Alkaline Soils Clay soils with a pH of more than 8.5 are classified as alkaline soils. The higher pH is caused by high quantities of salt, magnesium, and calcium. Furthermore, hard water can cause the pH of soils to rise to alkaline proportions. On the other hand, sodium carbonate is the dominant component in alkaline soil. Therefore, alkaline soils inflate when exposed to sodium carbonate. Saline Soils When there is an overabundance of sodium ions in the clay and soil complex that still includes exchangeable calcium, the soil is referred to as saline soil, brown alkali soil, or white alkali soil. This soil continues to be flocculated or granulated. As a result, it has air and water permeability. Agriculture on Saline and Alkaline Soils Coconut trees may be found in abundance in coastal settings. In addition, as previously stated, farming salt-tolerant crops such as dhaincha, berseem, and other grain legume crops may aid in the reclamation of these soils. Moreover, some of the suitable agriculture on saline-alkaline soil is mentioned below: Suitable Crops: Barley, Cotton, Sugar beet, Sugarcane, Rice, Mustard, Maize, Green Gram, Red Gram, Sunflower, Sesame, Linseed, Sorghum, Bajra, etc. Suitable Vegetables: Tomato, Cauliflower, Cabbage, Cucumber, Bitter guard, Pumpkin, Spinach, etc. Suitable Fruits: Guava, Beetroot, Asparagus, Coconut, Banana, Grape, Pomegranate, Date palm, etc. Features of Saline and Alkaline Soils The topsoil of Saline and Alkaline Soil is permeated (saturated or soaked with a material) with alkaline and saline efflorescences. Weathering produces calcium salts, magnesium, sodium, and sulfurous acid from inert rock pieces. In areas with a lower water table, salts permeate the subsurface, but in areas with high drainage, salts are washed away by running water. Certain salts are delivered in suspension by rivers. In places with a higher subsoil surface water, harmful salts are carried below by capillary forces during the summer months due to evaporation. Water with a high salt content becomes stationary in places with inadequate drainage and accumulates all of the salt contents in the soil layer as it dissipates. Alkaline and Saline Soil Areas in India Saline and Alkaline Soil covers an area of 68,000 square kilometers. These soils are formed in canal rinsed lands and locations with a higher subsurface water table. This type of soil may be found in parts of Karnataka, Telangana, Andhra Pradesh, Uttar Pradesh, Bihar, Punjab, Haryana, Rajasthan, Punjab, and Maharashtra. However, the build-up of the salts leaves the soil unproductive and unsuited for cultivation. The sea tides transporting salt-laden sediments damage the lands near the Khambhat Gulf of Gujarat. As a result, vast portions of the Mahi, Tapi, Narmada, and Sabarmati rivers are unproductive. When severe storms, salty sea waves invade coastal locations, rendering the soil unsuitable for farming.

1. Saline and Alkali Soil Properties
Course : Soil Fertility and Nutrient Management
Amrinder Singh
Ph.D. Scholar
RIMT – 23OS-0172

2. Saline Soils
 “Saline soils contain large amounts of soluble salts, appreciably more
soluble than calcium sulfate. Saline soil has a pH less than 8.5.
 Most commonly, these are salts of Na, Ca, and Mg, with chloride,
sulfate, and bicarbonate…soils are considered saline if their electrical
conductivity exceeds 4 dS m−1.
 Many plants suffer at this level.

3. In field conditions, saline soils can be recognized by the spotty growth of
crops and often by the presence of white salt crusts on the surface. When the
salt problem is only mild, growing plants often have a blue-green tinge.
Barren spots and stunted plants may appear in cereal or forage crops growing
on saline areas. The extent and frequency of bare spots is often an indication
of the concentration of salts in the soil. If the salinity level is not sufficiently
high to cause barren spots, the crop appearance may be irregular in vegetative
vigour.

4.  Moderate salinity, however, particularly if it tends to be uniform throughout the field, can
often go undetected because it causes no apparent injuries other than restricted growth.
 Leaves of plants growing in salt infested areas may be smaller and darker blue-green in colour
than the normal leaves. Increased succulence often results from salinity, particularly if the
concentration of chloride ions in the soil solution is high. Plants in salt-affected soils often
have the same appearance as plants growing under moisture stress (drought) conditions
although the wilting of plants is far less prevalent because the osmotic potential of the soil
solution usually changes gradually and plants adjust their internal salt content sufficiently to
maintain turgor and avoid wilting.
 Symptoms of specific element toxicities, such as marginal or tip burn of leaves, occur as a
rule only in woody plants. Chloride and sodium ions and boron are the elements most usually
associated with toxic symptoms. Non-woody species may often accumulate as much or more
of these elements in their leaves without showing apparent damage as do the woody species.

