Potassium sulfate is a physiological acid fertilizer. Because crops absorb more or faster potassium ions than sulfate ions, it will lead to the acidification of rhizosphere soil, thus improving the availability of soil phosphorus and trace elements. This physiological acidification is particularly important for rice seedling in North China. In order to cultivate strong seedlings and reduce plant diseases and insect pests, it is required to control the pH value of the seedbed soil or nutrient soil for rice seedling cultivation to 4.5-5.5. Therefore, in addition to acid regulating with sulfuric acid water and proper application of ammonium sulfate nitrogen fertilizer, potassium sulfate should be selected as potassium fertilizer, 50 g per square meter or 5 g per seedling plate. It is helpful to acidify rhizosphere soil.
