Agriculture Reference
In-Depth Information
However, in soil, full reduction-oxidation reactions (also known as redox reactions) take
This explains why most of the soil under the electric field will maintain an overall neutral
pH, except for those portions of soil very close to the electrodes where there may be a
predominantamountof hydrogen or hydroxyl ions.ThisabundanceinH + orOH - willresult
in an increase in the soil's acidity or alkalinity levels, respectively.
Since soil becomes acidic at the anode (+) and alkaline at the cathode (-), the H + ions
(protons) generated at the anode eventually begin to propagate towards the cathode. They
move electro-kinetically towards the cathode because opposite charges attract. This
traveling set of hydrogen ions, is known as an acidic or “acid” front. It serves to further
aid in releasing ions that that have been adhered to soil particles, increasing the mobilizing
effect. The result is that it thus helps nutrients that are bound to soil particles to become
loose and more available for uptake by neighboring plants. Conversely, the mobilized OH -
ions via reduction are collectively called an alkaline or “basic” front. The acid front moves
faster than the basic front because of the higher mobility of the H + ions compared to the
OH - ions. Furthermore, since the direction of electro-osmotic flow is toward the negative
electrode, it helps promote its propagation, too.
Up to a point, certain benefits are derived as a result from an increase in soil acidification.
As the acid front moves toward the negative terminal, it can cause dissolution of minerals
and other more complex nutrients. Yet, if the electric field is present for a long time, the
soil will become more acidic throughout its volume except very near the cathodic(-) zone
where hydroxyl ions are in abundance.
As the soil becomes more acidic, it can also bring about beneficial effects for the cellular
mechanisms within the plant. Bacteria species are tolerant to a pH between 5.0 and 9.0 8 .
The most benefit to plants comes from soils in a pH range of 6.0 to 6.5, which can include:
• Major increases in nutrient availability, uptake and assimilation
• Increases in leaf respiration
• Increases in root respiration which helps nitrogen fixing bacteria
• Increases in nitrogen-fixing bacterial action leads to increases in nutrient uptake,
increased growth rate and cell elongation.
On the flip-side, if the soil becomes too acidic, the performance and health of plants will
begin to suffer. At a pH of 5.0 to 4.0, a number of side effects may begin to occur such
as the slowing down of the activity of bacterial decomposers. Nutrients would then be tied
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