KasnoA., RachimA., IskandarI. and AdiningsihJ. S. (2004) “Relationship between K/Ca Ratios in the Soil Solution with the Dynamic of K in Ultisol and Vertisol of Upland Area”, Jurnal Ilmu Tanah dan Lingkungan, 6(1), pp. 7-13. doi: 10.29244/jitl.6.1.7-13.