EFFECTS OF WATER STRESS AT DIFFERENT
CRITICAL GROWTH STAGES ON THE
GROWTH AND YIELD OF PADDY
VARIETY TRS
CORIN JOHN
PEIPUSTUAAI
UNIVUSfTt IIAUYSIA Slllfl
DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF
THE REQUIREMENTS FOR THE DEGREE OF BACHELOR OF
AGRICULTURE SCIENCE WITH HONOURS
CROP PRODUCTION PROGRAMME
FACULTY OF SUSTAINABLE AGRICULTURE
UNIVERSITI MALAYSIA SABAH
PUMS 99: 1
UNIVERSITI MALAYSIA SABAH
BORANG PENGESAHAN TESIS
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Mengaku membenarkan tesis `(LPSM/Sarjana/Doktor Falsafah) ini disimpan di Perpustakaan Universiti Malaysia Sabah dengan syarat-syarat kegunaan seperti berikut: -
1. Tesis adalah hak milik Universiti Malaysia Sabah.
2. Perpustakaan Universiti Malaysia Sabah dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi pengajian
tinggi.
4. Sila tandakan (/)
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SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia seperti yang termaktub di AKTA RAHSIA RASMI 1972)
TERHAD (Mengandungi makiumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)
TIDAK TERHAD
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Catatan:
"Potong yang tidak berkenaan.
"Jika tesis ini SUUT dan TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT dan TERHAD.
"Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Sarjana Secara Penyelidikan atau disertai bagi pengajian secara kerja kursus dan Laporan Projek Sarjana Muda (LPSM).
DECLARATION
I hereby declare that this dissertation is based on my original work except for citations and quotations which have been duly acknowledged. I also declare that no part of this dissertation has been previously or concurrently submitted for a degree at this or any other university.
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CORIN JOHN BR13110032 29th NOVEMBER 2016 iiVERIFIFIED BY
1. Prof. Madya Datuk Haji Mohd. Dandan@Ame bin Haji Alidin
SUPERVISOR
2. Dr. Jupikeley James Silip CO-SUPERVISOR
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CH1TlJK NJ. MQ14D. DANDAN "
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FAKtJI PERTANIAN LESTARI 1lNWE 1 MALAYSIA SABAN,
KAMPUS SANDAKAN
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ACKNOWLEDGEMENT
First of all, I am very thankful to God for the good health, well-being and the spiritually strength He gave that were necessary for completing this research.
I would like to express my sincere gratitude to my supervisor Prof. Madya Datuk Haji Mohd. Dandan@Ame bin Haji Alidin for the continuous support throughout the accomplishment of my study, for his patience, motivation, diligence, and immense knowledge that he generously shared with me. His guidance helped me in all the time of study and writing of this thesis. He was always there throughout my proposal preparation and the conceptualization of my study. His relevant recommendations along with his professional instructions have greatly made the assembly and completion of my dissertation easier. I would not have been able to do the research and have meaningful experiences regarding my study without his dedication in supporting me. He also emphasized on self-discipline and how important sense of duty is throughout the journey in completing my thesis. I am so very thankful to him and his families for welcoming me with a nice treat and taking good care of me during a trip to Tuaran in order to complete my final year project. I am so honoured to have this precious opportunity.
I would also like to thank my parents and my only sister, Cecelia John for the encouragement by providing me with abundant moral and emotional supports. I am so blessed to have you all by my side.
I also want to acknowledge my colleague friends who were under the same supervisor with me for their kindness and excellent teamwork spirits that greatly ease the completion of my project.
Once again, I want to sincerely thank everyone for their supports and helps. I would not have been able to overcome all the obstacles that crossed my path in order be successful in Universiti Malaysia Sabah without their helps. Thus, I am so blessed and greatly thankful for everything.
