Heat stress is affecting Boro paddy fields in parts of the country soon after Nor’wester swept on April 4.
Heat stress at the flowering and grain-filling stages seriously affects the spikelet fertility and grain quality of rice.Extreme heatwave already damaged five per cent of paddy in 24 districts in the country. The worst- affected districts include Netrokona, Kishorganj and Bhola, said AKM Monirul Alam, Director of the Field Service Wing of Department of Agriculture Extension (DAE).
He said the temperature was more than 36 degree Celsius in the last couple of days, affecting the paddy plants which were at the flowering stage.
“No rainfall since the Nor’wester swept on April 4 and the increasing temperature affecting the paddy pollination in some areas,” he added.
“At least 12,400 hectares of Boro paddy were affected. DAE has been working to reduce the impact,” said the official.
Paddy in Kushtia, Rajshahi, Mymensingh, Gopalganj and some other areas were also affected by heat stress, said sources.
Former Bangladesh Rice Research Institute (BRRI) Director-General Jibon Krishna Biswas said the heat stress usually appears every few years later and continues for one or two days.He said extreme heatwave absorbed moisture from the paddy plant, damaging the paddy plants in their flowering stage.
High temperatures above 35 °C at the flowering stage inhibit another dehiscence and thus result in lower pollen shed on the stigma, resulting in incomplete fertilization.
Diurnal temperature fluctuations in most rice-producing areas are close to the optimum 28 and 22°C day and night mean temperatures, respectively.
Rice can maintain normal growth at temperatures ranging from 27 to 32°C without significant reduction in grain.
Temperatures above 32°C negatively affect all stages of rice plant growth and development, the most critical temperature was found to be 33°C or above during the flowering stage.
High temperature is harmful to most physiological processes including stomatal opening, photosynthesis, growth, and grain yield.
The highest temperature was recorded at 36°C on Tuesday while it was 36.4°C on Monday, according to Bangladesh Meteorological Department (BMD).
Boro season fulfils 60 per cent of the country's total rice demand.
Crop losses in the last Aus and Aman season affected the country’s cereal production and stock increases rice price and forced the government to import rice.
Boro has been cultivated 48.83 lakh hectares of land this year. The government expects to produce 2.05 crore tonnes of rice this year.