Relation Du Potassium Extrait Par Euf Et Quelques Méthodes Chimiques Avec Les Propriétés Du Sol Et Le Rendement Des Plantes

Abstract

The objectives of this study were to compare the EUF procedures (50, 200 and 400 V) and some chemical methods (1 N NH4OAc, 0.01 M CaCl2, 1 N HNO3) in order to estimate the K fertility levels of 60 Quebec soils. The EUF-50 V-K quantities corresponded to CaCl2-K while EUF-(50 + 200 + 400 V) to acetate-K. The relations between EUF-(50 V)-K, EUF-(200 V)-K to Acetate-K were improved when introducing clay contents, CEC values and K saturation levels. On the other hand, soil pH, carbonate and exchangeable (Ca+Mg) contents had significant effects on the relations between EUF-400 V-K and Acetate-K. A greenhouse experiment, using ryegrass as the test plant, was carried out on these soils with two treatments (complete fertilization with and without K). EUF-400 V-K, Acetate-K and EUF-(50 + 200 + 400 V)-K were the best criteria to estimate relative yields and K uptake by the plant. EUF-(50 + 200 V) underestimates K fertility level for soils rich in clay, having high pH (H2O) or exchangeable (Ca+Mg) contents. Higher correlation coefficients for K uptake by the plant were obtained in multiple regression where EUF-(50 + 200 V)-K and EUF-400 V-K were taken into account. The relation between plant K uptake and K values determined by all methods were improved by considering the K saturation levels on cation exchange sites. Acetate-K contents explained up to 88% of the variation in K uptake when K saturation level was introduced. Finally, this method can overestimate the K fertility levels for soils rich in clay or organic matter. Key words: Electro-ultrafiltration, available K, soil properties, exchangeable K

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

“…Tran et al (1987) also found that the amount of clay improved very significantly the prediction of K uptake of the cuts of rye-grass by EUF-I or by (Y) the sum of EUF-I and EUF-II. However this was not the case for the EUF-III fraction.…”

“…With the exception of the Coaticook soil, the total amount of K desorbed by EUF (EUF-I + EUF-II + EUF-80) was greater than the amount of K extracted by NH4OAc. On average, EUF extracted a significant portion (42 mg kg -~) of the slowly exchangeable K. Tran et al (1987) observed that the total amount of K desorbed (EUF-I + EUF-II + EUF-III) by EUF ~ over 35min was greater than the amount of NH4OAc-K on several soils of the area. However, in most studies, the amount of NH4OAc-K is greater than the total amount of K desorbed by EUF over a 35-minute period (Simonis and Nemeth, 1985;Venter, 1985) and over 65 minutes (Sinclair, 1980).…”

“…Tran et al (1987) have observed that a single extraction at 80°C best predicted the relative dry matter accumulation of three cuts of rye-grass. In the present study, alfalfa obtained a large part of its K from the slowly-exchangeable forms (Simard et al, 1990).…”

“…Sinclair (1980) found that the amount desorbed in 10 minutes (K-EUF-I) was better related to K uptake of a first cut of ryegrass than NH4OAc-K. However, when the uptake is measured over 2 or 3 successive cuts, this fraction is less successful than the amount desorbed over 35 minutes (EUF-I+EUF-II + EUF-III), the latter being as successful as NH4OAc-K in predicting plant-available K (Sinclair, 1980;Tran et al, 1987). When the uptake is measured on a long-term basis, most studies have shown that the total amount of K desorbed over 35 minutes (EUF-I + EUF-II + EUF-III) or 65 minutes is superior to NH4OAc-K in predicting plant uptake of soil K (Ramanathan and Nemeth, 1982;Richards and Bates, 1989;Sinclair, 1980;Wanasuria et al, 1981).…”

“…The EUF technique is able to desorb a certain portion of this slowly exchangeable fraction (Nemeth, 1979;Richards and Bates, 1989;Tran et al, 1987). The soils from Qu6bec hold important reserves of soil K in primary mineral forms (AI-Kanani et al, 1984;Simard et al, 1989).…”