Evaluation of the electro-ultrafiltration technique (EUF) as a measure of the K supplying power of Quebec soils

Abstract

The electro-ultrafiltration (EUF) method has been used to evaluate the short-term and long-term supplying power of soils for many essential plant nutrients. The objective of this study was to compare the capacity of EUF with other extraction techniques to predict the plant availability of soil K and K fertilizer responsiveness by 10 cuts of alfalfa (Medicago sativa L.) growing over a 366-day period. Increasingly higher average concentrations of soil K were extracted by EUF at 50V and 20°C (29 mg kg -~), EUF at 200 V and 20°C (48 mg kg-~), 0.002 M SrCI 2 (55 mg kg-l), EUF at 200 V and 80°C (85mgkg ~), 0.1 M HC1 (105mgkg-l), Mehlich 3 (119mgkg ~), 1 M NHaOAc (120mgkg -~) and boiling 1 M HNO 3 (601 mg kg-~). The large content of vermiculitic minerals in the silt and clay fractions is responsible for EUF desorbing more K in 55 minutes than NH4OAc in 29 out of 30 soils. The total amount of K desorbed by EUF at 80°C was as effective as Mehlich 3-extractable K in predicting K uptake for the first three cuts and was best among the extracting procedures after boiling 1 M HNO 3 in predicting the long-term K supply, the uptake of K from non-exchangeable sources and the relative yield of alfalfa over 10 cuts. The desorption of soil K with EUF provides a better evaluation of the K-supplying power of Quebec soils than the extractants currently used, especially on a long-term basis.

Integrating knowledge of nutrient forms and dynamics into improved nutrient management practices: Atribute to Régis Simard

“…Phosphorus desorbed by EUF was also closely related to P uptake by ryegrass, except where sparingly soluble Ca phosphates were present in the soil, in which case the EUF desorbed more P than the other methods evaluated (Tran et al 1992b). Potassium desorbed by EUF at 808C was effective at predicting the long-term availability of K to alfalfa and the relative yield of alfalfa over 10 cuttings and was superior to the methods in place at the time for evaluating the K-supplying power of Quebec soils (Simard et al 1991a). The EUF technique was used by Re´gis and his colleagues to describe the P and K status and kinetics of K release of the fine textured soils (Humic Gleysols) of the Abitibi-Temiscaming region (Quebec, Canada) (Table 1) (Ziadi et al 2001b).…”

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

“…The cation exchange capacity (CEC) was determined in 1 M NH 4 OAc at pH 7 and at a soil-solution ratio of 6:25 (Hendershot et al 1993). Mineralogy of these soils was reported by Simard et al (1991).…”

“…The soils from Abitibi (Ste-Gertrude and Palmarolle) have higher clay contents than those from Temiscaming (Laverlochère and Lorrainville). All soils can be classified as rich in Mehlich 3 extractable K contents with respect to Simard et al (1991), the clay mineralogy of these soil series is dominated by vermiculite, chlorite, and hydrous mica. Feldspars were also found in the clay fraction suggesting a low degree of weathering.…”

“…These extractants are not always reliable in estimating the plant-available K from slowly exchangeable sources [Kong and Steffens (1989) and Boguslawski and Lach (1971) cited by Mengel and Uhlenbecker (1993)]. This indicates that the rate of K release from rapidly and slowly exchangeable forms to soil solution must be considered in predicting plant-available K. This rate of release cannot be adequately described by static soil-testing methods (Simard et al 1990(Simard et al , 1991Cox and Joern 1997) and kinetic studies may be more appropriate (Martin and Sparks 1983;Barber 1995). Soil K availability to plants has been successfully predicted by kinetic studies Lopez-Pineiro and Navarro 1997).…”

“…Mengel and Uhlenbecker (1993) used EUF to measure the K release rate and to evaluate its availability to ryegrass (Lolium perenne L.). They found that plant K uptake was closely related to the soil K release rate as described by a parabolic diffusion equation and suggested that the K release rate represents a reliable indicator for the plant-availability of non-exchangeable soil K. In North America, the EUF has been investigated under controlled conditions (Richards and Bates 1989;Simard et al 1991;Liu et al 1992) and no results were reported from in situ studies.…”