In automated fertigation systems, it is standard practice to premix nutrients in a concentrated form in separate tanks. The concentration of these stock tanks is usually 100:1 which means that for every 100 liters (or gallons) of water that is delivered to the plant, you will add 1 liter (or gallon) of the concentrated nutrient solution. Instead of preparing nutrient solutions in the entire water source, you can rely on these concentrated stock solutions over an extended period often several days or even weeks thereby reducing labor requirements and minimizing the risk of human error in mixing.
One might wonder why concentrated fertilizer stock solutions cannot be combined into a single tank. The primary reason lies in the chemical incompatibility of certain fertilizers when mixed at high concentrations. For example, calcium-based fertilizers must always be kept separate from phosphate and sulfate compounds in concentrated form. When calcium is mixed in high concentrations with phosphate and sulfate in water, the elements will combine and form solid particles pr precipitates in the stock tank. These precipitates will become calcium sulfate (gypsum) or calcium phosphate.
The presence of these precipitates causes two problems. First, since the precipitates settle to the bottom of the stock tanks, it means that the intended nutrients do not even reach the plants, causing nutrient deficiency and wasted costs. Even if they do reach the plants, they will be in the form of a solid and the plants will not be able to take up the nutrients. Second, they will pose operational risks to the irrigation system by clogging irrigation components, such as drip lines, filters, and emitters. Such blockages can lead to uneven distribution of water and nutrients, increasing the risk of crop stress or damage.
To avoid these issues, the fertilizers are divided into two separate stock solutions—Tank A and Tank B—with incompatible compounds assigned to different tanks. Once the stock solutions are prepared, they are individually dosed into the irrigation system at a controlled dilution rate, where they are safely mixed and delivered to the plants in the appropriate concentration.