IJERD – International Journal of Environmental and Rural Development (2020) 11-2

Research article
erd

Agronomic and Yield Performances of Three Rice Cultivars(Oryza sativa L.) under Water Regimes in Dry Season
SAVOEURN LANG*
Faculty of Agronomy, Royal University of Agriculture, Phnom Penh, Cambodia
Email: savoeurnlang@gmail.com

SOPHAONARITH RO
Faculty of Agronomy, Royal University of Agriculture, Phnom Penh, Cambodia

SIRANET ROEURN
Faculty of Agronomy, Royal University of Agriculture, Phnom Penh, Cambodia

LYHOUR HIN
Faculty of Agricultural Engineering, Royal University of Agriculture, Phnom Penh, Cambodia
Received 31 December 2019

Accepted 12 Otober 2020(*Corresponding Author)

Abstract Rice (Oryza sativa. L) is widely cultivated in Cambodia, but it consumes
considerably more water than any other crops. In the context of water scarcity due to global
climate change, rice cultivation in Cambodia has been worsened by the effect of drought.
Development of a cultivation technique to minimize yield loss under drought stress or/and
limited water resource in rice production is of great strategic value. Therefore, the present
study aims to investigate growth and yield performances of three rice genotypes, namely
CAR 14, CAR 15 and CAR 16 under different water regimes including drought (at flowering
stage), alternative wet and dry (AWD), and flooded conditions. The experiment was
conducted from January to October 2019, at the Tonle Bati Agricultural Development Center,located in Bati District, Takeo Province, Cambodia. The soil is clay loam and is classified as
Toul Samrong (Soil Classification for Rice Production in Cambodia). Two-way ANOVA was
utilized to determine interaction between the genotypes and the water regimes. As a result,the genotype-water regime interaction was detected for grain yield. Water regimes affectedgrain filling percentage and yield, whereas rice genotypes affected plant height, 50%
flowering days, 100% flowering days, number of unfertile grains, grain yield, and 1000 grain
weight. Nevertheless, plant density, panicle length, and straw biomass were not affected byeither of the factors. In any water regimes, CAR16 grew the tallest at 94.4 cm and blossomed
2 to 4 days later than any other cultivars. In contrast, CAR 15 had the highest yield, observedin permanent flooding and in AWD. Although 27% of irrigation water was saved in AWD,
permanent flooding produced more yield. In short, drought conditions affected total yield.
Despite that, Car 15 was observed to be more suitable for any water regimes.
Keywords Rice cultivars, AWD, drought, rice yield, straw biomass

INTRODUCTION
Rice belongs to the genus Oryza sativa L. and is known as a remarkable semi-aquatic plant which
has been cultivated in tropical and subtropical regions for about 10,000 years (IRRI, 2013; Sivapalan,2015). Maintaining proper water level in paddy fields is critical for rice production, but rice plants
will die or suffer yield loss when the water is too deep (Eckardt, 2017). International Rice ResearchInstitute (2013) reported that rice alone provides food for nearly half of the world population that has
increased remarkably. Irrigated rice accounts for 55% of the world’s harvested rice area and increases
by 25% in the next 20 years. Inadequate irrigation causes agronomic problems for intensive ricecultivation (Sivapalan, 2015). It is reported that drought adversely affects rice production by limiting
growth and reducing yield by 25.4%, posing a serious threat to global food security (Zhang et al.,Ⓒ ISERD

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IJERD – International Journal of Environmental and Rural Development (2020) 11-2

