April 15, 2008
Emergency registration for EAB, know your water
By Jen Llewellyn,
OMAFRA Nursery Crops Specialist
Just before Christmas, the Ontario Ministry of Natural Resources applied for an emergency use registration for a product that may help protect non-infested ash trees against emerald ash borer (Agrilus planipennis). The proposed product is called TreeAzin, an injectable system (Ecoject) that uses neem (azadirachtin), a plant-derived insecticide. The Ecoject system was developed by Bioforest Technologies. This company has been working with the Canadian Forestry Service to carry out efficacy trials on the Ecoject system and various insecticides (imidacloprid, azadirachtin) over the last few years. This emergency use is a short-term solution until a full registration can be achieved. Emergency uses are usually granted one year at a time. We will have more information later this spring.
When I talk to nursery growers it seems as though there are more and more reports of high soluble salts in irrigation water sources (surface and ground water). Soluble salts are quantified by a measurement under the name Electrical Conductivity or EC. The unit for this measurement is usually in mS/cm or mmho/cm (units are the same). The higher the number, the saltier the water. Salt makes it more difficult for plant roots to absorb water (physiological drought). Generally speaking, if irrigation water has an EC of > 1-1.5 (mS/cm), then you will likely have some physiological drought and root burning issues, especially in smaller pot sizes. This type of water will not be suitable for propagation culture, many floriculture crops and/or many herbaceous perennials. To help compensate for higher soluble salt levels in irrigation water, nursery growers can try irrigating longer in order to leach the salts out of the pot and prevent salt build-up. Depending on the type of salts and their concentrations, growers may get away with using salty water if they leach between 20-40 per cent of the irrigation water from the pot (i.e. increase the leaching fraction) and never let the plants dry out. This is neither efficient, nor desirable, but has been the only option for a few ornamental growers in recent years. Aside from dilution with good quality water (e.g. rain water), there is no cost-effective way to treat irrigation water to reduce the level of soluble salts. The systems that can reduce soluble salts (e.g. reverse osmosis) are too costly and do not process enough volume of water to make it feasible for irrigating multiple acres of container nursery stock.
So what are these salts and where are they coming from? The most common elements that we see causing salinity problems in southern Ontario are sodium (Na), chlorides (Cl), sulphates (SO4), and bicarbonates (HCO3-). Generally speaking, desirable concentrations (in parts per million or ppm) for these elements are <70 ppm Na, <140 ppm Cl and <200 ppm SO4. In the last few years, I have seen some wicked water test results, many with 300-1000 ppm for these specific elements. Some of the sodium and chlorides in surface water can likely be attributed to road salt concentrations in spring runoff. Although the snow melt is great for boosting the level of your irrigation pond, accompanying salt levels may outweigh the benefits. A berm may be a more desirable option in the long run. In some cases, the spikes in soluble salt levels have come on the heels of recent residential development that is close to the property in question.
What about salts in ground water? I spoke to Dr. Theo Blom at the University of Guelph about soluble salts in irrigation water. He says that the sulphates in ground water are likely from an old layer of marine substrate (gypsum, which is calcium sulphate). High sulphates are a problem all along the Niagara Escarpment and have forced some ornamental growers to use alternate water sources for irrigation.
The other common problem with irrigation water in southern Ontario is high alkalinity (bicarbonates) and high pH. The most effective way to measure alkalinity is not pH, but to measure the levels of bicarbonates and carbonates in a certified laboratory. Although there is a general correlation between bicarbonate and pH, there are exceptions to the rule and therefore only the level of bicarbonate will give a true sense of how well the water can buffer against changes in pH. The more bicarbonate the water contains, the more difficult it is to lower the pH. Generally speaking, irrigation water that contains > 200 ppm bicarbonates will have a major impact on the pH of the media and the media solution (where roots absorb water and nutrients) over time.
Just like red oaks exhibit nutrient deficiency symptoms in alkaline soils, some ornamental crops will also exhibit deficiency symptoms in container culture when irrigated with alkaline water. Even if your media starts out at pH=5.0, the alkalinity will climb significantly because the acidity is neutralized by the bicarbonates in the irrigation water with every irrigation. The residues of calcium and magnesium that remain after the water has evaporated will cause unsightly deposits on foliage and cause havoc with irrigation nozzles and lines. Dr. Blom says that the bicarbonates commonly found in our ground water are from water sources in contact with calcitic lime (calcium carbonate) or dolomitic lime (calcium magnesium carbonate) that is found in those deep layer deposits. This is also the reason why well water in southern Ontario, with high bicarbonates, is usually also high in calcium and magnesium. The total level of calcium, magnesium and iron in water is usually indicated by the term hardness.
