Carbon dioxide is one of the major causes of climate change. However, there is another gas, CO₂’s twin brother, which is even more harmful than CO₂, methane gas. Rice fields produce large quantities of methane, which aggravates global warming.
How is methane gas produced?
Methane is produced by raising cattle and, in greater quantities, in swamps and wetlands. One of the activities that produces the most methane is the planting of rice. Rice fields produce 10% of the methane released into the atmosphere.
Rice cultivation is very different from that of other cereals. It is grown in fields flooded with water. It is a plant that absorbs a lot of water. Since this is so, rice is a semi-aquatic crop and this is what protects it against weeds and insects.
However, the problem is generated when oxygen is depleted below the water layer in rice fields. At that point, it is when the microorganisms that feed on organic matter generate a large amount of methane gas.
Rice paddies aggravate global warming
Rice cultivation covers a large percentage of our planet’s surface area. The methane it releases into the atmosphere accounts for 10% of total emissions worldwide. In turn, Asian countries, which are the largest rice producers, emit 15%. Vietnam, for example, releases more methane in its rice fields than its transportation system. This excessive methane emission prevents the soil from replenishing the necessary oxygen.
A possible partial solution is to drain the paddy fields and replenish the water several times during crop development. In this way, the bacteria that produce methane cannot develop. According to experts, by draining the rice fields three to four times per season, methane emissions can be reduced by 50%.
This technique is called alternate wetting and drying (AWD). The paddy fields are flooded with water, about 5 to 7 centimeters deep. Then it is drained so that the level drops to about 10 to 15 centimeters, reaching the subsoil, to finish the process by flooding again with new water. It is an effective way to protect our planet.
Complications that make it difficult to apply the wetting technique.
However, in some Asian countries this technique is very difficult to control. In Vietnam, Cambodia and Thailand, strict controls do not exist. In turn, in Southeast Asia, the rainy season makes its application almost impossible. Even if farmers want to apply this system, the fields are never drained because of the heavy rains.
Another alternative solution would be to plant rice in rows or furrows, between two mounds of soil. The furrows are flooded and form channels, which favors oxygenation and avoids methane emissions.
Likewise, it is fundamental, to clean the sowings of the remains of the previous harvest. The lack of cleaning favors the formation of microorganisms that feed on the leftovers and produce methane gas.