ABSTRACT
A field study was conducted to investigate the effects of water stress occurrence during critical growth stages of TR8 paddy variety. This study was carried out at Faculty of Sustainable Agriculture rain shelter in Universiti Malaysia Sabah, Sandakan, located at latitude
s-0
55' N and longitude 118° 02' E for four months (24th June 2016 to24th October 2016). The objectives of this study were to determine the effects on
vegetative growth and yield component of TR8 paddy variety due to the occurrence of water stress at different critical growth stages and to identify the most susceptible critical growth stage of TR8 paddy variety towards water stress. In this study, there were three critical growth stages of TR8 paddy variety that were induced with water stress. The selected critical growth stages were active tillering, panicle initiation and heading. Meanwhile, the rate of water stress was at 30% field capacity. There were 16 pots with dimension 29 cm diameter were used in this study. Each treatment had four replications and was laid out using Completely Randomized Design. The effects were measured through vegetative growth and yield components of paddy. The parameters of vegetative growth included plant height (cm), culm height (cm), number of tillers, and percentage of productive tillers. The yield components included number of panicles per hill, percentage of grains per panicle, percentage of filled grains (%), percentage of empty grains (%), lQOO-grains weight and extrapolated yield per hectare in one session while the soil fertility included soil pH, percentage of nitrogen content(%), and phosphorus content (ppm). Data was analysed with one-way ANOVA test. In term of vegetative components, the results showed there was significant difference among all the treatments except the number of tillers. T2 had the lowest means of plant height (93.63 cm), culm height (50.83 cm) and percentage of productive tillers (59.63%). Meanwhile, Tl had the lowest mean of number of tillers (29 tillers) among the treatments. Overall, panicle initiation growth stage (T2) was more susceptible with water stress compared to other critical growth stages. In term of yield components, the results showed that there was significant difference among all the treatments except in number of panicles per hill, panicle length and lOQO-grains weight. T2 had the lowest means of number of panicles per hill (19 panicles), panicle length (22.45 cm), percentage of filled grains (73.25%), lQOO-grains weight (20.08g) and extrapolated yield per hectare for a season (5.63 ton/ha). However, T2 had the highest mean of empty grains (31.65%). Overall, panicle initiation growth stage (treatment two) was more susceptible with water stress compared to other critical growth stages. In term of soil fertility, there was no significant difference among all the treatments. Control (C) had the lowest mean of soil pH value (5.47) after planting while T3 had the lowest mean of percentage of nitrogen content (2.39%) after planting. Last but not least, the results showed that Tl had the lowest mean of phosphorus content (0.11 ppm) after planting. Overall, soil fertility was not affected by water stress at different critical growth stages of paddy.Thus, when water shortage occurs, farmers should save water during heading growth stage (T3) instead of panicle initiation growth stage (T2)
in order to minimize the reduction of paddy yield.
ABSTRAK
Satu kajian untuk mengkaji kesan pengaruh kuantiti air pada peringkat pertumbuhan kritikal padi varieti TRB. Kajian ini dijalankan di rumah lindungan hujan Fakulti Pertanian Lestari, Universiti Malaysia Sabah, Sandakan yang terletak di latitud 55' N dan longitud 118° 02' E selama empat bulan (24"' Jun 2016 to 24th October 2016). Tujuan kajian ini dijalankan adalah untuk mengkaji kesan kuantiti air yang tidak mencukupi semasa peringkat pertumbuhan kritikal padi terhadap pertumbuhan dan hasil padi variety TR8 serta mengetahui peringkat pertumbuhan kritikal padi yang lebih sensitif terhadap pengaruh kuantiti air yang tidak mencukupi. Kajian