Changing rainfall and disappearing Aman

Food and water are indispensable elements of life, while rice is our staple food. Water is the most essential input for rice production. And rainfall is one of the main sources of water for growing rice. But from 1980 to 2012, a great variation can be seen in the rainfall patterns of Bangladesh, which has affected our rice growing seasons.
If we look at figures for 1980, seasonal Aush and Boro contributed to 25 percent of our total rice production, while Aman alone contributed 50 percent. Now, the picture has altered. Boro contribution is more than 55 percent of the total production, Aush is less than 7 percent and Aman has come down to 35 percent. Also, over the three decades Aush cultivation area has decreased, while Boro cultivation has increased dramatically, especially after severe floods triggered by extreme rainfall.
This has happened due to changing rainfall patterns, one of the most important factors than any other.  Normally, the amount of water required daily for rice varies from 6 to 10 mm/day and total water consumption ranges from 1,100 to 1,250 mm, depending on the agro climatic situation, duration of the variety and characteristics of the soil. In Bangladesh, Aush is generally sown in April and harvested is mid-August. In this case, April month is the main field preparation and nursery stage for Aush, May and June are vegetative growth stage, July is flowering and grain filling stage, and the first half of August is ripening and harvesting period.
But the average rainfall in the months of April, May, June, July and August is 127.01, 288.04, 452.28 500.03 and 402.55 mm respectably, and for all those months, rainfall is decreasing. In April, when it is time for field preparation and growing seedlings for Aush, there is not enough rain; water requirement is almost 180 mm, but average rainfall availability is only 130mm. After the middle of August, when it is time for  ripening and harvesting, there is no need for standing water but we get plentiful rainfall and the excess water inundates paddy fields, leading to crop loss. For this dilemma, farmers are abandoning Aush cultivation and moving towards other crops.
 On the other hand, Aman rice is totally rain fed, sown in July and harvested in November. The average rainfall in the months of July, August, September, October and November is 561.9, 480.4, 416.1, 183.3 and 32.7 mm respectably, and that, too, is a decreasing trend, except in October. Field preparation and nursery stage for Aman is July when flood waters start to recede. If flood water receding is delayed, Aman sowing is delayed. October is flowering and grain filling stage for Aman when water requirement is almost 510 mm, but the average rainfall at this stage is only 160 mm, which is much lower than the requirement.
For reasons of water scarcity during planting time and uncertainty about harvesting due to floods, farmers are already inclined towards cultivating only Boro and Aush. Now, there is uncertainty about Aman planting time and water scarcity during flowering and grain filling stage, all due to changing rainfall patterns and decrease in cultivation area. On the other, scientists and researchers are more interested to conduct their research on Boro, rather than Aush or Aman, due to favourable climatic conditions and availability of more varieties. This may have a negative effect on farmers’ minds and they will be motivated to go for another crop or season. That will increase dependency on Boro, a single season rice, and  endanger our food security. So, it is time to take preventive measures before Aman rice goes the same way as Aush.

Writers: Hossain is Assistant Engineer, Local Government Engineering Department (LGED), Bangladesh; Li is Professor at Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agriculture Sciences (CAAS), Beijing.
Photos: Courtesy.

Changing rainfall and disappearing Aman

Food and water are indispensable elements of life, while rice is our staple food. Water is the most essential input for rice production. And rainfall is one of the main sources of water for growing rice. But from 1980 to 2012, a great variation can be seen in the rainfall patterns of Bangladesh, which has affected our rice growing seasons. If we look at figures for 1980, seasonal Aush and Boro contributed to 25 percent of our total rice production, while Aman alone contributed 50 percent. Now, the picture has altered. Boro contribution is more than 55 percent of the total production, Aush is less than 7 percent and Aman has come down to 35 percent. Also, over the three decades Aush cultivation area has decreased, while Boro cultivation has increased dramatically, especially after severe floods triggered by extreme rainfall. This has happened due to changing rainfall patterns, one of the most important factors than any other. Normally, the amount of water required daily for rice varies from 6 to 10 mm/day and total water consumption ranges from 1,100 to 1,250 mm, depending on the agro climatic situation, duration of the variety and characteristics of the soil. In Bangladesh, Aush is generally sown in April and harvested is mid-August. In this case, April month is the main field preparation and nursery stage for Aush, May and June are vegetative growth stage, July is flowering and grain filling stage, and the first half of August is ripening and harvesting period. But the average rainfall in the months of April, May, June, July and August is 127.01, 288.04, 452.28 500.03 and 402.55 mm respectably, and for all those months, rainfall is decreasing. In April, when it is time for field preparation and growing seedlings for Aush, there is not enough rain; water requirement is almost 180 mm, but average rainfall availability is only 130mm. After the middle of August, when it is time for ripening and harvesting, there is no need for standing water but we get plentiful rainfall and the excess water inundates paddy fields, leading to crop loss. For this dilemma, farmers are abandoning Aush cultivation and moving towards other crops. On the other hand, Aman rice is totally rain fed, sown in July and harvested in November. The average rainfall in the months of July, August, September, October and November is 561.9, 480.4, 416.1, 183.3 and 32.7 mm respectably, and that, too, is a decreasing trend, except in October. Field preparation and nursery stage for Aman is July when flood waters start to recede. If flood water receding is delayed, Aman sowing is delayed. October is flowering and grain filling stage for Aman when water requirement is almost 510 mm, but the average rainfall at this stage is only 160 mm, which is much lower than the requirement. For reasons of water scarcity during planting time and uncertainty about harvesting due to floods, farmers are already inclined towards cultivating only Boro and Aush. Now, there is uncertainty about Aman planting time and water scarcity during flowering and grain filling stage, all due to changing rainfall patterns and decrease in cultivation area. On the other, scientists and researchers are more interested to conduct their research on Boro, rather than Aush or Aman, due to favourable climatic conditions and availability of more varieties. This may have a negative effect on farmers minds and they will be motivated to go for another crop or season. That will increase dependency on Boro, a single season rice, and endanger our food security. So, it is time to take preventive measures before Aman rice goes the same way as Aush. Writers: Hossain is Assistant Engineer, Local Government Engineering Department (LGED), Bangladesh; Li is Professor at Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agriculture Sciences (CAAS), Beijing. Photos: Courtesy.