Release of potassium from K-bearing minerals: Effect of plant roots under P deficiency

Pot experiments were conducted, with ryegrass ( Lolium perenne L.) maize (Zea mays L ND60) and pak-choi (Brassica campestris L. ssp. chinensis (L.) Mokina. var. cammunis Tsen et Lee, cv. Wuyueman), to investigate plant mobilization of mineral K in gneiss and feldspar under P-deficient conditions. For both pak-choi and maize grown in gneiss, P-starvation led to a significant increase in K concentration in their shoots, and the net release of K from the mineral K pool was significantly enhanced when the crops grew in feldspar. The enhanced mobilization of mineral K might be attributed to the release of organic acids from the plant roots. When gneiss of various particle sizes was exposed to malic and tartaric acids, both acids had a direct positive influence on the release of mineral K from gneiss. More release of K was observed with increasing concentration of both organic acids, much more so for finer particle size fractions.