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[Bali life] Alternate wetting and drying for rice work as climate change adaptation and mitigation.

Updated: Apr 7, 2021

I meant to write about yesterday but somehow failed to do so is AWD (Alternate wetting and drying). Usually, water is kept in the paddy fields at all times, but in this method, water is kept in the paddy fields for some time and then dried to about 15cm above the surface to reduce the amount of water used in rice farming.

When I was taught this farming method by a very famous professor more than a decade ago, I finally realised that although rice cultivation is a plant that needs water, it does not mean that it likes artificial flooding. It is a plant that can cope with flooding because its stems are straw-like. So if you just want to grow rice, you can grow it with much less water. In reality, however, we have created paddy fields to artificially create a flood situation. Why is this? Not so much for the sake of the plants but to reduce the drudgery of farming. By creating a flooded situation, other weeds cannot grow in the paddy fields, and certain types of fertilisers and pesticides can be spread over a wider area with less labour in a flooded situation. As a result, rice cultivation has spread so widely in Asia.

However, these paddy fields and rice cultivation have become a problem for climate change. In terms of carbon dioxide emissions, greenhouse gases started to increase before the industrial revolution, when many fossil fuels were consumed. Before the industrial revolution, there were two greenhouse gas sources: deforestation in Europe and paddy fields in Asia. They create a constant flooding situation, so anaerobic fermentation takes place in the soil, which produces a lot of methane gas. Now we have the problem of greenhouse gases from chemical fertilisers. Before chemical fertilisers, the methane gas from these paddy fields was probably the biggest greenhouse gas emission from agriculture in Asia. Methane gas has a greenhouse effect relative to carbon dioxide that depends on how far it rises in the atmosphere and how much of it remains in the form of methane, a ratio that can be as high as 25 or more than 100 times. It is estimated that AWD can reduce the production of methane by around 49%.

Simultaneously, water consumption can be reduced by 30% to 40%, making it an effective climate change adaptation measure after a period of increasing aridity. As I have written in previous blogs, for example, CMIP5 RCP4.5, a relatively conservative climate change projection, says that southern Indonesia, including Bali, will become drier. So if we can reduce water consumption by more than 30%, we can significantly reduce the water consumption in Bali. In a previous report to the United Nations on the impact of climate change, it was stated that Bali would be the province that would suffer the most from the reduction of water resources.

I'll write more about this tomorrow with some personal experiences.

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