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Agronomic performance of high-yielding rice variety grown under alternate wetting and drying irrigation
Field Crops Research 126 (2012) 16–22
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Agronomic performance of high-yielding rice variety grown under alternate wetting and drying irrigation Fengxian Yao a , Jianliang Huang a , Kehui Cui a , Lixiao Nie a , Jing Xiang b , Xiaojin Liu a , Wei Wu a , Mingxia Chen c , Shaobing Peng a,∗ a Crop Physiology and Production Center (CPPC), National Key Laboratory of Crop Genetic Improvement, MOA Key Laboratory of Crop Physiology, Ecology and Cultivation (The Middle Reaches of Yangtze River), Huazhong Agricultural University, Wuhan, Hubei 430070, China b State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, Zhejiang 310006, China c College of Life Science, Henan Normal University, Xinxiang, Henan 453002, China
a r t i c l e
i n f o
Article history: Received 6 August 2011 Received in revised form 23 September 2011 Accepted 23 September 2011 Keywords: Alternate wetting and drying irrigation Grain yield Nitrogen use efficiency “Super” hybrid rice Water productivity
a b s t r a c t Alternate wetting and drying (AWD) irrigation has been proven to be an effective water-saving technology for irrigated rice system. There is limited information on the performance of “super” hybrid rice varieties under AWD conditions. This study was conducted to compare grain yield and other related traits between a “super” hybrid rice variety and a water-saving and drought-resistance rice (WDR) variety and to identify plant traits which were responsible for varietal difference in grain yield under AWD conditions. Yangliangyou 6 (YLY6, a “super” hybrid rice variety) and Hanyou 3 (HY3, a WDR variety) were grown under AWD and continuously flood-irrigated (CF) conditions across different levels of nitrogen input in Hubei, China in 2009 and 2010. Grain yield, yield attributes, total water input, water productivity, and nitrogen use efficiency were measured. AWD saved 24% and 38% irrigation water compared with CF in 2009 and 2010, respectively. There was insignificant difference in grain yield between AWD and CF. On average, YLY6 produced 21.5% higher yield than HY3 under AWD conditions. Like grain yield, YLY6 showed consistently higher water productivity and physiological nitrogen use efficiency than HY3. Both total dry weight and harvest index contributed to higher grain yield of YLY6. Among the yield components, large sink size which was caused by more spikelets per panicle was mainly responsible for high grain yield of YLY6 compared with HY3. These results suggest that high-yielding varieties developed for the continuously flood-irrigated rice system could still produce high yield under safe AWD experienced in this study. “Super” hybrid rice varieties do not necessarily require more water input to produce high grain yield. Increasing the number of spikelets per panicle should be a primary target of breeding high-yielding rice varieties for AWD conditions. © 2011 Elsevier B.V. All rights reserved.
1. Introduction China is facing a severe problem of scarcity in water resources, with less than one-quarter of the world average per capita (Li, 2006). Rice production alone consumes about 50% of the freshwater resources in China (Cai and Chen, 2000). More than 95% of the rice is produced under flood-irrigated conditions in China (Maclean et al., 2002). At the field level, flood-irrigated rice requires two to three times more water than other cereal crops such as wheat and maize (Bouman et al., 2007). The scarcity of freshwater resources now threatens rice production in China (International Water Management Institute (IWMI), 2000). Thus, there is an
∗ Corresponding author. Tel.: +86 27 8728 8380; fax: +86 27 8728 8380. E-mail address: [email protected] (S. Peng). 0378-4290/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2011.09.018
urgent need for reducing water consumption for rice production by developing water-saving irrigation technologies. China has pioneered various water-saving irrigation technologies to achieve more water-efficient irrigation for agricultural systems (Peng, 2011; Zhang, 2011). For rice, water-saving technologies include alternate wetting and drying (AWD) irrigation, saturated soil culture, and aerobic rice (Bouman et al., 2007). AWD is one of the most commonly practiced water-saving irrigation technologies in Asia (Kukal et al., 2005; Li, 2001; Tuong et al., 2005). In AWD, irrigation water is applied to achieve intermittent flooded and non-flooded soil conditions. The frequency of irrigation and duration of non-flooding can be determined by re-irrigating (to achieve flooded conditions) after a fixed number of non-flooded days, when a certain threshold of soil water potential is reached, when the ponded water table level drops to a certain level below the soil surface, when cracks appear on the soil surface or when plants show visual symptoms of water shortage (Peng and Bouman,
F. Yao et al. / Field Crops Research 126 (2012) 16–22
2007). Yield penalty was commonly observed under AWD compared with continuously flood-irrigated (CF) rice (Bouman and Tuong, 2001). In general, AWD increased water productivity with respect to total water input because the yield reduction was smaller than the amount of water saved. Variety has a large influence on the grain yield of AWD (Peng and Bouman, 2007). Six out of 30 different varieties demonstrated higher yields in AWD than CF (De Datta et al., 1973a,b). More recently, Virk et al. (2003) evaluated seven hybrids and 37 inbred varieties under AWD and CF during the 2003 dry season at IRRI. Overall, AWD saved 17% of the water used in CF. Yield losses under AWD ranged from 3 to 23% for hybrids and from −6 to 26% for inbreds. There were three hybrids and six inbred varieties that were adapted to AWD conditions. Both studies, De Datta et al. (1973a,b) and Virk et al. (2003), suggest that genetic variability in adaptability to AWD conditions exists in rice. However, these studies did not identify the plant traits that contributed to varietal difference in yield performance under AWD conditions. The development of water-saving and drought-resistance rice (WDR) is another strategy to produce more rice with less water (Luo, 2010; Serraj et al., 2011). WDR aims to produce the same yield as paddy rice with much less water consumption (50% water saving compared with the normal paddy rice) under irrigated conditions. At the same time, WDR should have the ability of drought tolerance to minimize yield loss under water-limited conditions. Hanyou 3 (HY3), which is an elite WDR, was developed and released to farmers for commercial rice production (Luo, 2010). Several field studies were conducted to determine grain yield, water saving, water productivity and drought tolerance of HY3 (Huang et al., 2008; Liu et al., 2009; Si et al., 2010; Yu et al., 2005). HY3 demonstrated an ability of drought tolerance. Water saving and relatively high yield was also achieved in HY3. However, these studies did not compare HY3 with high-yielding varieties for the continuously flood-irrigated rice system such as “super” hybrid rice varieties. China’s “super” hybrid varieties have increased rice yield potential by 8–15% compared with ordinary hybrid and inbred varieties (Peng et al., 2008, 2009; Yuan, 2001). Increased sink size due to large and heavy panicles and improved biomass production due to great canopy light interception are responsible for high yield potential of “super” hybrid rice (Katsura et al., 2007; Zhang et al., 2009). Up to now, about 70 “super” hybrid rice varieties were commercially released in China (Zhu et al., 2010). In recent years, “super” hybrid rice varieties have occupied about 20% rice planting areas in China. However, the high-yielding of “super” hybrid rice varieties was often achieved when water was amply supplied. It is unknown if these varieties that were developed for the continuously flood-irrigated rice system are suitable for AWD conditions. In current study, a “super” hybrid rice variety (Yangliangyou 6) and a WDR variety (HY3) were grown under AWD and CF conditions across different levels of N input. The objectives were (1) to determine if “super” hybrid rice variety could still produce high yield under AWD conditions, (2) to determine if the drought-tolerant trait of WDR was needed for a safe AWD experienced in this study, and (3) to identify plant traits which were responsible for varietal difference in grain yield under AWD conditions.
2. Materials and methods Experiments were conducted in 2009 and 2010 in two adjacent fields at Zhangbang Village, Dajin Township, Wuxue County, Hubei Province, China (29◦ 51 N, 115◦ 33 E). The soil properties of the two fields are shown in Table 1. Monthly mean temperature and monthly total rainfall were obtained from the Meteorological Bureau of Wuxue County and are presented in Table 2.