2018). The problem is even exacerbated when the demand for clean water is not fulfilled because
competition between irrigation and household use has formed.
In Cambodia, rice is grown in both wet and dry seasons depending on availability of water
sources. However, prolonged drought has been considered one of the main affecting factors that limit
annual rice planting areas. In 2015, severe drought occurred in the country, resulting in dire water
shortages and affecting several million people, while in 2012, thousands of hectares of rice fields
were destroyed (Climate Change Adaptation, 2019). In response, new rice varieties are studied andbred in hopes of producing drought tolerability. As a result, several varieties such as CAR 14, CAR
15 and CAR 16 have been released, but they are not yet widely available. Besides that, recognizing
their effectiveness is still unclear (CARDI, 2019). To address these issues, a proper irrigation
technique is required to maintain the yield although drought-tolerant rice varieties are used. A
promising solution to rice cultivation with water scarcity is alternative wetting and drying (AWD)
designed to irrigate paddy fields when needed, to save water. Large numbers of research results showthat AMD significantly reduced water use while maintaining yield (Howell et al., 2015). Therefore,
testing different irrigation methods may be beneficial for sustainable rice production within the
country.
OBJECTIVE
The research aims to investigate growth and yield performances of the three rice genotypes under
different water regimes classified as drought (at flowering stage), alternative wetting and drying
irrigation (AWD), and flooded conditions, known as flooding in three rice varieties: CAR 14, CAR
15 and CAR 16.
METHODOLOGY
The experiment was conducted at the Tonle Bati Agricultural Development Center, located in Bati District,
Takeo Province, Cambodia, starting from January to October 2019. Three rice cultivars were planted onclay loam, classified as Toul Samroang based on the Cambodian soil classification for rice production.
Those cultivars were CAR 14, CAR 15, and CAR 16, and they were planted under three different water
regimes designed for drought conditions at flower stage, alternative wetting and drying irrigation (AWD),
and flooded conditions, known as flooding. The experimental plots were neatly prepared, bunded, andlined in polythene plastic at the depth of 30 cm. Rice seeds were broadcasted at rates of 125 kg ha-1, withurea and DAP fertilizer applied at rates of 50 kg ha-1 each after land preparation and at 100 kg ha-1 at thevegetable stage.
In drought conditions, the water level was maintained at 5.0 cm above the ground, but the plots werecompletely drained at the flowering stage. Draining activities were repeated in case of rain to ensure nowater was left in the field. In AWD, PVC tubes were placed in the plots at 40 cm underground and at 20
cm above the ground. The tubes were 40.0 cm in length and 15.0 cm in diameter, perforated with 0.5 cm
diameter holes spaced 2.0 cm apart and covered in cloth to prevent clogging. The water level in the AWD
plots was maintained at 5.0 cm above the ground and repetitive irrigation was needed when it decreased
5.0 cm below the ground. This practice was discontinued at the flowering stage. In flooding, the paddy
fields were kept submerged at 3.0 - 5.0 cm above the ground and then at 5.0 - 7.0 cm until the booting
stage. At milking stage, the plots were completely drained.
Three months after planting, the plant height was measured from 10 randomly selected plants withineach plot, while plant density was evaluated from 3 random locations within each plot using a 1.0-m-2
frame area. In addition, 50% and 100% flowering was evaluated by counting the number of days required
from planting to half-full and full blossom. In each plot, panicle length and the number of grains per
panicle were measured from 10 randomly selected plants and rice yield from 3 locations using a 4.0-m-2
square frame area. Manual threshing was done to collect grains for drying and weighing to calculate therice yield in all treatments. Then the straw biomass left was dried using an oven at 800C for 48 hours.
Grain weight was measured based on 1000-grain quantity (Tian et al., 2017). Firstly, grains were dried toreach 140C. Then 1000 grains from each plot samples were randomly taken and weighed. Afterwards,
grains were split into categories, full or imperfect, and then counted for comparison.
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IJERD – International Journal of Environmental and Rural Development (2020) 11-2

Fig. 1 Experimental plots arranged in RCBD and placed under three water regimes
The experiment arranged for this study was a randomized complete block design comprising threerice cultivars grown in three different water regimes. This combination constituted 6 treatments replicatedthree times, generating 27 plots. Each plot was 4.0 m by 4.0 m and had spacing of 1.0 m. Two-way
ANOVA was performed to determine the interaction between the varieties and the water regime used.
Statistical differences were stated by using LSD-test with an error of 5%.

