How to determine the nitrogen in the soil. phosphorus. The lack of potassium?

Total soil N is generally divided into five levels: <0.05%, 0.05-0.09%, 0.1-0.19%, 0.2-0.29%, and >0.3%. Total nitrogen <0.05% is a serious nitrogen deficiency in the soil, the crop grows thin, the leaves are light green, and nitrogen fertilizer must be added in time. >0.2% is rich in nitrogen, and its crops are thick and dark green. Most of the phosphorus in the soil is in a delayed state, so soil total phosphorus content can not be used as an indicator of soil phosphorus supply, high total phosphorus content does not mean that the phosphorus supply is sufficient, while the total phosphorus content is lower than At a certain level, it may mean that the supply of phosphorus is insufficient. 0.03 mol/l nh4f-0.25 mol/l hcl method 0-15 ppm low, 16-30 ppm, >30 ppm high; 0.5 mol/l nahco3 method 0-5 ppm low, 6-10 ppm, >10 ppm high. The total potassium content in soil is generally 1-2%, the highest can reach 3%, and the lower one can be lower than 0.2%. The structure of potassium accounted for about 90-98%, slow-acting potassium accounted for 2-8%, available potassium 1-2% (<30ppm is extremely low, 30-70ppm is low; 70-125ppm, potassium is ineffective; 125-170ppm High, do not need potassium).

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