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Table 1 Soil properties of the top 0–15 cm layer in two experimental fields at Wuxue County, Hubei Province, China in 2009 and 2010. Soil properties
2009
2010
pH Organic matter (g kg−1 ) Alkali hydrolysable N (mg kg−1 ) Olsen-P (mg kg−1 ) Exchangeable K (mg kg−1 )
5.68 34.6 202.0 15.4 30.2
5.53 27.6 137.3 19.0 102.2
Table 2 Monthly mean maximum temperature (Tmax ), minimum temperature (Tmin ), and rainfall at Wuxue County, Hubei Province, China in 2009 and 2010. Data were obtained from the Meteorological Bureau of Wuxue County. Month
June July August September
Tmax (◦ C)
Tmin (◦ C)
Rainfall (mm)
2009
2010
2009
2010
30.5 34.3 32.2 29.1
24.6 33.3 35.4 29.1
23.3 23.7 24.0 20.3
20.6 25.1 24.4 20.7
2009 159 280 107 44
2010 107 302 157 148
Experimental design was split–split plot with four replications in both years. The main plots were two water treatments (CF and AWD). The sub-plots were three N treatments: zero N control, moderate N rate (MN, 108 kg ha−1 ), and high N rate (HN, 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010). The sub-sub-plots were two rice varieties: Yangliangyou 6 (YLY6, “super” hybrid rice) and Hanyou 3 (HY3, WDR). To minimize seepage between plots, all bunds were covered with plastic film and the plastic film was installed to a depth of 20 cm below soil surface. The main plots were separated with double bunds to prevent water flow from CF to AWD treatments. Ponded water depth in the entire field was kept between 1 and 3 cm during the first 10 days after transplanting. After this, the water level was allowed to fluctuate between 1 and 10 cm in the CF regime during the whole rice growing season. In AWD treatment, PVC tubes (25 cm long and 10 cm in diameter) were installed to a depth of 15 cm below soil surface (Tuong et al., 2009). Holes (about 0.5 cm in diameter and 2 cm apart) were perforated on all sides of the tube. When the ponded water disappeared in the PVC tubes, then irrigation was applied to re-flood the field up to 5 cm in AWD treatment. This cycle was repeated throughout the season. In both water treatments, no mid-season drainage was imposed before panicle initiation. The amount of irrigation water was monitored with a flow meter installed in the irrigation pipelines. The amount of rainfall during the rice growing season was recorded by two rain gauges located around the experimental field. The depth of the groundwater table was monitored using 200-cm-long PVC pipes with a diameter of 5 cm, whose lower circular surface (120 cm) was perforated with 0.5-cm holes at 2-cm intervals. The groundwater tubes were installed on the bunds to a depth of 150 cm from the soil surface. YLY6, which is a two-line hybrid rice variety, has characteristics of high yield, good quality and strong resistance to disease (Zhao et al., 2006). HY3, which is a three-line hybrid rice variety, has characteristics of drought resistance and water-saving (Yu et al., 2005; Luo, 2010). Seedlings were raised in the seedbed with sowing date of 16 May in 2009 and 12 May in 2010. Transplanting was done on 12 June in 2009 and 7 June in 2010 at a hill spacing of 13.3 cm × 30 cm with two seedlings per hill. Nitrogen was applied three times: 39% as basal, 28% at tillering and 33% at panicle initiation. The amounts of other fertilizers applied as basal were 60 kg P ha−1 , 45 kg K ha−1 and 5 kg Zn ha−1 . Potassium was topdressed at panicle initiation at a rate of 45 kg ha−1 . Weeds, diseases and insects were intensively controlled throughout the
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F. Yao et al. / Field Crops Research 126 (2012) 16–22
entire rice growth periods in both years. No noticeable crop damage from weeds, insects or diseases was observed in the experiments. At maturity, 12 hills were taken diagonally from a 5-m2 area where grain yield was determined on 5–8 September for HY3 and 22 September to 1 October for YLY6. Panicle number was recorded from those 12 hills. Plant samples were separated into straw and panicles. The dry weight of straw was determined after ovendrying at 70 ◦ C to constant weight. Panicles were hand-threshed and the filled spikelets were separated from unfilled spikelets with a blower. Three subsamples of 30 g of filled spikelets taken for counting the number of filled spikelets. All unfilled spikelets were counted to determine the number of unfilled spikelets. Dry weights of rachis and filled and unfilled spikelets were determined after oven-drying at 70 ◦ C to constant weight. Aboveground total biomass was the total dry matter of straw, rachis, and filled and unfilled spikelets. Spikelets per panicle, grain-filling percentage (100 × filled spikelet number/total spikelet number), and harvest index (100 × filled spikelet weight/aboveground total biomass) were calculated. Grain yield was determined from a 5-m2 area in each plot and adjusted to the standard moisture content of 0.14 g H2 O g−1 fresh weight. Water productivity was defined as the grain yield per unit of total water input including irrigation and precipitation. Tissue N concentration was determined by micro Kjeldahl digestion, distillation, and titration (Bremner and Mulvane, 1982) to calculate aboveground total N uptake. Physiological N use efficiency (PE) was calculated as grain yield divided by total N uptake. Fertilizer N recovery efficiency (RE) was calculated as the ratio of the increase in total N uptake at maturity that resulted from N fertilizer to the fertilizer N rate. Agronomic N use efficiency (AE) was calculated as the increase in grain yield per kg N applied. Data were analyzed following analysis of variance (SAS Institute, 2003) and means were compared based on the least significant difference (LSD) test at the 0.05 probability level.
3. Results Average temperature from June to September was similar between 2009 and 2010, but the hottest month was July in 2009 and August in 2010 based on maximum temperature (Table 2). Total rainfall from June to September was higher in 2010 than in 2009, and the difference was the greatest in September when the rice crop was in the grain filling period (Table 2 and Fig. 1a and b). In 2009, CF received 10–12 times of irrigation from transplanting to maturity, while 7–8 times of irrigation was applied to AWD. The number of irrigation was reduced in 2010, when 8–9 and 6 times of irrigation were applied to CF and AWD, respectively. On average, AWD reduced the number of irrigation by about 3 compared with CF. Total rainfall from transplanting to maturity was about 510 mm in 2009 and 630 mm in 2010, which represented approximately 70% of total water input during the same period (Table 3). The amount of irrigation water input in CF was 67 mm and 126 mm higher than in AWD in 2009 and 2010, respectively. On average, AWD saved 24% irrigation water in 2009 and 38% irrigation water in 2010 compared with CF. Groundwater table depths during the experiments are shown in Fig. 1c and d. The groundwater table depth was within 30 and 40 cm for most of the rice growing season during 2009 and 2010, respectively. The higher groundwater table depth in 2009 than in 2010 was due to the different location of the two fields. The field used for 2010 experiment was located in slightly high land compared with the field used for 2009 experiment. Field water depth showed a clear difference between the two water treatments. As expected, CF had deeper field water depth than AWD for the most of the rice growing season during both years (Fig. 1e and f).
Table 3 Irrigation, rainfall, and total water input (irrigation plus rainfall) during growing period under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Irrigation water included 60 mm for land preparation for all treatments. Rainfall was measured in the experimental fields. Varietya
2009 YLY6 HY3 2010 YLY6 HY3 a b
Irrigation (mm)
CF
AWD
296 ± 3b 253 ± 2
224 ± 3 192 ± 5
334 ± 4 334 ± 4
208 ± 7 208 ± 5
Rainfall (mm)
Total water input (mm) CF
AWD
533 489
829 742
758 681
684 579
1018 914
892 787
YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. Data are averages (mean ± SE) of three N treatments.
Table 4 Analysis of variance for grain yield, water productivity (WP ), aboveground total dry weight (TDW), harvest index (HI), and total N uptake (TN ) at harvest at Wuxue County, Hubei Province, China in 2009 and 2010. Source of variation 2009 Water regime (W) Nitrogen (N) Variety (V) W×N W×V N×V W×N×V 2010 W N V W×N W×V N×V W×N×V
Yield
WP
TDW
ns
*
**
**
**
**
ns ns
ns ns
*
*
ns
ns
ns
HI
TN
ns
ns
ns
**
**
**
**
**
*
ns ns ns ns
ns ns ns
ns ns ns ns
*
**
ns
ns
ns
**
**
**
**
**
**
**
**
**
*
ns ns ns ns
ns ns ns ns
ns ns ns ns
ns ns
ns ns ns ns
*
ns
ns = non significant. * Significant at p ≤ 0.05. ** Significant at p ≤ 0.01.
