The pH factor of soil reflects its acidity level, which is important to consider because all plants require different levels for proper growth. Testing pH levels is important, particularly when planting a garden for the first time in new soil whose acidity is unknown.
Soil pH or soil reaction is an indication of the acidity or alkalinity of soil and is measured in pH units. Soil pH is defined as the negative logarithm of the hydrogen ion concentration.
The pH scale goes from 0 to 14 with pH 7 as the neutral point. As the amount of hydrogen ions in the soil increases the soil pH decreases thus becoming more acidic.
From pH 7 to 0 the soil is increasingly more acidic and from pH 7 to 14 the soil is increasingly more alkaline or basic. Descriptive terms commonly associated with certain ranges in soil pH are: The most accurate method of determining soil pH is by a pH meter. Many dyes change color with an increase or decrease of pH making it possible to estimate soil pH.
In making a pH determination on soil, the sample is saturated with the dye for a few minutes and the color observed.
This method is accurate enough for most purposes. Kits pH containing the necessary chemicals and color charts are available from garden stores. There may be considerable variation in the soil pH from one spot in a field or lawn to another.
To determine the average soil pH of a field or lawn it is necessary to collect soil from several locations and combine into one sample. Fourteen of the seventeen essential plant nutrients are obtained from the soil. Before a nutrient can be used by plants it must be dissolved in the soil solution.
Most minerals and nutrients are more soluble or available in acid soils than in neutral or slightly alkaline soils. Phosphorus is never readily soluble in the soil but is most available in soil with a pH range centered around 6.
Extremely and strongly acid soils pH 4. A pH range of approximately 6 to 7 promotes the most ready availability of plant nutrients. But some plants, such as azaleas, rhododendrons, blueberries, white potatoes and conifer trees, tolerate strong acid soils and grow well.
Also, some plants do well only in slightly acid to moderately alkaline soils. However, a slightly alkaline pH 7. The soil pH can also influence plant growth by its effect on activity of beneficial microorganisms Bacteria that decompose soil organic matter are hindered in strong acid soils.
This prevents organic matter from breaking down, resulting in an accumulation of organic matter and the tie up of nutrients, particularly nitrogen, that are held in the organic matter.
Changes in Soil pH Soils tend to become acidic as a result of: Strongly acid soils are usually the result of the action of these strong organic and inorganic acids.
Lime is usually added to acid soils to increase soil pH. The addition of lime not only replaces hydrogen ions and raises soil pH, thereby eliminating most major problems associated with acid soils but it also provides two nutrients, calcium and magnesium to the soil.
Lime also makes phosphorus that is added to the soil more available for plant growth and increases the availability of nitrogen by hastening the decomposition of organic matter. Liming materials are relatively inexpensive, comparatively mild to handle and leave no objectionable residues in the soil.
Some common liming materials are: The amount of lime to apply to correct a soil acidity problem is affected by a number of factors, including soil pH, texture amount of sand, silt and claystructure, and amount of organic matter.
In addition to soil variables the crops or plants to be grown influence the amount of lime needed. In addition to monitoring soil pH the nutrient status of the soil should be examined. To obtain soil sampling instructions and kits along with specific recommendation contact Cornell Cooperative Extension listed in your local phone book under United States Government Offices - Agriculture Department.
Illustration by Robert Schmedicke.The overall effect on soil pH is close to neutral. However, in reality, we often over apply ammonium-based N fertilizers to compensate for the nitrate leached from the soil, thus soil pH is reduced over time, partly because of the accumulation of H + released through nitrification process.
Page 1 Guides for Educators Soil pH is a measure of soil acidity or alkalinity. It is an important indicator of soil health.
It affects crop yields, crop suitability, plant nutrient availability, and soil micro-organism activity which influence key soil processes.
When soil pH drops, aluminium becomes soluble and the amount of aluminium in the soil solution increases. As a rule of thumb, soil aluminium concentration of parts per million (ppm) is toxic to the roots of sensitive plant species and above 5ppm is toxic to tolerant species.
Inherent Factors Affecting Soil pH Inherent factors affecting soil pH such as climate, mineral content and soil texture cannot be changed. Natural soil pH reflects the combined effects ofsoil-forming factors parent material, (time, relief or topography, climate, and organisms).
The pH of newly formed soils is determined by. Fertilizers and Soil Acidity Mosaic Fertilizer Technology Research Centre - April Source: Fertiliser Technology Resarch Centre, The University of Adelaide, Australia Fertilizers and Soil Acidity - Potassium fertilizers have little or no effect on soil pH.
The pH level is naturally changed by encounters with other materials. In the encounters between water and soil, soil is generally the most changed of the two, while water tends to stay the same or be purified by its encounter, moving closer to a neutral pH level.