zeke99
Active member
http://ohioline.osu.edu/hyg-fact/1000/1249.html
Ohio State University Extension
Horticulture and Crop Science
pH = H+ and OH-
The pH is a measure of the concentration of the hydrogen protons (H+) and hydroxide (OH-) in a solution. If hydrogen protons predominate, the solution is acidic. If hydroxides predominate, the solution is basic. pH is measured on a 0 to 14 scale. A pH of 7 indicates neutrality. pH values below 7 indicate acidic conditions; pH values above 7 indicate basic conditions.
Alkalinity: The Power to Neutralize Acids
Water alkalinity is a measure of the capacity of the water to neutralize acids. If an acid is added to water, the pH of the water will decrease because the acid adds H+. However, the decrease in pH will be more pronounced and faster for waters with low alkalinity (low capacity to neutralize an acid) than for waters with high alkalinity (high capacity to neutralize an acid). A larger amount of acid will be required to reduce one pH unit of a given volume of water with high alkalinity than the same volume of water with low alkalinity.
How pH and Alkalinity Affect Fertility
Water pH, water alkalinity, and the pH of the growing mix are closely connected. Over time, all three factors affect fertility. For example, high or low soil pH values usually produce minor element deficiencies or toxicities. Of the two, water alkalinity is more important than water pH in influencing media pH. Water with high pH but low alkalinity will have little effect on media pH over time. However, highly alkaline irrigation water, regardless of its pH, may have a profound effect on media pH. Water pH is a poor indicator of the capacity of water to modify the pH of the growing mix; alkalinity, however, is an excellent indicator. Growers who intend to manage media pH must know the alkalinity of their water. Water pH can also affect the stability of some pesticides and growth regulators. Acidifying the spray water is advisable when water pH is 7 or higher and alkalinity is 150 ppm or more.
cont.
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http://www.uaex.edu/Other_Areas/publications/PDF/FSA-6061.pdf
James Robbins Professor - Ornamentals
Univ. of Arkansas - Division of Agriculture
Irrigation Water for Greenhouses and Nurseries
pH
In general terms, pH is a measure of the hydrogen ion concentration. The pH can vary on a scale from 0-14 with a pH of 7 being neutral, less than 7 considered acid and above 7 called basic or alkaline. Irrigation water with a pH of 4 might be termed very acid and water with a pH of 8.5 very alkaline. The pH is an important parameter to know since it will influence the relative solubility of certain nutrients and can impact the solubility of certain chemicals or pesticides used in grower operations. The pH of irrigation water is not generally as critical a measurement as the pH of the media. While the term pH is often used interchangeably with alkalinity, these are two totally different parameters.
While pH is a measure of the hydrogen ion concentration, alkalinity is a relative measurement of the capacity of water to resist a change in pH or the ability of the water to change the pH of the growing media. You may wish to think of alkalinity as the buffering capacity of the water – how well it resists or causes a change in pH. It is not uncommon to have irrigation water with a pH of 7.5 (alkaline) but with a low alkalinity value that is quite acceptable for growing plants.
cont.
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http://extension.unh.edu/agric/Docs/IrriWtrQal.pdf
Irrigation Water Quality
Geoffrey Njue, Extension Educator Agricultural Resources
Brian A. Krug, Extension Specialist – Greenhouse/Floriculture
pH and Alkalinity
These two are important factors in determining the solubility of water for irrigating ornamental plants. pH is a measure of the concentrations of hydrogen ion (H+) in water or other liquids. pH is an important chemical property related to plant growth because of its effect on nutrient availability. It is therefore important to monitor and control pH during the growth of your crop. Water for irrigation should have a pH between 5.0 and 7.0. However, it is the relationship between water pH and alkalinity, namely the presence of high alkalinity that will have a more significant impact on pH control of soils and growing media. Alkalinity is a measure of the water’s ability to neutralize acidity. An alkalinity test measures the level of bicarbonates, carbonates and hydroxides in water. The results are expressed as ppm of calcium carbonate (CaCo3). Levels between 30 and 60 ppm are considered optimum for most plants.
When water having both high pH and high alkalinity is used for irrigation over time, it will significantly elevate the growing media pH to undesirable levels causing reductions in plant growth and quality. Trace elements deficiencies and imbalances of calcium (Ca) and magnesium (Mg) can result from irrigating with high alkalinity water. The problem is more serious when plants are grown in small containers because small volumes of growing media are poorly buffered to pH change. Carbonates and bicarbonates in high alkalinity water can also clog nozzles of sprayers and drip irrigation systems. These salts will also form unsightly precipitates on leaves. The activity of some pesticides and growth regulators is reduced by high alkalinity.
When the alkalinity of the water is only marginally high the use of an acidic fertilizer can be used to remedy the problem. High alkalinity waters may require acid injection as a proper solution. Common acids used are sulfuric, nitric, phosphoric and citric acids. Use caution when using nitric or phosphoric acids as they will increase the amount of nitrogen or phosphorus, respectively, to your irrigation water and your fertilizer practices may need to be adjusted. Sulfuric acid is the most common acid used due to it effectiveness without the need to change fertilization, and cost.
cont.