Table 4 shows the analysis of variance for grain yield, water productivity, above ground total dry weight, harvest index, total N uptake at maturity in each year. All these traits were significantly affected by N levels and varieties during both years. Water regime had a significant effect on water productivity in the two years. Only interaction between N and variety had a consistent effect on harvest index across the two years. Grain yield of YLY6 was significantly higher than that of HY3 in the two years regardless of N levels and water treatments (Table 5). On average, YLY6 produced 26.5% and 21.5% higher yield than HY3 in CF and AWD, respectively. Application of N at rate of 108 kg ha−1 significantly increased grain yield over the zero-N control. Further increase in N rate did not significantly increase grain yield and even reduced grain yield significantly for YLY6 grown under CF in 2010. There was no consistent difference in grain yield between CF and AWD. Grain yield in 2009 was about 13% higher than that in 2010 for CF and the difference was reduced by half for AWD. Like grain yield, YLY6 showed consistently higher water productivity than HY3. The average water productivity of YLY6 was 0.73–1.03 kg m−3 under both water regimes, significantly higher than those of HY3 with 0.63–0.96 kg m−3 . Application of N generally increased water productivity compared with zero-N control. Greater water productivity was consistently observed in AWD than in CF. The difference in total dry weight between the two varieties was significant and consistent across N levels, water treatments and years (Table 6). On average, YLY6 produced 12.5% and 17.7% higher
F. Yao et al. / Field Crops Research 126 (2012) 16–22
19
140 (a)
(b)
(c)
(d)
(e)
(f)
Rainfall (mm)
120 100 80 60 40 20
Groundwater table depth (cm)
0 10 0 -10 -20 -30 -40 -50
CF AWD
Field water depth (cm)
-60 15 10 5 0 -5 -10
CF AWD
-15 0
20
40
60
80
100
120 0
20
40
60
80
100
120
Days after transplanting Fig. 1. Rainfall, groundwater table depth, and field water depth under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 (a, c, and e) and 2010 (b, d, and f). Error bars are ±SE (e and f).
total dry weight than HY3 in 2009 and 2010, respectively. Total dry weight was increased with N application and there was insignificant difference in total dry weight between MN and HN. In general, YLY6 demonstrated a higher harvest index than HY3. Application of N resulted in a decrease in harvest index. There was inconsistent difference in total dry weight and harvest index between the two water treatments. Spikelets per m2 for YLY6 were higher than that for HY3 which was mainly due to more spikelets per panicle in YLY6 than in HY3 (Table 7). There was no clear difference in panicles per m2 between the two varieties. The two varieties had no difference in grain filling percentage in 2009, but HY3 had a significantly higher grain filling percentage than YLY6 in 2010. Grain weight of HY3 was significantly higher than that of YLY6, especially in 2010. Application of N increased spikelets per m2 mainly due to an increase in panicles per
m2 , while N treatments had a small influence on spikelets per panicle. There was insignificant difference in spikelets per m2 between MN and HN. Grain filling percentage was generally reduced by the N application. There was inconsistent difference in grain weight among N treatments. Overall, water treatments had insignificant effects on yield components. Total N uptake of YLY6 was higher than that of HY3, but the difference was statistically significant only for CF (Table 8). YLY6 had 11–16% higher PE than HY3. There was small and inconsistent difference in RE and AE between the two varieties. Total N uptake increased and PE decreased as the rate of N application increased. There was insignificant difference in RE between MN and HN. In general, HN reduced AE compared with MN. No consistent difference in total N uptake and N use efficiencies was observed between CF and AWD.
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F. Yao et al. / Field Crops Research 126 (2012) 16–22
Table 5 Grain yield and water productivity of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Grain yield (t ha−1 )
Water productivity (kg m−3 )
CF
AWD
CF
AWD
ZN MN HN Mean ZN MN HN Mean
7.31 b 8.45 a 8.95 a 8.23 A 6.15 b 7.02 a 6.80 a 6.66 B
7.26 b 8.40 a 8.28 a 7.98 A 6.08 b 7.06 a 6.60 ab 6.58 B
0.87 b 0.99 a 1.05 a 0.97 A 0.81 b 0.92 a 0.89 a 0.88 B
0.94 b 1.08 a 1.08 a 1.03 A 0.91 a 1.00 a 0.95 a 0.96 B
ZN MN HN Mean ZN MN HN Mean
6.88 b 8.12 a 7.29 b 7.43 A 5.10 b 6.28 a 5.85 ab 5.74 B
6.60 b 8.10 a 7.95 a 7.55 A 5.39 b 6.64 a 6.58 a 6.20 B
0.67 b 0.80 a 0.71 b 0.73 A 0.56 b 0.68 a 0.63 a 0.63 B
0.74 b 0.91 a 0.88 a 0.85 A 0.68 b 0.86 a 0.82 ab 0.79 B
Nb
2009 YLY6
HY3
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6; HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , and HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010.
Table 6 Aboveground total dry weight and harvest index of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Total dry weight (t ha−1 )
Harvest index (%)
CF
AWD
CF
AWD
ZN MN HN Mean ZN MN HN Mean
12.40 b 15.05 a 16.38 a 14.61 A 10.99 b 13.64 a 14.06 a 12.90 B
11.64 b 16.41 a 14.98 a 14.34 A 11.28 b 13.50 a 13.76 a 12.85 B
54.2 a 49.0 b 47.3 b 50.2 A 47.1 a 46.3 a 45.4 a 46.3 B
54.2 a 49.8 b 47.1 c 50.4 A 49.0 a 46.6 ab 45.3 b 46.9 B
ZN MN HN Mean ZN MN HN Mean
12.39 b 15.59 a 15.35 a 14.44 A 11.31 b 12.10 ab 13.02 a 12.37 B
12.34 b 15.06 a 15.92 a 14.44 A 10.55 b 12.88 a 13.69 a 12.15 B
52.6 a 48.3 b 42.9 c 47.9 A 45.9 a 47.1 a 44.4 a 45.8 B
52.1 a 50.8 a 46.7 b 49.9 A 44.1 a 46.6 a 45.2 a 45.3 B
Nb
2009 YLY6
HY3
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010.
4. Discussion The hydrological conditions of our experimental site were representative for many large-scale irrigated lowland rice areas in China because the groundwater tables of this study were comparable to the experiments previously conducted in Hubei and Zhejiang provinces by Belder et al. (2004) and Cabangon et al. (2004). In addition, the amount and distribution pattern of total rainfall during the
rice growing seasons in 2009 and 2010 were not much different from the 10-year average (data not shown). Following evidences suggest that rice plants in AWD of this study did not experience water stress during the entire growing season: (1) a minimum of 681 mm of total water input (irrigation plus rainfall) was received from land preparation to harvest, (2) shallow groundwater table (less than 40 cm) was observed during most time of growing season, and (3) AWD received only 11% less water input than CF. Total rainfall from transplanting to maturity accounted for approximately 70% of total water input. When rainfall was not considered, AWD saved 24% irrigation water in 2009 and 38% irrigation water in 2010 compared with CF. There was insignificant difference in grain yield between AWD and CF because no water stress occurred in AWD in this study. Belder et al. (2004) reported that the soil water potential (<−10 kPa) during the rice-growing season was usually not a limitation factor for plant growth and yield formation when safe AWD was practiced in Hubei Province. Tuong et al. (2009) stated that no yield penalty was observed when safe AWD was practiced. Bouman and Tuong (2001) summarized 31 field experiments on AWD and they found the yield reductions of 0–70% in AWD treatments compared with continuously flooded controls in 92% of the experiments. The large variability in the performance of AWD was caused by differences in the irrigation interval, soil properties and hydrological conditions across the experiments. In addition, variety is a major factor that influences the performance of AWD (Peng and Bouman, 2007). In this study, the “super” hybrid rice variety (YLY6) outyielded the WDR variety (HY3) under AWD conditions consistently across the two years. The yield difference between the two varieties in CF was similar to that in AWD. On average, YLY6 produced 1.5 t ha−1 more grain yield than HY3 in AWD. These results suggest that highyielding varieties developed for the continuously flood-irrigated rice system could still produce high yield under safe AWD experienced in this study. The yield of HY3 in the farmers’ fields was 10% higher than that of Shanyou 63, with saving 50% irrigation water in both lowland and upland (Huang et al., 2008; Si et al., 2010; Yu et al., 2005). Shanyou 63 is an ordinary hybrid variety that was developed for flood-irrigated rice system. In our study, however, there was a yield gap of more than 20% between YLY6 and HY3 under AWD conditions. One would argue that HY3, as a WDR variety, will perform better than YLY6 if both experience severe water stress. Our results suggest that the trait of drought tolerance in WDR might not be necessary when safe AWD was practiced in rice planting regions with shallow groundwater table. China’s “super” hybrid rice varieties have an obvious advantage in yield potential over ordinary hybrid and inbred rice varieties in flood-irrigated rice system (Peng et al., 2008; Zhang et al., 2009). This offers another opportunity to increase the water productivity of flood-irrigated lowland rice (Peng and Bouman, 2007). In the past field experiments on AWD, only inbred or ordinary hybrid varieties were used (Belder et al., 2004; Bouman and Tuong, 2001; Cabangon et al., 2004, 2011; Matsuo and Mochizuki, 2009; Yang et al., 2007). Many researchers have assumed that “super” hybrid rice varieties need ample supply of water to fully express their yield potential. The yield of “super” hybrid rice variety did not significantly vary between AWD and CF in our study, which strongly suggests that “super” hybrid rice varieties do not necessarily require more water input to produce high grain yield. Similarly, in irrigated lowland rice area with a shallow groundwater table, “super” hybrid varieties still seem to be a better choice for AWD. Varietal difference in grain yield under AWD conditions was reported in previous studies (De Datta et al., 1973a,b; Virk et al., 2003). In these studies, varieties that were bred for continuously flood-irrigated rice system were evaluated under AWD conditions. Several hybrid and inbred varieties did not show yield reduction