ini mengkaji tiga peringkat pertumbuhan kritikal padi iaitu beranak aktif, permulaan pembentukan panikel, dan terbit. Kadar pengaruh air yang tidak mencukupi ialah pada 30% nilai 'field capacity' (FC). Sebanyak 16 pasu plastic yang mempunyai diameter 29 cm telah digunakan dengan setiap satu rawatan mempunyai empat replikasi dan disusun menggunakan rekabentuk Completely Randomized Design (CRD). Parameter yang diukur termasuk pertumbuhan vegetatif padi, komponen hasil padi dan kesuburan tanah. Parameter pertumbuhan vegetatif termasuk ketinggian padi (sm), ketinggian 'culm' (sm), bilangan anak padi, dan peratus bilangan anakan produktif. Manakala, parameter komponen hasil padi merangkumi bilangan panikel serumpun, peratus butiran penuh serumpun (%), peratus butiran kosong serumpun (%), panjang panikel (sm), berat 1000 butir (g) dan unjuran hasil per hektar bagi semusim (tan/ha/musim) dalam satu rawatan. Komponen kesuburan tanah pula merangkumi nilai pH tanah, peratus kandungan nitrogen (%), dan kandungan fosforus dalam tanah (ppm). Semua data dianalisis dengan menggunakan Analisa Varians (ANAVA). Dari segi komponen pertumbuhan vegetatif, keputusan menunjukkan terdapat perbezaan signifikasi antara rawatan kecuali bilangan anakan padi. T2 mempunya purata yang paling rendah dari segi ketinggian padi (93.63 sm), ketinggian 'culm' (50.83 sm), dan peratusan bilangan anak produktif (59.63%). T1 pula menunjukkan purata bilangan anakan padi yang paling rendah (29 anak padi) antara trawatan. Secara keseluruhannya, peringkat pertumbuhan permulaan pembentukkan panikel (T2) lebih sensitif terhadap kuantiti air yang tidak mencukupi jika dibandikangkan dengan peringkat pertumbuhan kritikal padi yang lain. Dari segi komponen hasil padi, keputusan menunjukkan terdapat perbezaan signifikasi antara semua rawatan kecuali, bilangan padi serumpun, panjang panikel dan berat 1000 buitr. T2 mempunyai purata paling rendah dari segi bilangan panikel serumpun (19 panikel), panjang panikel (22.45 cm), bilangan butiran penuh serumpun (73.25%), berat 1000 butir (20.08g) dan unjuran hasil per musim (5.63 ton/ha). Tetapi, T2 mempunyai purata yang paling tinggi dalam bilangan butiran kosong serumpun (31.65%). Oleh itu, ini menunjukkan peringkat pertumbuhan permulaan pembentukkan panikel (rawatan dua) lebih sensitif terhadap kuantiti air yang tidak mencukupi jika dibandikangkan dengan peringkat pertumbuhan kritikal padi yang lain. Dari segi kesuburan tanah, keputusan menunjukkan tidak terdapat perbezaan signifikasi antara rawatan. Kontrol (C) menunjukkan purata nilai pH tanah (5.47) terendah selepas tanam. Manakala, T3 menunjukkan purata peratusan kandungan nitrogen (2.39%) selepas tanam yang paling rendah. T1 pula menunjukkan purata kandungan fosforus (0.11 ppm) dalam tanah selepas tanam yang paling rendah. IN menunjukkan, kesuburan tanah tidak dipengaruhi oleh kuantiti air yang tidak mencukupi. Oleh itu, sekiranya kekurangan bekalan air berlaku, petani perlu menjimatkan air pada peringkat pertumbuhan terbit (T3) dan menggelakan pengurangan air pada permulaan pembentukan panikel (T2) untuk meminimakan pengurangan hasil padi.
TABLE OF CONTENT Content DECLARATION VERIFICATION ACKNOWLEDGEMENT ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES
LIST OF SYMBOLS, UNITS AND ABBREVIATIONS LIST OF FORMULAE CHAPTER 1 INTRODUCTION 1.1 Background of Paddy 1.2 Justification 1.3 Significant of Study 1.4 Objective 1.5 Hypothesis Page ii iv v vi vii ix x xii xiii 1 1 3 4 4 5
CHAPTER 2 LITERATURE REVIEW 6
2.1 Rice 6
2.2 Morphology of rice 7
2.2.1 Stages of paddy growth 8
2.3 Paddy variety TR8 10
2.4 Importance of water management in paddy field 11 2.5 Effects of water stress on rice production 11 2.5.1 Effects of water tress on morphological parameters 12 2.5.2 Effects of water stress on booting stage 12 2.5.3 Effects of water stress on flowering stage 12 2.5.4 Effects of water stress on yield contributing characters and yield 14
2.6 Soil-water-plant relationship 14
2.6.1 Soil water balance 14
2.6.2 Soil water potential 16
2.6.3 Crop root depth 17
