Be able to define an acid. - Any substance that increases the hydrogen ion concentration in a solution.
Know the two ions considered acids in soils. - Hydrogen (H+) and Aluminum (Al3+).
Understand how aluminum contributes to soil acidity - Hydrolosis.
Al(H2O)6 3+ = Al(H2O)5(OH) 2+ and H+
Understand the two basic types of soil acidity discussed in class. - Active and exchangeable acidity.
Know the relationship between pH and H+ concentration in solution. - High pH = low H+ concentration
Low pH = high H+ concentration
Understand the meaning of % base saturation with respect to soil acidity. - an expression of the relative
amounts of non-acidic cations to acid cations on the exchange sites. (exchangeable bases/CEC).
Understand why many Florida soils tend to be acidic. - Due to low base saturation and the weathering of
soils which releases Al3+.
Be able to define a base. - Any substance that decreases the hydrogen ion concentration of a solution.
Be able to identify the most common base used to raise pH and how it works to change solution pH. -
Calcium carbonate
Ca dissociates from CO3 and binds with H+ with CO3 to make bicarbonate and neutralizes
Understand soil pH buffering. - Basically a soil's resistance towards pH change.
, Understand the relationship between CEC and % B.S. in terms of the ease or difficulty in raising pH. - CEC
determines the number of negative sites and base saturation determines the number of sites are
occupied by acid cations. Higher CEC and/or base saturation requires more liming.
Know the principal cause of soil salinity and alkalinity. What is the major effect relative to plants of high
soil salinity? - Alkalinity: low rainfall, exchange sites are dominated by base cations, and there is a
presence of carbonates
Salinity: Lack of leaching
Salinity inhibits plant growth through osmotic consequences
Know how soil salinity is typically measured and the threshold for what are considered saline soils. -
Salinity is measured through electrical conductivity (salt content of the solution). The threshold for a
saline soil is when the electrical conductivity is greater than 4 dS/m.
Know the principal method by which saline soils are reclaimed. - Leaching with High-Quality Irrigation
Water with Adequate Drainage.
Know the two most common ways that soil alkalinity is mitigated. (how to decrease pH) - Elemental
sulfur or iron sulfate are added to the soil.
Review the soil classification primer posted on Canvas. Focus on basic elements rather than the details.
More will be addressed in the review session. - .
Know which organisms are the most numerous in soils. - Bacteria
Know the differences between aerobic and anaerobic heterotrophs, particularly with respect to typical
elements used as electron acceptors. - Aerobic heterotrophs use oxygen as electron acceptors and
anaerobic heterotrophs use other elements, such as sulfur and nitrogen, as electron acceptor.
Know how aerobic and anaerobic conditions influence the decomposition of organic matter. - Aerobic
conditions allow higher rates of decomposition and anaerobic conditions inhibit these rates.
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