New varieties of rice being bred at the world renowned International Rice Research Institute (IRRI) at Los Bãnos in the Philippines promise to help rice farmers fight climate change and increase yields. Achieving a secure supply of food from a sustainable agriculture demands an integrated approach to crop production, planting the best new varieties and adopting improved agronomic techniques, such as no-till cultivations with paraquat for weed control.
New varieties of rice are resisting flooding and other climate problems
The Economist magazine has described the benefits that IRRI’s1 flood-resistant rice varieties are already bringing to five million farmers. Rice is a major crop in many environments considered to be at high risk from the adverse impacts of climate change. Although most rice in Asia is grown in paddy fields, deep water can devastate crops. Traditional rice growing systems themselves can exacerbate global warming because of the methane released from submerged, decaying plant material. Paraquat can help here.
New rice varieties
The Economist article2 describes how IRRI rice varieties with flood resistant genes are dramatically increasing yields when crops have been flooded-out for long periods. One farmer in the Indian state of Uttar Pradesh used to grow crops yielding about 1 tonne/hectare on his one hectare field. However, when he grew an IRRI variety with the ‘Sub 1’ flood resistance gene in a year with serious flooding he harvested 4.5 tonnes/hectare.
Figure 1. Annual rice yields in Asia and Africa (FAOSTAT)3.
It is reckoned that for every extra billion people on the planet, farmers need to grow another 100 million tonnes of rice each year to feed them. The ‘Green Revolution’, which saw the introduction of high yielding, short-straw varieties, had succeeded in producing enough extra rice to keep up with population growth in Asia since the 1960s, but this is levelling-off. Globally, rice yields are now increasing at barely half the rate needed to keep-up with population growth
In Africa, one third of the population depends on rice as a staple food and demand is rising by 20% each year. Much of the rice grown in Africa is grown on dry land, just like other cereals, and is subject to drought and heat stress. IRRI rice breeders are researching how to build-in tolerance to environmental stresses such as high salinity, heat and drought, as well as flooding, and are developing new varieties with these traits. Higher temperatures, especially at night when crops are flowering, mean that pollen is not released properly, flowers are not fertilized and grains fail to set. IRRI researchers have found a gene that instructs rice to flower in the early morning, so avoiding the mid-day heat. These new varieties are not genetically modified organisms, but are being bred using advanced technologies to make it easier to find useful genes and to produce new varieties faster.
Better agronomy with paraquat
Rising sea levels are causing flooding and salinity problems in the huge river delta areas in Asia, such as the Ganges-Brahmaputra in Bangladesh; Ayeyarwaddy in Myanmar; and the Mekong and Red River in Vietnam. Rice farmers in Indonesia are taking advantage of paraquat’s fast action to ensure weeds are controlled in fields that are subjected to frequent tidal flooding. Paraquat is the only herbicide that can act fast enough between tides to kill weeds because it is absorbed by leaves before it can be washed off – in just the same way that it is rainfast in less than half an hour. Fields do not need to be plowed when paraquat is used for weed control. Land preparation, which previously took up to two months on a typical one hectare farm, is reduced to around one week. A farming family can now manage crops on two to four hectares. Using paraquat, farmers can harvest two crops of high yielding varieties each year. With a paraquat-based system typically costing only 20% of traditional methods, tidal rice farmers can triple their income.
No-till rice cultivation systems using paraquat can help to mitigate the effects of climate change another way. After burial by plowing and flooding, weeds and crop remains decay in anaerobic conditions, producing methane, which is released from the soil to the atmosphere.4 Methane is 25 times more potent than carbon dioxide as a greenhouse gas and it has been estimated that, as such, rice paddies contribute between 5% and 20% of all man-made impact on global warming. Leaving dead weeds and other plant material on the surface after weed control with paraquat in a no-till system allows access to oxygen and avoids the production of methane. Research in Indonesia has shown that integrating the use of no-till, improved drainage regimes and paraquat for earlier planting markedly reduced methane emissions and increased overall crop productivity.
References
- International Rice Research Institute (IRRI)
- A bigger rice bowl. The Economist. 10 May 2014
- FAOSTAT
- Intergovernmental Panel on Climate Change. IPPC guidelines for national greenhouse gas inventories: agriculture