Salinity: A Challenge to Paddy Cultivation in Sri Lanka

Drought, floods, salinity and iron toxicity are among the key environmental factors that affect  paddy cultivation in Sri Lanka, an island nation in the Indian Ocean. Of these, salinity is a problem that fluctuates from time to time and has the potential to be a serious issue in some years, but is not adequately addressed.

The article aims to shed light on this issue, using the findings of field observations conducted in several areas of the island that have been severely affected by salinity. Two such areas, Uraniya in the Bundala area, and Manajawa in the Ambalantota area, are situated in Hambantota District,close to the coast in the deep south of the island. Field observations were also made in several villages in the Anamaduwa and Kottukachchiya areas located inland, in the Puttalam District in the north-western part of the country.

What is salinity?

Salinity is the result of the accumulation of various salts in paddy fields. The salts are dissolved in water and deposited in the soil when water is evaporated, causing salinity. Higher rates of evaporation can cause higher salinity.

There are two types of salinity in the country based on where it occurs. The first is coastal salinity, which is caused by the intrusion of seawater into  coastal lands through sea level rise, tidal activity and dry weather. This situation is increased by human activities such as sand mining. Coastal salinity is caused by salts of ions such as fluoride, sulfate, sodium, and magnesium. This type of salinity is common in areas close to the sea and seen mainly in coastal districts such as Mannar, Puttalam, Jaffna, Trincomalee, Ampara, Hambantota, Galle, Kalutara and Matara.

The second type of salinity is inland salinity seen in inland areas of the country. The reasons for this salinity include carbonate and bicarbonate salts formed with ions such as calcium, magnesium and sodium. Anuradhapura, Polonnaruwa, Puttalam, Hambantota and Ampara are districts that are most affected by inland salinity. Inland salinity is reported to be gradually increasing in some areas at least since 2007. Salinity has also recently been identified in some of the Mahaweli regions, which is a key paddy producing area in the country.

The total paddy area cultivated in the country during the Maha cropping season (the key cropping season from October to March) is about 800,000 hectares, while the area cultivated is reduced to about 450,000 hectares during the other cropping season, the Yala (May to August). The area of paddy lands estimated to be affected by salinity is significant; about 100,000 hectares..

However, the area affected by salinity can vary due to water availability: during the Maha season, where rain is usually plentiful, paddy fields are less affected by salinity; and during the Yala season, when the weather is drier and paddy depends on reservoir-stored water, the impact of salinity is prominent.

The severity of salinity increases with the effects of the level of drought and higher evaporation. Also, with climate change, the risk of salinity increases, mainly due to rising temperatures, higher evaporation, increased intensity of drought, water scarcity and rising sea levels.

How salinity affects plants

Salinity is measured using the electrical conductivity of water and the unit is deciSiemens per meter. Most of the crop plants can tolerate salinity within the range of 2-8 deciSiemens per meter. Plants are less tolerant to salinity higher than 8 deciSiemens per meter.

High salinity leads to a decrease in paddy productivity or the yield per hectare, rather than the death of the entire crop. Salinity results in salt toxicity and plant fatigue. The impact of salinity is higher during seed germination and plant growth and the effect is less during the flowering and mature stages of paddy. If the effect on the growth stage can be controlled or reduced, the overall adverse effect on the plants can be minimized. Different paddy varieties and agricultural practices have been developed and used to reduce the effect of salinity.

New rice varieties introduced to overcome salinity

The task of the several Rice Research Institutes in Sri Lanka such as Bathalagoda and Ambalantota is to produce paddy varieties that are resilient to various environmental conditions and resistant to diseases that affect paddy cultivation while producing a higher yield. So far, more than ninety improved paddy varieties have been introduced to the farmers by these research institutes. Salinity is one such environmental condition identified as a challenge to paddy cultivation and the table below mentions key salinity-tolerant important paddy varieties introduced by these institutions.