2.6.4 Field capacity, saturation and wilting point 18 2.6.5 Evapotranspiration (Etc) and Crop Coefficient (Kc) 19 2.6.6 Soil water balance in rice water requirement 20 CHAPTER 3 METHODOLOGY
3.1 Study site and management
3.2 Period of study 3.3 Materials
3.4 Treatment
3.5 Experimental design and layout 3.6 Parameter
3.7 Experiment setup
3.7.1 Taking soil sample 3.7.2 Soil analysis
3.7.3 Preparation of the paddy seed 3.7.4 Preparation of planting pot 3.8 Statistical analysis 23 23 23 24 24 26 27 28 28 29 29 30 31 vii
CHAPTER 4 RESULTS 32 4.1 Effects of water stress at different critical growth stages on vegetative 32
growth of paddy variety TR8
4.1.1 Plant height 32
4.1.2 Number of tillers 35
4.1.3 Culm height 37
4.1.4 Percentage of productive tillers 38
4.2 Effects of water stress at different critical growth stages on yield of paddy 39 Variety TR8
4.2.1 Number of panicles per hills 39
4.2.2 Panicle length 40
4.2.3 Percentage of filled grains 42 4.2.4 Percentage of empty grains 43
4.2.5 1000-grains weight 44
4.2.6 Extrapolated yield per hectar per season 45
4.3 Soil fertility 46
4.3.1 Soil pH 46
4.3.2 Percentage of nitrogen in soil 47 4.3.3 Phosphorus content in soil 48
CHAPTER 5 DISCUSSION 50
5.1 Effects of water stress at different critical growth stages on vegetative 50 Growth of paddy variety TR8
5.1.1 Plant height 50
5.1.2 Number of tillers 51
5.1.3 Culm height 51
5.1.4 Percentage of productive tillers 52 5.2 Effects of water stress at different critical growth stages on yield of paddy 52
Variety TR8
5.2.1 Number of panicles per hills 52
5.2.2 Panicle length 53
5.2.3 Percentage of filled grains 53 5.2.4 Percentage of empty grains 53
5.2.5 1000-grains weight 54
5.2.6 Extrapolated yield per hectare per season 54
5.3 Soil fertility 55
5.3.1 Soil pH 55
5.3.2 Percentage of nitrogen in soil 55 5.3.3 Phosphorus content in soil 56 CHAPTER 6 Conclusion
6.1 Vegetative growth of paddy 6.2 Yield of paddy
6.3 Soil fertility of Silabukan soil 6.4 Recommendation REFERENCES APPENDDC 57 57 57 58 58 59 62 92 viii
LIST OF TABLE
TABLE
2.6.5 The Kc of rice at different growth stages 20
LIST OF FIGURES
Figure Page
2.2.1 The different growth stages of paddy 10
2.6.1 Soil water balance 15
2.6.2 Soil water potential for different soil types 17 2.6.4 Field capacity, saturation and wilting point 19 2.6.6 (i) Rice crop water requirement 21 2.6.6 (ii) Water balance component of rice crop 22 3.5 The layout of the pots for each treatment using the 26
CRD design
4.1.1 (i) Mean of plant height from week one to week ten for 33 different treatments (active tillering started at week
two, panicle initiation at week six, and heading at week nine).
4.1.1 (ii) Mean of plant height due to water stress at different 34 critical growth stages of paddy on week ten
4.1.2 (i) Mean of number of tillers from week one to week ten 35 for different treatments (active tillering started at week
two, panicle initiation at week six, and heading at week nine)
4.1.2 (ii) Mean of number of tillers due to water stress at 36 different critical growth stages of paddy on week ten
4.1.3 Means of culm height due to water stress at different 37 critical growth stages of paddy on week twelve
4.1.4 Means of productive tillers due to water stress at 38 different critical growth stages of paddy.
4.2.1 Means of number of panicle per hill due to water stress 40 at different critical growth stage of paddy.
4.2.2 Means of panicle length due to water stress at different 41 critical growth stages of paddy
4.2.3 Means of percentage of filled grains for every treatment 42 due to water stress at different critical growth stages of
paddy.
4.2.4 Means of percentage of empty grains due to water 43 stress at different critical growth stages of paddy.
4.2.5 Means of 1000-grains weight due to the water stress at 44 different critical growth stages of paddy
4.2.6 Means of extrapolated yield per hectare per session 45 (ton/ha) due to the water stress at different critical
growth stages of paddy
4.3.1 Means of soil pH of Silabukan soil before and after 46 planting due to water stress at different critical growth
stages of paddy.
