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RICE

Postanthesis Moderate Wetting Drying Improves Both Quality and Quantity of Rice Yield

^a Key Lab. of Crop Genetics and Physiology of Jiangsu Province, Yangzhou Univ., Yangzhou, Jiangsu, China
^b Dep. of Biology, Hong Kong Baptist Univ., Hong Kong, China

^* Corresponding author (jcyang{at}yzu.edu.cn).

A major challenge in rice (Oryza sativa L.) production in China is to cope with a declining availability of fresh water without compromising grain yield and grain quality. This study was designed to determine if alternate wetting and moderate soil drying during grain filling could maintain grain yield and grain quality. Two rice cultivars, Zhendao 88 (japonica) and Shanyou 63 (indica), were field-grown at Yangzhou, China. Three irrigation treatments, alternate wetting and moderate soil drying (WMD, rewatered when soil water potential reached –25 kPa at 15–20 cm depth), alternate wetting and severe soil drying (WSD, rewatered when soil water potential reached –50 kPa), and conventional irrigation (CI, continuously flooded), were conducted from 6 d after heading to harvestable maturity. Root oxidation activity, the photosynthetic rate of the flag leaf, and activities of key enzymes in sucrose-to-starch conversion in grains during the late grain-filling stage were significantly increased under WMD, whereas they were significantly reduced under WSD. The grain yield was increased by 9.3 to 9.5% under WMD, while it was reduced by 7.5 to 7.8% under WSD, when compared with that under CI. Water applied to WMD was 44% and to WSD was 25% of the amount applied to CI. The WMD significantly improved milling, appearance, and cooking qualities, while WSD decreased these qualities. We conclude that a moderate wetting drying regime during the grain-filling phase of rice holds great promise to both increase yield quantity and quality and also could save precious fresh water resources.

Abbreviations: AWD, alternate wetting and drying irrigation • CI, conventional irrigation • DAH, days after heading • RVA, rapid viscoanalyzer • WMD, moderate soil drying • WSD, severe soil drying

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Received for publication May 21, 2007.