***
http://www.staugorchidsociety.org/PDF/IPAWaterQuality.pdf
Understanding pH management and plant nutrition
Part 2: Water quality
Bill Argo, Ph.D.
pH and Alkalinity are two different aspects of water quality
There is a great deal of confusion when it comes to understanding the definition of water pH and water alkalinity, and why they are important to the health of your plants.
The term pH is a direct measurement of the balance between acidic hydrogen ions (H+) and basic hydroxide ions (OH-), and can be measured with a pH meter. The pH of a solution can range between 0 (very acidic) and 14 (very basic). At a pH of 7.0, the concentrations of H+ and OH- are equal, and the solution is said to be neutral. When the pH is above 7.0, the concentration of OH- is higher than H+, and the solution is said to be basic or alkaline (not to be confused with alkalinity). When the solution is below 7.0, the concentration of H+ is higher than OH-, and the solution is said to be acidic.
Alkalinity is a measure of how much acid it takes to lower the pH below a certain level, also called acid-buffering capacity. Alkalinity is usually measured with a test kit where dilute acid is added until a color change occurs at a specific pH. Alkalinity is not a specific ion, but rather includes the concentration of several ions that affect acid-buffering capacity. Under most conditions, the ions that have the greatest effect on alkalinity are bicarbonates like calcium, magnesium, or sodium bicarbonate and, to a lesser extent, carbonates like calcium or sodium. Several other ions including hydroxides, phosphates, ammonium, silicates, sulfides, borates, and arsenate also can contribute to alkalinity, but their concentration is usually so low that they can be ignored.
In a water sample, the concentration of all of the ions that makes up the alkalinity term are combined and reported as equivalents of calcium carbonate (CaCO3, which is the main component of lime). Alkalinity can therefore be thought of as the “liming content” of the water. The units used to report alkalinity can be parts per million (ppm), mg/liter, or millequivalents (meq.).
Water alkalinity has a big effect on substrate pH.
When it comes to managing the pH of a substrate, the alkalinity concentration has a much greater effect than does water pH. Alkalinity (calcium bicarbonate, magnesium bicarbonate, and sodium bicarbonate) and limestone (calcium and magnesium carbonate) react very similarly when added to a substrate. And just like too much limestone, the use of irrigation water containing high levels of alkalinity can cause the pH of the substrate to increase above acceptable levels for healthy plant growth.
cont.
***
Learn it, love it, live it.
Ohio State University Extension
Horticulture and Crop Science
pH = H+ and OH-
The pH is a measure of the concentration of the hydrogen protons (H+) and hydroxide (OH-) in a solution. If hydrogen protons predominate, the solution is acidic. If hydroxides predominate, the solution is basic. pH is measured on a 0 to 14 scale. A pH of 7 indicates neutrality. pH values below 7 indicate acidic conditions; pH values above 7 indicate basic conditions.
Alkalinity: The Power to Neutralize Acids
Water alkalinity is a measure of the capacity of the water to neutralize acids. If an acid is added to water, the pH of the water will decrease because the acid adds H+. However, the decrease in pH will be more pronounced and faster for waters with low alkalinity (low capacity to neutralize an acid) than for waters with high alkalinity (high capacity to neutralize an acid). A larger amount of acid will be required to reduce one pH unit of a given volume of water with high alkalinity than the same volume of water with low alkalinity.
How pH and Alkalinity Affect Fertility
Water pH, water alkalinity, and the pH of the growing mix are closely connected. Over time, all three factors affect fertility. For example, high or low soil pH values usually produce minor element deficiencies or toxicities. Of the two, water alkalinity is more important than water pH in influencing media pH. Water with high pH but low alkalinity will have little effect on media pH over time. However, highly alkaline irrigation water, regardless of its pH, may have a profound effect on media pH. Water pH is a poor indicator of the capacity of water to modify the pH of the growing mix; alkalinity, however, is an excellent indicator. Growers who intend to manage media pH must know the alkalinity of their water. Water pH can also affect the stability of some pesticides and growth regulators. Acidifying the spray water is advisable when water pH is 7 or higher and alkalinity is 150 ppm or more.
cont.
***
http://www.uaex.edu/Other_Areas/publications/PDF/FSA-6061.pdf
James Robbins Professor - Ornamentals
Univ. of Arkansas - Division of Agriculture
Irrigation Water for Greenhouses and Nurseries
pH
In general terms, pH is a measure of the hydrogen ion concentration. The pH can vary on a scale from 0-14 with a pH of 7 being neutral, less than 7 considered acid and above 7 called basic or alkaline. Irrigation water with a pH of 4 might be termed very acid and water with a pH of 8.5 very alkaline. The pH is an important parameter to know since it will influence the relative solubility of certain nutrients and can impact the solubility of certain chemicals or pesticides used in grower operations. The pH of irrigation water is not generally as critical a measurement as the pH of the media. While the term pH is often used interchangeably with alkalinity, these are two totally different parameters.
