Salinity Affecting Prosperity
By Ama H. Vanniarachchy
Soil is among one of the main reasons why life exists on earth. Plants grow on soil and many lives depend on plants. There is a large number of living species that live inside the soil. These plants and animals are the life of the earth. And their existence decides our existence.
Life on earth will not be successful if the soil is not healthy. Bad soil or degraded soil quality negatively affects the millions of lives of plants and animals. The quality and quantity of our food depend on the quality of the soil. Our health, our economy, and our entire social structures depend on our food. This means bad soil can completely ruin our social structures. This is why soil is one of the utmost important natural elements on earth.
Healthy soil is also essential for water filtration and healthy soil supports combating climate change. It is also said that soil stores more carbon than all of the world’s forests would do.
On this year’s World Soil Day (5 December) we will understand the importance of our soil and take a look at the situation in Sri Lanka. We have been talking about our soil in recent times as the issue of chemical fertiliser has been the talk of the town. First, it was a fertiliser ban, and then it was about organic fertiliser being imported to Sri Lanka.
This year’s theme is ‘Halt Soil Salinisation, Boost Soil Productivity’. We shall focus on the fertiliser issue in Sri Lanka, aligning it with this year’s theme. How will this affect our soil quality? What are the possible negative and positive impacts we might face in the future with regards to these new bans and decisions? How will this affect our food production?
Joining us in conversation is Prof. Saman Dharmakeerthi, Head of the Department – Department of Soil Science, Faculty of Agriculture, University of Peradeniya.
He explained to us the importance of soil as it is a non-renewable and limited natural resource that should not be misused and exploited. Many think that soil is unlimited but it is not.
What is soil?
Soil is a combination of organic matter, minerals, gases, liquids, and organisms that supports life on earth. The earth’s body of soil is called the pedosphere and it has four significant functions;
- It’s a medium for plant growth
- It is a medium of water storage and purification
- It is a modifier of the earth’s atmosphere
- It is a habitat of organisms
- These four functions, in return, modify the soil.
What is Soil Health?
As the professor explained to us, when the soil is healthy all the functions that are supposed to be done by the soil will happen without any obstacles.
“Soil quality is the more technical term and it means, the capacity of a soil to function naturally in the ecosystem. There are so many functions that soil plays which support the lives of plants and animals and the entire ecosystem as a whole. In order to play all these functions, the soil has to be of good quality.”
When it comes to agricultural soil, good soil will always provide the required conditions for optimum plant growth and maximum productivity. Optimum conditions in the soil mean that soil includes microbiological activities, biodiversity, low pollution with heavy metal, the required level of plant nutrients, low level of soil salinity, and enough moisture, and so on.
Soil salinisation is a global issue
Soil salinisation and sodification are major soil degradation processes that threaten ecosystems. This is currently recognised as being among the most important problems at a global level for agriculture, food security, and sustainability in arid and semi-arid regions.
What are the natural and other methods of soil salinisation?
Salinsation occurs due to the accumulation of soluble salt in the soil, said the professor. Soluble salts are iron, calcium, sodium, magnesium, and potassium mostly. There are also cations as well as anions like sulfate, bicarbonate, carbonate, etc. Those are the main soluble salts.
“If you take, for example, calcium carbonate, it is a soluble salt. So the association of soluble salt in the soil to cations and anions will create the soil salinity”, explained prof. Dharmakeerthi.
Now the question is from where these soluble salts come to a soil. As the professor explained there are several ways.
Soil is usually derived from rock and if the rock contains soluble salt, the soil naturally will become saline.
Seawater inclusion – Seawater has salts in them and if seawater is included in the groundwater then the soil becomes saline. This can also happen through the sea breeze. The sea breeze can bring and deposit salt on the cultivated lands located close to the coastal areas.
Irrigation water – Irrigation water can contain soluble salts. If you use bad quality irrigation water then they will bring salt and deposit them in the agricultural fields and gradually will increase the soluble salt amount in the soil.
“There are several other environmental conditions as well. Low precipitation, low rainfall, and high evapo-transpiration are among the many natural causes.”
High evapo-transpiration means when it is very windy, and when the temperature is very high, the water in the soil evaporates. And with that the salt in the bottom layers of the soil will come and deposit at the top. That is where you can see a salty crust in some soil.
Usually, saline soil can be mostly found in the dry zone in Sri Lanka. And there is a seawater inclusion in some areas like Galle and in certain wetlands areas as well.
Salinisation’s impact on agriculture and forestry
As prof. Dharmakeerthi explained, salinisation has no huge notable negative impact on natural forestry. It is because there will not be any artificial additions to the forest soils through anthropogenic activities.
