Post by Ask Jan on Apr 25, 2011 15:08:07 GMT -8
In a solution--the degree of acidity or alkalinity of a substance.
"P" stands for "potenz"
"H" stands for hydrogen
pH Scale-0--14 ( 7 neutral) 0-strong acid 14-strong alkaline. Disease thrives in acidity!
HOW pH AFFECTS PLANT GROWTH
PH AND HOW IT AFFECTS PLANT GROWTH
The concentration of the hydrogen ion [H+] activity in a solution determines pH. pH or hydrogen power in a solution determines the degree of acidity or alkalinity of a substance.
An acid is a chemical that releases hydrogen H+ ions when it is dissolved in water (neutral). Giving it a pH value below seven (7).
An alkali is the opposite of acid. It removes hydrogen ions from a solution. When an alkali is added to an acid (in the correct proportions), it neutralizes the acid. Alkalis have very low hydrogen ion concentrations.
pH is the potential for attracting hydrogen (water).
0 7 14
Acid Neutral Alkaline
he soil pH value is a measure of soil acidity or alkalinity. Soil pH directly affects nutrient availability. The pH scale ranges from zero to fourteen (0-14), with seven (7) as neutral. Numbers less than seven indicate acidity while numbers greater than seven (7) indicate alkalinity.
The pH value of a soil or medium is one of a number of environmental conditions that affects the quality of plant growth. The soil pH value directly affects nutrient availability. Plants thrive best in different soil pH ranges.
Plants thrive best in different soil pH ranges. Blueberries and conifers thrive best in acid soils (5.0—6.5). Vegetables and grasses do best in slightly acid soils (5.8—6.5). pH values above or below these ranges may result in less vigorous growth and nutrient deficiencies.
Nutrients for healthy plant growth are divided into categories: macronutrients (elements needed in larger amounts) which are divided into primary and secondary nutrients and micronutrients (elements needed in small amounts). Most secondary and micronutrient deficiencies are easily corrected by keeping your medium at the optimum pH value.
The major impact that extremes in pH have on plant growth are related to the availability of plant nutrients or the soil concentration of plant-toxic minerals. In highly acid soils, aluminum and manganese can become more available and more toxic to the plant. Also at low pH values, calcium, phosphorous and magnesium are less available to the plant. At pH values of 6.5 and above, phosphorous and most of the micronutrients become less available.
With hydroponic methods, beneficial microorganisms traditionally play a much less significant role in plant growth than gardening in soil. Instead of relying on microorganisms to help chelate and transport nutrients into the plant, fresh nutrients are continuously brought into contact with plant roots by the hydroponic system. Maximum nutrient absorption rates under these circumstances tend to occur around 5.5. When gardening in soil (especially organically) nutrients are not constantly brought into contact with the roots by a hydro-system. Instead, microorganisms living in the soil produce complex carbohydrates that the plant uses for energy, living enzymes that facilitate a number of biological activities in the plant, and fulvic and humic acids, which chelate large nutrient molecules into smaller molecules that the plant can readily absorb.
Furthermore, beneficial fungus in the soil called mycorrhizae act as a very substantial secondary root system and help transport these substances to the plants roots in exchange for substances excreted by plant roots, which the mycorrhizae use as a food source.
For these processes to occur, the beneficial microorganisms must be well fed to keep working efficiently. These microorganisms prefer a pH of 6.5. So if gardening in organic soil, you want a pH of 6.5. The easiest way to adjust the pH in an organic soil is to add two or three teaspoons of hydrated lime for each gallon of soil. Alternatively, use a quarter cup of clean oak wood ash to every gallon of soil. This will add calcium and phosphorous and adjust the pH.
In general, most plants grow by absorbing nutrients from the soil. Their ability to do this depends on the nature of the soil. Depending on its location, a soil contains some combination of sand, silt, clay and organic matter. The makeup of a soil (soil texture) and its acidity (pH) determine the extent to which nutrients are available to plants.
Soil pH is one of the most important properties that affect the availability of nutrients. If the pH is correct, then microbial populations will increase. These microbes convert nitrogen and sulfur into forms that plants can use. Just throwing out fertilizers does not help. All fertilizers must be changed into elements that plants can use (absorb). It is the microorganisms, the bacteria, the fungi that do these jobs for and with our plants.
The pH of a plant influences its growth in that it affects the availability of needed nutrients. A low pH can affect the soil’s ionic balance. It can drain nutrients from the soil so they do not reach plant roots. Soil pH also controls the solubility of nutrients and minerals that are needed for plants to grow. Solubility is important because fourteen of the seventeen plant nutrients that are necessary for plant growth are derived from the soil solution.
i. Chelate - to combine with (a metal) to form a hydrogen bond. A compound formed by chelation. Of trace metals in nutrient solutions.
ii. Mycorrhizae-the symbiotic association of the mycelium of a fungus (basidiomycetes and ascomycetes) with the roots of a seed plant in which the hyphae form an interwoven mass investing the root tips or penetrate the root wall.
iii. Hydroponic-the growing of plants in nutrient solutions with or without sand, gravel, or other inert medium to provide mechanical support.