Agriculture Reference
In-Depth Information
• Concentration of dissolved electrolytes
• Temperature and phase of pore fluid
• Amount and composition of
colloids
Thestructureofsoilanditsmoisturehasahugeeffectonsoilfertility.Thisisdueinpartto
theabilityofsolublenutrientstoflowacrossporeboundariesandtobeavailableforuptake
by root systems. When the soil is non-compacted and porous, the soil has a greater water
capacity and thus has a greater capacity to hold onto electrolytic fluids. Non-compacted
soils also have a greater capacity to store and make available gases like nitrogen and
oxygen.
Incontrasttotheabovechartswhichcomparetherelativeconductivities ofrocks,asimilar
comparisoncanbemadeonfluids,e.g.theconcentrationofionsinagivenamountoffluid,
also known as salinity. For example:
• Tap water has a minimal conductivity of around .01 S/m with a salinity of about
40 ppm (parts per million)
• Seawater has a rough conductivity of 3.3 S/m with a salinity of 30,000 ppm.
Sinceseawaterhasagreaterconductanceandamuchgreatermeasureofsalinitycompared
to tap water, it conducts electricity much easier. While salts allow for greater amounts of
soil conductivity, they also need to be controlled since the presence of too much salt in the
soilcanharmplantlife.Whilethepresenceofelectrolytesisneededtopromotethehealthy
growth of plants, it needs to be balanced as either too little or too much can be harmful as
well.
It has been found that plants respond favorably to growing in warmer areas. This may be
due to the fact that the temperature of the ground affects ionic mobility since it increases
with temperature. Higher temperatures means more nutrients are available to be desorbed
from soil particles and into the soil solution.
The electrical resistivity/conductivity of soils is rather complicated, with many factors
affecting it. One of the biggest contributing factors that makes the measurement of
conductivity difficult is that land areas are typically non-uniform. What this means is that
no matter how smooth the ground looks from above, it is really composed of a mixture
of topsoil, clays, rocks and minerals, decayed matter, and likely other materials, too.
Furthermore, the fact that all of these components are of different sizes create situations
where the land mass contains a large range of pore sizes. Since resistivity is primarily
related to porosity, it becomes difficult to know the true conductivity of soil, especially in
