Grain yield, water productivity and CH4 emission of irrigated rice in response to water management in south China

Reducing water input and CH4 emission while maintaining grain yield is important for the sustainable rice production in south China. However, water-saving technology has not been widely adopted by farmers because of constrains in handling, effectiveness and reliableness. Recently a simplified and easy-to-use alternate wetting and drying technology, namely “safe” AWD, has been developed and recommended to farmers in Asian countries. However, the performance of the safe AWD technology has not yet been evaluated in south China. The objective of this study was to determine whether the safe AWD technology could maintain grain yield with reduced water input and CH4 emission as compared to the conventional farmer’s practice (FP) in south China. Two on-station field experiments were conducted in Guangzhou, Guangdong province during 2014 early and late seasons. In the early season, a hybrid rice variety, Tianyou 3618 (TY3618), was arranged in a randomized complete block design with three water treatments, i.e., AWD15, AWD30 and continuous flooding (CF). In the late season, a split-plot design was employed with four water management (AWD15, AWD30, CF and FP) as main plots and two varieties as subplots. The two varieties were TY3618 and Hefengzhan (HFZ, inbred). Field water level and soil water potential were recorded daily and the CH4 emission was monitored at 7-day intervals. Crop growth, grain yield and water productivities were measured. Results showed that grain yields under AWD15 and AWD30 were comparable with CF, while water input and total CH4 emissions were significantly reduced under the two AWD treatments for both seasons. In the late season, there were no significant differences in grain yield among the four irrigation treatments for HFZ. While for TY3618, grain yield in AWD30 was significantly lower than AWD15. Irrigation water input in AWD15 and AWD30 was 19.4% and 29.7% lower, and irrigation water productivity was 31.7–37.6% and 48.4–53.2% higher than FP, respectively. Over all, no significant differences were found in maximum tiller number, leaf area index, total aboveground dry weight, among the four irrigation treatments for HFZ. While for TY3618, the crop growth rate during grain-filling stage in AWD30 was significantly lower than CF and FP. The CH4 emission under AWD15 and AWD30 were 37.4–45.7% and 61.1–77.1% lower than FP, respectively. Multi-location on-farm comparisons were conducted in north, central, and southwest region of Guangdong province and the results confirmed that AWD15 could obtain comparable grain yield as FP with fewer irrigations. These findings suggested that the AWD15 could be used for water-saving and CH4 emission mitigation while maintaining grain yield in rice production in south China. This is the first report on the performance of safe AWD in south China.