Performance of temperate aerobic rice under different water regimes in North China

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Abstract

Since the late 1990s, aerobic rice varieties have been released to farmers in the North China Plain to grow rice as a supplementary-irrigated upland crop to cope with water scarcity. Little is known about their yield potential, water use, water productivity (WP), and flood tolerance. In 2001–2002, experiments with aerobic rice varieties HD502 and HD297 and lowland rice variety JD305 were conducted under aerobic and flooded conditions. Under aerobic conditions, five irrigation treatments were implemented. Under flooded conditions, JD305 yielded up to 8.8 t ha−1, HD502 up to 6.8 t ha−1, and HD297 up to 5.4 t ha−1. Under aerobic conditions, the aerobic varieties yielded higher than the lowland variety. HD502 produced 3–3.5 t ha−1 with 450–500 mm total water input and 5.3–5.7 t ha−1 with 650 mm water input and more. HD297 produced 3–3.5 t ha−1 with 450–500 mm total water input and 4.7–5.3 t ha−1 with 650 mm water input and more. The water productivity of aerobic rice under aerobic conditions was higher or on a par with that of the lowland variety under flooded conditions, reaching values of 0.6–0.8 g grain kg−1 water. The relatively high yields of the aerobic varieties under aerobic soil conditions were obtained under “harsh” conditions for growing rice. The soil contained more than 80% sand, was permeable, and held water above field capacity for a few hours after irrigation only. The groundwater table was deeper than 20 m, the soil moisture content in the rootzone was mostly between 50 and 80% of saturation, and soil moisture tension went up to 90 kPa. We conclude that the aerobic rice varieties HD502 and HD297 are suitable for water-scarce environments, and can stand being periodically flooded.

Introduction

Rice is the most important cereal crop in Asia (Maclean et al., 2002). In China, most of the rice is produced on some 30 million ha in the irrigated lowlands (China Agricultural Almanac, 2000). However, lowland rice fields have relatively high water requirements and their sustainability is threatened by increasing water shortages (Bouman and Tuong, 2001). Water is especially scarce in the North China Plain, that contains 26% of the China's cultivated land, 30% of it's irrigated land, and 24% of it's total grain production (Geng et al., 2001). Rainfall is barely sufficient to support a one-season crop and grain production relies heavily on irrigation. However, since the plain also contains 24% of China's population and supports large cities and industry, competition for water is severe. Surface- and groundwater resources are overdrafted, leading to diminished river flows, lowering of groundwater tables, land subsidence, and the formation of cracks and sink holes (Postel, 1997, Geng et al., 2001).

The severe water shortages are prompting the Chinese government to take extreme measures, both locally, such as the ban on flooded rice cultivation around Beijing since 2001, and nationally, such as the schemes to divert water from the Yangtze River into the North China Plain. Since about 90% of all fresh water diverted is used in agriculture (Barker et al., 1999), a lot of attention focuses on the development of water-saving irrigation technologies. Though rice is not the cereal with the largest area in the North China Plain (Geng et al., 2001), it is an important target for potential reductions in water use because of its large water requirements compared with those of other food crops (Wang et al., 2002). Water-saving irrigation techniques based on the concept of alternate wetting (flooding) and drying (nonflooding) have been shown to save water (Bouman and Tuong, 2001, Tabbal et al., 2002, Belder et al., 2004) and are widely adopted in China (Zhi, 1993, Li, 2001). However, these technologies still maintain flooded conditions for most of the time and generally use more water than nonflooded aerobic systems such as used for wheat and maize (Bouman, 2001).

A new concept of reducing water requirements for rice is “aerobic rice” in which rice is grown like an upland crop with high inputs and supplementary irrigation when rainfall is insufficient (Bouman, 2001). In China, breeders have been developing special rice varieties for aerobic conditions since the 1980s, which are locally known as “Han Dao” varieties (Wang et al., 2002). These varieties have a high yield potential and differ from the traditional upland rice varieties (in Chinese, “Ju Dao”) that are targeted at the unfavorable and drought-prone uplands and have a low yield potential. After the release of early-generation aerobic rice varieties from 1985 to 1990, new elite varieties were released in the late 1990s, such as Han Dao 277, Han Dao 297, and Han Dao 502. In 2000, the China National Aerobic Rice Network estimated from individual spot checks in the field, inquiries with county and township-level agricultural bureaus and townships, and various unpublished data that, in the North China Plain, aerobic rice varieties are grown on some 80,000 ha (Wang et al., 2002). However, until now, little is known about the yield potential, water requirements, and water productivity (WP) of these new aerobic rice systems. Also, it is not known whether Han Dao varieties can stand flooding, since many water-short areas in the North China Plain are also prone to periodic flooding with heavy rainfall in mid-summer. Therefore, in 2001, we started field experiments with the objective to quantify and compare the yield, water use, and water productivity of aerobic rice varieties grown under aerobic and flooded conditions. In this paper, we report on the first 2 years of experimentation.

Section snippets

Aerobic fields

The aerobic field experiments were carried out from April to October in 2001 and 2002 at the Changping Experiment Station (40°02′N, 116°10′E; elevation of 43 m) of the China Agricultural University (CAU) in Beijing. The groundwater table is below 20 m. The soil is a sandy soil (Fluvisol) derived from river sediments. The texture and bulk density of the soil are given in Fig. 1, and the pF curve in Fig. 2. Whereas the soil texture was the same for the fields in 2001 and 2002, there was some

Weather

Monthly mean weather data are given in Table 3. In both years, rainfall was concentrated in June–August and was nearly absent during crop emergence in May. This same month, because of relatively high wind speeds, high solar radiation, and low humidity, atmospheric evaporative demand was high, with measured pan evaporation rates of more than 10 mm d−1. Temperatures were relatively high for rice growing from June till August, with maximum values recorded of 41.2 °C in 2001 and 40.1 °C in 2002, both

Conclusions and discussion

We conclude that the aerobic rice varieties HD502 and HD297 performed well under both aerobic and flooded soil conditions, confirming their suitability for water-scarce environments that periodically get flooded. As expected, lowland variety JD305 yielded higher than the aerobic varieties under flooded conditions. However, JD305 had a longer duration than the aerobic varieties, which may have contributed to its higher yield potential (Bouman et al., in press). Under aerobic conditions, the

Acknowledgments

The research reported here was partly supported by the Swiss Agency for Development and Cooperation (SDC) through the Water Workgroup of the Irrigated Rice Research Consortium (IRRC), and by the Dutch Government through the project “Potentials of water-saving technologies in rice production: an inventory and synthesis of options” of the Comprehensive Assessment of Water Management in Agriculture.

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