Fertigation is the process of delivering nutrients to plants through irrigation. In hydroponic systems, this method fertilizes the root zone directly based on plant requirements, allowing plants to absorb nutrients and water efficiently while minimizing nutrient leaching.
The two types of fertigation systems are batch and inline injection. Each has its pros and cons, and choosing the best system depends on factors such as operation size and complexity, budgetary constraints and need for scalability.
Batch versus inline injection
The primary difference between batch and inline-injection fertigation is the timing of fertilizer mixing:
- With a batch system, also called a dilute tank control system, growers premix fertilizer to the desired concentration before irrigation and store the nutrient solution in tanks or reservoirs. It is then drawn from a reservoir for fertilization.
- With an inline-injection system, fertilizer is mixed with water during irrigation, either within an irrigation line or through a small mixing tank, allowing growers to vary nutrient solutions throughout the crop life cycle and adjust them during irrigation using system flow rates or electroconductivity (EC) and pH sensors.
Both systems can be manual or automated. With batch, growers can mix nutrient solutions manually or let an automated system mix them based on EC and pH levels. Inline injection can range from direct mechanical injection,[1] which draws a set amount of the nutrient solution to mix in the irrigation line, to advanced automated systems that store formulas and adjust nutrient delivery in real time based on EC and pH readings.
These systems also adjust the nutrient concentration delivered to the irrigation line based on water flow. Click here for a visual example of each system. Moreover, automation can be based on a fixed schedule or in response to moisture sensors placed in the growing medium, allowing for multiple short feedings every day, ensuring consistent nutrient delivery.
[1] If the system is not pressurized, a repressurizing pump will be required to distribute the solution.
Pros and cons of each system
Batching offers greater precision in nutrient solution preparation. Growers can ensure the correct nutrient ratios before application, and the nutrient solution remains uniform regardless of the flow rate. However, adjusting the solution during application can be difficult.
Inline injection is less precise because fertilizers are mixed during delivery. Low buffer volumes or poor blending can lead to dosing inaccuracies, resulting in poor uniformity. However, inline injection offers growers the flexibility to adjust the nutrient solution in response to the plant needs and the crop life cycle.
Inline injection is also more efficient in terms of both resources and equipment. Nutrients and water are delivered simultaneously, avoiding the risk of nutrient waste due to excess mixing and eliminating the need for large reservoirs to store premixed nutrient solutions. This makes it ideal for large-scale operations with multiple crop zones. By integrating zone controls, growers can feed crops at different growth stages from a single system.
Despite its efficiency, inline injection has steeper startup costs, especially for automated systems that require dosing pumps, injectors and sometimes advanced monitoring equipment. Batch fertigation is simpler and cheaper, requiring only a reservoir, nutrient mixing equipment, EC and pH sensors and a repressurizing pump for nutrient delivery. Modern automated inline systems, however, often integrate real-time monitoring of pH, EC and nutrient levels, with automatic adjustments based on sensor readings.
The following table provides a simplified comparison of the two fertigation systems.
Parameter
Batch
Inline injection
Nutrient solution control
Greater precision due to mixing the nutrient solution prior to fertigation
Less precision due to mixing the nutrient solution during fertigation
Nutrient solution adjustments
Harder to adjust during applications
Easier to adjust during applications
Resource efficiency
Greater risk of nutrient waste and larger equipment needed to hold the nutrient solution
Less risk of nutrient waste and smaller equipment needed
Cost
Lower upfront costs
Higher upfront costs
Ideal operation size
Small- and medium-sized operations
Large-scale, automated operations
Monitoring
Less monitoring required
Higher level of monitoring required
Ideal growing scenario
When a whole crop can be administered with a single feed solution
When irrigation scheduling and nutrient dosing are integrated
Choosing a fertigation method
Both systems have distinct advantages. The choice depends on your budget, grow-room size and crop nutrient needs:
- The batch method is best suited for operations where the entire crop can be fed with a single nutrient solution. It’s also well-suited for smaller operations that have budget constraints or don’t need multiple tanks, while offering better quality control.
- Inline injection is best suited for large-scale operations requiring multiple nutrient solutions to support crops at various growth stages or to adapt the feed strength to changing conditions without requiring numerous large reservoirs.
Ultimately, it’s best to choose the simplest method that meets a grower’s needs, as automated systems require larger budgets and greater operator vigilance.[1]
[1] Flood, David. 2013. “Nutrient Dosing.” Greenhouse Product News, August. https://gpnmag.com/article/nutrient-dosing/.
Emerald Harvest Team
[1] VPD can also be measured in pounds per square inch (psi).
[2] Jin, Dan, Shengxi Jin, and Jie Chen. 2019. “Cannabis Indoor Growing Conditions, Management Practices, and Post-Harvest Treatment: A Review.” American Journal of Plant Sciences 10: 925-946. https://doi.org/10.4236/ajps.2019.106067.
[3] Bernard-Perron, David. 2018. “Humidity for a Healthy Grow.” Cannabis Business Times, May 2. https://www.cannabisbusinesstimes.com/home/article/15696276/humidity-for-a-healthy-grow.