Valuable Lesson for Soil Salinity Management

Soil salinity can improve soil structure but can also negatively impact both the plant growth and the crop yield. 

Soil salinity occur when high amounts of salts accumulate in the root zone. Salt can negatively affect the plant growth or even kill it. However, there are various farm management practices which help prevent or cure soil salinity. 

Since the ancient times, salt in the soil has been a well-known problem in farming. But, early farmers didn’t know how to manage or even prevent this problem. Therefore, this led to the massive abandonment of rich farmlands.  

Salt in soils can come from two main sources: geo-historical processes and the human activity-usually irrigation. Who would say that an ordinary farm practice such as irrigation, can make so much damage to both the soil and the plant?! Not only irrigation provides saline soils. There are also other mismanagement practices responsible for soil salinity.  

Although irrigation water provides beneficial nutrients to the soil and plant, it also includes certain amount of dissolved substances, called salts. The main salts in water, and therefore, in soils are calcium sulfate, magnesium sulfate, sodium sulfate, and potassium sulfate. Based on the type of sulfate found in the soil, there are several types of salt-affected soils.  

What Causes the Soil Salinity? 

Soil salinity problems are caused mainly from an excess of salts in the plant root zone along with the inadequate drainage. Salts often originate from the earth’s crust, but they also can result from weathering, in which small amounts of rock and other deposits are dissolved over time and carried away by water. This slow weathering may cause salts to accumulate in both surface and underground waters as well as in the root zone.   

Saline soils are characterized by white or light brown crusts on the surface and usually have an EC of more than 4 mmhos/cm.  

Saline soils contain water-soluble salts in amount that affect crop growth. There are several reasons responsible for creation of saline soils; 

  • climate- the available amount of rain 
  • type of soil texture- sandy, clay or loamy soil 
  • type of topography- slopes or flat surface 

Effects of Soil Salinity on Crop Development 

Soil salinity is a problem when high amounts of salts accumulate in the root zone. At that moment, various negative effects occur in the soil and affect the plant growth 

  • increased plant stress; stunted plant growth, small leaves, wilting, poor flowering   
  • slower seed germination 
  • reduced water uptake and availability of plant nutrients  
  • reduced activity of soil microorganisms 
  • drawn water from the plant roots into the soil, causing plant cells to collapse 
  • changed soil surface colour into white 
  • standing water on soil surface 

In moderately saline soils, high in moisture, plants do not show any negative effects of soil salinity. This is due to the fact that soil solution is diluted. However, at the moment when moisture level drops, the salt concentration increases and causes damage on plants.  

How to Determine Soil Salinity? 

Although saline soils change their surface colour and affect the plant growth, it’s impossible to know how saline the soil really is. For this reason, farmers test their soil for total salt content, the soil pH, and electrical conductivity (EC). Soil samples should be taken from the field locations on which plant growth is sparse, stunted or completely omitted. The practice is to take samples at each 15 cm (6 in) depth down to 60 cm (2ft).  

Crop Tolerance on Salt 

None of the common crops grow well on strongly saline soils. Too saline soils may even kill the plant. However, some plants can withstand moderate levels of soil salinity. Consequently, forage crops are the most tolerant on salt in the soil, cereals are moderate tolerant while fruit crops are the most sensitive ones.  

The soil salinity level tolerance shows the degree of salinity a plant can withstand without being affected in its growth and development.  The salinity level for various crops are shown in the table below.   

Low tolerance 

0-4 mmhos/cm 

Moderate tolerance 

4-8 mmhos/cm 

High tolerance 

8-15 mmhos/cm 

Field bean  Sunflower  Barley 
Soybean  Flax  Rape 
Peas  Corn  Sugar beet 
Carrot  Sorghum  Date palm 
Bean  Lettuce  Beet 
Strawberry  Clover  Spinach 
Blackberry  Pepper  Asparagus 
Orange  Cabbage  Cotton 
Plum  Tomato  Grasses 
Peach  Sugarcane   

 

How to Manage Soil Salinity? 

Soil salinity is a significant problem in poor drainage soils exposed to excess irrigation or some other farm practices. Managing of soil salinity actually means an improvement of salt balance in the soil 

A few farm practices are recommended to manage saline soils:   

  • planting of salt-tolerant crops; forage crops are the most tolerant 
  • soil drainage; it removes the excess water and salts and breaks up the soil surface  
  • leaching; adding of low-salt irrigation water or heavy rainfall can leach out the salts and move them below the root zone 
  • reducing evaporation; by applying crop residue or mulch to the soil  
  • applying of different fertilizer types; before applying, soil analysis is highly recommended 
  • proper soil tillage to break compacted soil layer  

Soil salinity is a common problem among farmers. Having a saline soil doesn’t mean that a farmer can’t have a successful crop production. By applying recommended farm practices, a farmer can easily manage soil salinity and achieve maximum crop potential.  

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  • Tasos on December 8, 2021 @ 18:50:49

This post was created by Filip Gerin on July 20, 2021.