G
Guest
pH
The pH is a measurement of the hydrogen ions in solution; the more hydrogen ions present, the lower the pH level. The pH of your water typically doesn’t have a direct impact on the pH of your soilless growing media, but it does influence the solubility of the fertilizer and efficacy of pesticides and growth regulators applied to your crops. Generally, a water pH between 5.5-6.5 is recommended for irrigation and spray applications.
Alkalinity The water alkalinity is one of the most important factors influencing your media pH, which, in turn, affects the availability of the fertilizer nutrients to the plant. Alkalinity is a measure of the water’s buffering capacity or defined as a measure of the water’s capacity to neutralize acid. It is commonly described as liquid lime. The higher the water alkalinity, the more acid required to lower it, and the more impact it has on the media pH. Even though alkalinity is a combination of calcium, magnesium, and sodium bicarbonates and carbonates, it is usually reported as ppm or mg/l of calcium carbonate. The bicarbonates (HCO3-) and carbonates (CO3-) combine with hydrogen ions (H+) in the media, creating carbon dioxide (CO2) and water (H2O). Essentially the carbonates tie up or neutralize the free hydrogen ions. The higher the water alkalinity, the more hydrogen ions are tied up, which results in an increase of the media pH. Many factors influence the optimum alkalinity level of your irrigation water, such as the lime incorporated in the media, fertilizer selection, watering practices, and plant material being grown. The container size also influences the impact of the water alkalinity. Since a smaller soil volume contains less hydrogen, and is watered more frequently, the same water alkalinity level will cause the media pH to rise quicker in a smaller container compared to a large container. This is why a water alkalinity level of 60-80 ppm CaCO3 is recommended for plug & liner production, while 120-140 ppm CaCO3 is recommended for bedding flats and larger containers.
High alkalinity. Reduce your water alkalinity by acidifying the water with an inorganic acid, such as phosphoric, sulfuric, or nitric acid, sulfuric acid being the most common acid used. Acidifying with two types of acid may be required if you have a high water alkalinity (greater than 350 ppm CaCO3). Use sulfuric acid to lower your water alkalinity by 175-200 ppm CaCO3, then either phosphoric or nitric acid to lower it to your desired level, depending on the type of irrigation pipe in the greenhouse and crops being grown. Reducing your high water alkalinity with only one type of acid may result in excess accumulation of the nutrient associated with the acid, (such as sulfate toxicity). It’s also possible to use an organic acid, such as Citric Acid, to reduce your water alkalinity—a safe but expensive option. The organic acid can also be added directly to the fertilizer stock tank when you desire to reduce the alkalinity of the water being applied to certain crops, such as plugs and liners. Low alkalinity. You may have the opposite problem, having a low water alkalinity (less than 45 ppm CaCO3) instead of a high alkalinity. Because low-alkalinity water has minimum buffering capacity, the fertilizer applied will have more of an impact on the media pH. Feeding plants with an acid-based fertilizer, such as 20-10-20, will lower the media pH when the water alkalinity is too low. Some growers are injecting potassium bicarbonate into their water to increase their alkalinity level, but you can also maintain the correct media pH by proper fertilizer selection. Feeding with a more ‘neutral’ fertilizer, such as 17-5-17, will stabilize the media pH. Or you can alter the acid fertilizer with a basic fertilizer, such as 13-2-13 or 15-0-15 to maintain the proper media pH level. Adjust your water alkalinity to the desired range, and then test your media pH on a frequent basis to determine if the alkalinity is at the proper level. If the media pH gradually decreases over time, increase the alkalinity slightly, or feed more often with a basic fertilizer. If the media pH continues to increase over time, decrease your water alkalinity or feed with more acidic-type fertilizers.