Thankfully, high bicarbonate levels may be neutralized by acidifying the irrigation water or using ammonium containing fertilizers. When acidifying water, you’ll want to use just enough acid to neutralize all but about 60 ppm of the bicarbonate. The remaining 60 ppm will give the water some buffering capacity and provide a safeguard against over-acidification. So if the water test indicates your bicarbonate levels are 250 ppm, you will want to add just enough acid to neutralize 190 ppm bicarbonate. If you look at Table 2-4 in OMAFRA publication 370, Production Recommendations for Greenhouse Floriculture, you may calculate that it will take 20.5 L of nitric acid (67 per cent) to neutralize 190 ppm of bicarbonate in 100,000 L of water. Use proper safety precautions with using nitric acid! Never attempt to neutralize irrigation water without a proper water test that will show the exact level of bicarbonates. Always check the pH of the acidified water afterwards, as a safety mechanism.
Regular water testing will help you gain valuable information on water chemistry, so you may assess water quality issues and avert problems. Collect water samples in a clean, dry, 500 mL drinking water bottle. Keep the sample cool until delivered to the lab; microbes in the water can actually change some elemental concentrations at room temperature. There is a list of accredited labs in table 2-1 of OMAFRA publication 383, Nursery and Landscape Plant Production & IPM. Water tests usually fall under “greenhouse” or “horticultural” analysis packages and a complete test will cost about $40 per sample. All irrigation water sources should be tested. Ground water chemistry is usually more constant and should be tested at the beginning of each crop cycle. Surface water systems are much more variable and should be tested monthly during the crop cycle. Acidified and fertilized water should also be tested periodically to check the accuracy of your equipment and your calculations. Results should be filed for easy access and preferably recorded in a data software program that can chart test results over time, which can be coupled with plant health monitoring observations. I know it seems like a lot of work. I also know that you are busy. But, I guarantee that this information is going to give you greater control over crop quality and irrigation system maintenance.
Jen Llewellyn can be reached at (519) 824-4120, ext. 52671 or by e-mail at jennifer.llewellyn@ontario.ca
OMAFRA Nursery Crops Specialist
Just before Christmas, the Ontario Ministry of Natural Resources applied for an emergency use registration for a product that may help protect non-infested ash trees against emerald ash borer (Agrilus planipennis). The proposed product is called TreeAzin, an injectable system (Ecoject) that uses neem (azadirachtin), a plant-derived insecticide. The Ecoject system was developed by Bioforest Technologies. This company has been working with the Canadian Forestry Service to carry out efficacy trials on the Ecoject system and various insecticides (imidacloprid, azadirachtin) over the last few years. This emergency use is a short-term solution until a full registration can be achieved. Emergency uses are usually granted one year at a time. We will have more information later this spring.Water quality and Ontario: What’s going on?
I don’t think too many of us are bound to forget the long, hot and dry growing season of 2007, and how it took a large toll on our surface water resources. With the series of storms that occurred throughout Ontario and Quebec in late winter and the ample melt they are providing, hopefully it will put us in a better position for water quality and quantity this year. Up until 2008, milder winters were blamed for warmer than average temperatures of the Great Lakes (+2.5 C) and much reduced ice cover. These conditions led to significantly higher levels of evaporation. It may help explain the huge reduction in lake levels. Many of us are hoping this spring melt will boost the levels of our Great Lakes, hopefully back to a little closer to where they were 10-15 years ago.When I talk to nursery growers it seems as though there are more and more reports of high soluble salts in irrigation water sources (surface and ground water). Soluble salts are quantified by a measurement under the name Electrical Conductivity or EC. The unit for this measurement is usually in mS/cm or mmho/cm (units are the same). The higher the number, the saltier the water. Salt makes it more difficult for plant roots to absorb water (physiological drought). Generally speaking, if irrigation water has an EC of > 1-1.5 (mS/cm), then you will likely have some physiological drought and root burning issues, especially in smaller pot sizes. This type of water will not be suitable for propagation culture, many floriculture crops and/or many herbaceous perennials. To help compensate for higher soluble salt levels in irrigation water, nursery growers can try irrigating longer in order to leach the salts out of the pot and prevent salt build-up. Depending on the type of salts and their concentrations, growers may get away with using salty water if they leach between 20-40 per cent of the irrigation water from the pot (i.e. increase the leaching fraction) and never let the plants dry out. This is neither efficient, nor desirable, but has been the only option for a few ornamental growers in recent years. Aside from dilution with good quality water (e.g. rain water), there is no cost-effective way to treat irrigation water to reduce the level of soluble salts. The systems that can reduce soluble salts (e.g. reverse osmosis) are too costly and do not process enough volume of water to make it feasible for irrigating multiple acres of container nursery stock.
