Testing the ability of plants to access potassium from framework silicate minerals
David A C Manning, Joana Baptista, Mallely Sanchez Limon, Kirsten Brandt
The availability of K, essential for plant growth, from syenite (a silicate rock in which potassium feldspar is the dominant mineral; N 90 wt%), and phlogopite mica has been demonstrated using carefully designed plant growth pot experiments in which the only added source of K was the mineral of interest, with no loss of nutrients through drainage. Using pure quartz sand as a soil, both growth (increase in diameter) of leek plants and K-content of the plant material showed a dose-dependent positive response to the application (114–43000 mg K/pot) of milled syenite with increases in plant diameter of 0.5–0.7 mm/week, increasing with application rate. Phlog- opite mica (114–6000 mg K/pot) supported the highest observed increase in diameter (approx. 1 mm/week) and plant K-content, both similar to that observed for a positive control (KCl). These experiments demonstrate that plants can obtain K for growth from milled syenite, in which feldspar is the dominant K-bearing mineral, and con- firm previous observations that micas can be an effective source of K.