How Ozonated Irrigation Water Improved Root Development and Reduced Greenhouse Crop Losses by Millions

Water quality is one of the most important and most overlooked parts of commercial greenhouse production. Dirty irrigation water carries pathogens, algae, and biofilm that weaken roots, slow growth, and drive up crop losses. A large study at Metrolina Greenhouses put numbers to what better water can do, and they are hard to argue with: faster rooting, shorter crop cycles, less fungicide, and a drop in crop shrink worth millions of dollars a year.

The challenge: pond and well water at scale

Metrolina is one of the largest greenhouse operations in the country, growing millions of plants a year for major retailers. Like most large facilities, it leans on pond and well water for irrigation. That is cost-effective, but untreated it brings algae in the lines, biofilm in the pipes and filters, pathogens in the water, slower rooting in young plants, and more disease pressure. All of that eventually shows up in plant quality and cost. Before the water treatment upgrade, the operation was dumping between 1.7 and 5.4 million dollars in crop every year.

The solution: ozone on the pond water

To clean up the irrigation water, the greenhouse put in an ozone system that treats pond water before it ever reaches the plants. Ozone is a strong oxidizer. It destroys pathogens and microorganisms, breaks down organic contaminants, holds back algae, clears biofilm out of the lines, and delivers cleaner water straight to the roots. Unlike a lot of chemical treatments, it breaks back down into oxygen and leaves no residue.

The trial: pansy roots after 14 days

A controlled trial compared pansy plugs grown on three water sources: ozonated pond water, raw pond water, and raw well water. After 14 days, the plugs on ozonated pond water had clearly stronger roots, with faster expansion, greater density, better early vigor, and more uniform growth across the trays. Strong early roots matter because they let plants establish faster and move through production more efficiently. The Cool Wave spreading pansies told the same story: bigger plants early, more consistent trays, and faster establishment after transplanting.

What the full system delivered

After the trial, Metrolina installed a full ozone system, and the production gains were measurable. Most liners finished 7 to 10 days faster. Begonias, petunias, and marigolds ran up to two weeks faster. Pansies in 88-cell trays came in three weeks faster, and in 288-cell trays a week faster. All told, cropping cycles shrank by two to four weeks. When you grow millions of plants a year, even a few days per crop adds up to a lot more capacity.

The wins did not stop at speed. Cleaner water cut disease pressure enough to reduce fungicide use by 20 percent, which lowers cost and improves worker safety. Stronger root systems meant less shipping damage, better shelf life at retail, more drought tolerance, and higher overall quality, all of which cut returns and rejected shipments. And continuous ozone kept the irrigation infrastructure itself clean, clearing biofilm from pipes and algae from filters and emitters, which meant more uniform watering, less maintenance, and longer equipment life.

The financial impact

The clearest measure was crop shrink, the plants dumped each year. Here is how the dump losses fell as water treatment improved.

Fiscal year	Dump loss	Percent of sales
2008	$5,430,933	4.31%
2009	$4,281,259	3.29%
2010	$2,881,092	2.31%
2011	$1,789,432	1.38%
2012	$2,037,239	1.45%
2013	$2,817,851	1.93%
2014	$827,153	0.53%

By 2014, after the ozone system was in, dump losses had fallen to $827,153, just 0.53 percent of sales, down from over four percent. That is millions of dollars in recovered revenue every year.

For a grower producing millions of plants, a small gain in plant health or production speed compounds into a very large number at the end of the year.

Questions growers ask

What does ozone actually do to the water?

It disinfects irrigation water before it reaches the plants, destroying bacteria, algae, and pathogens and breaking down organic contaminants. Because it decomposes into oxygen, it leaves no chemical residue in the system.

Can irrigation water really affect root development?

Yes. Water carrying pathogens or a heavy organic load stresses roots and slows growth. Clean, well-treated water supports stronger roots and better nutrient uptake, which is exactly what the Metrolina trial showed.

Why do large greenhouses treat their water?

To keep crop quality consistent and prevent disease outbreaks. Treatment protects plants from pathogens, keeps irrigation systems clean, and makes production far more reliable.

Curious what cleaner irrigation water could do for your operation? See our plant agriculture solutions.