So what are these salts and where are they coming from? The most common elements that we see causing salinity problems in southern Ontario are sodium (Na), chlorides (Cl), sulphates (SO4), and bicarbonates (HCO3-). Generally speaking, desirable concentrations (in parts per million or ppm) for these elements are <70 ppm Na, <140 ppm Cl and <200 ppm SO4. In the last few years, I have seen some wicked water test results, many with 300-1000 ppm for these specific elements. Some of the sodium and chlorides in surface water can likely be attributed to road salt concentrations in spring runoff. Although the snow melt is great for boosting the level of your irrigation pond, accompanying salt levels may outweigh the benefits. A berm may be a more desirable option in the long run. In some cases, the spikes in soluble salt levels have come on the heels of recent residential development that is close to the property in question.
What about salts in ground water? I spoke to Dr. Theo Blom at the University of Guelph about soluble salts in irrigation water. He says that the sulphates in ground water are likely from an old layer of marine substrate (gypsum, which is calcium sulphate). High sulphates are a problem all along the Niagara Escarpment and have forced some ornamental growers to use alternate water sources for irrigation.
The other common problem with irrigation water in southern Ontario is high alkalinity (bicarbonates) and high pH. The most effective way to measure alkalinity is not pH, but to measure the levels of bicarbonates and carbonates in a certified laboratory. Although there is a general correlation between bicarbonate and pH, there are exceptions to the rule and therefore only the level of bicarbonate will give a true sense of how well the water can buffer against changes in pH. The more bicarbonate the water contains, the more difficult it is to lower the pH. Generally speaking, irrigation water that contains > 200 ppm bicarbonates will have a major impact on the pH of the media and the media solution (where roots absorb water and nutrients) over time.
Just like red oaks exhibit nutrient deficiency symptoms in alkaline soils, some ornamental crops will also exhibit deficiency symptoms in container culture when irrigated with alkaline water. Even if your media starts out at pH=5.0, the alkalinity will climb significantly because the acidity is neutralized by the bicarbonates in the irrigation water with every irrigation. The residues of calcium and magnesium that remain after the water has evaporated will cause unsightly deposits on foliage and cause havoc with irrigation nozzles and lines. Dr. Blom says that the bicarbonates commonly found in our ground water are from water sources in contact with calcitic lime (calcium carbonate) or dolomitic lime (calcium magnesium carbonate) that is found in those deep layer deposits. This is also the reason why well water in southern Ontario, with high bicarbonates, is usually also high in calcium and magnesium. The total level of calcium, magnesium and iron in water is usually indicated by the term hardness.
Thankfully, high bicarbonate levels may be neutralized by acidifying the irrigation water or using ammonium containing fertilizers. When acidifying water, you’ll want to use just enough acid to neutralize all but about 60 ppm of the bicarbonate. The remaining 60 ppm will give the water some buffering capacity and provide a safeguard against over-acidification. So if the water test indicates your bicarbonate levels are 250 ppm, you will want to add just enough acid to neutralize 190 ppm bicarbonate. If you look at Table 2-4 in OMAFRA publication 370, Production Recommendations for Greenhouse Floriculture, you may calculate that it will take 20.5 L of nitric acid (67 per cent) to neutralize 190 ppm of bicarbonate in 100,000 L of water. Use proper safety precautions with using nitric acid! Never attempt to neutralize irrigation water without a proper water test that will show the exact level of bicarbonates. Always check the pH of the acidified water afterwards, as a safety mechanism.
Regular water testing will help you gain valuable information on water chemistry, so you may assess water quality issues and avert problems. Collect water samples in a clean, dry, 500 mL drinking water bottle. Keep the sample cool until delivered to the lab; microbes in the water can actually change some elemental concentrations at room temperature. There is a list of accredited labs in table 2-1 of OMAFRA publication 383, Nursery and Landscape Plant Production & IPM. Water tests usually fall under “greenhouse” or “horticultural” analysis packages and a complete test will cost about $40 per sample. All irrigation water sources should be tested. Ground water chemistry is usually more constant and should be tested at the beginning of each crop cycle. Surface water systems are much more variable and should be tested monthly during the crop cycle. Acidified and fertilized water should also be tested periodically to check the accuracy of your equipment and your calculations. Results should be filed for easy access and preferably recorded in a data software program that can chart test results over time, which can be coupled with plant health monitoring observations. I know it seems like a lot of work. I also know that you are busy. But, I guarantee that this information is going to give you greater control over crop quality and irrigation system maintenance.
Jen Llewellyn can be reached at (519) 824-4120, ext. 52671 or by e-mail at jennifer.llewellyn@ontario.ca