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The degree to which a given amount of lime per unit of soil volume will increase soil pH depends on the buffer capacity of the soil (this is generally related to soil cation exchange capacity or CEC). Most acid soils are saturated with aluminum rather than hydrogen ions. Soil acidity generally results from hydrolysis of aluminum. [4]
Then, using the initial soil pH and the aluminium content, the amount of lime needed to raise the pH to a desired level can be calculated. [68] Amendments other than agricultural lime that can be used to increase the pH of soil include wood ash, industrial calcium oxide , magnesium oxide, basic slag (calcium silicate), and oyster shells.
Some effects of agricultural lime on soil are: it increases the pH of acidic soil, reducing soil acidity and increasing alkalinity [1] it provides a source of calcium for plants; it improves water penetration for acidic soils; it improves the uptake of major plant nutrients (nitrogen, phosphorus, and potassium) of plants growing on acid soils. [2]
Soil acidification is the buildup of hydrogen cations, which reduces the soil pH. Chemically, this happens when a proton donor gets added to the soil. The donor can be an acid, such as nitric acid, sulfuric acid, or carbonic acid. It can also be a compound such as aluminium sulfate, which reacts in the soil to release protons.
Effect of soil pH on cation-exchange capacity. The amount of negative charge from deprotonation of clay hydroxy groups or organic matter depends on the pH of the surrounding solution. Increasing the pH (i.e. decreasing the concentration of H + cations) increases this variable charge, and therefore also increases the cation-exchange capacity.
While Albrecht was a highly respected soil scientist, [3] [7] he discounted soil pH, stating that "plants are not sensitive to, or limited by, a particular pH value of the soil." Instead, he believed that the benefits of liming soil stem from the additional calcium available to the plant, not the increase in pH.
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The addition of a small amount of lime, Ca(OH) 2, will displace hydronium ions from the soil colloids, causing the fixation of calcium to colloids and the evolution of CO 2 and water, with little permanent change in soil pH. The above are examples of the buffering of soil pH.