“However, forestry can also become vulnerable to climate change,” he added.
“If the temperature increases and the rainfall decreases, in such situations and if the groundwater has soluble salt they will come and deposit and affect the forest vegetation as well.”
As he further explained, the situation is not the same when it comes to agricultural soil. In the 1980s it was estimated that about 112,000 hectares of land was affected by salinity in Sri Lanka. In 2014 there was another scientific publication saying that 230,000 hectares of agricultural lands have become salt affected or salinised. This is about 10 per cent of total agricultural land that has been affected by salinisation.
“Because we cannot control the environmental factors and the way that people irrigate their crops, salinisation is now becoming a global problem and the lands that succumb to salinity are increasing day by day. The impact of salinisation on soil is huge”, prof. Dharmakeerthi expressed his concern.
“That is why The World Soil Day theme is, ‘Halt Salinisation and Boost Soil Productivity’.”
The Northern peninsula in Sri Lanka is one of the major areas that are affected by salinisation and has a notable negative impact on agriculture. As prof. Dharmakeerthi explained, the yields of these paddy fields will be as low as two tons per hectare and the national average is somewhere around 4.8. This includes the varieties that can tolerate some of the salt conditions.
“If the soil salinisation in these areas continues at this speed, then there won’t be any single crop growing. Then it will be extremely difficult to fix the problem. That is why we need to be vigilant about this and take appropriate action now.”
What can we do?
What we need to do is to regulate illegal mining and prevent seawater inclusion, said the professor.
“We have seen that in some areas there are lots of illegal mining happening. This result in lowering of the inland groundwater level and there will be seawater coming in.
Secondly, we have to develop better salt-resistant varieties as crops. For paddy, we have at least four different salt-resistant varieties in addition to some of the additional varieties such as Pokkali, in the northern region. Although their yield levels are low, the hybrid varieties have a higher yield even under saline conditions. We need to develop better salt-resistant varieties that can combat salinisation of the soil.”
The use of irrigation water is also a major cause of salinisation. One of the major issues in the dry zone areas is that about 50,000 of the agro wells have saline water, which is not good for the soil. Therefore, regulation of irrigation water extraction is another area the Government has to intervene in and find solutions.
There are different irrigation techniques to flush down the soluble salt from the soil. And as the professor explained, we need to educate farmers on better irrigation practices. These should be adapted in salt-affected areas. These technologies are developed by the agricultural department and they need to be popularised among the farmers.
“We also need to promote organic matter application in agriculture.”
How will organic farming help?
Answering our question prof. Dharmakeerthi said that one of the causes for salinisation in some countries is the overuse of chemical fertiliser. If the chemical fertiliser usage can be decreased then there will be a low risk of salinisation.
However, as he claimed, in Sri Lanka we don’t have a problem of excessive use of chemical fertiliser. However, adapting organic fertiliser and reducing the usage of chemical fertiliser can definitely lower the risk of salinisation of the soil. He said that an immediate measure for saline soil is to apply more organic matter. Hence, the application of organic matter or shifting into organic agriculture could be beneficial to reduce some of the possible risks of salinisation due to chemical fertiliser in those areas.
“But organic matter alone cannot do that. We need to have certain other best management practices like having high resilient plant varieties, water management practices, and so on. All in all, I can say that the application of organic matter to saline soil can be recommended and we encourage it. Application of organic matter by this national policy would be a good thing.”
Prof. Dharmakeerthi said that the Soil Science Society of Sri Lanka has conducted an awareness event on 2 December. The webinar was on the theme, ‘Halt Soil Salinisation, Boost soil Productivity’ and there will be another webinar organised by the Department of Soil Science that is in Sinhala medium and the theme is, wasa wisen thora pasak, saubhagyamath hetak. This will be followed by a panel discussion moderated by Nalaka Gunawardena.
The World Soil Day
World Soil Day (WSD) is held annually on 5 December as a means to focus attention on the importance of healthy soil and to advocate for the sustainable management of soil resources. The day corresponds with the official birthday of King Bhumibol Adulyadej of Thailand, who had officially sanctioned the event. In 2016, this day was officially recognised in memory and with respect for the monarch after he died in October 2016 working as the head of state for seven years.
An international day to celebrate Soil was recommended by the International Union of Soil Sciences (IUSS) in 2002. Under the leadership of the Kingdom of Thailand and within the framework of the Global Soil Partnership, Food and Agriculture Organisation (FAO) has supported the formal establishment of World Soil Day as a global awareness-raising platform.