Optimizing the application of potassium sulfate fertilizer based on the variation in soil mineral accumulation and tobacco growth: a 10-year field experiment

Potassium (K) is an essential element in tobacco production, especially in Shandong, the main tobacco-growing province in China, where the improvement of tobacco yield and quality is limited by soil K deficiency, thus potassium sulfate (K 2 SO 4 ) fertilizer is popularly applied by farmers. However, it is unknown how soil physicochemical characteristics and tobacco growth respond to the utilization of K 2 SO 4 fertilizer in the long term. This study aimed to determine the optimal application amount of K 2 SO 4 fertilizer to improve soil health and enhance tobacco leaf K content without yield loss. Four treatments were tested, namely mixes of 82.5 kg a.i. ha −1 K 2 O + 66.0 kg a.i. ha −1 sulfur (K 82.5 + S 66 ), 165.0 + 95.7 (K 165 + S 95.7 ), 247.5 + 125.4 (K 247.5 + S 125.4 ) and no fertilizer (CK). Excessive use of K 2 SO 4 fertilizer led to soil acidification and a significant decrease in arylsulfatase activity. Soil available potassium (AK) and pH, that exhibited diverse responses over course of 10 years, increased and decreased with the amount of K 2 SO 4 fertilizer applied, respectively. Moreover, the K content in tobacco plants significantly increased after K 2 SO 4 fertilizer application, with that in tobacco leaves being 162.3% and 45.2% higher than that in tobacco roots and stems, respectively. Soil AK exhibited a significant positive correlation with the K content in tobacco roots, stems, and leaves, while soil pH showed the opposite performance. Soil pH is a pivotal factor influencing soil physicochemical characteristics, total dry matter and the K content in tobacco tissue. The application of K 165 + S 95.7 was more reasonable and economical in terms of matter accumulation. We concluded that the optimal application rate in Shandong was K 165 + S 95.7 , which not only improved soil health and tobacco leaf K content but also reduced input without causing yield loss.