Variety and time for harvesting

• Bg 310, 95-100 days
• Bg 369, 105 days
• Bg 353, 3.5 months
• Bg 354, 3.5 months
• At 401, 4-4.5 months

Most of the improved varieties introduced are short-aged (or quick-growing) varieties. Therefore, the period during which the crop should be protected from excess salinity in the paddy field is shorter.

Bg 310 paddy is the most widely cultivated variety among the salinity tolerant paddy varieties. This variety was cultivated in an area of more than 10,000 hectares in 2019. Bg 369, which is more salinity tolerant, is also cultivated in some of the affected areas. At 354, another high salinity tolerant variety is widely grown in Galle, Matara and Hambantota districts in the Southern Province of the Island. The highest yield per hectare under saline conditions has been obtained from Bg 369 and Bg 310.

Traditional paddy varieties have been used to develop some of the improved varieties. For example, one of the parental lineages of both Bg 310 and at 354 is the traditional variety known as Pokkali. Also, Bg 369 has been developed using Nona Bokra as one of the parents. (Both these varieties are cultivars of foreign origin and are traditionally cultivated.) It has been possible to produce the above mentioned high-yielding paddy varieties by utilizing the characteristics of these traditional varieties.

However, other factors influence the selection of these salinity-tolerant improved varieties by the farmers for cultivation. For instance, the demand for varieties in the market and the traders and the consumer preference are among these limiting factors.

Cultivation of suitable paddy varieties

One solution to rising salinity is the introduction of salt-tolerant rice varieties, including traditional paddy varieties as well as improved paddy varieties.

According to paddy farmers interviewed during the field observations conducted in salinity-affected areas in Ambalantota, Bundala and Kottukachchiya, there were salinity-tolerant traditional paddy varieties cultivated in the past. Among the traditional varieties that provided a better yield in saline soil were varieties such as Pokkali, Pachchaperumal and Madathavalu. The cultivation of these paddy varieties was later abandoned with the onset of improved varieties. However, the need to cultivate salinity-tolerant varieties of paddy emerged when it was evident that the improved paddy varieties could not be cultivated in these saline fields. Various organizations and groups were involved in reintroducing traditional paddy varieties for this purpose. For example, one such project was launched in the Hambantota district after the tsunami of 2004. An organization named 'Practical Action' initially expanded the cultivation to some areas in the district based on an experiment conducted in the Ambalantota area using ten varieties of paddy. As Athula Weeraratne pointed out, traditional paddy varieties have been cultivated using organic agricultural practices and modern technology. Later, the Southern Provincial Development Authority intervened and assisted in popularizing this work.

Chandrasoma Weeraratne, a farmer activist, spoke to us about an initiative that commenced in the Bundala area at that time and is still successfully operated by the farmers. It was difficult to cultivate any other paddy varieties in the Uraniya paddy land in the area due to  salinity. Pokkali is the most suitable traditional paddy variety grown in saline paddy fields and Pachchaperumal, Madathavalu, Dahanala and Rathdel are cultivated in some fields. Meanwhile, in Kottukachchiya area, paddy varieties such as Pachchaperumal, Murungakayam, Dik Vee and Hengimuttan were cultivated in salinity-affected paddy fields with moderate success in the past.

Agricultural practices that can reduce salinity

Some of the agricultural practices to reduce the salinity in affected paddy fields are described briefly below. These practices are being promoted by the agricultural authorities and are being used by the farmers.