F. Yao et al. / Field Crops Research 126 (2012) 16–22
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Table 7 Yield components of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Nb
Panicles per m2
Spikelets per panicle
Spikelets per m2 (×103 )
Grain filling (%)
1000-Grain weight (g)
CF
CF
CF
AWD
CF
AWD
CF
AWD
AWD
AWD
2009 YLY6
HY3
ZN MN HN Mean ZN MN HN Mean
198 b 241 a 264 a 234 A 188 b 225 a 249 a 220 B
195 b 263 a 249 a 235 A 185 b 224 a 240 a 216 B
143 a 143 a 137 a 141 A 116 a 120 a 111 a 116 B
140 a 136 a 133 a 136 A 123 a 115 a 111 a 116 B
28.6 b 34.5 a 36.1 a 33.1 A 21.8 c 27.1 a 27.9 a 25.6 B
27.2 b 35.8 a 33.0 a 32.0 A 22.7 b 25.7 ab 26.7 a 25.0 B
86.6 a 79.0 b 79.0 b 81.5 A 82.6 a 81.7 a 81.3 a 81.9 A
86.7 a 83.5 ab 79.8 b 83.3 A 83.9 a 84.3 a 83.0 a 83.7 A
27.0 a 26.8 a 26.9 a 26.9 B 28.5 a 28.3 a 27.9 a 28.2 A
26.5 b 27.1 a 26.6 b 26.7 B 28.7 a 28.2 ab 27.9 b 28.2 A
ZN MN HN Mean ZN MN HN Mean
178 b 223 a 222 a 208 A 170 b 202 a 217 a 196 A
165 c 198 b 231 a 198 A 163 b 207 a 213 a 194 A
173 b 181 ab 195 a 183 A 124 a 123 a 114 a 121 B
177 b 197 a 179 ab 184 A 118 a 121 a 123 a 121 B
30.9 b 40.3 a 43.4 a 38.2 A 21.2 b 25.0 a 24.7 a 23.6 B
29.5 b 39.0 a 41.3 a 36.6 A 19.3 b 25.1 a 26.2 a 23.5 B
83.4 a 75.8 b 62.4 c 73.9 B 84.8 a 79.6 b 81.5 ab 81.9 A
86.1 a 78.6 b 71.0 c 78.6 B 83.3 a 81.2 a 82.0 a 82.2 A
25.3 a 23.8 b 22.6 c 23.9 B 28.9 a 28.6 a 28.7 a 28.7 A
25.3 a 24.0 b 23.7 b 24.4 B 28.9 a 29.4 a 28.8 a 29.0 A
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010. Table 8 Total N uptake, physiological N use efficiency (PE), agronomic N use efficiency (AE), and N recovery efficiency (RE) of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Nb
Total N uptake (kg ha−1 )
PE (kg kg−1 )
CF
CF
AWD
CF
AWD
CF
AWD
AWD
AE (kg kg−1 )
RE (%)
2009 YLY6
HY3
ZN MN HN Mean ZN MN HN Mean
116 c 181 b 216 a 171 A 102 b 171 a 194 a 156 B
112 c 178 b 206 a 165 A 106 c 165 b 198 a 157 A
63.6 a 46.9 b 41.3 b 50.6 A 60.6 a 41.2 b 35.0 b 45.6 B
65.1 a 47.6 b 40.5 c 51.1 A 57.7 a 43.7 b 34.0 c 45.1 B
– 60.5 a 53.3 a 56.9 A – 63.6 a 48.7 a 56.1 A
– 60.9 a 49.7 a 55.3 A – 54.5 a 48.9 a 51.7 A
– 10.5 a 8.6 a 9.6 A – 8.1 a 3.4 b 5.7 B
– 10.5 a 5.3 b 7.9 A – 9.0 a 2.7 b 5.8 A
ZN MN HN Mean ZN MN HN Mean
102 c 164 b 202 a 156 A 97 c 142 b 177 a 139 B
99 c 151 b 188 a 146 A 88 b 151 a 163 a 134 A
67.0 a 49.9 b 36.2 c 51.0 A 53.3 a 44.4 b 34.3 c 44.0 B
67.5 a 54.3 b 42.9 c 54.9 A 61.1 a 44.4 b 40.4 b 48.6 B
– 56.6 a 52.8 a 54.7 A – 41.8 a 42.6 a 42.2 A
– 48.1 a 47.3 a 47.7 A – 57.7 a 39.3 a 48.5 A
– 11.5 a 2.2 b 6.8 A – 10.9 a 4.0 b 7.4 A
– 13.9 a 7.1 b 10.5 A – 11.6 a 6.2 b 8.9 A
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010.
under AWD conditions compared with CF. A few varieties demonstrated even higher yields in AWD than CF. These results suggest that genetic variability in adaptability to AWD conditions exists in rice. Peng and Bouman (2007) proposed a strategy of crop improvement for high water productivity: that is to breed rice varieties with high grain yield under water-saving technologies such as AWD. Both total dry weight and harvest index contributed to higher grain yield of YLY6 in AWD and CF compared with HY3. On average, YLY6 had 22 days longer growth duration than HY3 in both AWD and CF, which also explains the yield difference between the two varieties. Among the yield components, large sink size which was caused by more spikelets per panicle was mainly responsible for high grain yield of YLY6 compared with HY3 in AWD. In continuously flood-irrigated rice system, improved yield potential with “super” hybrid rice is attributed to increased sink size due to large
and heavy panicles and improved biomass production due to great canopy light interception (Katsura et al., 2007; Zhang et al., 2009). The same strategy of developing varieties with large and heavy panicles can be used for increasing yield potential of AWD. Therefore, increasing the number of spikelets per panicle should be a primary target of breeding high-yielding rice varieties for AWD conditions. Acknowledgments This study was a part of the PhD thesis research of the first author. Funding was provided by the Major Project of International Cooperation, National Natural Science Foundation of China (No. 30821140349). It was also supported by the National Basic Program of China (No. 2009CB118600), and MOA Special Fund for Agroscientific Research in the Public Interest of China (No. 201203096).
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F. Yao et al. / Field Crops Research 126 (2012) 16–22
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Maclean, J.L., Dawe, D.C., Hardy, B., Hettel, G.P., 2002. Rice Almanac, third ed. Inter˜ Philippines, pp. 1–253. national Rice Research Institute (IRRI), Los Banos, Matsuo, N., Mochizuki, T., 2009. Growth and yield of six rice cultivars under three water-saving cultivations. Plant Prod. Sci. 12, 514–525. Peng, S., 2011. Water resources strategy and agricultural development in China. J. Exp. Bot. 6, 1709–1713. Peng, S., Bouman, B.A.M., 2007. Prospects for genetic improvement to increase lowland rice yields with less water and nitrogen. In: Spiertz, J.H.J., Struik, P.C., van Laar, H.H. (Eds.), Scale and Complexity in Plant Systems Research: Gene–Plant–Crop Relations. , pp. 251–266. Peng, S., Khush, G.S., Virk, P., Tang, Q., Zou, Y., 2008. Progress in ideotype breeding to increase rice yield potential. Field Crops Res. 108, 32–38. Peng, S., Tang, Q., Zou, Y., 2009. Current status and challenges of rice production in China. Plant Prod. Sci. 12, 3–8. SAS Institute, 2003. SAS Version 9.1.2. 2002–2003. SAS Institute, Inc., Cary, NC. Serraj, R., Mcnally, K.L., Loedin, I.S., Kohli, A., Haefele, S.M., Atlin, G., Kumar, A., 2011. Drought resistance improvement in rice: an integrated genetic and resource management strategy. Plant Prod. Sci. 14, 1–14. Si, Q., Wang, F., Zhang, G., Li, Z., 2010. Demonstration and applied prospect of drought-resistant hybrid rice Hanyou 3 in rainfed area of northeastern Sichuan. Hybrid Rice 25, 48–50 (in Chinese, with English abstract). Tuong, T.P., Bouman, B.A.M., Lampayan, R., 2009. A simply tool to effectively implement water saving alternate wetting and drying irrigation for rice. ICID Newsletter 2009/4:5. www.icid.org/nl2009-4.pdf. Tuong, T.P., Bouman, B.A.M., Mortimer, M., 2005. More rice, less water-integrated approaches for increasing water productivity in irrigated rice-based systems in Asia. Plant Prod. Sci. 8, 231–241. Virk, P.S., Balasubramanian, V., Virmani, S.S., Lopena, V., Cabangon, R., Nanda, G.S., 2003. Enhancing water and land productivity in irrigated rice in two Asian river basins. In: Poster presented at Baseline Conference for the CGIAR Challenge Program on Water and Food, Nairobi, 2–6 November. Yang, J., Liu, K., Wang, Z., Du, Y., Zhang, J., 2007. Water-saving and high-yielding irrigation for lowland rice by controlling limiting values of soil water potential. J. Integr. Plant Biol. 49, 1445–1454. Yu, X., Mei, H., Li, M., Liang, W., Xu, X., Zhang, J., Luo, L., 2005. Development and application of water-saving or drought tolerant hybrid rice. Mol. Plant Breed. 3, 637–641 (in Chinese, with English abstract). Yuan, L., 2001. Breeding of super hybrid rice. In: Peng, S., Hardy, B. (Eds.), Rice Research for Food Security and Poverty Alleviation. International Rice Research ˜ Institute, Los Banos, Philippines, pp. 143–149. Zhang, J., 2011. China’s success in increasing per capita food production. J. Exp. Bot. 62, 3707–3711. Zhang, Y., Tang, Q., Zou, Y., Li, D., Qin, J., Yang, S., Chen, L., Xia, B., Peng, S., 2009. Yield potential and radiation use efficiency of “super” hybrid rice grown under subtropical conditions. Field Crops Res. 114, 91–98. Zhao, B., Wang, P., Zhang, H., Zhu, Q., Yang, J., 2006. Source-sink and grain-filling characteristics of two-line hybrid rice Yangliangyou 6. Rice Sci. 13, 17–25. Zhu, D., Cheng, S., Zhang, Y., Lin, X., Chen, H., 2010. Analysis of status and constraints of rice production in the world. Agric. Sci. China 43, 474–479.
