Difference between revisions of "PH"
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Soil pH controls many chemical processes that take place in the soil. It specifically affects plant nutrient availability by changing the chemical form in which these nutrients are available. The optimum pH range for most plants is between 6 and 7.5, but many plants have adapted to pH values outside this range. | Soil pH controls many chemical processes that take place in the soil. It specifically affects plant nutrient availability by changing the chemical form in which these nutrients are available. The optimum pH range for most plants is between 6 and 7.5, but many plants have adapted to pH values outside this range. | ||
| + | [[File:World Soil pH - WikiM Com.png|500px|thumb|left|Global variation in soil pH. '''<font color=red>Red</font>''' = acidic soil. '''<font color=yellow>Yellow</font>''' = neutral soil. '''<font color=blue>Blue</font>''' = alkaline soil. '''Black''' = no data.]] | ||
== Classification of soil pH ranges == | == Classification of soil pH ranges == | ||
Revision as of 07:08, 15 January 2012
- Topic in Gardening courses
Soil pH is a measure for how many H+ ions a soil contains.
pH is defined as the negative logarithm (base 10) of the activity of hydrogen ions (H+) in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic.[1] A pH of 6 means that there are 10 times more H+ ions in the soil compared to pH 7, while a pH of 3 means, for example, that there are 10,000(104) times more H+ ions in solution compared to pH 7.
Soil pH controls many chemical processes that take place in the soil. It specifically affects plant nutrient availability by changing the chemical form in which these nutrients are available. The optimum pH range for most plants is between 6 and 7.5, but many plants have adapted to pH values outside this range.
Classification of soil pH ranges
| Denomination | pH range |
|---|---|
| Ultra acid | <3.5 |
| Extreme acid | 3.5 - 4.4 |
| Very strong acid | 4.5 - 5.0 |
| Strong acid | 5.1 - 5.5 |
| Moderate acid | 5.6 -6.0 |
| Slight acid | 6.1 -6.5 |
| Neutral | 6.6 - 7.3 |
| Slightly alkaline | 7.4 - 7.8 |
| Moderately alkaline | 7.9 - 8.4 |
| Strongly alkaline | 8.5 -9.0 |
| Very strongly alkaline | >9.0 |
Source: The United States Department of Agriculture Natural Resources Conservation Service
