Key points of purchase and identification：

1. Check the composition index: give priority to the "3 20% gold ratio" products with alginic acid ≥ 20%, organic matter ≥ 20% and nitrogen, phosphorus and potassium ≥ 20%, and at the same time confirm the contents of cytokinin and medium and trace elements to avoid purchasing products with vague composition labels.

2. Verify qualifications and processes: identify production licenses, implementation standards and anti-counterfeiting traceability codes, and give priority to low-temperature extraction or physical extraction process products to avoid inferior products that cause loss of active ingredients due to high-temperature processes.

3. Intuitive identification of quality: high-quality black seaweed essence is dark green when exposed to water, snowflake-like active substances emerge after stirring, and there is no obvious precipitation after dissolution; If it is turbid, pungent smell, or too light or too black (dyed products), it should be purchased carefully.

4. Distinguish between black and white seaweed essence: black seaweed has high cost performance and strong soil improvement ability, and is suitable for early growth promotion and soil restoration. The green model has higher purity, does not pollute the fruit surface, is suitable for the fruit swelling and color changing period, and can be selected according to needs to avoid misuse.