RESULTS AND DISCUSSION
Plant height and Plant density
No significant interactions between the varieties and the water regimes were observed for plant height(P=0.086). The water regimes (p=0.200) also had no effects on plant height, but there were significant
differences among the varieties (p<0.001). CAR 16 varieties had significantly higher stems, whencompared to CAR 14 and CAR 15, regardless of irrigation techniques. In contrast, CAR 14 had theshortest stems. In addition, the plant height was significantly greater in AWD than in flooding anddrought conditions. In Flooding, the plant height for CAR 14, CAR 15, and CAR 16 was 91.0, 90.6,
and 96.8 cm, respectively. In AWD, they were 93.5, 91.7, and 98.1 cm, respectively. In drought, theplant stems for different rice cultivars were the shortest, averaging less than 93.0 cm. In short, drought
affected rice growth, stunting the stems. Regarding plant density, there were no interactions between
the varieties and the water regimes. In addition, no significant differences were found among the two
factors. Regardless of the varieties and the irrigation technique used, the plant density ranged from61 to 73 plants m-2.
Flowering Stage
Days to flowering were counted in this experiment starting from the day of sowing until 50% and100% blossom. However, no signification interactions between the varieties and the water regimes
were observed. Different water regimes also had no significant effects on flowering days, but there
were significant differences among the varieties, which means that different rice cultivars started toblossom at different days. It was observed that CAR 14 started to flower faster, when compared toother varieties. In addition, CAR 16 produced flowers at the slowest pace. In all regimes, CAR 14began to flower 50% at day 64 after planting, followed by CAR 15 and CAR 16 that produced 50%Ⓒ ISERD

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IJERD – International Journal of Environmental and Rural Development (2020) 11-2

blossom at days 67 and 68. Full blossom was observed 2 days after 50% flowering. In short, drought
did not have effects on flowering dates, and but different varieties did.
Panicle Length
In the experiment, the panicle length of the different varieties was measured at harvest time. There
were no significant interactions between the varieties and the water regimes used. In addition, neitherof the two factors affected the panicle. These mean that the tested varieties had similar panicle length.
Regardless of the water regimes used, the panicle length was observed to lie within the range of 24.8
to 25.9 mm
Table 1 Comparison of vegetative and reproductive growth in three seed varieties plantedin three water regimes (Different alphabets mean statistical difference at 5% error)
Water Regime(WR)
Drought

AWD

Flooding

Seedvariety(SV)
Car 14Car 15Car 16Car 14Car 15Car 16Car 14Car 15Car 16SE
F-test probabilities
WRSV
WR x SV

Plant height
(cm)

Plant
density(plants/m2)

50%
flowering
days

100%
floweringdays

Paniclelength (cm)89.1 cd
92.3 b
92.9 a89.1 d91.7 bc
93.5 b
91.0 bcd
90.6 bcd
96.8 b
19.87

64.3
61.2
64.9
65.9
66.6
65.0
70.9
68.0
73.6
4.81

64.7 c67.0 b68.0 a65.0 c67.0 b68.0 a64.7 c67.3 ab68.0 aN/A

66.7 c69.0 b70.0 a68.0 c69.0 b70.0 a67.5 c70.0 ab70.3 a
N/A

24.8
25.3
24.9
25.9
25.6
25.8
24.9
24.9
25.0
2.1

0.200
<0.001***0.086300.054
0.61670.760400.721<0.001***
0.52150

0.831<0.001***
0.52450

0.113
0.990
0.965

*Significantly different p at 0.05; **significantly different p at 0.01; and ***significantly different p at 0.001

Table 2 Comparison of vegetative and reproductive growth in three seed varieties plantedin three water regimes (Different alphabets mean statistical difference at 5% error)
Water Regime(WR)
Drought

AWD

FloodingSE
F-test probabilities
WRSV
WR x SV

Seed
variety(SV)
Car 14Car 15Car 16Car 14Car 15Car 16Car 14Car 15Car 16

Yield(Ton/ha)1000-grain
weight (g)Strawbiomass(Ton/ha)Harvestindex (%)

Water used
(m3 ha-1)

