A complete fertilizer is a fertilizer blend or mix that contains the three main plant nutrients: nitrogen (N), phosphorus (P), and potassium (K), in the forms of potash, phosphoric acid, and nitrogen.

“N“ is the chemical symbol for nitrogen. Nitrogen takes on an array of different functions in the plant and is therefore particularly important. Mainly, it is responsible for plant growth and regeneration. If there is too little nitrogen present, the plants do not grow sufficiently and any yield decreases. An excess, however, has several disadvantages: it leads to delayed flowering and fruit ripening; plant tissue becomes very soft and therefore less stable; and eventually, diseases and pests are more likely, which is what leads to a reduction in yield.

The letter „P“ refers to Phosphorus, which is also a main nutritional element in plants. The essential functions of phosphorus care for the transmission and storage of chemical energy, as well as root formation. In addition, it is essential for photosynthesis. Thus, phosphorus is helpful from the beginning, meaning that it supports the seed, for example, during fertilization. But also later during the blooming period. A lack of phosphorus causes plants to remain small and stunted and stalks to remain thin. What's more, the leaves turn color, the roots hardly grow and flowering is delayed.

The letter „K“ stands for Potassium, the third essential nutrient. This material provides for water absorption and thus for an appropriate balance of water in the plant. That also leads to strong plant tissue and a high resilience and resistance. At the same time, it promotes resistance to diseases, extreme weather conditions, such as the cold, etc. A lack of potassium makes the plant become limp and impairs formation of the root. In addition, the plant transpires more during dry periods and takes less water. Too much potassium causes a disadvantageous concentration of salt and thus a reduced intake of positive nutrients, such as magnesium, etc. In addition to the three main nutritional elements mentioned above, which are present in large quantities in NPK fertilizer, plants still need other important nutrients such as calcium, magnesium and sulfur, and trace elements (copper, zinc, iron, etc.) for growth and the formation of biomass. Therefore, these are also found in fertilizers, but only in smaller amounts.