• Avoid deep ploughing — less ploughing is suitable during Yala season and drought-affected seasons as water scarcity can increase salinity and deeper ploughing can mix salts deep in the soil. Discussions with farmers in the Kottukachchiya and Athungoda area showed that farmers who have been cultivating saline fields for a long time are well aware of this fact. They sometimes only do ground leveling. Also, in villages such as Wadatta, where salinity is common, the Kekulama method involving minimum land preparation is practiced.
• Washing paddy fields several times before sowing —  it is advisable to wash the paddy field several times before sowing in saline lands. This was a regular practice for the farmers as we observed. However, the lack of sufficient water supply in some areas for repeated washes is a problem mentioned by farmers. Most of the saline paddy fields are either irrigated by minor irrigation or entirely by rainwater. In such cases, it is difficult to remove the salts by washing the field before sowing. This is more severe during the Yala season when the water supply is limited. This is one of the problems observed in some areas of Puttalam District.
• Addition of organic matter to the soil — salinity can be reduced by applying organic fertilizer and other organic matter. Different materials are used for this purpose. The application of biochar or rice husk charcoal, cow dung, poultry manure and compost are some of those. They control the salinity of the soil and provide nutrients required for paddy cultivation.
• Paddy cultivation by Parachute method — a technique of tossing rice seedlings, uprooted from plastic trays containing a lump of soil. Since the paddy seedlings planted are about 12 days old, they are less affected by salinity in the paddy field during the growing stage. Therefore, the parachute method is suitable for sowing paddy in saline paddy fields.

Problems coping with salinity

An effort was made during the reporting of this story to learn more about  problems encountered by farmers dealing with salinity. A key issue that emerges is the lack of adequate understanding among farmers about the seriousness of salinity. The fact that the effect of salinity may differ from season to season is a cause for less attention on the gravity of the issue. When the effect of salinity is low in one season, farmers may neglect the importance of the practices needed to be followed to minimize the impact of salinity in the next season. Also, it seems that the cultivation of salt-tolerant paddy varieties is not often considered.

There is difficulty in obtaining seed paddy of salt-tolerant varieties, as revealed by at least by some farmers during the interviews. This is a well-known fact for both traditional as well as improved varieties, and the farmers are used to cultivating any available paddy varieties in such a situation. Therefore, it is important to ensure that there is an adequate supply of suitable varieties through intervention by the state. In addition, seed paddy production by farmers should be promoted by providing necessary inputs. Further to this, it was also evident that there was a lack of knowledge about the addition of sufficient organic matter.

Water is an important factor for reducing salinity in paddy fields. Steps can be taken to provide proper water supply in affected areas where there is a need for a water supply. Also,  proper maintenance of irrigation systems such as tanks and canals is important to distribute water efficiently. This is especially important during the Yala cropping season when farming is done under drier conditions with irrigated water, such as in the Kottukachchiya area.

Sowing paddy using the parachute method can minimize the effect of salinity. Although this method has been introduced to farmers, farmers have encountered practical problems with its use. One problem is  getting used to the technology — elderly farmers found it difficult to adopt as revealed by farmers in Kottukachchiya and Anamaduwa areas. In addition, the cost of the trays used in this method is a limiting factor. If the government can intervene at least in areas where this technology is effective, there is an opportunity to motivate farmers to overcome the salinity in paddy fields.

Another setback is related to training provided to farmers by the Department of Agriculture. These training exercises are done through meetings, and. there are some problems with the dissemination of knowledge in this way. According to several agriculture officials, the lack of participation of actual farmers is an issue, as sometimes it is the women in the family that participate in the meetings.

It is important to mention that most of the saline paddy lands are not irrigated by major irrigation canals and are largely cultivated for the subsistence needs of the farmers themselves. One of the main problems with the failure of such paddy lands is that it affects their food security. Salinity also affects the cultivation of other crops besides paddy. If the cultivation continues to fail, these farmers tend to leave their villages in search of alternative employment opportunities. This could cause social and family problems. This situation is worsened in areas where the people are resettled from their original settlements. Therefore, the government has a responsibility to provide solutions for the salinity and continue to pay attention to the food security of them as well as the country.

This story was produced with support from the Internews’ Earth Journalism Network. It was originally published in Tamil in Vidusara on 12 January 2022. It has been translated to English and lightly edited for length and clarity.

Banner image: A paddy field in Sri Lanka / Credit: Simone D. McCourtie for World Bank via Flickr.