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Agronomic performance of high-yielding rice variety grown under alternate wetting and drying irrigation Fengxian Yao a , Jianliang Huang a , Kehui Cui a , Lixiao Nie a , Jing Xiang b , Xiaojin Liu a , Wei Wu a , Mingxia Chen c , Shaobing Peng a,∗ a Crop Physiology and Production Center (CPPC), National Key Laboratory of Crop Genetic Improvement, MOA Key Laboratory of Crop Physiology, Ecology and Cultivation (The Middle Reaches of Yangtze River), Huazhong Agricultural University, Wuhan, Hubei 430070, China b State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, Zhejiang 310006, China c College of Life Science, Henan Normal University, Xinxiang, Henan 453002, China
a r t i c l e
i n f o
Article history: Received 6 August 2011 Received in revised form 23 September 2011 Accepted 23 September 2011 Keywords: Alternate wetting and drying irrigation Grain yield Nitrogen use efficiency “Super” hybrid rice Water productivity
a b s t r a c t Alternate wetting and drying (AWD) irrigation has been proven to be an effective water-saving technology for irrigated rice system. There is limited information on the performance of “super” hybrid rice varieties under AWD conditions. This study was conducted to compare grain yield and other related traits between a “super” hybrid rice variety and a water-saving and drought-resistance rice (WDR) variety and to identify plant traits which were responsible for varietal difference in grain yield under AWD conditions. Yangliangyou 6 (YLY6, a “super” hybrid rice variety) and Hanyou 3 (HY3, a WDR variety) were grown under AWD and continuously flood-irrigated (CF) conditions across different levels of nitrogen input in Hubei, China in 2009 and 2010. Grain yield, yield attributes, total water input, water productivity, and nitrogen use efficiency were measured. AWD saved 24% and 38% irrigation water compared with CF in 2009 and 2010, respectively. There was insignificant difference in grain yield between AWD and CF. On average, YLY6 produced 21.5% higher yield than HY3 under AWD conditions. Like grain yield, YLY6 showed consistently higher water productivity and physiological nitrogen use efficiency than HY3. Both total dry weight and harvest index contributed to higher grain yield of YLY6. Among the yield components, large sink size which was caused by more spikelets per panicle was mainly responsible for high grain yield of YLY6 compared with HY3. These results suggest that high-yielding varieties developed for the continuously flood-irrigated rice system could still produce high yield under safe AWD experienced in this study. “Super” hybrid rice varieties do not necessarily require more water input to produce high grain yield. Increasing the number of spikelets per panicle should be a primary target of breeding high-yielding rice varieties for AWD conditions. © 2011 Elsevier B.V. All rights reserved.
1. Introduction China is facing a severe problem of scarcity in water resources, with less than one-quarter of the world average per capita (Li, 2006). Rice production alone consumes about 50% of the freshwater resources in China (Cai and Chen, 2000). More than 95% of the rice is produced under flood-irrigated conditions in China (Maclean et al., 2002). At the field level, flood-irrigated rice requires two to three times more water than other cereal crops such as wheat and maize (Bouman et al., 2007). The scarcity of freshwater resources now threatens rice production in China (International Water Management Institute (IWMI), 2000). Thus, there is an
∗ Corresponding author. Tel.: +86 27 8728 8380; fax: +86 27 8728 8380. E-mail address: [email protected] (S. Peng). 0378-4290/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2011.09.018
urgent need for reducing water consumption for rice production by developing water-saving irrigation technologies. China has pioneered various water-saving irrigation technologies to achieve more water-efficient irrigation for agricultural systems (Peng, 2011; Zhang, 2011). For rice, water-saving technologies include alternate wetting and drying (AWD) irrigation, saturated soil culture, and aerobic rice (Bouman et al., 2007). AWD is one of the most commonly practiced water-saving irrigation technologies in Asia (Kukal et al., 2005; Li, 2001; Tuong et al., 2005). In AWD, irrigation water is applied to achieve intermittent flooded and non-flooded soil conditions. The frequency of irrigation and duration of non-flooding can be determined by re-irrigating (to achieve flooded conditions) after a fixed number of non-flooded days, when a certain threshold of soil water potential is reached, when the ponded water table level drops to a certain level below the soil surface, when cracks appear on the soil surface or when plants show visual symptoms of water shortage (Peng and Bouman,
F. Yao et al. / Field Crops Research 126 (2012) 16–22
2007). Yield penalty was commonly observed under AWD compared with continuously flood-irrigated (CF) rice (Bouman and Tuong, 2001). In general, AWD increased water productivity with respect to total water input because the yield reduction was smaller than the amount of water saved. Variety has a large influence on the grain yield of AWD (Peng and Bouman, 2007). Six out of 30 different varieties demonstrated higher yields in AWD than CF (De Datta et al., 1973a,b). More recently, Virk et al. (2003) evaluated seven hybrids and 37 inbred varieties under AWD and CF during the 2003 dry season at IRRI. Overall, AWD saved 17% of the water used in CF. Yield losses under AWD ranged from 3 to 23% for hybrids and from −6 to 26% for inbreds. There were three hybrids and six inbred varieties that were adapted to AWD conditions. Both studies, De Datta et al. (1973a,b) and Virk et al. (2003), suggest that genetic variability in adaptability to AWD conditions exists in rice. However, these studies did not identify the plant traits that contributed to varietal difference in yield performance under AWD conditions. The development of water-saving and drought-resistance rice (WDR) is another strategy to produce more rice with less water (Luo, 2010; Serraj et al., 2011). WDR aims to produce the same yield as paddy rice with much less water consumption (50% water saving compared with the normal paddy rice) under irrigated conditions. At the same time, WDR should have the ability of drought tolerance to minimize yield loss under water-limited conditions. Hanyou 3 (HY3), which is an elite WDR, was developed and released to farmers for commercial rice production (Luo, 2010). Several field studies were conducted to determine grain yield, water saving, water productivity and drought tolerance of HY3 (Huang et al., 2008; Liu et al., 2009; Si et al., 2010; Yu et al., 2005). HY3 demonstrated an ability of drought tolerance. Water saving and relatively high yield was also achieved in HY3. However, these studies did not compare HY3 with high-yielding varieties for the continuously flood-irrigated rice system such as “super” hybrid rice varieties. China’s “super” hybrid varieties have increased rice yield potential by 8–15% compared with ordinary hybrid and inbred varieties (Peng et al., 2008, 2009; Yuan, 2001). Increased sink size due to large and heavy panicles and improved biomass production due to great canopy light interception are responsible for high yield potential of “super” hybrid rice (Katsura et al., 2007; Zhang et al., 2009). Up to now, about 70 “super” hybrid rice varieties were commercially released in China (Zhu et al., 2010). In recent years, “super” hybrid rice varieties have occupied about 20% rice planting areas in China. However, the high-yielding of “super” hybrid rice varieties was often achieved when water was amply supplied. It is unknown if these varieties that were developed for the continuously flood-irrigated rice system are suitable for AWD conditions. In current study, a “super” hybrid rice variety (Yangliangyou 6) and a WDR variety (HY3) were grown under AWD and CF conditions across different levels of N input. The objectives were (1) to determine if “super” hybrid rice variety could still produce high yield under AWD conditions, (2) to determine if the drought-tolerant trait of WDR was needed for a safe AWD experienced in this study, and (3) to identify plant traits which were responsible for varietal difference in grain yield under AWD conditions.
