In Inner Mongolia, a major potato-producing region of China, suboptimal potassium (K) fertilization often compromises tuber quality and affects yield. A two-year field study (2022–2023) evaluated the effects of different K application rates and blending ratios with polyhalite (POLY4) on the mid-to-late maturing cultivar ‘Dafeng 10′. In 2022, five treatments were established: no K (2T1); conventional K (K2O 300 kg hm−2) with 13% (2T2) or 37% (2T3) POLY4; and reduced K (K2O 200 kg hm−2) with 18.5% (2T4) or 31.5% (2T5) POLY4. In 2023, four treatments were set: no K (3T1); conventional K (K2O 315 kg hm−2, 3T2); and two reduced K treatments (K2O 240 kg hm−2, 3T3; and the same blend as 2T4, 3T4). Reduced K treatments enhanced K partial factor productivity and agronomic efficiency. Specific blends (e.g., 2T3, 2T4, 3T3, 3T4) significantly (p < 0.05) improved photosynthetic parameters at 70–90 days after planting. Critically, a moderate K reduction combined with a low POLY4 ratio (18.5% in 2T4/3T4) achieved the highest yield increases (35.6% in 2022, 22.6% in 2023) without a significant yield penalty, while promoting stem K accumulation. Thus, tailored K-POLY4 blending with 18.5% POLY4 under a reduced total K rate (200 kg K2O ha−1, i.e., approximately 33–36% less than the conventional rate) is an optimal strategy for synergistically improving yield, K use efficiency, and sustainability in local potato production.
Wang et al. (Sat,) studied this question.