Exploitation potential for nonexchangeable potassium of Lupinus albus L. and Triticum aestivum L.

Abstract

White lupin (Lupinus albus L.) and summer wheat (Triticum aestivum L.) were cultivated in a green house experiment, 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 percentage from the K0 treatment was in wheat 107% and in lupin 108%. This indicates that both plants have a good exploitation potential for nonexchangeable K+, eventhough wheat roots are three times longer than those of white lupin. The exploitation potential of wheat for nonexchangeable K+ is explained by a high root length density and by a low K+ uptake m-1 root length day-1, which enhances the release of nonexchangeable K+. It is assumed, that the exploitation potential of white lupin for nonexchangeable 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 nonexchangeable K+ of the soil.