Rice production systems 

Rice is fundamental for food security with approximately three billion people, about half of the world population, eating rice every day. Many of the poorest and most undernourished in Asia depend on rice as their staple food. Approximately 144 million ha of land is cultivated under rice each year. The waterlogged and warm soils of rice paddies make this production system a large emitter of methane. Rice production is and will be affected by changes in climate. Irregular rainfall, drier spells in the wet season (damaging young plants), drought and floods are all having an effect on yields. This has also caused outbreaks of pests and diseases, with large losses of crops and harvested products.

A number of methods and practices are being adopted to address these challenges. For example, production systems have been adapted by altering cropping patterns, planting dates and farm management techniques. For instance, embankments have been built to protect rice farms from floods and new drought and submergence tolerant varieties of rice are being produced and distributed by government institutions and the private sector. In addition, many farmers are diversifying their production systems, growing other cereals, vegetables and rearing fish and animals (such as pigs and chickens). The residues and waste from each system are being composted and used on the land, thereby reducing the need for external inputs. This diversification has increased incomes, improved nutrition, built resilience to shocks and minimized financial risks. The development of advanced modeling techniques, mapping the effect of climate change on rice-growing regions and providing crop insurance are other examples of managing risks and reducing vulnerability. Research on rice cultivation has identified that emissions mainly occur in the few months of the year when the ground is fully waterlogged. A more integrated approach to rice paddy irrigation and fertilizer application has therefore been found to substantially reduce emissions. The use of ammonium sulphate supplements have also been used to promote soil microbial activity and reduce methanogens. In addition, urea deep placement (UDP) technology has been developed where urea in the form of super granules or small briquettes is placed under the soil near the plant roots and out of the floodwater where it is susceptible to loss. In Bangladesh, this practice has shown 50-60 percent savings in urea use and yield increases of about 1 ton per ha. 

Mitigating methane emissions through new Irrigation Schemes (Bohol, Philippines)

Bohol Island is one of the biggest rice-growing areas in the Philippines' Visayas regions. Before the completion of the Bohol Integrated Irrigation System (BIIS) in 2007, two older reservoirs (Malinao and Capayas Dam) were beset by problems and unable to ensure sufficient water during the year's second crop (November to April), especially for farmers who live farthest downstream from the dam. This problem was aggravated by the practice of unequal water distribution and a preference by farmers for continuously flooded rice growing conditions.

In the face of declining rice production, the National Irrigation Administration (NIA) created an action plan for the BIIS. This included the construction of a new dam (Bayongan Dam; funded by a loan from the Japan Bank for International Cooperation) and the implementation of a water-saving technology called Alternate-Wetting and Drying (AWD) which was developed by the International Rice Research Institute (IRRI) in cooperation with national research institutes. The visible success of AWD in pilot farms, as well as specific training programmes for farmers, were able to dispelled the widely held perception of possible yield losses from non-flooded rice fields. Ample adoption of AWD facilitated an optimum use of irrigation water, so that the cropping intensity could be increased from ca. 119 % to ca. 160 % (related to the maximum of 200 % in these double-cropping systems). Moreover, according to the revised IPCC methodology (IPCC 2006, National Guidelines for Greenhouse Gas Inventories), 'multiple aeration', to which the AWD corresponds, potentially reduces methane emissions by 48 % compared to continuous flooding of rice fields. AWD therefore generates multiple benefits related to methane emission reduction (mitigation), reducing water use (adaptation where water is scarce), increasing productivity and contributing to food security (Bouman, B.A.M., Lampayan, R.M. and Toung, T.P., 2007, Water management in irrigated rice: coping with water scarcity). 

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last updated:  Thursday, December 6, 2012