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The soil pH usually increases when the total alkalinity increases, but the balance of the added cations also has a marked effect on the soil pH. For example, increasing the amount of sodium in an alkaline soil tends to induce dissolution of calcium carbonate , which increases the pH.
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.
In low rainfall areas, unleached calcium pushes pH to 8.5 and with the addition of exchangeable sodium, soils may reach pH 10. [125] Beyond a pH of 9, plant growth is reduced. [ 126 ] High pH results in low micro-nutrient mobility, but water-soluble chelates of those nutrients can correct the deficit. [ 127 ]
Nutrients in the soil are taken up by the plant through its roots, and in particular its root hairs.To be taken up by a plant, a nutrient element must be located near the root surface; however, the supply of nutrients in contact with the root is rapidly depleted within a distance of ca. 2 mm. [14] There are three basic mechanisms whereby nutrient ions dissolved in the soil solution are brought ...
Soil has a crucial function in the global carbon cycle, with the global soil carbon pool estimated to be 2,500 gigatons. This is 3.3 times the amount of the atmospheric pool at 750 gigatons and 4.5 times the biotic pool at 560 gigatons.
It is very difficult to measure pH values of less than two in aqueous solution with a glass electrode, because the Nernst equation breaks down at such low pH values. To determine p K values of less than about 2 or more than about 11 spectrophotometric [ 60 ] [ 61 ] or NMR [ 62 ] [ 63 ] measurements may be used instead of, or combined with, pH ...
The oxidation reaction proceeds as follows: CH 2 O + H 2 O → CO 2 + 4H + + 4e −, with standard free energy of –27.4 kJ mol −1 (half-reaction). [11] Once all of the oxygen is used up, bacteria can carry out an anoxic sequence of chemical reactions as an energy source, all with negative ∆G°r values, with the reaction becoming less ...
For example, a 10-10-15 fertilizer has 10 percent nitrogen, 10 percent available phosphorus (P 2 O 5) and 15 percent water-soluble potassium (K 2 O). Sulfur is the fourth element that may be identified in a commercial analysis—e.g. 21-0-0-24 which would contain 21% nitrogen and 24% sulfate.