When we face irrigation management in hydroponic crops and want to do it precisely and efficiently to achieve optimal production and quality levels, we must rely on various devices and sensors integrated into our fertigation system.
In any case, the design of the irrigation installation is an essential factor that is not always given proper attention in many cases. Starting with the chosen dripper, continuing through the pipe network, and ending with the irrigation head and all its components. The design and sizing of an irrigation installation for hydroponic cultivation is crucial to guarantee a uniform and homogeneous distribution of water across the farm, as well as the precise dosing of water and nutrients in this highly demanding type of crop, where margins for error are very tight.
The different modalities of hydroponic crops require distinct, specific solutions. For crops in substrate bags, coconut coir, perlite, or rockwool slabs, we will propose different devices and strategies from those we would apply in substrate-free crops, such as NFT channels or floating trays. Now we are going to focus on the first case: crops in substrate bags or rockwool.
Basically, it is about replacing the water consumed by the crop, setting an established depletion level over the available water (readily available water + reserve water). Generally, it is recommended to activate irrigation when 5% of the available water has been consumed, adding the established drainage. We call this the % depletion level, and it can vary depending on the crops and circumstances. A table that can serve as a guide for the different substrates is as follows:
In the case of coconut coir, the available water accounts for approximately 27% of the bag’s total volume. A 5% depletion of the 27% useful water represents 0.14% of the bag’s total volume, and if we add a 30% drainage, we get 0.18%. If the bag is 30 liters, the irrigation dose is 0.54 liters of water.
To activate irrigation automatically, we can use our TDR substrate probe, which accurately measures the volumetric moisture percentage, pore EC, and temperature. But additionally, it measures the plant’s water assimilation at all times, as can be seen in the following graphs. In these, we can see an example of automatic irrigation control using the TDR substrate probe and an assimilation graph at different moisture percentages, which will help us establish the moisture range where optimal assimilation occurs.
But if we want to be more precise, we must monitor the drained percentage in each irrigation, as well as the EC and pH of the drained solution. We do this using our drainage control tray, where we combine all the aforementioned parameters through the drainage control irrigation mode. This takes the most determining parameter in water assimilation as a reference for watering: solar radiation. Specifically, the accumulated solar energy for irrigation.
We will obtain a graph like the one in the image, where we see that irrigations occur within the established period and accumulate more in the middle of the day, varying the accumulated energy level for irrigation depending on the measured drainage percentage.
An example can be seen in the drainage irrigation tracking chart. In it, we see the irrigations carried out throughout a day, with all essential parameters monitored, allowing us to perfectly regulate irrigation based on the crop’s demand throughout the day.
In summary, we propose an irrigation management system for hydroponic crops with substrate that is highly practical and efficient, measuring the essential parameters with our drainage control tray and regulating the irrigation frequency based on accumulated solar energy. It is automatically controlled by our fertigation equipment and the drainage control irrigation mode.
To complement this control, we can monitor environmental parameters such as VPD, leaf temperature, PAR radiation, etc., which will allow us to precisely and efficiently manage irrigation needs and optimize production.