While pH is a measure of the hydrogen ion concentration, alkalinity is a relative measurement of the capacity of water to resist a change in pH or the ability of the water to change the pH of the growing media. You may wish to think of alkalinity as the buffering capacity of the water – how well it resists or causes a change in pH. It is not uncommon to have irrigation water with a pH of 7.5 (alkaline) but with a low alkalinity value that is quite acceptable for growing plants.
cont.
***
http://extension.unh.edu/agric/Docs/IrriWtrQal.pdf
Irrigation Water Quality
Geoffrey Njue, Extension Educator Agricultural Resources
Brian A. Krug, Extension Specialist – Greenhouse/Floriculture
pH and Alkalinity
These two are important factors in determining the solubility of water for irrigating ornamental plants. pH is a measure of the concentrations of hydrogen ion (H+) in water or other liquids. pH is an important chemical property related to plant growth because of its effect on nutrient availability. It is therefore important to monitor and control pH during the growth of your crop. Water for irrigation should have a pH between 5.0 and 7.0. However, it is the relationship between water pH and alkalinity, namely the presence of high alkalinity that will have a more significant impact on pH control of soils and growing media. Alkalinity is a measure of the water’s ability to neutralize acidity. An alkalinity test measures the level of bicarbonates, carbonates and hydroxides in water. The results are expressed as ppm of calcium carbonate (CaCo3). Levels between 30 and 60 ppm are considered optimum for most plants.
When water having both high pH and high alkalinity is used for irrigation over time, it will significantly elevate the growing media pH to undesirable levels causing reductions in plant growth and quality. Trace elements deficiencies and imbalances of calcium (Ca) and magnesium (Mg) can result from irrigating with high alkalinity water. The problem is more serious when plants are grown in small containers because small volumes of growing media are poorly buffered to pH change. Carbonates and bicarbonates in high alkalinity water can also clog nozzles of sprayers and drip irrigation systems. These salts will also form unsightly precipitates on leaves. The activity of some pesticides and growth regulators is reduced by high alkalinity.
When the alkalinity of the water is only marginally high the use of an acidic fertilizer can be used to remedy the problem. High alkalinity waters may require acid injection as a proper solution. Common acids used are sulfuric, nitric, phosphoric and citric acids. Use caution when using nitric or phosphoric acids as they will increase the amount of nitrogen or phosphorus, respectively, to your irrigation water and your fertilizer practices may need to be adjusted. Sulfuric acid is the most common acid used due to it effectiveness without the need to change fertilization, and cost.
cont.
***
http://www.staugorchidsociety.org/PDF/IPAWaterQuality.pdf
Understanding pH management and plant nutrition
Part 2: Water quality
Bill Argo, Ph.D.
pH and Alkalinity are two different aspects of water quality
There is a great deal of confusion when it comes to understanding the definition of water pH and water alkalinity, and why they are important to the health of your plants.
The term pH is a direct measurement of the balance between acidic hydrogen ions (H+) and basic hydroxide ions (OH-), and can be measured with a pH meter. The pH of a solution can range between 0 (very acidic) and 14 (very basic). At a pH of 7.0, the concentrations of H+ and OH- are equal, and the solution is said to be neutral. When the pH is above 7.0, the concentration of OH- is higher than H+, and the solution is said to be basic or alkaline (not to be confused with alkalinity). When the solution is below 7.0, the concentration of H+ is higher than OH-, and the solution is said to be acidic.
Alkalinity is a measure of how much acid it takes to lower the pH below a certain level, also called acid-buffering capacity. Alkalinity is usually measured with a test kit where dilute acid is added until a color change occurs at a specific pH. Alkalinity is not a specific ion, but rather includes the concentration of several ions that affect acid-buffering capacity. Under most conditions, the ions that have the greatest effect on alkalinity are bicarbonates like calcium, magnesium, or sodium bicarbonate and, to a lesser extent, carbonates like calcium or sodium. Several other ions including hydroxides, phosphates, ammonium, silicates, sulfides, borates, and arsenate also can contribute to alkalinity, but their concentration is usually so low that they can be ignored.
In a water sample, the concentration of all of the ions that makes up the alkalinity term are combined and reported as equivalents of calcium carbonate (CaCO3, which is the main component of lime). Alkalinity can therefore be thought of as the “liming content” of the water. The units used to report alkalinity can be parts per million (ppm), mg/liter, or millequivalents (meq.).
Water alkalinity has a big effect on substrate pH.
When it comes to managing the pH of a substrate, the alkalinity concentration has a much greater effect than does water pH. Alkalinity (calcium bicarbonate, magnesium bicarbonate, and sodium bicarbonate) and limestone (calcium and magnesium carbonate) react very similarly when added to a substrate. And just like too much limestone, the use of irrigation water containing high levels of alkalinity can cause the pH of the substrate to increase above acceptable levels for healthy plant growth.
cont.
***
Learn it, love it, live it.