2. Materials and methods Experiments were conducted in 2009 and 2010 in two adjacent fields at Zhangbang Village, Dajin Township, Wuxue County, Hubei Province, China (29◦ 51 N, 115◦ 33 E). The soil properties of the two fields are shown in Table 1. Monthly mean temperature and monthly total rainfall were obtained from the Meteorological Bureau of Wuxue County and are presented in Table 2.
17
Table 1 Soil properties of the top 0–15 cm layer in two experimental fields at Wuxue County, Hubei Province, China in 2009 and 2010. Soil properties
2009
2010
pH Organic matter (g kg−1 ) Alkali hydrolysable N (mg kg−1 ) Olsen-P (mg kg−1 ) Exchangeable K (mg kg−1 )
5.68 34.6 202.0 15.4 30.2
5.53 27.6 137.3 19.0 102.2
Table 2 Monthly mean maximum temperature (Tmax ), minimum temperature (Tmin ), and rainfall at Wuxue County, Hubei Province, China in 2009 and 2010. Data were obtained from the Meteorological Bureau of Wuxue County. Month
June July August September
Tmax (◦ C)
Tmin (◦ C)
Rainfall (mm)
2009
2010
2009
2010
30.5 34.3 32.2 29.1
24.6 33.3 35.4 29.1
23.3 23.7 24.0 20.3
20.6 25.1 24.4 20.7
2009 159 280 107 44
2010 107 302 157 148
Experimental design was split–split plot with four replications in both years. The main plots were two water treatments (CF and AWD). The sub-plots were three N treatments: zero N control, moderate N rate (MN, 108 kg ha−1 ), and high N rate (HN, 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010). The sub-sub-plots were two rice varieties: Yangliangyou 6 (YLY6, “super” hybrid rice) and Hanyou 3 (HY3, WDR). To minimize seepage between plots, all bunds were covered with plastic film and the plastic film was installed to a depth of 20 cm below soil surface. The main plots were separated with double bunds to prevent water flow from CF to AWD treatments. Ponded water depth in the entire field was kept between 1 and 3 cm during the first 10 days after transplanting. After this, the water level was allowed to fluctuate between 1 and 10 cm in the CF regime during the whole rice growing season. In AWD treatment, PVC tubes (25 cm long and 10 cm in diameter) were installed to a depth of 15 cm below soil surface (Tuong et al., 2009). Holes (about 0.5 cm in diameter and 2 cm apart) were perforated on all sides of the tube. When the ponded water disappeared in the PVC tubes, then irrigation was applied to re-flood the field up to 5 cm in AWD treatment. This cycle was repeated throughout the season. In both water treatments, no mid-season drainage was imposed before panicle initiation. The amount of irrigation water was monitored with a flow meter installed in the irrigation pipelines. The amount of rainfall during the rice growing season was recorded by two rain gauges located around the experimental field. The depth of the groundwater table was monitored using 200-cm-long PVC pipes with a diameter of 5 cm, whose lower circular surface (120 cm) was perforated with 0.5-cm holes at 2-cm intervals. The groundwater tubes were installed on the bunds to a depth of 150 cm from the soil surface. YLY6, which is a two-line hybrid rice variety, has characteristics of high yield, good quality and strong resistance to disease (Zhao et al., 2006). HY3, which is a three-line hybrid rice variety, has characteristics of drought resistance and water-saving (Yu et al., 2005; Luo, 2010). Seedlings were raised in the seedbed with sowing date of 16 May in 2009 and 12 May in 2010. Transplanting was done on 12 June in 2009 and 7 June in 2010 at a hill spacing of 13.3 cm × 30 cm with two seedlings per hill. Nitrogen was applied three times: 39% as basal, 28% at tillering and 33% at panicle initiation. The amounts of other fertilizers applied as basal were 60 kg P ha−1 , 45 kg K ha−1 and 5 kg Zn ha−1 . Potassium was topdressed at panicle initiation at a rate of 45 kg ha−1 . Weeds, diseases and insects were intensively controlled throughout the
18
F. Yao et al. / Field Crops Research 126 (2012) 16–22
entire rice growth periods in both years. No noticeable crop damage from weeds, insects or diseases was observed in the experiments. At maturity, 12 hills were taken diagonally from a 5-m2 area where grain yield was determined on 5–8 September for HY3 and 22 September to 1 October for YLY6. Panicle number was recorded from those 12 hills. Plant samples were separated into straw and panicles. The dry weight of straw was determined after ovendrying at 70 ◦ C to constant weight. Panicles were hand-threshed and the filled spikelets were separated from unfilled spikelets with a blower. Three subsamples of 30 g of filled spikelets taken for counting the number of filled spikelets. All unfilled spikelets were counted to determine the number of unfilled spikelets. Dry weights of rachis and filled and unfilled spikelets were determined after oven-drying at 70 ◦ C to constant weight. Aboveground total biomass was the total dry matter of straw, rachis, and filled and unfilled spikelets. Spikelets per panicle, grain-filling percentage (100 × filled spikelet number/total spikelet number), and harvest index (100 × filled spikelet weight/aboveground total biomass) were calculated. Grain yield was determined from a 5-m2 area in each plot and adjusted to the standard moisture content of 0.14 g H2 O g−1 fresh weight. Water productivity was defined as the grain yield per unit of total water input including irrigation and precipitation. Tissue N concentration was determined by micro Kjeldahl digestion, distillation, and titration (Bremner and Mulvane, 1982) to calculate aboveground total N uptake. Physiological N use efficiency (PE) was calculated as grain yield divided by total N uptake. Fertilizer N recovery efficiency (RE) was calculated as the ratio of the increase in total N uptake at maturity that resulted from N fertilizer to the fertilizer N rate. Agronomic N use efficiency (AE) was calculated as the increase in grain yield per kg N applied. Data were analyzed following analysis of variance (SAS Institute, 2003) and means were compared based on the least significant difference (LSD) test at the 0.05 probability level.
3. Results Average temperature from June to September was similar between 2009 and 2010, but the hottest month was July in 2009 and August in 2010 based on maximum temperature (Table 2). Total rainfall from June to September was higher in 2010 than in 2009, and the difference was the greatest in September when the rice crop was in the grain filling period (Table 2 and Fig. 1a and b). In 2009, CF received 10–12 times of irrigation from transplanting to maturity, while 7–8 times of irrigation was applied to AWD. The number of irrigation was reduced in 2010, when 8–9 and 6 times of irrigation were applied to CF and AWD, respectively. On average, AWD reduced the number of irrigation by about 3 compared with CF. Total rainfall from transplanting to maturity was about 510 mm in 2009 and 630 mm in 2010, which represented approximately 70% of total water input during the same period (Table 3). The amount of irrigation water input in CF was 67 mm and 126 mm higher than in AWD in 2009 and 2010, respectively. On average, AWD saved 24% irrigation water in 2009 and 38% irrigation water in 2010 compared with CF. Groundwater table depths during the experiments are shown in Fig. 1c and d. The groundwater table depth was within 30 and 40 cm for most of the rice growing season during 2009 and 2010, respectively. The higher groundwater table depth in 2009 than in 2010 was due to the different location of the two fields. The field used for 2010 experiment was located in slightly high land compared with the field used for 2009 experiment. Field water depth showed a clear difference between the two water treatments. As expected, CF had deeper field water depth than AWD for the most of the rice growing season during both years (Fig. 1e and f).
Table 3 Irrigation, rainfall, and total water input (irrigation plus rainfall) during growing period under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Irrigation water included 60 mm for land preparation for all treatments. Rainfall was measured in the experimental fields. Varietya
2009 YLY6 HY3 2010 YLY6 HY3 a b
Irrigation (mm)
CF
AWD
296 ± 3b 253 ± 2
224 ± 3 192 ± 5
334 ± 4 334 ± 4
208 ± 7 208 ± 5
Rainfall (mm)
Total water input (mm) CF
AWD
533 489
829 742
758 681
684 579
1018 914
892 787
YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. Data are averages (mean ± SE) of three N treatments.
