Potassium (K) management is vital for global food security, yet both K deficit and surplus coexist in China’s rice cultivation, revealing a structural distortion. Using household-level data from over 430,000 farmers from 2003 to 2020, this study quantified the K balance and K use efficiency (KUE) across whole Chinese rice-producing regions. The results showed that China’s K balance of rice cultivation shifted from deficit to surplus overtime, with marked disparities between K-stabilizing regions and K-supplementing regions. In K-stabilizing regions, KUE remained relatively constant, improving from a slight deficit (KUE=1.2) in 2003 to a mild surplus (KUE=0.87) in 2020. In contrast, the K-supplementing regions experienced a turning point in 2011, with KUE declining by 45% during 2003–2020. Fertilizer application and straw return were the key drivers of K imbalance. Multi-scenario simulations suggest that optimizing fertilizer composition, adjusting nutrient structure, and implementing region-specific straw recycling can effectively correct current policy distortions and enhance sustainable K management.
 

Rice cultivation,Potassium,Smallholder farms,Material flow analysis,Potassium use efficiency