Water management in irrigated lowland rice

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Cultivated rice (Oryza sativa) is an annual grass that evolved from a semi-aquatic ancestor. To ensure sufficient water, most rice farmers aim to maintain flooded conditions in their field. Lowland rice is grown in bunded fields (paddies) that are continuously flooded from crop establishment to close to harvest.<br><br>

Because of its flooded nature, lowland rice fields require a low of water. Worldwide, there are about 133 million ha of (harvested) lowland rice, of which some 79 million ha are equipped with irrigation facilities. The estimated water use (by evapotranspiration) of all harvested rice fields in the world is some 859 km3 per year. It takes on average 1,432 liters of evapotranspired water to produce 1 kg of rough rice. Irrigated rice receives an estimated 34-43% of the total world’s irrigation water, or about 24-30% of the entire world’s developed fresh water resources.<br><br>

Worldwide, water for agriculture is becoming increasingly scarce. Because of its semi-aquatic ancestry, rice is extremely sensitive to water shortage. When the soil water content drops below saturation, most rice varieties develop symptoms of water stress. Sound water management practices are needed to use water wisely and maximize rice yield. The sections in this chapter give guidelines on good water management practices for irrigated lowland rice.