2. The inorganic phosphorus in the soil in the north of China is mainly calcium phosphate, and in the south it is mainly iron phosphate and aluminum salt. A considerable part of it is aluminum iron phosphate wrapped by iron oxide film, which is called closed phosphorus storage.
3. The soil total phosphorus content in China increased gradually from south to north. For example, the total phosphorus content of black soil and albic soil in Northeast China is generally 0.06% ~ 0. 15%, and that of red soil and latosol in South China is generally 0.0 1% ~ 0.03%.
4. The soil total potassium content in China is generally low in the south and high in the north. In latosol in the south, the average total potassium content is only about 0.4%, while in red soil in central and eastern China, the total potassium content is about 0.9%, while in northern China, including North China Plain, Northwest Loess Plateau and Northeast Black Soil Area, the total potassium content is generally about 65,438 0.7%.
5. The Huang-Huai-Hai Plain in China, the Northwest Loess Plateau and even Xinjiang are all short of phosphorus. However, due to long-term application of phosphorus, the effect of phosphorus fertilizer decreased in the areas originally lacking phosphorus, mainly referring to some phosphorus-deficient paddy soils in Central China and South China.
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