EC levels Water quality also reflects the nutrient quality of your water. This includes the soluble salt level and the nutritional level. The soluble salt level, commonly referred as EC (Electrical Conductivity), is a measure of the total dissolved ionized material in the water. It does not tell you what specific nutrients are in the water, but gives an indication of how pure the water source is. There is an increased chance of root damage when irrigating crops with a high water EC, particularly when the elevated EC is due to high chloride and/or sodium levels, or allowing the media to dry down too far. Some plants, such as young impatiens seedlings, are very sensitive to water EC level greater than 0.25 mmhos/cm, which may cause abortion of the growing tip when irrigated overhead. Generally, an EC between 0.5-1.0 mmhos/cm is acceptable for most crops, but water with higher EC levels can be safely used when managed correctly. Ensure crops are thoroughly irrigated to leach out the excess soluble salts, use fertilizers with a low salt level, or irrigate the salt sensitive crops with a reverse osmosis-blended water source to lower the water EC level.
Generally, a high EC water contains high levels of magnesium &/or calcium ions, but this needs to be verified via a complete water analysis. Fertilizer selection is based off of the specific nutrients in the water. For example, if your water source contains a high level of boron, you may not need to provide supplemental boron to high boron-demanding crops, such as Petunias & Pansies, or you may need to use a boron-free fertilizer on crops sensitive to high boron levels, such as Poinsettias. There are also fertilizer formulations with varying levels of calcium and magnesium. The best formulation to use is based off of your calcium and magnesium levels in your irrigation water, determined by a complete water analysis. Test your water to help determine the best fertilizer formulation for the crops being grown. The water quality will vary across the country and even between neighboring greenhouses. It is imperative to have your water tested at least twice a year, testing before plug/bedding plant production and again before Poinsettia season. It should also be retested during periods of drought, which can increase the water alkalinity, or following periods of heavy rainfall, which may lower the water alkalinity. Check your water quality by in-house pH, EC, and alkalinity testing, and by sending a water sample to an agricultural testing lab. Allow the water to run for a while to flush the old water out of the line, collecting the sample close to the water source such as the well or pond. When sending a water sample to a laboratory, fill the container 100% full without any air trapped under the lid. Be proactive in your crop production via knowing your water quality, adjusting the water alkalinity and fertilizer selection based on the crops being grown to prevent nutrient problems and enhancing plant quality.
The pH is a measurement of the hydrogen ions in solution; the more hydrogen ions present, the lower the pH level. The pH of your water typically doesn’t have a direct impact on the pH of your soilless growing media, but it does influence the solubility of the fertilizer and efficacy of pesticides and growth regulators applied to your crops. Generally, a water pH between 5.5-6.5 is recommended for irrigation and spray applications.
Alkalinity The water alkalinity is one of the most important factors influencing your media pH, which, in turn, affects the availability of the fertilizer nutrients to the plant. Alkalinity is a measure of the water’s buffering capacity or defined as a measure of the water’s capacity to neutralize acid. It is commonly described as liquid lime. The higher the water alkalinity, the more acid required to lower it, and the more impact it has on the media pH. Even though alkalinity is a combination of calcium, magnesium, and sodium bicarbonates and carbonates, it is usually reported as ppm or mg/l of calcium carbonate. The bicarbonates (HCO3-) and carbonates (CO3-) combine with hydrogen ions (H+) in the media, creating carbon dioxide (CO2) and water (H2O). Essentially the carbonates tie up or neutralize the free hydrogen ions. The higher the water alkalinity, the more hydrogen ions are tied up, which results in an increase of the media pH. Many factors influence the optimum alkalinity level of your irrigation water, such as the lime incorporated in the media, fertilizer selection, watering practices, and plant material being grown. The container size also influences the impact of the water alkalinity. Since a smaller soil volume contains less hydrogen, and is watered more frequently, the same water alkalinity level will cause the media pH to rise quicker in a smaller container compared to a large container. This is why a water alkalinity level of 60-80 ppm CaCO3 is recommended for plug & liner production, while 120-140 ppm CaCO3 is recommended for bedding flats and larger containers.
