K fertilizer was studied on calcareous soil in Shanxi to see its effects on rice yield. The results showed that K fertilizer significantly increased rice yield by boosting effective ears and solid seed percentage. Specifically, K fertilizer increased ears and solid seed percent by 0.732X and 0.0836X, respectively. The regression equation between potash fertilizer and yield was determined to be Y = 6973.5 + 7.388X - 0.0280X^2.