Fertigation is currently one of the main methods for providing crops with nutrients. However, the quality of fertigation will depend on rigorous control that maximizes the use of every drop of water and every gram of fertilizer. This process is also related to the water鈥檚 electrical conductivity, as the level of dissolved salts directly influences the effectiveness of nutrient absorption by plants.
For this reason, systems have been developed that allow for extended applications and synchronize fertilizer dosing with irrigation times. These systems help prevent both over-application and insufficient dosing, which is crucial in fertilizer control.
Injecting fertilizers simultaneously during the maximum period within the irrigation schedule ensures a constant and balanced supply of nutrients over time, evenly distributed throughout the soil or substrate profile. This avoids salt spikes during fertilization periods, as well as decreases in substrate fertility between applications, ensuring that plants perform at their best throughout the entire growing cycle. Additionally, by properly managing the set point of the fertigation system, the amount of dissolved fertilizers can be precisely controlled, preventing issues such as salt accumulation.
Moreover, these systems help mitigate the risk of precipitation in pipelines and emitters, which can damage or clog irrigation systems, leading to economic losses and reduced fertilizer effectiveness.
What is EC in water?
Electrical Conductivity (EC), also known as the EC of water, is the ability of a solution to conduct electrical current and is directly related to the concentration of dissolved salts in the water. It is expressed in milliSiemens/cm (mS/cm) and serves as an indirect but reliable indicator of the amount of dissolved fertilizers. Therefore, controlling the EC of the water is essential in fertigation, as it allows the adjustment of fertilizer dosing based on the concentration of salts before and after the injection of fertilizers.
Adjustment of P, PI, and PIQ
Proportional algorithm-based (P) systems set an injection flow rate proportional to the difference between the reading and the set point. These systems are suitable for control in closed-loop circuits, such as a tank or pool. However, when used in-line, it is necessary to adjust the proportionality factor, alarms, and hysteresis to prevent excessive fluctuations in the water’s electrical conductivity.
Another more advanced system is the PI (Proportional-Integral) approach. In this case, the algorithm takes into account both the difference between the reading and the set point, as well as past errors. This provides greater stability in controlling the water’s EC and improves the accuracy of fertilizer dosing, optimizing plant performance.
Finally, the PIQ control mode adjusts the water’s EC through a PI algorithm conditioned by the water flow to be treated. Using the PEC (initial EC set point parameter), an initial dosage proportional to the water flow is established, which is later corrected through a PI curve, ensuring stability even under variable irrigation conditions.