High alkalinity. Reduce your water alkalinity by acidifying the water with an inorganic acid, such as phosphoric, sulfuric, or nitric acid, sulfuric acid being the most common acid used. Acidifying with two types of acid may be required if you have a high water alkalinity (greater than 350 ppm CaCO3). Use sulfuric acid to lower your water alkalinity by 175-200 ppm CaCO3, then either phosphoric or nitric acid to lower it to your desired level, depending on the type of irrigation pipe in the greenhouse and crops being grown. Reducing your high water alkalinity with only one type of acid may result in excess accumulation of the nutrient associated with the acid, (such as sulfate toxicity). It’s also possible to use an organic acid, such as Citric Acid, to reduce your water alkalinity—a safe but expensive option. The organic acid can also be added directly to the fertilizer stock tank when you desire to reduce the alkalinity of the water being applied to certain crops, such as plugs and liners. Low alkalinity. You may have the opposite problem, having a low water alkalinity (less than 45 ppm CaCO3) instead of a high alkalinity. Because low-alkalinity water has minimum buffering capacity, the fertilizer applied will have more of an impact on the media pH. Feeding plants with an acid-based fertilizer, such as 20-10-20, will lower the media pH when the water alkalinity is too low. Some growers are injecting potassium bicarbonate into their water to increase their alkalinity level, but you can also maintain the correct media pH by proper fertilizer selection. Feeding with a more ‘neutral’ fertilizer, such as 17-5-17, will stabilize the media pH. Or you can alter the acid fertilizer with a basic fertilizer, such as 13-2-13 or 15-0-15 to maintain the proper media pH level. Adjust your water alkalinity to the desired range, and then test your media pH on a frequent basis to determine if the alkalinity is at the proper level. If the media pH gradually decreases over time, increase the alkalinity slightly, or feed more often with a basic fertilizer. If the media pH continues to increase over time, decrease your water alkalinity or feed with more acidic-type fertilizers.
EC levels Water quality also reflects the nutrient quality of your water. This includes the soluble salt level and the nutritional level. The soluble salt level, commonly referred as EC (Electrical Conductivity), is a measure of the total dissolved ionized material in the water. It does not tell you what specific nutrients are in the water, but gives an indication of how pure the water source is. There is an increased chance of root damage when irrigating crops with a high water EC, particularly when the elevated EC is due to high chloride and/or sodium levels, or allowing the media to dry down too far. Some plants, such as young impatiens seedlings, are very sensitive to water EC level greater than 0.25 mmhos/cm, which may cause abortion of the growing tip when irrigated overhead. Generally, an EC between 0.5-1.0 mmhos/cm is acceptable for most crops, but water with higher EC levels can be safely used when managed correctly. Ensure crops are thoroughly irrigated to leach out the excess soluble salts, use fertilizers with a low salt level, or irrigate the salt sensitive crops with a reverse osmosis-blended water source to lower the water EC level.
Generally, a high EC water contains high levels of magnesium &/or calcium ions, but this needs to be verified via a complete water analysis. Fertilizer selection is based off of the specific nutrients in the water. For example, if your water source contains a high level of boron, you may not need to provide supplemental boron to high boron-demanding crops, such as Petunias & Pansies, or you may need to use a boron-free fertilizer on crops sensitive to high boron levels, such as Poinsettias. There are also fertilizer formulations with varying levels of calcium and magnesium. The best formulation to use is based off of your calcium and magnesium levels in your irrigation water, determined by a complete water analysis. Test your water to help determine the best fertilizer formulation for the crops being grown. The water quality will vary across the country and even between neighboring greenhouses. It is imperative to have your water tested at least twice a year, testing before plug/bedding plant production and again before Poinsettia season. It should also be retested during periods of drought, which can increase the water alkalinity, or following periods of heavy rainfall, which may lower the water alkalinity. Check your water quality by in-house pH, EC, and alkalinity testing, and by sending a water sample to an agricultural testing lab. Allow the water to run for a while to flush the old water out of the line, collecting the sample close to the water source such as the well or pond. When sending a water sample to a laboratory, fill the container 100% full without any air trapped under the lid. Be proactive in your crop production via knowing your water quality, adjusting the water alkalinity and fertilizer selection based on the crops being grown to prevent nutrient problems and enhancing plant quality.
