GLSCRP WATER USE IN SMALLHOLDER FARMING SYSTEMS:
HOW TO DEAL WITH SALINITY IN SOIL AND WATER
Background
Soil salinity is the salt content in the soil; the process of increasing the salt content is known as
salinization. Salts occurnaturally within soils and water.Salination can be caused by natural
processes such as mineral weathering.It is also common in hot and drier areas, where the fast
evaporation of water pulls salts up to thesurface of the soil and concentrates them there.Growing
plants use the water in the soil, leaving the salts behind toaccumulate. The salts also dissolve into
the groundwater in these areas.
Some farming and environmental practices can increase salinity and should be avoided.
These include forexample:
➢Removal of trees and deep-rooted plants from the environment
➢Devegetation and erosion of soil
➢Over- use of groundwater
➢Inappropriate application of fertilizer- excess nitrogen speeds up salinization
➢Excessive ploughing and bare soils – leading to compaction and lack of drainage
➢Inappropriate irrigation practices
From: https://eos.com/blog/soil-salinization/
Above: Salinization in a mustard spinach field
Right: Salt damage in maturing green beans_ Emvuleni Cooperative-Mayephu July 2023
This accumulation of water-soluble salts, mostly table salt (NaCl), but also
others, affects plant growth. Plants cannot absorb the available water
properly even when the soil is wet and wilt, are stunted, show signs of
stress and eventually die.
What can we do to avoid and manage salt build-up in our soils
The best wayto deal with soil salinization is not to let it happen. In case it did, it is important
to eradicate the problem
– the sooner, the better,
before the consequences
get toosevere. So, soil
salinization solutions
deal with prevention and
management.
Looking after the soil is the
most central requirement. A living soil with high levels of organic matter can manage
salinization a lot better than a hard, dry, infertile soil.
AA local practise to test if the water is too salty
for household use and irrigation is to make a
cup of tea with ‘Cremora’. If this milk
substitute separates in the cup, then the
water has a high level of salt.
Optimize irrigation
1.1.Alternate water sources
If your water source, such as borehole, is salty, alternate using this water, with another source,
such as rainwater, greywater or water from a river to leach some ofthe salts in the soil out
of the rootzone.
1.2.Implement good irrigation practices
There are two practices at both household
and field level that work well –short
furrow irrigation and drip irrigation.
Short furrow irrigation is a type of flood
irrigation, which adds high volumes of
water over a short time –allowing
leaching of salt below root zones.
Drip irrigation, provides small quantities of
water over a longer period, allowing soil
to remain moist and also reduces
evaporation and soil compaction,which
is common for sprinkler irrigation
systems.
Right: Short furrow irrigation in a household garden
in Mayephu and
Far right: Drip irrigation of mustard spinach at the
Duvadzi cooperative in Loloka
It is also important not to irrigate during the hottest part of the day, but preferably in thelate
afternoon. Do notover- irrigate.
Add organic matter and manure to keep
moisture in the soil.
Always add as much organic matter intothe
soil as possible, including manure,
compost, or compostable materials such
as green and dry plant material.
Use cover crops or mulch to protect the
ground surface.
Right: Example of kale intercropped with an
indigenous leafy vegetable (Cleome), in a homestead
garden in Mayephu and
Far right: Citrus trees with irrigation basins filled
with mulch. The shade of the trees further help to
reduce evaporation
Always ensure that the soil is covered, whether by mulch or a diverse range of crops. Large areas
of bare soil increase evaporation and salinization.
Plant a diverse range of crops, plants and
trees
Used mixed cropping in household garden
beds as well as fields. Plant trees in and
around the cropping area and plant a
range of multipurpose plants of
different sizes and rooting depths. This
allows access to water in the soil at
different rooting depths, different
levels of nutrient usage and reduction of
upward movement of salts in the soil.
Right: An example of a multi-cropped garden in
Mayephu, showing mixed vegetable beds,
interspersed with larger herb plants and fruit trees,
and
Far-right: Bananas planted along the edge ofa
vegetable garden in deep trenches will with organic
matter and mulched.
Plough as little as possible
Introduce systems of minimum tillage and conservation
agriculture in larger fields and refrain from using
heavy machinery. One way to do this is to construct
semi-permanent furrows and ridges in the field.
Right: The Matsambo Ngamba project in Dzumeri where Delina uses
drip irrigation – permanent furrows and ridges and mulching to
manage her soils and water. She does not intercrop, but practices
crop rotation.
Choose salt tolerant crops
Some crops are naturally more tolerant to higher levels of
salinity than others.
Below is a list of common crops in the Giyani area.
High tolerance
Medium tolerance
Low tolerance
Lucerne
Jugo beans
Maize
Sorghum
Cowpeas
Peanuts
Oats, wheat and
barley
Potatoes
Pumpkins and
marrows
Kale
Sunflower
Chinese cabbage
Beetroot
Cabbage
Lettuce
Peppers
Swiss chard
Carrots
Okra
Tomatoes
Green beans
Brinjal
Onions
Peas