By Pat Bell
Rice is one of the most important crops in the world. More than 3.5 billion people consider rice their staple crop and many people around the world consume rice with every meal. The global demand for rice in 2014/2015 was forecast to be 500.1 million tonnes while the global production forecast for the same period is of 496.2 million tonnes. Assessing the demand for water used to cultivate rice and methods for decreasing that water demand, could help save hundreds of millions of gallons.
The conventional method of rice production involves vast amounts of water. It is estimated that the production of 1 kg of rice grain requires between 800 to 5000 liters of water. Being such a water intensive process, it is important to understand how rice is grown and ways we can improve water efficiency. It is also important to note that the following description is relevant only to flooded rice production, which accounts for 75% of the world’s rice production.
To grow rice, a field is set aside and seeded with rice seeds. The small plot remains saturated to slightly flooded throughout the process. After around 21 days, the seedlings are ready to be “transplanted” into the field where they will actually be grown.
This other field has already been completely flooded with water and the soil has been worked over to turn the water-soil mixture into a soup like consistency. The seedlings are then transplanted (often by hand) into the field and placed into so-called “hills” that contain 3-4 seedlings each. From here, the rice grows in a flooded condition for most of the growing season, which can vary between 100-160 days depending upon the variety. About a week before the harvest, the field is allowed to dry in order to facilitate the process.
With the growing demand for rice and water, it is essential for alternative options of rice production to be explored that can maintain or increase yields while reducing water consumption. Failure to do so will result in increased disruptions in rice production and possible increases in poverty amongst rice farmers worldwide.
With this background of rice cultivation established, here are some strategies to decrease water demand from rice production:
- Alternate Wetting and Drying (AWD): For AWD systems, the rice field is flooded and then allowed to dry for a period of between 1 and 2 weeks and then re-flooded again. This decreases the total amount of water needed for irrigation by 20-50% while still retaining the benefits of flooding the field (i.e. weed control). However, this requires irrigation schemes capable of managing water effectively as well as trained farmers and extension agents to determine when the flooding periods are to occur. Additionally, yield reductions of 0-70% compared to continuously flooded rice has been reported.
- System of Rice Intensification (SRI): This is an alternative rice production system that was developed in Madagascar. The basic tenants of SRI include earlier seedling transplanting, increasing the plant spacing, and controlling water through AWD or by using lower levels of flooding, and planting only 1 plant per hill. This reduction in water use and potential for similar yields as flooded conditions make SRI a possible strategy in the future. However, results have been variable globally and more research is needed to assess which regions will benefit from SRI. Additionally, SRI reduces the amount of seeds needed to cultivate in a given area as it uses 1 seedling per hill instead of 3-4 seedlings per hill. However, SRI typically requires more labor for weeding throughout the season.
- Dry direct seeding: These systems skip the nursery step in rice production and instead plant seeds directly into the field they will be grown in. Depending on the region, this can result in water savings between 12-33%. This is very much similar to the common methods of wheat and maize production. In doing so, the field is not flooded prior to planting and thus requires less irrigation water. After the seeds are planted and covered with soil, the field can be flooded. A downside to this method is the increased competition from weeds due to the un-flooded condition during seedling establishment.
- Aerobic rice: Aerobic rice systems are a drastic change from the traditional flooded rice system. Rice is planted and grown in soils that are not flooded or saturated. This requires new varieties of rice suitable for these conditions; however, the agronomic management of this system is very similar to other crops like wheat, maize, and sorghum. The field can still be irrigated or rain-fed; however, the goal is to not allow the soil to become saturated or flooded. While this seems like an obvious solution to reducing water demand in rice systems, farmers are sometimes hesitant to adopt this system due to cultural ingrained rice growing traditions. Additionally, some regions are not suitable for aerobic rice systems as they are frequently flooded due to natural conditions.
To achieve the above efficiency improvements, here are some strategies that can help move water use in rice systems in the right direction:
- More research. This seems very simple and obvious, especially as some of the bigger debates in rice science and rice research are due to lack of data from various systems (such as SRI) that make it difficult to determine their effectiveness and suitability for smallholder farmers.
- Participatory research with farmers includes the farmers in the design, implementation, and data analysis of the research. Often times farmers are reluctant to try new technologies because they do not fully understand them or do not fully understand how researchers “know” this system to be productive. Participatory research helps to break down this barrier and also provides the researchers with invaluable feedback and local knowledge from the farmers.
- Water pricing. Many countries still do not price water or price it incorrectly for their local situation. Effective pricing of water insures necessary infrastructure for irrigated rice is maintained while providing incentives for farmers to increase water use efficiency in their systems.
Because rice is such an important part of the global food system and demands a large amount of water, it is essential that policies, research, and programs seeking to increase rice productivity be aware of alternate rice systems and their benefits and drawbacks.
From even just this short overview, it is apparent that water saving practices will vary in efficacy by regions around the world. This basic understanding of the importance of rice, the traditional methods of rice production, as well as the possible alternate production systems can help move the dialogue and implementation of programs that more effectively address water issues in rice production. Failure to do so will have far reaching implications on both the global food systems as well as national and international politics.
*This article was originally published by Sense & Sustainability on April 1, 2015.