2.47 e2.96 cde2.62 de3.12 bcde
4.00 a2.72 de3.45 abc
3.70 ab3.18 bcd
0.42

25.0 c28.4 ab29.8 a24.8 c27.9 b
28.9 ab25.6 c28.8 ab30.0 a
7.80

6.80
6.98
6.90
5.94
7.85
5.51
8.80
7.92
7.85
0.72

26.8
29.8
30.7
35.1
33.9
32.9
28.2
31.8
29.0
2.18

4,824

<0.001***<0.001***
0.021*

0.175<0.001***
0.980

0.066
0.527
0.517

0.093
0.730
0.807

*Significant different p at 0.05; **significant different p at 0.01; and ***significantly different p at 0.001Ⓒ ISERD

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4,968

6,768

N/A

Number of grain per panicle

IJERD – International Journal of Environmental and Rural Development (2020) 11-2

160
140
120
100
80
60
40
20
0
Car 14 Car 15 Car 16 Car 14 Car 15 Car 16 Car 14 Car 15 Car 16
Drought

AWD

Flooding

Water regimes

Fig. 2 Comparison of full and imperfect grains for each rice cultivars grownin different water regimes (mean ± SD; n = 30).
Weight in 1000 Rice Grains
After harvest, the grain was sun-dried until they arrived at 14% moisture. Then, 1000 grains wererepeatedly taken from the different varieties, weighed and compared. Statistically, no interactions
between the varieties and the water regimes were observed (p=0.980). Significant differences in
1000-grain weight were not detected among the water regimes (p=0.175). However, there weresignificant differences in the weight among the varieties (p<0.001). Regardless of the irrigation
conditions, 1000-grain weight was similar between CAR 15 and CAR 16 but was the lowest in CAR
14. On average, 1000 grains of CAR 15 and CAR 16 weighed 28 to 30 g, whereas the same amountof CAR 14 weighed only 25 g.
Number of Panicle Grains
Effects of drought were detected based on separation of full and imperfect grains. No interactions
between the varieties and the water regimes were observed for imperfect grains (p=0.377) and forfull grains (0.360). Significant differences in imperfect grains were found among the varieties used
(p<0.001), but not the water regimes (p=0.081). In contrast, full grains were significantly affected by
the water regimes (p=0.001), not by the varieties (p=0.222). Among the varieties planted, CAR 14
had greater numbers of full grains in AWD and drought, compared to other varieties. Likewise, CAR
16 was seen to have more full grains in flooding. Both of these varieties had few imperfect grams
than CAR 15 did. Regarding the total grain number, CAR 15 had the most and CAR 16 had the least,
while CAR 14 was in the middle.
Rice Yield, Straw Biomass, Harvest Index, and Water Use
Significant interactions between the varieties and the water regimes were observed in rice yield(p=0.021), and these two factors also affected the yield (p<0.001). It can be seen that the yield
harvested in the drought treatment was significantly lower than in other treatments, regardless of thevarieties used. Similar rice yield was obtained both in AWD and flooding treatments. In drought
condition, the yield for the three varieties was less than 3 tons ha-1. Drought reduced the yield was
reduced by 28 % for CAR 14, 20% for CAR 15, and 17% for CAR 16. The result was similar in thestudies by Zhang et al. (2018), which identified the effect of drought by 25.4%. Besides that, the rice
yield of CAR 14 and CAR 15 was lower in this study than in the report by CARDI (2018a & 2018b).
Straw biomass was also collected from all treatments for comparison and for calculating harvest
index. Significant interaction between the varieties and water regimes was not observed (p=0.517),
nor were there significant differences in straw biomass (p=0.066; p=0.527). It was found that drought
had no effects on biomass that varied from 5.5 to 8.8 tons ha-1 among all treatments. SignificantⒸ ISERD

