“…The quantitative relationship between both percentages shows that a part of potassium in kalsilite is gradually released from PSF and taken up by the plant. In previous studies, the mineralogical composition, percentage of potassium released, and potassium-use efficiency of PSF have been investigated (Ando et al, 1987;Santos et al, 2016;Wu & Liu, 2007;Yao et al, 2003Yao et al, , 2005; however, the question of which potassium-containing mineral is used by plant has not been addressed. To the best of our knowledge, this study provides the first experimental evidence that AC-and CA20-extractable potassium, that is, potassium in potassium-magnesium silicate, is rapidly released from PSF and is readily available for the plant even in a short cultivation period.…”