Can Bangladesh produce enough cereals to meet future demand?

Bangladesh faces huge challenges in achieving food security due to its high population, diet changes, and limited room for expanding cropland and cropping intensity. The objective of this study is to assess the degree to which Bangladesh can be self-sufficient in terms of domestic maize, rice and wheat production by the years 2030 and 2050 by closing the existing gap (Yg) between yield potential (Yp) and actual farm yield (Ya), accounting for possible changes in cropland area. Yield potential and yield gaps were calculated for the three crops using well-validated crop models and site-specific weather, management and soil data, and upscaled to the whole country. We assessed potential grain production in the years 2030 and 2050 for six land use change scenarios (general decrease in arable land; declining ground water tables in the north; cropping of fallow areas in the south; effect of sea level rise; increased cropping intensity; and larger share of cash crops) and three levels of Yg closure (1: no yield increase; 2: Yg closure at a level equivalent to 50% (50% Yg closure); 3: Yg closure to a level of 85% of Yp (irrigated crops) and 80% of water-limited yield potential or Yw (rainfed crops) (full Yg closure)). In addition, changes in demand with low and high population growth rates, and substitution of rice by maize in future diets were also examined. Total aggregated demand of the three cereals (in milled rice equivalents) in 2030 and 2050, based on the UN median population variant, is projected to be 21 and 24% higher than in 2010. Current Yg represent 50% (irrigated rice), 48-63% (rainfed rice), 49% (irrigated wheat), 40% (rainfed wheat), 46% (irrigated maize), and 44% (rainfed maize) of their Yp or Yw. With 50% Yg closure and for various land use changes, self-sufficiency ratio will be > 1 for rice in 2030 and about one in 2050 but well below one for maize and wheat in both 2030 and 2050. With full Yg closure, self-sufficiency ratios will be well above one for rice and all three cereals jointly but below one for maize and wheat for all scenarios, except for the scenario with drastic decrease in boro rice area to allow for area expansion for cash crops. Full Yg closure of all cereals is needed to compensate for area decreases and demand increases, and then even some maize and large amounts of wheat imports will be required to satisfy demand in future. The results of this analysis have important implications for Bangladesh and other countries with high population growth rate, shrinking arable land due to rapid urbanization, and highly vulnerable to climate change.

Effect of Climate Change and CO2 Concentration on Growth and Yield of Rice and Wheat in Punjab: Simulations Using CSM-CERES-Rice and CSM-CERES-Wheat Models

Recent trends of a decline or stagnation in the yield of rice and wheat in rice-wheat (RW) systems of the Indo-Gangetic Plains (IGP) have raised serious concerns about the regional food security. The effect of future climate change on crop production adds to this complex problem. The validated CSM-CERES-Rice and CSM-CERES-Wheat (Ver. 4.0) data were used to test the sensitivity of the models in Punjab, India. The models were sensitive to climatic parameters (temperature, CO2 concentration, solar radiation and rainfall) on yields of both crops. Simulated rice yields were sensitive to weather as there was 13% less yield of rice in 1999 than in 2001. Similarly, simulated wheat yields were also sensitive to weather, with the highest yield in 2001, and the lowest in 2003. Increments in both maximum and minimum temperatures by 4°C, decreased rice yield by 34% and wheat yield by 4% as compared to base scenario with current weather data. By increasing 4°C for both maximum and minimum temperature along with an increase in solar radiation by 1MJ/m2/day, rice yield decreased by 32% as compared to base scenario while wheat yields were not affected. With the increase in maximum and minimum temperatures by 4°C, and also an increase in CO2 concentration by 20 ppm from the standard CO2 concentration of 335 ppm, the reduction in rice yield was 33%, but in wheat yield was only 3%. Rainfed wheat yield increased by 7%, by increasing daily rainfall by 1.5 times, and by 13%, by doubling the rainfall, both after 96 days of sowing (DAS) to maturity. Lowering rainfall to zero, for each day after 96 DAS to until maturity reduced wheat yield by 18%. The increasing maximum and minimum temperatures irrespective of whether the CO2 concentration increased or not, seemed to have more adverse effects on rice than to wheat. Simulations demonstrated that CSM-CERES-Rice and CSM-CERES- Wheat are sensitive to CO2 and climatic parameters, and can be used to study the impact of future climate change on rice and wheat productivity in RW systems in Asia. Key words: CSM-CERES-Rice, CSM-CERES-Wheat, climate change, yield, phenology J. Inst. Agric. Anim. Sci. 27:103-110 (2006)

Effect of raised beds, irrigation and nitrogen management on growth, water use and yield of rice in south-eastern Australia

To remain economically and environmentally sustainable, Australian rice growers need to be able to readily respond to market opportunities and increase cropping system productivity and water productivity. Water availability is decreasing whereas its price is increasing. Alternative irrigation layouts and water management approaches could contribute to reduced water use and increased irrigation efficiency. This paper reports results for the first crop (rice) in a cropping system experiment to compare permanent raised bed and conventional layouts on a transitional red-brown earth at Coleambally, New South Wales. The performance of conventional ponded rice grown on a flat layout was compared with rice grown on 1.84-m wide, raised beds with furrow and subsurface drip irrigation. In addition, deep and shallow ponded water depth treatments (15 and 5 cm water depth over the beds) were imposed on the rice on beds during the reproductive period. A range of nitrogen (N) fertiliser rates (0–180 kg N/ha) was applied to all treatments. The traditional flat flooded treatment (Flat) achieved the highest grain yield of 12.7 t/ha, followed by the deep (Bed 15) and shallow (Bed 5) ponded beds (10.2 and 10.1 t/ha, respectively). The furrow (Furrow) irrigated bed treatment yielded 9.4 t/ha and the furrow/drip (Furr/Drip) treatment yielded the lowest grain yield (8.3 t/ha). Grain yield from all bed treatments was reduced owing to the wide furrows (0.8 m between edge rows on adjacent beds), which were not planted to rice. Rice crop water use was significantly different between the layout–irrigation treatments. The Flat, Bed 5 and Bed 15 treatments had similar input (irrigation + rainfall – surface drainage) water use (mean of 18.3 ML/ha). The water use for the Furrow treatment was 17.2 ML/ha and for the Furr/Drip treatment, 15.1 ML/ha. Input WP of the Flat treatment (0.68 t/ML) was higher than the raised bed treatments, which were all similar (mean 0.55 t/ML). This single season experiment shows that high yielding rice crops can be successfully grown on raised beds, but when beds are ponded after panicle initiation, there is no water saving compared with rice grown on a conventional flat layout. Preliminary recommendations for the growing of rice on raised beds are that the crop be grown as a flooded crop in a bankless channel layout. This assists with weed control and allows flooding for cold temperature protection, which is necessary with current varieties. Until we find effective herbicides and other methods of weed control and N application that do not require ponding, there is little scope for saving water while maintaining yield on suitable rice soil through the use of beds.