Table 4 Analysis of variance for grain yield, water productivity (WP ), aboveground total dry weight (TDW), harvest index (HI), and total N uptake (TN ) at harvest at Wuxue County, Hubei Province, China in 2009 and 2010. Source of variation 2009 Water regime (W) Nitrogen (N) Variety (V) W×N W×V N×V W×N×V 2010 W N V W×N W×V N×V W×N×V
Yield
WP
TDW
ns
*
**
**
**
**
ns ns
ns ns
*
*
ns
ns
ns
HI
TN
ns
ns
ns
**
**
**
**
**
*
ns ns ns ns
ns ns ns
ns ns ns ns
*
**
ns
ns
ns
**
**
**
**
**
**
**
**
**
*
ns ns ns ns
ns ns ns ns
ns ns ns ns
ns ns
ns ns ns ns
*
ns
ns = non significant. * Significant at p ≤ 0.05. ** Significant at p ≤ 0.01.
Table 4 shows the analysis of variance for grain yield, water productivity, above ground total dry weight, harvest index, total N uptake at maturity in each year. All these traits were significantly affected by N levels and varieties during both years. Water regime had a significant effect on water productivity in the two years. Only interaction between N and variety had a consistent effect on harvest index across the two years. Grain yield of YLY6 was significantly higher than that of HY3 in the two years regardless of N levels and water treatments (Table 5). On average, YLY6 produced 26.5% and 21.5% higher yield than HY3 in CF and AWD, respectively. Application of N at rate of 108 kg ha−1 significantly increased grain yield over the zero-N control. Further increase in N rate did not significantly increase grain yield and even reduced grain yield significantly for YLY6 grown under CF in 2010. There was no consistent difference in grain yield between CF and AWD. Grain yield in 2009 was about 13% higher than that in 2010 for CF and the difference was reduced by half for AWD. Like grain yield, YLY6 showed consistently higher water productivity than HY3. The average water productivity of YLY6 was 0.73–1.03 kg m−3 under both water regimes, significantly higher than those of HY3 with 0.63–0.96 kg m−3 . Application of N generally increased water productivity compared with zero-N control. Greater water productivity was consistently observed in AWD than in CF. The difference in total dry weight between the two varieties was significant and consistent across N levels, water treatments and years (Table 6). On average, YLY6 produced 12.5% and 17.7% higher
F. Yao et al. / Field Crops Research 126 (2012) 16–22
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140 (a)
(b)
(c)
(d)
(e)
(f)
Rainfall (mm)
120 100 80 60 40 20
Groundwater table depth (cm)
0 10 0 -10 -20 -30 -40 -50
CF AWD
Field water depth (cm)
-60 15 10 5 0 -5 -10
CF AWD
-15 0
20
40
60
80
100
120 0
20
40
60
80
100
120
Days after transplanting Fig. 1. Rainfall, groundwater table depth, and field water depth under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 (a, c, and e) and 2010 (b, d, and f). Error bars are ±SE (e and f).
total dry weight than HY3 in 2009 and 2010, respectively. Total dry weight was increased with N application and there was insignificant difference in total dry weight between MN and HN. In general, YLY6 demonstrated a higher harvest index than HY3. Application of N resulted in a decrease in harvest index. There was inconsistent difference in total dry weight and harvest index between the two water treatments. Spikelets per m2 for YLY6 were higher than that for HY3 which was mainly due to more spikelets per panicle in YLY6 than in HY3 (Table 7). There was no clear difference in panicles per m2 between the two varieties. The two varieties had no difference in grain filling percentage in 2009, but HY3 had a significantly higher grain filling percentage than YLY6 in 2010. Grain weight of HY3 was significantly higher than that of YLY6, especially in 2010. Application of N increased spikelets per m2 mainly due to an increase in panicles per
m2 , while N treatments had a small influence on spikelets per panicle. There was insignificant difference in spikelets per m2 between MN and HN. Grain filling percentage was generally reduced by the N application. There was inconsistent difference in grain weight among N treatments. Overall, water treatments had insignificant effects on yield components. Total N uptake of YLY6 was higher than that of HY3, but the difference was statistically significant only for CF (Table 8). YLY6 had 11–16% higher PE than HY3. There was small and inconsistent difference in RE and AE between the two varieties. Total N uptake increased and PE decreased as the rate of N application increased. There was insignificant difference in RE between MN and HN. In general, HN reduced AE compared with MN. No consistent difference in total N uptake and N use efficiencies was observed between CF and AWD.
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Table 5 Grain yield and water productivity of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Grain yield (t ha−1 )
Water productivity (kg m−3 )
CF
AWD
CF
AWD
ZN MN HN Mean ZN MN HN Mean
7.31 b 8.45 a 8.95 a 8.23 A 6.15 b 7.02 a 6.80 a 6.66 B
7.26 b 8.40 a 8.28 a 7.98 A 6.08 b 7.06 a 6.60 ab 6.58 B
0.87 b 0.99 a 1.05 a 0.97 A 0.81 b 0.92 a 0.89 a 0.88 B
0.94 b 1.08 a 1.08 a 1.03 A 0.91 a 1.00 a 0.95 a 0.96 B
ZN MN HN Mean ZN MN HN Mean
6.88 b 8.12 a 7.29 b 7.43 A 5.10 b 6.28 a 5.85 ab 5.74 B
6.60 b 8.10 a 7.95 a 7.55 A 5.39 b 6.64 a 6.58 a 6.20 B
0.67 b 0.80 a 0.71 b 0.73 A 0.56 b 0.68 a 0.63 a 0.63 B
0.74 b 0.91 a 0.88 a 0.85 A 0.68 b 0.86 a 0.82 ab 0.79 B
Nb
2009 YLY6
HY3
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6; HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , and HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010.
Table 6 Aboveground total dry weight and harvest index of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Total dry weight (t ha−1 )
Harvest index (%)
CF
AWD
CF
AWD
ZN MN HN Mean ZN MN HN Mean
12.40 b 15.05 a 16.38 a 14.61 A 10.99 b 13.64 a 14.06 a 12.90 B
11.64 b 16.41 a 14.98 a 14.34 A 11.28 b 13.50 a 13.76 a 12.85 B
54.2 a 49.0 b 47.3 b 50.2 A 47.1 a 46.3 a 45.4 a 46.3 B
54.2 a 49.8 b 47.1 c 50.4 A 49.0 a 46.6 ab 45.3 b 46.9 B
ZN MN HN Mean ZN MN HN Mean
12.39 b 15.59 a 15.35 a 14.44 A 11.31 b 12.10 ab 13.02 a 12.37 B
12.34 b 15.06 a 15.92 a 14.44 A 10.55 b 12.88 a 13.69 a 12.15 B
52.6 a 48.3 b 42.9 c 47.9 A 45.9 a 47.1 a 44.4 a 45.8 B
52.1 a 50.8 a 46.7 b 49.9 A 44.1 a 46.6 a 45.2 a 45.3 B
Nb
2009 YLY6
HY3
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010.
