Cost effective, environment friendly boro rice cultivation
Perforated PVC pipe(left)
BORO rice in Bangladesh, either HYV (High Yielding Variety) or traditional variety covering more than 4.5 million ha, is entirely irrigated production, mostly with underground water. Irrigation has become a very costly input in rice production because of increasing cost of fuel. Farmers pay about 25-30% of the price of their harvest for irrigation. For producing 1 kg of paddy, it is estimated that a farmer has to use 3-4 thousand liters of water for maintaining pond water during the growing stage of plants. As a result, besides the increased cost of irrigation, groundwater level is also declining due to excessive withdrawal threatening the environment. Therefore research has been conducted through BRRI-IRRI collaboration for long to develop water saving techniques in rice cultivation by the alternate wetting and drying (AWD) method. Water resources are becoming scarce worldwide, Bangladesh is of no exception. As surface water supply is decreasing day by day, irrigation pressure is mounting on groundwater resource. But this resource is not unlimited and in intensive tube well areas water level is declining gradually in each dry season. Recently, arsenic contamination is being reported in groundwater as well as in the food chain, which is threatening consumption. So the judicial use of water resources in intensive irrigated area is a crucial need for maintaining both sustainable crop production and accessible water level. Generally, in Bangladesh, irrigation is applied in dry season. According to the recent estimates, out of 8.4 Mha of cultivable land, about 4.8 Mha has been brought under irrigation. It implies that about 57% of total cultivable lands are irrigated. Both surface and groundwater is used for the purpose. At present more than 70% of the irrigated area is served by groundwater and less than 30% by surface water. Groundwater is being extracted through 11,28,991 shallow tubewells (STWs), 27,117 deep tubewells (DTWs), 826 force mode pumps (FMP), and 1,15,876 un-mechanized (manually operated hand tubewells, treadle and rower) pumps for irrigation and domestic purposes. There are also 99,115 low-lift pumps (LLPs) and 5,01,431 traditional irrigation units in operation for lifting surface water. A huge arrangement, indeed. Therefore practice of irrigation technology like AWD can play a remarkable role in reducing water losses and cost of irrigation for crop production. This AWD tool is a single device designed to observe water level in rice field for deciding the time of irrigation. It involves installation of a perforated pipe (preferably PVC) in rice field to allow observation of water level. In one part, such pipe of 10 cm diameter and 30 cm long is installed having 10 cm above and 20 cm below the ground surface. Field practice: A study was conducted by BRRI on AWD technology for water saving in Boro rice cultivation during 2007-08 in the three selected districts near by BRRI regional stations (Rangpur, Kushtia, Feni) under different irrigation systems (DTW, STW,LLP) with 90 sample farmers. The water management practice in the command area was done as per researcher's recommendation. Water status during the whole season was monitored. Irrigation was provided when water level reached 20 cm below the ground surface. The depth of water supply in each irrigation was 5-7 cm. After transplanting, shallower irrigation depth (2-4 cm) was maintained during the settling period of young seedlings. AWD practice was maintained after 15-20 days of transplanting up to booting stage for a period of 50-60 days depending on rice varieties from booting to milk stages. Benefits :The study indicates that numbers of irrigation used by AWD technology showed, on an average, short duration variety like BRRI dhan28 received 8 irrigations in AWD practice from vegetative to reproductive stage, whereas in case of farmers' practice it was 12. As a result about 4 irrigations were saved compared to the farmers' practice. Similarly for long duration variety like BRRI dhan29 on an average 5 irrigations were saved during Boro season. Comparative water used under AWD and farmers' practices showed that for short duration variety about 23% water was saved, whereas 25% was saved for long duration variety. On an average the additional financial benefit from water saving and yield in AWD method over farmers' management practice was Tk 7287 /ha for BRRI dhan28, whereas this was Tk 4595 /ha for BRRI dhan29. Scope and strategies: AWD has been widely adopted in China. It is also a recommended practice in northwest India, and is being tested by farmers in the Philippines. The AWD fields had the same yield as with continuous flooding, but this new method saved 16-24% water costs and 20-25% production costs. In Bangladesh, AWD technology using PVC pipe in rice field can save estimated Tk. 3 billion during Boro season as the method reduces reasonable fuel consumption. Also research result indicated that at field level AWD can save 20-30% irrigation cost in terms of water, fuel and time.
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