SSC 100 Soil pH & Sources of Soil Acidity

soil pH is also a measure of soil ___

soil acidity is also called...

pH measures concentration of ___ or ___

H^+ or OH^+ is measured by...

soil pH affects

solubility of elements, CEC, activity of soil organisms

nutrient solubility is affected by ___ levels

soil pH affects ___ solublity

certain elements become deficient or toxic at varying ___ levels

pH affects elements how

pH can change the charges of ___

colloid charge can be changed by ___ levels

low soil pH (acidic), colloids are...

at ___ colloids are filled with H^+ and become positively charged

high soil pH (basic), colloids are...

at ___ colloids have free exchange sites and are negatively charged

humus, oxides, and some 1:1 clays are pH (dependent/independent)

___ are pH dependent and/or have variable charges

2:1 clays have pH's that are (dependent/independent)

___ are pH independent

anion exchange capacity increases as pH (rises/lowers)

the lower the pH, the higher the ___ exchange capacity

cation exchange capacity increases as pH (rises/lowers)

the higher the pH, the higher the ___ exchange capacity

what pH is aluminum toxic

below a pH of 5 ___ is toxic

fungi are (tolerant/intolerant) of pH changes

___ are tolerant of pH changes

bacteria are (tolerant/intolerant) of pH changes

___ are intolerant of pH changes

chemical reactions in soil increase acidity by...

____ release H^+ and OH^+

biological activity increases soil acidity by...

___ respires oxygen and releases CO2

plant nutrient uptake increases acidity by...

___ exchanges H^+ ions for other nutrients

acid cations increase acidity by...

___ tend to hydrolyze water and release H^+ ions

basic cations are...

any cation that does not increase acidity is called...

high rainfall increases acidity by...

___ forms carbonic acid in the air, which increases soil acidity

weathering increases acidity by...

___ causes releasing and leaching of basic cations and hydrolyzing minerals, which increases soil acidity

minerals with aluminum are more (acidic/basic)

minerals with ___ are more acidic

excessive nitrogen fertilization (increases/decreases) soil pH

excessive ___ increases soil pH

combustion of fossil fuels increases soil acidity by...

elements from ___ combine with water to increase soil acidity