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interaction between the varieties and water regimes were not detected for the harvest index (p=0.093).
There were also no significant differences among the two factors (p=0.730; p=0.807). In alltreatments, the harvest index averaged 31%. Regarding the water use, it can be seen that the flooding
treatment consumed considerably more water than other treatments, while the amount of water usedin the drought condition and AWD was quite similar. In this research, the amount of water consumed
was 4,824 for drought, 4,968 for AWD and 6,768 m3 ha-1 for flooding. When compared, flooding
consumed 26.6% more water than AWD, but the rice yield between these treatments was not muchdifferent. Likewise, CGIAR (2014) also mentioned in a report and Kumar and Rajitha (2019) in theirstudies that using AWD could save water up to 25%.
CONCLUSION
In this research, three different rice cultivars CAR 14, CAR 15, and CAR 16 were planted in threedifferent water regimes, namely drought, AWD, and flooding, to find out their effects on rice growthand yield, as well as aiming to select the most suitable varieties. In the results, CAR 16 produced thegreatest plant length among the experimented cultivars, but began to flower a bit late, when comparedto other varieties. However, they had similar panicle length. CAR 15 and CAR 16 produced higher
yield, regardless of the water regimes although the straw biomass and harvest index among thetreatment were not different. In conclusion, drought conditions tend to affect total rice yield, while
flooding and AWD were more favorable for rice plants. For drought tolerance, CAR 15 and 16 should
be selected for cultivation. For flooded conditions, all of the varieties were suitable and for AWD,CAR 14 and CAR 15 were better.
REFERENCESCARDI. 2018a. Early-duration rice variety CAR 14. Cambodian Agricultural Research and Development
Institute, Phnom Penh.
CARDI. 2018b. Early-duration rice variety CAR 15. Cambodian Agricultural Research and Development
Institute, Phnom Penh.
CARDI. 2019. Rice service. Cambodian Agricutural Research and Development Institute, http://www.
cardi.org.kh/?page=productlist&pcateid=5&menu1=10&ctype=article&id=10&lg=en&paginate=2.
CGIAR. 2014. New irrigation technique can ease drought effects for rice farmers. Consultative Group forInternational Agricultural Research, https://ccafs.cgiar.org/fr/blog/new-irrigation-technique-can-easedrought-effects-rice-farmers#.Xe-Dx5Mza00.
Climate Change Adaptation. 2019. Cambodia, looking to the horizon, prepares for drought. United Nation
Development Program, https://www.adaptation-undp.org/cambodia-looking-horizon-prepares-drought.
Eckardt, N. 2017. How rice thrives in flooded fields. The plant cell. In a Nutshell, https://plantae.org/
research/how-rice-thrives-in-flooded-fields/.
Howell, K.R., Shrestha, P. and Dodd, I.C. 2015. Alternate wetting and drying irrigation maintained rice yields
despite half the irrigation volume, but is currently unlikely to be adopted by smallholder lowland rice
farmers in Nepal. Food Energy Secur, 4 (2), 144-157.
IRRI. 2013. Rice almanac, 4th Ed., International Rice Research Institute. Manila, Philippines, Global Rice
Science Partnership, http://books.irri.org/9789712203008_content.pdf.
Kumar, K.A. and Rajitha, G. 2019. Alternate wetting and drying (AWD) irrigation, A smart water saving
technology for rice, A review. International Journal of Current Microbiology and Applied Sciences, ISSN:
2319-7706 8 (03).
Sivapalan, S. 2015. Water balance of flooded rice in the tropics. In 98 Irrigation and Drainage - Sustainable
Strategies and Systems, 92-118. Frank Wise Institute of Tropical Agriculture, Department of Agriculture
and Food, Kununurra, Australia, IntechOpen, http://dx.doi.org/10.5772/59043.
Tian, Z., Li, J., He, X.,Jia, X., Yang, F. and Wang, Z. 2017. Grain yield, dry weight and phosphorus (Oryza
sativa L.), Varieties as affected by salt-alkali and phosphorus. Sustainability, (9), 1461. doi:10.3390/su
9081461.
Zhang, J., Zhang, S., Cheng, M., Jiang, H., Zhang, X., Peng, C., Lu, X., Zhang, M. and Jin, J. 2018. Effect ofdrought on agronomic traits of rice and wheat, A meta-analysis. Int. J. Environ. Res. Public Health, 15 (5),839. doi: 10.3390/ijerph15050839.

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