5. Excess soil salinity causes poor and spotty stands of crops, uneven and stunted
growth and poor yields, the extent depending on the degree of salinity. The
primary effect of excess salinity is that it renders less water available to plants
although some is still present in the root zone. This is because the osmotic
pressure of the soil solution increases as the salt concentration increases. Apart
from the osmotic effect of salts in the soil solution, excessive concentration
and absorption of individual ions may prove toxic to the plants and/or may
retard the absorption of other essential plant nutrients.
Salinity and plant growth

6. Reclamation and management
Salt leaching
The amount of crop yield reduction depends on such factors as crop growth, the salt content of
the soil, climatic conditions, etc. In extreme cases where the concentration of salts in the root
zone is very high, crop growth may be entirely prevented. To improve crop growth in such soils
the excess salts must be removed from the root zone. The term reclamation of saline soils refers
to the methods used to remove soluble salts from the root zone. Methods commonly adopted or
proposed to accomplish this include the following:
Scraping: Removing the salts that have accumulated on the soil surface by mechanical means has
had only a limited success although many farmers have resorted to this procedure. Although this
method might temporarily improve crop growth, the ultimate disposal of salts still poses a major
problem.
Flushing: Washing away the surface accumulated salts by flushing water over the surface is
sometimes used to desalinize soils having surface salt crusts. Because the amount of salts that can
be flushed from a soil is rather small, this method does not have much practical significance.
Leaching: This is by far the most effective procedure for removing salts from the root zone of
soils. Leaching is most often accomplished by ponding fresh water on the soil surface and
allowing it to infiltrate.
Drainage
Irrigation is the most effective means of stabilizing agricultural production in areas where the
rainfall is either inadequate for meeting the crop requirements or the distribution is erratic. Before
the introduction to an area of large quantities of water through irrigation, there exists a water
balance between the rainfall on the one hand and stream flow, groundwater table, evaporation and
transpiration on the other.

7. Crop plants differ a great deal in their ability to survive and yield satisfactorily when grown
in saline soils. Information on the relative tolerance of crops to a saline soil environment is
of practical importance in planning cropping schedules for optimum returns. There are
situations where farmers have to live with salinity problems, for example, in areas having
saline water as the only source of water for irrigation. In other situations where good
quality water is available for reclamation of saline soils, it is often helpful to grow crops
simultaneously with reclamation efforts to make reclamation economic.
Sensitivity Chloride (mg/L) Sodium (mg/L) Affected crop
Sensitive <178 <114
Almond, apricot,
citrus, plum
Moderately Sensitive 178–355 114–229
Capsicum, grape,
potato, tomato
Moderately tolerant 355–710 229–458
Barley, cucumber,
sweetcorn
Tolerant >710 >458
Cauliflower, cotton,
safflower,
sesame, sorghum,
sunflower
Crops in Saline Soils

8. • Natural causes: Weathering of rock minerals or sediments with high salt
content, flooding by sea or ocean water (after flood waters retreat, they
leave behind large quantities of salt).
• Human activity: Salinity on agricultural lands is mainly caused by
continuous application of irrigation waters with high salt concentration.
When this water is removed via evaporation and transpiration salt crystals
are left behind. Salinization can also occur from the upward rise of
groundwater to the root zone, or from application of fertilizers and soil
amendments.

9. Alkaline Soils
 Alkali, or Alkaline, soils are clay soils with high pH (greater than 8.5), a
poor soil structure and a low infiltration capacity. Often they have a hard
calcareous layer at 0.5 to 1 metre depth. Alkali soils owe their
unfavorable physico-chemical properties mainly to the dominating
presence of sodium carbonate, which causes the soil to swell and difficult
to clarify/settle. They derive their name from the alkali metal group of
elements, to which sodium belongs, and which can induce basicity.
Sometimes these soils are also referred to as alkaline sodic soils.
 Alkaline soils are basic, but not all basic soils are alkaline.

10. Causes
• Soil is made alkaline by the presence of calcium, magnesium, or
sodium(read more about sodic soils). All are present in most soils, but
exist in higher amounts under certain conditions. Sodium salts are highly
soluble, so are present only in very small amounts in any soil that is well-
drained and gets appreciable amounts of rainfall.
• Calcium, or calcium and magnesium together, are only slightly soluble,
and are the causes of most soil alkalinity.

11. Where to find ?
• Alkaline soils are common in areas where the base rock is limestone
(Calcium carbonate), or in arid regions, where calcium is not washed out
of the soil. Regions that receive less than 20 inches of rain a year usually
have alkaline soil.
• Alkalinity can also come from irrigation water. Hard water with a high
lime content will make soil increasingly alkaline. In regions that have dry
periods with seasonally heavy rainfall, as occurs in much of California,
alkalinity from irrigation water builds up until the rainy season, then is
reduced by heavy rainfall over the winter.
• Sometimes alkalinity is very local, due to a local situation. One common
cause of local alkalinity is new cement work. Portland cement is lime-
based, and lime leaches out of new cement for a while, making the soil
close to it alkaline. Anything that spills lime on the soil can cause local
alkalinity, such as washing cement tools or an accidental spill of
agricultural lime.

12. Signs of high ph in soil
• Plants growing in soil that is too alkaline develop symptoms that indicate
iron deficiencies: new leaves become chlorotic, with the veins staying
green but the tissue between the veins turn yellow because the plant is
unable to get iron.
• This symptom can be told from the common nitrogen-deficiency
chlorosis from the fact that the newest leaves are most affected, and the
chlorosis is interveinal—the leaf tissue between the veins looses color,
becoming pale green or yellow, while the veins remain dark green.
Nitrogen-deficiency chlorosis affects the oldest leaves first, and the leaves
turn evenly pale or yellow.
• Iron is probably present in the soil, but in an unavailable form. Changing
the soil pH makes it once again available to plants.

13. Agricultural problems
• Alkaline soils are difficult to take into agricultural production. Due to the
low infiltration capacity, rain water stagnates on the soil easily and, in dry
periods, irrigation is hardly possible. Agriculture is limited to crops
tolerant to surface waterlogging (e.g. rice, grasses) and the productivity is
low.

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