Das Aneignungsvermögen von Weißer Lupine und Sommerweizen für Nichtaustauschbares Kalium

Abstract

Summer wheat and white lupin were grown in small Mitscherlich pots under greenhouse conditions. Both plants were cultivated in a treatment with (K₁) and without (K₀) K fertilization The soil contained 230 g clay kg⁻¹ soil and was low in Ca-exchangeable K (47 mg K kg⁻¹ soil). The response in grain yield, as a precentage of the K₀ treatment was 107% in wheat and 108% in lupin. The relative K uptake from nonexchangeable K was between 60 and 68% of the total K uptake in white lupin and summer wheat, respectively. This indicates that both plants have a good exploitation potential for clay-fixed K, even though wheat roots were three times longer than those of white lupin. The exploitation potential of wheat for clay-fixed K is explained by a high root density and by a low K uptake m^−l root length day⁻¹, which enhances the release of nonexchangeable K. However, in contrast to phosphorus, K had noeffect on the number of proteoid root clusters of white lupin roots grown in soil. It is assumed, that the exploitation potential of white lupin for clay-fixed K is based on an excretion of citric acid by roots of white lupin. Addition of citric acid in a quantity analyzed in the rhizosphere of the proteoid roots of white lupin, increased the amount of electro-ultrafiltration (EUF) extractable clay-fixed K of the soil.