 1994 to 1996. The desorption was carried out for 58 min (4, 4, and every 5 min thereafter for a total of 12 desorptions) at 400 V and 80°C. The amount of K desorbed was between 199 and 342 mg kg -1 . Cumulative K desorption was described by the following six equations: power function, simplified Elovich, extended Elovich, parabolic diffusion, zero-order, and first-order. An incremental first-order equation was also tested. The studied soils have large K supplying capacities as suggested by forage K-uptake and total soil K desorption by EUF. In general, all tested equations adequately described the K release by EUF from the four soils. The incremental first-order equation, used for the first time, described well the soil K release data. The k rate constant from this model was significantly related to forage K uptake (R 2 = 0.58).Results from this study indicate that the investigated soils have large K reserves and that the incremental first-order equation and most of the cumulative ones are suitable for describing the kinetics of the large K release from these fine-textured Gleysols. Les sols à l'étude ont une grande capacité à fournir du K aux plantes tel que suggéré par le prélèvement végétal et le K total désorbé par EUF. En général, tous les modèles étudiés ont décrit adéquatement le K désorbé par EUF. Le modèle incrémentiel de premier ordre, utilisé ici pour la première fois, a décrit précisément la désorption du K. La constante de taux de désorption du K estimé par le modèle incrémentiel est significativement reliée au prélèvement du K par les fourrages (R 2 = 0.58). Les résultats obtenus indiquent que les sols étudiés ont une réserve importante en K et que le modèle incrémentiel de premier ordre ainsi que la majorité des équations cumulatives sont appropriés pour décrire la cinétique de désorption du K de ces Gleysols à texture fine.