Complex fertilizers

Classification of complex fertilizers

By the number of components, complex fertilizers are classified as:

• double, for example, containing phosphorus-potassium, nitrogen-phosphorus, or nitrogen-potassium;
• triple, containing nitrogen, phosphorus, and potassium.

By production method:

• complex;
• complex-mixed (combined);
• mixed.

By aggregate state:

• solid;
• liquid.

Application of complex fertilizers

The advantages of complex fertilizers are their high nutrient content combined with the presence of several elements at once. The production cost of complex fertilizers (per unit of nutrient) is higher than that of simple fertilizers, but the costs of delivery, storage, and application are significantly lower compared with simple fertilizers. The overall cost of using complex fertilizers, taking into account production costs, is approximately 10% lower than that of simple fertilizers.

The presence of several nutrients in one granule promotes more uniform distribution over the soil surface.

Complex fertilizers provide good availability of nutrients to the root system. According to experiments, with separate nutrition by nitrogen, phosphorus, and potassium (when they were placed in different parts of the vessel), maize developed worse and absorbed less phosphorus than with combined application with nitrogen and potassium.

The effectiveness of equal doses of complex fertilizers and of a mixture of straight fertilizers is the same in their effect on yield.

Depending on the crops, soils, and climatic conditions, complex fertilizers with different ratios and contents of nitrogen, phosphorus, and potassium are required. They are characterized by the mass ratio N:P₂O₅:K₂O, for example, 1:1.5:0.5 (nitrogen is taken as unity), or by the percentage ratio N:P₂O₅:K₂O according to the content of active ingredients, for example, 12:18:6 or 12-18-6; the sum of the percentages gives the total content of active ingredients in the fertilizer.

The most common are three-component fertilizers of grades 1:1:1; 1:1.5:1; 1:1:1.5; 1:1.5:1.5; 1:1:0.5 and two-component ones — 1:2.5:0; 1:4:0; 1:1:0; 0:1:1; 0:1:1.5.

The ratio between components in the fertilizer composition does not always correspond to crop requirements when grown on soils with different nutrient supply, therefore in such cases straight fertilizers or appropriate fertilizer mixtures are additionally applied.

Sources

1. Yagodin B. A., Zhukov Yu. P., Kobzarenko V. I. (2002). Agrochemistry. Edited by B. A. Yagodin. Moscow: Kolos.
2. Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Edited by V. G. Mineev. Moscow: Publishing House of the D. N. Pryanishnikov VNIIA.