Salt tolerant rice varieties bring hope to BD farmers
Staff Correspondent: In the 1970s, Nandi Dulal, a 70-year-old paramedic-turned-farmer from Mukandapur village in Satkhira’s Kaliganj upazila, bred 25 varieties of rice with his fellow farmers.
By then, they discovered that their field was becoming saltier with time and that the rice field was becoming sterile.
“As the arable land became saltier, it hindered production and caused a huge loss for us, since we used to breed rice taking loans. For at least seven to eight months a year, the lands were barren. Shrimp farming has become an alternative for some people. Farmers have also begun growing fish by introducing saltwater to the land,” said Dulal.
Due to climate change, saltwater intrusion poses a huge problem for rice cultivation in Bangladesh’s coastal belt, because the local variety of rice is a saline-sensitive crop. Thousands of hectares of land have become barren in coastal Bangladesh because of salinity.
With a booming population increasing the demand for the staple, rice, there have also been growing calls for a salt-tolerant variety for the salinity-prone areas of Bangladesh.
Looking for alternative and adaption to the salinity, in 2006 the Bangladesh Rice Research Institute (BRRI), with the help of the International Rice Research Institute (IRRI), invented the first successful salt-tolerant variety, BRRI-47, which can tolerate salt 12 dS m-1 (deci Siemens per metre) at the seedling stage and 10 dS/m-1 during the growth stage. However, the traditional varieties of most crops can withstand salinity of up to 0.7dS/m only.
Based on wild rice, the Uri-Dhan can tolerate 10 dS/m-1.
The first salt tolerant variants were invented after scrutinising 385 varieties of rice that farmers were cultivating across the country, especially in the coastal districts, said Dr Abdus Salam who led the research.
Salam, who himself has invented 21 stress- and salt-tolerant varieties of rice, said, “The invention completely changed the rice breeding and adaption scenario in 19 of Bangladesh’s coastal districts which cover the country’s 25% rice production.”
Noting the increased rice production due to the salt-tolerant varieties being cultivated in Satkhira, the most climate-vulnerable district, Md Nurul Islam,
deputy director of Satkhira Agriculture Extensions, said, “In 2018, a total of 119 hectares were cultivated with BRRI-67, a salt-tolerant variety. Now in 2022, it stands at 5,216 hectares. The breeding of Binadhan-10, another salt variety, also increased; in 2017 around 778 hectares were used to breed Binadhan-10, while it is now over 2,000 hectares.
Bangladesh Institute of Nuclear Agriculture (BINA) Senior Scientific officer Md Babul Akhter said, “After nearly 30 years of being uncultivated due to salinity, we have been able to bring 240 hectares of land under boro cultivation in the last two seasons.”
“Our days have changed with the innovation of salt-tolerant rice varieties; rice cultivation has started again in Satkhira. It’s been growing steadily for the past decade,” said Nandi Dulal.
According to the Satkhira Agricultural Extension Department, currently the most popular saline tolerant BRRI Dhan-67 can tolerate salinity up to 12 dS/m (equivalent to 678 parts per million) for seedling stage up to three weeks and 8 dS/m (equivalent to 512 parts per million) for whole growth.
Fatema Begum, a farmer of Tala upazila said, “I have been cultivating rice as we are getting better production in recent years. In the last three years, we have been cultivating rice in shrimp orchards. This year BRRI-67 was planted.
Salinity and the search for adaption
Farmers in Bangladesh breed rice in Bangladesh in the three seasons Aus, T-Aman, and Boro, across four ecotypes, including irrigated, rainfed upland, rainfed lowland, and deep water. Rice farming is highly vulnerable to extreme weather such as floods, droughts, storm surges, and cyclones.
According to the study of the Bangladesh Soil Resource Development Institute (SRDI) in 2010, the area affected by salinity in Bangladesh has increased by 26% over the past four decades. There were 1.056 million hectares of arable land affected by different degrees of salinity in 19 coastal districts in 2009, compared to 0.833 hectares in 1973. As per the SRDI, Bangladesh has 2.86 million hectares of coastal and off-shore arable lands.
The SRDI study found in 2009 that some 3,28,430 hectares of the area affected low to very slight from 2.0 – 4.0 dS m-1 salinity, some 2,74,220 hectares by slight salinity which is 4.1-8.0 dS m-1, some 3,51,690 hectares arable land affected by moderate strong and strong salinity ranges from 8.1-16.0 dS m-1 and some 1,01,920 hectares by very strong, which is over 16.0 dS m-1 salinity.
Though the currently available rice is tolerant of 8.0-10.0 dS m-1 salinity stress in Bangladesh, the salinity in more than half the arable land in five coastal districts has gone well past the 8 dS/m levels.
For 560,000 hectares in five coastal districts – Khulna, Satkhira, Bagerhat, Patuakhali, and Barguna – the salinity level now ranges between 8.1 and 16 dS/m.
BRRI said they are still struggling to cope with the salinity and around 5000,000 hectares of land still remains out of cultivation due to high salinity.
According to a research article in 2020 of BRRI titled “Enhancing Rice Productivity in the Unfavorable Ecosystems of Bangladesh”, rice production in the saline ecosystem might increase by 11.75% by 2050, respectively subject to the dissemination of the saline tolerant rice cultivars in 75% of total salinity affected areas up to 12dS m-1.
It also suggested that “the higher yield potential and salinity tolerance (up to 12 dS m-1 for whole growth period) rice cultivars need to be developed.”
How did the journey start?
Wild Uri-Dhan (Porteresia coarctata) is found in the saline estuarine coastal areas that can tolerate 10 dS/m-1 saline.
Recounting the first invention, Dr Abdus Salam said, “We were looking for the solution within the crisis-prone area as a process of adaption. IRRI helped us in our research to find out the solution.
“As part of our research, we sat with our expert member, Norwegian scientist Dr Michael, in London. Michael’s first question was how many dS/m-1 salt tolerant rice we wanted to invent,” said Salam.
“Everyone was looking at one another as we did not know how much dS/m-1 salt-tolerant rice grows in our country,” said Salam.
“Suddenly, Uri-Dhan came to my mind as it can tolerate 10 dS/m-1 salt. I told him so. After passing the resolution we returned to the country; that was the beginning …,” added Dr Salam.
Now Bangladesh has around 16 salt-tolerant variants breeding on the 710km long coast of the Bay of Bengal.
BRRI Chief Scientific Officer and Director (Research) Mohammad Khalequzzaman said, “BRRI has developed 10 more salt-tolerant rice varieties in the last 15 years. Two new salinity tolerant varieties BRRI Dhan-97 and BRRI Dhan-99 have been developed for the latest Boro season. These two varieties can tolerate salt 14 dS/m-1 in seeding time and full life circle it can tolerate from 8-10 dS/m-1.
“As salinity is increasing along the coast of the country, BRRI is currently working on a total of 12,610 pollinators from 12 crosses to develop more sustainable and short-lived rice varieties,” said Khalequzzaman.
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