Journal of Food, Agriculture & Environment, Vol.12 (2), April 2014 465 www.world-food.net Journal of Food, Agriculture & Environment Vol.12 (2): 465-472. 2014 WFL Publisher Science and Technology Meri-Rastilantie 3 B, FI-00980 Helsinki, Finland e-mail: info@world-food.net Received 8 February 2014, accepted 4 April 2014. Progress and constraints of dry direct-seeded rice in China Hongyan Liu, Hussain Saddam, Manman Zheng, Liming Sun, Fahad Shah, Jianliang Huang, Kehui Cui and Lixiao Nie * National Key Laboratory of Crop Genetic Improvement, MOA Key Laboratory of Crop Ecophysiology and Farming System in the Middle Reaches of the Yangtze River, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, Hubei 430070, China. *e-mail: nielixiao@mail.hzau.edu.cn Abstract Imminent water crisis, labour scarcity and climate change threaten the sustainability and profitability of traditional transplanted rice. Direct-seeded rice (DSR) technology has been proposed to reduce water requirement, save labour demand, mitigate greenhouse gas emission and improve environmental sustainability. It involves three principal methods viz., dry seeding, wet seeding, and water seeding, among which dry DSR is gaining momentum due to relatively high grain yield, less water consumption, reduced labour intensity, facilitating to mechanization during crop establishment, and less greenhouse gases emission. In China, DSR is mainly planted in Jiangsu, Anhui, Zhejiang, Guangdong, Yunnan, Hubei, and Xinjiang provinces. Based on the existing evidence, here we review the progress and constraints of dry direct-seeded rice in China. The major challenges confronting the development of dry DSR in China are poor crop establishment, weed infestation, lodging susceptibility, N 2 O emission, weedy rice, yield decline under continuous cropping, and variety breeding; and the strategies which may help in mitigating the constraints to dry DSR. In spite of these constraints, we believe that it is a promising strategy to maintain the sustainability of rice production under future water shortage caused by global climate changes. Nonetheless, before the wide adoption of this technology, all the above constraints should be resolved. Key words: Dry direct-seeded rice, constraints, greenhouse gas emission, mitigating strategies, water saving, weeds. Introduction Rice is the most important crop and is a staple food for more than half of the world’s population. More than 28% of the total global rice is produced in China and the stability of rice production in China plays an important role in the world’s food security 1 . It is one of the prominent cereal crops in China, and about 65% of Chinese people rely on rice 2 . Nearly 95% of the rice grown in China is produced under traditional puddled transplanted conditions in China with prolonged periods of flooding 3 . However, several factors have threatened the sustainability and productivity of traditional puddled transplanted rice production system. Transplanted rice leads to higher losses of water through puddling, surface evaporation and percolation 4 . Puddling consumes up to 30% of the total rice water requirement 5 . In China, traditional flood-transplanted rice uses more than 50% of the fresh water resources diverted for human uses such as agriculture, urban use, 14 industries and hydropower 6 . Furthermore, the frequency of drought has markedly increased in many rice production areas of China due to global climate change 7 and per capita availability of water is decreasing day by day (Fig. 1). Labour shortage in rural areas is another constraint to the traditional rice production because of the increasing labour costs resulting from continuous migration of labour from rural areas to cities 6 . In many rural areas, it is difficult to engage labour for seedling-pulling and transplanting, resulting in poor crop management and decrease of rice production. In addition, the labour costs for rice production increased 2 - 3 times in recent years even for the poor quality of labour. The traditional transplanted rice is also a major source of greenhouse gas (GHG) emission, particularly methane causing global warming and climate change 8, 9 . Furthermore, repeated puddling operations adversely affect soil physical properties by dismantling soil aggregates, reducing permeability in subsurface layers, and forming hard-pans at shallow depths 10 , all of which can negatively affect the following non-rice upland crop in rotation 11 . Looming water crisis and labour shortage accompanied with all above factors ramble to develop strategies to increase sustainability and profitability of rice production systems. Direct-seeded rice (DSR) technology has been proposed to reduce water and other inputs requirement, save energy and labour demand, lowers the risk of methane emission and increase system productivity. DSR refers to the process of establishing the crop from seeds sown in the field rather than by transplanting seedlings from the nursery. In the world, 23% of rice is grown under DSR system 13 . In China, the planting area for DSR is increasing rapidly. By 2012, the percentage of DSR area to total rice planting area in China increased to 28%, and most of DSR area is located in the middle and lower reaches of Yangtze River in Jiangsu, Anhui, Zhejiang, Guangdong, Yunnan, Hubei, and Xinjiang provinces 14 . Taking Jiangsu province as an example, DSR planting area was enhanced by 10 times from 2001 to 2008 (Fig. 2). There are three principal methods of DSR systems: dry seeding, (sowing dry seeds into dry soil), wet seeding (sowing pre- germinated seeds on puddled soil), and water seeding (seeds