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PROBLEM SOILS

Problem Soils: High Salts and Salinity

One of the tactics used by the Romans in their war with Photo by Brett Peshek
Carthage was to salt the crop fields so that Carthage starved.
Unfortunately, it seems like the Romans must have traveled
more than we thought, because we have soils too salty for
good growth over way too much of the world. Salt definitely
makes cropping more difficult, but it does not mean that it
is impossible to grow plants on salty soil. There are man-
agement techniques to help us do so, and of course those Photo by Keith Berns
techniques involve the use of cover crops.

Saline tolerant crops like barley and sweet clover can be used to begin the healing
process of high salinity soils—not only will this get organic mulch on the ground
but will also start to jump start the biology of these soils also.
If the soil is so salt affected that crop growth is very diffi-
cult, it may be the best option to seed the land back down
to salt tolerant perennial vegetation. Perennial forage
plants that tolerate salt include tall wheatgrass (the variety
Photo by Dale Strickler or Alkar), Saltlander green wheatgrass, fourwing saltbush
Hercules is far more palatable than older ones like Jose

(an evergreen shrub that holds its high protein leaves all

related perennial forage plant that does not spread and also
The Romans did not do this, but the end result is the same. This high salinity field winter) forage kochia (not the weed kochia, but a distantly
in South Dakota will be very unproductive unless action is taken to remedy the stays green all winter long), alfalfa, strawberry clover, and
situation. Notice all of the white salt residue on the soil surface that is left after birsdsfoot trefoil. If the soil is also very high in sodium,
excess water evaporates. application of gypsum can help move excess sodium off
Salt affects plants primarily because salt has an attraction for the soil cation exchange and out into the soil solution so it
water and can pull water away from plants. Therefore, tech- can move downward with water. Another highly effective
niques to help increase the supply of soil moisture will help way to help plants deal with salt is to inoculate with my-
plants deal with salt. Primary among those is the creation of corrhizal fungi, which not only helps the plants compete
a mulch on the soil surface, which will help increase rainfall with salt for water, but the fungal hyphae also will move
infiltration and slow evaporation. When rainfall infiltrates salt out into little “fingers” in the hyphae, and will encap-
the soil, salt is moved down in the soil, away from the root sulate the salt into sealed off hyphal fragments where they
zone. When soil moisture evaporates, salt moves back up to cannot pull water away from plants.
the soil surface and into the root zone or even the seed ger-
mination zone. A means of eliminating salt from a soil in-
volves the installation of underground drainage tubing that
empties somewhere downhill from the field, then flushing
the salt out with irrigation or rainfall; in either case, a good
mulch from residue of either a cash crop or a cover crop (or
both) is very helpful in aiding this process.

Since few cash crops tolerate salt very well, it is often the job
of a cover crop to create the initial mulch layer. Cover crops
that tend to be somewhat tolerant of salt include barley, rape-
seed, sugar beets, sorghum-sudan, Japanese millet, sweetclo-
ver, and rye. Another approach is to simply plant a very high
seeding rate of a cheap sorghum blend, just to get as many
plants out there as possible to create the initial mulch. Very salt tolerant perennials like tall wheatgrass or forage kochia may be called for
in extremely salty soils to bring them back to life and productivity.

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