4. Discussion The hydrological conditions of our experimental site were representative for many large-scale irrigated lowland rice areas in China because the groundwater tables of this study were comparable to the experiments previously conducted in Hubei and Zhejiang provinces by Belder et al. (2004) and Cabangon et al. (2004). In addition, the amount and distribution pattern of total rainfall during the
rice growing seasons in 2009 and 2010 were not much different from the 10-year average (data not shown). Following evidences suggest that rice plants in AWD of this study did not experience water stress during the entire growing season: (1) a minimum of 681 mm of total water input (irrigation plus rainfall) was received from land preparation to harvest, (2) shallow groundwater table (less than 40 cm) was observed during most time of growing season, and (3) AWD received only 11% less water input than CF. Total rainfall from transplanting to maturity accounted for approximately 70% of total water input. When rainfall was not considered, AWD saved 24% irrigation water in 2009 and 38% irrigation water in 2010 compared with CF. There was insignificant difference in grain yield between AWD and CF because no water stress occurred in AWD in this study. Belder et al. (2004) reported that the soil water potential (<−10 kPa) during the rice-growing season was usually not a limitation factor for plant growth and yield formation when safe AWD was practiced in Hubei Province. Tuong et al. (2009) stated that no yield penalty was observed when safe AWD was practiced. Bouman and Tuong (2001) summarized 31 field experiments on AWD and they found the yield reductions of 0–70% in AWD treatments compared with continuously flooded controls in 92% of the experiments. The large variability in the performance of AWD was caused by differences in the irrigation interval, soil properties and hydrological conditions across the experiments. In addition, variety is a major factor that influences the performance of AWD (Peng and Bouman, 2007). In this study, the “super” hybrid rice variety (YLY6) outyielded the WDR variety (HY3) under AWD conditions consistently across the two years. The yield difference between the two varieties in CF was similar to that in AWD. On average, YLY6 produced 1.5 t ha−1 more grain yield than HY3 in AWD. These results suggest that highyielding varieties developed for the continuously flood-irrigated rice system could still produce high yield under safe AWD experienced in this study. The yield of HY3 in the farmers’ fields was 10% higher than that of Shanyou 63, with saving 50% irrigation water in both lowland and upland (Huang et al., 2008; Si et al., 2010; Yu et al., 2005). Shanyou 63 is an ordinary hybrid variety that was developed for flood-irrigated rice system. In our study, however, there was a yield gap of more than 20% between YLY6 and HY3 under AWD conditions. One would argue that HY3, as a WDR variety, will perform better than YLY6 if both experience severe water stress. Our results suggest that the trait of drought tolerance in WDR might not be necessary when safe AWD was practiced in rice planting regions with shallow groundwater table. China’s “super” hybrid rice varieties have an obvious advantage in yield potential over ordinary hybrid and inbred rice varieties in flood-irrigated rice system (Peng et al., 2008; Zhang et al., 2009). This offers another opportunity to increase the water productivity of flood-irrigated lowland rice (Peng and Bouman, 2007). In the past field experiments on AWD, only inbred or ordinary hybrid varieties were used (Belder et al., 2004; Bouman and Tuong, 2001; Cabangon et al., 2004, 2011; Matsuo and Mochizuki, 2009; Yang et al., 2007). Many researchers have assumed that “super” hybrid rice varieties need ample supply of water to fully express their yield potential. The yield of “super” hybrid rice variety did not significantly vary between AWD and CF in our study, which strongly suggests that “super” hybrid rice varieties do not necessarily require more water input to produce high grain yield. Similarly, in irrigated lowland rice area with a shallow groundwater table, “super” hybrid varieties still seem to be a better choice for AWD. Varietal difference in grain yield under AWD conditions was reported in previous studies (De Datta et al., 1973a,b; Virk et al., 2003). In these studies, varieties that were bred for continuously flood-irrigated rice system were evaluated under AWD conditions. Several hybrid and inbred varieties did not show yield reduction
F. Yao et al. / Field Crops Research 126 (2012) 16–22
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Table 7 Yield components of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Nb
Panicles per m2
Spikelets per panicle
Spikelets per m2 (×103 )
Grain filling (%)
1000-Grain weight (g)
CF
CF
CF
AWD
CF
AWD
CF
AWD
AWD
AWD
2009 YLY6
HY3
ZN MN HN Mean ZN MN HN Mean
198 b 241 a 264 a 234 A 188 b 225 a 249 a 220 B
195 b 263 a 249 a 235 A 185 b 224 a 240 a 216 B
143 a 143 a 137 a 141 A 116 a 120 a 111 a 116 B
140 a 136 a 133 a 136 A 123 a 115 a 111 a 116 B
28.6 b 34.5 a 36.1 a 33.1 A 21.8 c 27.1 a 27.9 a 25.6 B
27.2 b 35.8 a 33.0 a 32.0 A 22.7 b 25.7 ab 26.7 a 25.0 B
86.6 a 79.0 b 79.0 b 81.5 A 82.6 a 81.7 a 81.3 a 81.9 A
86.7 a 83.5 ab 79.8 b 83.3 A 83.9 a 84.3 a 83.0 a 83.7 A
27.0 a 26.8 a 26.9 a 26.9 B 28.5 a 28.3 a 27.9 a 28.2 A
26.5 b 27.1 a 26.6 b 26.7 B 28.7 a 28.2 ab 27.9 b 28.2 A
ZN MN HN Mean ZN MN HN Mean
178 b 223 a 222 a 208 A 170 b 202 a 217 a 196 A
165 c 198 b 231 a 198 A 163 b 207 a 213 a 194 A
173 b 181 ab 195 a 183 A 124 a 123 a 114 a 121 B
177 b 197 a 179 ab 184 A 118 a 121 a 123 a 121 B
30.9 b 40.3 a 43.4 a 38.2 A 21.2 b 25.0 a 24.7 a 23.6 B
29.5 b 39.0 a 41.3 a 36.6 A 19.3 b 25.1 a 26.2 a 23.5 B
83.4 a 75.8 b 62.4 c 73.9 B 84.8 a 79.6 b 81.5 ab 81.9 A
86.1 a 78.6 b 71.0 c 78.6 B 83.3 a 81.2 a 82.0 a 82.2 A
25.3 a 23.8 b 22.6 c 23.9 B 28.9 a 28.6 a 28.7 a 28.7 A
25.3 a 24.0 b 23.7 b 24.4 B 28.9 a 29.4 a 28.8 a 29.0 A
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010. Table 8 Total N uptake, physiological N use efficiency (PE), agronomic N use efficiency (AE), and N recovery efficiency (RE) of two varieties under continuous flooding (CF) and alternate wetting and drying (AWD) irrigation at Wuxue County, Hubei Province, China in 2009 and 2010. Varietya
Nb
Total N uptake (kg ha−1 )
PE (kg kg−1 )
CF
CF
AWD
CF
AWD
CF
AWD
AWD
AE (kg kg−1 )
RE (%)
2009 YLY6
HY3
ZN MN HN Mean ZN MN HN Mean
116 c 181 b 216 a 171 A 102 b 171 a 194 a 156 B
112 c 178 b 206 a 165 A 106 c 165 b 198 a 157 A
63.6 a 46.9 b 41.3 b 50.6 A 60.6 a 41.2 b 35.0 b 45.6 B
65.1 a 47.6 b 40.5 c 51.1 A 57.7 a 43.7 b 34.0 c 45.1 B
– 60.5 a 53.3 a 56.9 A – 63.6 a 48.7 a 56.1 A
– 60.9 a 49.7 a 55.3 A – 54.5 a 48.9 a 51.7 A
– 10.5 a 8.6 a 9.6 A – 8.1 a 3.4 b 5.7 B
– 10.5 a 5.3 b 7.9 A – 9.0 a 2.7 b 5.8 A
ZN MN HN Mean ZN MN HN Mean
102 c 164 b 202 a 156 A 97 c 142 b 177 a 139 B
99 c 151 b 188 a 146 A 88 b 151 a 163 a 134 A
67.0 a 49.9 b 36.2 c 51.0 A 53.3 a 44.4 b 34.3 c 44.0 B
67.5 a 54.3 b 42.9 c 54.9 A 61.1 a 44.4 b 40.4 b 48.6 B
– 56.6 a 52.8 a 54.7 A – 41.8 a 42.6 a 42.2 A
– 48.1 a 47.3 a 47.7 A – 57.7 a 39.3 a 48.5 A
– 11.5 a 2.2 b 6.8 A – 10.9 a 4.0 b 7.4 A
– 13.9 a 7.1 b 10.5 A – 11.6 a 6.2 b 8.9 A
2010 YLY6
HY3
Within a column for each year, means followed by the same letter are not significantly different according to LSD (0.05). Lower-case and upper-case letters indicate comparisons among three N treatments and between two varieties, respectively. a YLY6 = Yangliangyou 6 and HY3 = Hanyou 3. b ZN = zero N control, MN = moderate N rate at 108 kg ha−1 , HN = high N rate at 189 kg ha−1 in 2009 and 175.5 kg ha−1 in 2010.
under AWD conditions compared with CF. A few varieties demonstrated even higher yields in AWD than CF. These results suggest that genetic variability in adaptability to AWD conditions exists in rice. Peng and Bouman (2007) proposed a strategy of crop improvement for high water productivity: that is to breed rice varieties with high grain yield under water-saving technologies such as AWD. Both total dry weight and harvest index contributed to higher grain yield of YLY6 in AWD and CF compared with HY3. On average, YLY6 had 22 days longer growth duration than HY3 in both AWD and CF, which also explains the yield difference between the two varieties. Among the yield components, large sink size which was caused by more spikelets per panicle was mainly responsible for high grain yield of YLY6 compared with HY3 in AWD. In continuously flood-irrigated rice system, improved yield potential with “super” hybrid rice is attributed to increased sink size due to large
and heavy panicles and improved biomass production due to great canopy light interception (Katsura et al., 2007; Zhang et al., 2009). The same strategy of developing varieties with large and heavy panicles can be used for increasing yield potential of AWD. Therefore, increasing the number of spikelets per panicle should be a primary target of breeding high-yielding rice varieties for AWD conditions. Acknowledgments This study was a part of the PhD thesis research of the first author. Funding was provided by the Major Project of International Cooperation, National Natural Science Foundation of China (No. 30821140349). It was also supported by the National Basic Program of China (No. 2009CB118600), and MOA Special Fund for Agroscientific Research in the Public Interest of China (No. 201203096).
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