Most paddy fields in China are potassium (K) insufficient, while soil inorganic amendments such as zeolite are good strategies to increase soil K content. There is limited information on the interactive effects of zeolite and K applications on rice (Oryza sativa L.) productivity, apparent K balance, and soil K balance. This two-year field study using a split-plot design with three replicates investigated the effects of zeolite and K applications on grain yield, soil available K dynamics, apparent K balance, and soil K balance in a paddy rice system. The main plots were three zeolite application rates (0, 5, and 10 t ha−1; Z0, Z5, and Z10). Within each main plot were subplots subjected to three K application rates (0, 30, and 60 kg ha−1; K0, K30, and K60). Zeolite was only applied in the first year while K was applied in both years. Results revealed that zeolite and K application, alone or in combination, significantly increased rice grain yield and economic benefit (based on resource inputs and grain value). In both years, the combination of 5 t ha−1 zeolite with 30 kg ha−1 K fertilizer (i.e., Z5K30) increased grain yield by up to 6.4% and economic benefit by up to 6.6%, relative to the most commonly used practice (i.e., Z0K60). With 5 and 10 t ha−1 zeolite amended, the highest K application rate (K60) did not further increase grain yield, but it decreased economic benefit, relative to the lower K application rate (K30). Zeolite and K application, alone or in combination, significantly increased topsoil (0–30 cm) average available K content, post-harvest aboveground K uptake, and apparent K balance in the paddy rice system. Zeolite and K application alone significantly increased soil K balance. The results of this study demonstrated that zeolite amendments increased topsoil available K, enhanced rice K uptake, alleviated negative K balance, and improved productivity and agricultural profitability of paddy cultivation. The recommended treatment Z5K30 is suitable for rice cultivation due to its higher economic and environmental benefit as compared with the commonly used farmer practices.