Continued Irrigation in Drip Systems: How a Living Water Reservoir Can Reduce the Dose to 1:10.000
- Florian Strobel
- Nov 4
- 5 min read
Imagine your irrigation tank as a quiet partner. While the pump rests, the system keeps working. In the cistern, pipes, and emitters, beneficial microbes settle, form biofilms, detach again, and continuously re-seed the circulating water. The tank becomes a living water reservoir. This very effect allows you, after a targeted start dose, to lower the maintenance dose of our microbes in a recirculating drip system to 1:10,000. Not because less efficacy is needed, but because the system itself turns into a bioreactor. Studies on recirculating nutrient solutions show clearly that once water stays in a loop, bacterial communities increase and shift dynamically.
Why drip systems make the difference
Drip lines and tanks give microorganisms exactly what they need: residence time, surface area, and a steady, low nutrient trickle. Biofilms build quickly in drip networks, especially at emitter inlets, then decrease along the flow path. This has been reported repeatedly and also explains why biofilm can narrow passages in practice. For us that is not a malfunction as long as filtration, flushing intervals, and monitoring are set up properly. Then the biofilm becomes a reservoir that continuously enriches the water with cells.That biofilm is a real reservoir is shown by measurements in irrigation pipes: the number of bacteria bound in biofilm can at times exceed those in free water and visibly shape the microbial quality of irrigation water. With each flush impulse, cells are released and distributed throughout the network.
What our strains do in the tank
Many of our core strains are Bacillus formulations with spores. Spores are robust, withstand storage and dosing, and germinate when the right signals appear. One of the strongest germinants is the amino acid L-alanine, recognized by the GerA receptor in the spore membrane. Once germination starts, the cell continues to grow vegetatively. This mechanism is what makes recirculating tanks so valuable, because even faint organic signals from make-up water, substrate fines, or root exudates are enough to activate the starter population and multiply it in the loop.
The aha moment in the field: water, soil, plant
Under drip or deficit irrigation, PGPR reliably improve water use efficiency (WUE) and stabilize yields. This is documented in controlled trials and reviews.At the same time, bacterial exopolysaccharides (EPS) do heavy lifting in soil. EPS promote micro- and macro-aggregation, increase stability and water holding capacity, and thus provide a physical foundation for humus formation and resilient soil structure. These functions are widely described, from reviews to experimental studies.
How 1:1000 becomes a 1:10,000 maintenance dose
Start-up phase
In recirculating drip systems you dose once into the cistern, typically 1:1000. The goal is establishment in water and on surfaces.
Maintenance mode
After establishment you reduce to about 1:10,000 per make-up refill. The population is supported by growth in the tank and biofilm reservoirs. Prerequisites are sensible operating conditions: hydraulic retention time ideally 24–48 h, dissolved oxygen in a moderate range, pH roughly 6 to 8, and no residual disinfectants in the make-up water. Where necessary, degas first or run through activated carbon. This logic is consistent with the literature on microbial changes in recirculating loops and on biofilm formation in drip networks.
Comfort with a safety net
Biofilm needs to be managed. This is state of the art: screen or disc filters, documented flushing plans, and watching differential pressure. If narrowing becomes significant, physical and chemical cleanings work, after which you should re-inoculate, for example once at 1:1000, to rebuild the desired community. Current reviews and studies on emitter clogging provide clear guidance.
Quality rather than disinfection on autopilot
In greenhouse and horticultural loops it is well known that disinfection strategies can suppress pathogens but also reduce beneficial microbes. Modern guidance therefore favors risk management and monitoring over constant use of oxidants. For our protocol this means: hygiene yes, but targeted, so that the living reservoir remains the performance driver.
FAQ
When is 1:10,000 realistic?When the system recirculates, the tank provides residence time, there are no residual disinfectants, and filtration plus flushing are active. In straight through-flow systems, the standard 1:1000 to 1:5000 remains appropriate.
How long does establishment take after the start dose?Usually a few weeks, depending on temperature, pH, oxygen, flushing regime, and nutrient trace inputs.
Is it compatible with fertigation?Yes, as long as EC and pH stay in the usual range and no strong oxidants are used directly before or after microbial dosing.
How do we measure success in operation?Pragmatically: EC, pH, temperature, dissolved oxygen, filter differential pressure, uniformity of emitter flow. Optionally ATP or plate counts at the tank.
What if biofilm narrows emitters?Increase filtration and flushing. After chemical cleaning, re-inoculate. This matches the evidence on clogging and biofilm management.
Key takeaway
Recirculating drip irrigation turns the tank into a biologically active reservoir. This is well supported scientifically and explains why, after the start dose, a maintenance dose of about 1:10,000 is sufficient. The result: less fresh water, stable microbial performance, stronger soils, healthier plants.
Sources and further reading
Dynamics in recirculating nutrient solutions: Dong CJ et al., 2020, PLOS ONE. Clear shifts in bacterial communities in recirculating systems.
Biofilm in drip emitters: Ma C et al., 2024, Agricultural Water Management. Biofilm accumulates at emitter channel inlets.
Geometry vs. clogging: Yan D., 2009, Journal of Environmental Sciences. Channel geometry influences clogging.
Biofilm as bacterial reservoir: Investigations on irrigation pipes and effects on microbial water quality.
Spore germination by L-alanine: Atluri S. et al., 2006, Journal of Bacteriology/PMC. Mechanistic work on GerA receptors.
Germinant receptors overview: Aspholm M. et al., 2019, Journal of Bacteriology. Roles of receptor subunits.
PGPR and WUE: Abd El-Mageed TA et al., 2022, Horticulturae/PMC. Under drip with limited water, WUE and yield parameters improve.
WUE in practice: Le TA et al., 2018, HortScience. Deficit irrigation with high WUE.
EPS and aggregate stability: Bhagat N. et al., 2021, Microorganisms/PMC. EPS promote microaggregation, structure, and water retention.
EPS and water holding: Sher Y. et al., 2020, Soil Biology & Biochemistry. EPS improve aggregate stability and water retention.
EPS and soil structure: Zhang H. et al., 2024, Microorganisms (MDPI). Relevance of EPS-producing bacteria for aggregation.
Risk management in irrigation water: Raudales RE et al., 2014, Agricultural Water Management. Strategies for controlling pathogens, biofilms, algae in horticultural systems.
Emitter clogging and treatment: Dehghanisanij H. et al., 2025, Scientific Reports. Efficacy of cleaning strategies; consider re-inoculation after cleaning.
Garden Stock photos by Vecteezy: https://www.vecteezy.com/free-photos/garden
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