How Clean Is Your Greenhouse Irrigation System?


High concentrations of total suspended solids due to buildup of organic matter such as peat moss, dead algae, and plant materials, or sand particles, can clog irrigation lines and reduce the efficacy of sanitation.

Water quality is a key factor affecting irrigation efficiency and crop health. Chemical, physical, and biological parameters affect the suitability of irrigation water.



Start with a standard complete nutrient analysis. Use water alkalinity and specific salts to match to fertilizers.

When it comes to cleanliness of the irrigation system, water chemistry is a major culprit for clogging irrigation systems. Iron, manganese, and calcium precipitate and clog irrigation lines. This usually happens when these elements are at high concentrations and when the water pH is above 7.0. If you notice rust or white scale on your pipes, you might want to check these numbers.

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Water pH affects the efficacy of agrochemicals (pesticides and plant growth regulators) and chlorine-based sanitizers. For example, at pH 6.0 or lower, chlorine is present mostly as hypochlorous acid, which is a strong sanitizer. At higher pH, chlorine is present mainly as hypochlorite ion, a weak sanitizer. The efficacy of chlorine, like some agrochemicals, is pH dependent.

Growers should test their water sources at least twice a year. The chemistry of the water may not change much from year to year, yet the goal is to be proactive and prevent problems. In the Northeast, we have seen sodium and chloride levels rise during summer months. We suspect the concentration of salts increases because the water levels decrease during the summer, resulting in higher salt per volume of water.


Total suspended solids (TSS) refers to the number of particles that are captured by a filter. TSS comes from a buildup of organic matter (e.g., peat moss, dead algae, or plant material, etc.) or sand particles. High concentration of TSS can clog irrigation lines and reduce the efficacy of sanitation. When cleaning surfaces or water, first remove the debris, and then sanitize.

Pond and recirculated water tends to have high TSS levels, whereas well, municipal, and rainwater tend to be clean in this aspect.

Filtration is the solution to remove suspended solids from the water. The ideal system should have multiple stages of filtration, going from coarse to fine pore filters. Right now, when most greenhouses are empty, it is a great opportunity to clean the filters, flush the irrigation lines, and clean storage tanks.


Water can be a source or dispersal mechanism for plant pathogens, algae, and biofilm. Growers don’t need to test for specific organisms unless there is an actual problem. The Guelph Lab Services is a laboratory that can screen for specific plant pathogens in water sources. To prevent plant disease, the main recommendation is to follow integrated crop management guidelines. A sanitizer at a low dose can also be applied on a continuous basis as a preventive strategy.