Compound fertilizers are used to express their composition with the corresponding
percentage of N-P2O5-K2O.
If a certain compound fertilizer contains 10% N, 520% P2O, and 10% K2O, the compound fertilizer is expressed as 10-20-10. Some are also marked with S after the K2O content number, such as 12-24-12 (S), which means that it contains K2SO4.
The minimum of each nutrient in the ternary compound fertilizer is not less than 4%, and the general total content is in the range of 25% to 60%. Those with a total content of 25%-30% are low-concentration compound fertilizers, those with 30%-40% are medium concentration compound fertilizers, and those with more than 40% are high-concentration compound fertilizers