Greenhouse Canada

Features Structures & Equipment Water and irrigation

January 29, 2008  By Joel Ceausu

Quality water is synonymous with quality plants. So, how often do you test your water?  Surface and shallow groundwater is more likely to undergo seasonal changes and present sudden contamination.

Regular water testing is essential for optimal crop production. Since 1992, the Québec Ministry for Parks, Environment and Sustainable Development, (MDDEP) has carried out a program tracking pesticides in rivers and wells in the agricultural milieu, according to government agronomist Richard Desrosiers.

Ministry sampling, for example, has found herbicides in the majority of Québec rivers, along with up to 20 different pesticides in the summer.


Successive micro-doses of undesirable elements in water drawn from such sources will soon burn the roots of plants and ultimately affect crop production.

In addition to private labs, Québec producers can have their water analyzed through a centre affiliated with the ministry, which provides specialized services, including lab analyses, accreditation, eco-toxicological studies and terrain surveys.

A very simple test can be done with cress, says Desrosiers, a plant that grows quickly and reacts quickly to contaminants and herbicides. It is enough to simply sow and observe the reaction. “But be sure to have an accompanying sample fed with tap or distilled water to be sure of what is really the cause,” he says. 

Rivers, ponds and lakes offer variable quality throughout the year, and often show the presence of organic contaminants like algae, pathogens and, quite often, pesticides and fertilizers.

“Rainwater is an excellent quality source with few contaminants, but you require a large tank capacity, along with the construction costs, and your supply is dependent on the climate,” says Desrosiers.

Similarly, municipal systems provide excellent aesthetic, chemical and bacteriological quality, “but their sources are varied and are dependent on a network.” Indeed, in the event of breakdown, the system can leave chlorine traces, which can damage sensitive crops. Quality can vary between points in the distribution system.

Surface and shallow groundwater is more likely to undergo seasonal changes and present sudden contamination. Often found are pythium, phytophtora and fusarium, algae, viruses and pesticides. Moreover, the presence of herbicide residues can cause damage or a slowing of plant growth, with symptoms varying along with their degree of severity. Typical damage includes yellowing (chlorosis) or tanning (necrosis) of foliar tissue, halting of growth, root atrophy, and stunted or malformed leaves and stems.

As far as wells are concerned, MDDEP results generally show the presence of pesticide residues in concentrations less than those found in surface water.

Collected surface, drainage and snowmelt waters constitute a potential source of supply water, but quality issues are about the same as those for surface water, including potential herbicide residues from treated fields, along with pathogenic organisms and suspended matter. Shallow wells and ponds must be strategically located to reduce potential contamination.

Sourcing water from a river is risky and, at minimum, requires activated carbon filtration.

Quality water is synonymous with quality plants, he says. Poor water quality is costly to use because of the number of inputs required, such as fungicides. Sometimes these inputs are not enough to counteract contaminants.

Regular water testing is essential. “Once you know the quality of your water, it will be easier to make the necessary adjustments,” says Desrosiers. “Don’t wait to lose your production and say, ‘I should have done something earlier.’ Choose a good source, and monitor it closely.”

Joel Ceausu is a freelance writer in Québec.

Print this page


Stories continue below