Soil
Salinity (or soluble salts) in mmhos/cm (1part soil
to 2 parts water method).
The total
dissolved solids (ppm or mg/L) can be approximated by
multiplying the soluble salts
(mmhos/cm) by 1280.
(Values in chart
refer to the soluble salts in mmhos/cm)
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Soil Textural Classification |
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Probable Relationship to Plant
Growth |
Sand (<15% Clay) |
Loams (15-26% Clay) |
Clay Loams (27-40% Clay) |
Clays (>40% Clay) |
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|
0.05-0.15 |
0.10-0.20 |
0.15-0.30 |
0.20-0.50 |
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Salt Buildup-CAUTION |
0.15-0.30 |
0.20-0.50 |
0.30-1.00 |
0.50-2.00 |
|
Excessive Salts |
0.30+ |
0.50+ |
1.00+ |
2.00+ |
Most salt problems develop directly from
salts added by irrigation water, therefore,
salts must be removed by leaching before
they accumulate and become a problem.
Proper
irrigation management and adequate drainage
are essential to prevent salinity problems.
The only way to remove salts from the soil is by leaching
them below the rootzone.
With adequate rainfall, leaching may not be required.
However, during drought
conditions,
leaching by applying excessive irrigation water is necessary to prevent
salinity
problems.
Where a restrictive soil layer prevents the downward movement of water, lateral
tile
drains installed directly above the restrictive layer are needed.
To leach salts below the rootzone, “extra” water is needed beyond that required to
“wet” the rootzone. The amount of the “extra” water needed to
leach salts increases with
turfgrass sensitivity and with the salt
content of the water. The best method to
help prevent
the buildup of salts in soil is by
watering turfgrass as infrequently as possible, but
deeply
irrigating when water is applied.
Where restrictive layers develop in
the rootzone, cultivation or aeration may be
required before attempting to leach salts
through the soil. Deep-tine aeration is
an effective
way to improve water movement through a
layer in the top 10 to 12 inches of the rootzone.
When sodium constitutes a significant amount of the salts
found in soil or in the
irrigation
water, additions of gypsum may be necessary. The calcium in gypsum
replaces
the
sodium on the soil particles and allows water to move the sodium below the rootzone.
Soil tests
will indicate the need for amendments such as gypsum.