4.3.2 Means of percentage of nitrogen content of Silabukan 47 soil before and after planting due to water stress at
different critical growth stages of paddy
4.3.3 Means of phosphorus content of Silabukan soil before 48 and after planting due to water stress at different
critical growth stages of paddy
IF
LIST OF SYMBOLS, UNITS, AND ABBREVIATIONS % X cm L ml 9 Kg ha K P N M MOP TSP ppm FC Ton ha"' ANOVA DAE DAP UMS TR8 CRD SSA SPSS Percentage multiply centimetre liter milliliter gram kilogram hectare potassium phosphorous nitrogen molarity Muriate of Potash Triple Super Phosphate
part per million Field capacity tons per hectare Analysis of variance days after emergence days after planting
Universiti Malaysia Sabah paddy variety Sen Aman
Completely Randomized Design School of Sustainable Agriculture Statistical Package for Social Science
LIST OF FORMULAE Formula
3.4 Moisture content of soil during 30% field capacity (%)
= 0.3 X moisture content of soil during 100% field capacity (%)
Page 25
4.1.4 Percentage of productive tillers 38
Number of panicles per hill
.x1 nn
Number of tillers per hill " -ýý
CHAPTER I
INTRODUCTION
1.1 Background
Water is the most important out of the four soil physical factors that affect plant growth (mechanical impedance, water, aeration, and temperature) as reported by Shaw (1952) and Kirkham (1973). A classic analysis was done by Boyer (1982) to determine the reasons for crop losses over a four-decade period in the United States. He found that drought causes 40.8% of crop losses and excess water causes 16.4%. Insects and diseases amount to 7.2% of the losses. Thus, soils that are too dry or too wet are the major reasons for lost productivity
Subsequently, the past years have seen a growing scarcity of water worldwide. The pressure to reduce water use in irrigated agriculture is mounting, especially in Asia where it accounts for 90% of total diverted fresh water. Rice is an obvious target for water conservation as it is grown on more than 30% of irrigated land and accounts for 50% of irrigation water (Barker et al., 1999). Reducing water input in rice production can have high societal and environmental impact if the water saved can be diverted to areas where competition is high. A reduction of 10% in water used in irrigated rice would free-up 150,000 million m3, corresponding to about 25% of the total fresh water used globally for non-agriculture purposes (Klemm, 1999). However, rice is very sensitive to water stress. Attempts to reduce water in rice production may result in yield reduction and may threaten food security in Asia. Thus, the main challenge is to develop socially acceptable, economically viable, and environmentally sustainable novel rice-based systems that allow rice production to be maintained or increased in the face of declining water availability. According to Postel (1997); Shah et a/., (2000) and Shu
et al., (2001), there is evidence that water scarcity already prevails in rice growing areas.
Consequent overexploitation of groundwater the last decades has caused serious problems in China and south Asia. Groundwater tables have dropped on average by 1-3 m y' in the North China Plain, by 0.5-0.7 m y' in the Indian states Punjab, Haryana, Rajasthan, Maharashtra, Karnataka and northern Gujarat, and by about 1, m y' in Tamil Nadu and hard-rock southern India. This has led to increased costs of pumping, salinity intrusion, fluoride contamination, land subsidence and the formation of cracks and sinks holes (North China Plain). These major groundwater- depletion areas affect rice production in the rice-wheat growing areas in northern India, Pakistan and China, and the rice growing areas in Tamil Nadu. In the Ganges delta of Bangladesh, overdrafting of groundwater in the dry season leads to wells falling dry in rice producing areas, but water levels are restored during the wet season. A specific problem caused by falling groundwater tables here (and in parts of eastern India) is the appearance of poisonous arsenic.
Heavy upstream water use along some major rivers in Asia is causing severe water shortages downstream. China's Yellow River, which flows 4,600 kilometers through some of Asia's richest farmland, has run dry nearly every year since 1972 (Postel, 1997; Shu Geng et a/., 2001). Such is the demand on its water that, in 1997, its final 600 kilometers was dry for more than four months. The Chinese government has taken measure by prohibiting flooded rice cultivation in parts of Shandong province and around Beijing (Wang Hua Qi; personal communication). In South Asia, the Ganges and Indus Rivers have little to no outflow to the sea in the dry season. Less dramatic, but more important for rice-growing areas, heavy competition for river water between States and different sectors (city, industry) is causing water scarcity for agriculture in southern India's Cauvary delta and in Thailand's Chao Phra delta (Postel,
1997).
Irrigated rice production is also increasingly facing competition from other sectors. The irrigated rice area in China was reduced by 4 million ha between the 1970s and the 1990s (Barker et a/., 1999). Though it is not possible to claim that this reduction in irrigated rice area is entirely due to water scarcity, there is evidence that the reduced area is related to the reduction in the amount of water that is diverted to
irrigate rice land. For example, in the 160,000 ha Zhanghe Irrigation System (Hubei Province, China), the share of water allocated for irrigation was dominant (about 80%) until the 1980s. Afterwards, Zhanghe reservoir water was increasingly used to meet the growing demand for water by cities and industry and for hydropower generation, and the amount of water allocated for irrigation has declined to about 20% in the late nineties. The irrigated rice area in the 1990s was reduced by about 20% from the level in the 1980s. As a consequence, rice production was also reduced (Dong Bin et a/., 2001). Similar examples of increased competition exist elsewhere in Asia. Water from the Angat reservoir in Bulacan Province, the Philippines, is increasingly diverted toward Manila at the expense of downstream water availability for agriculture (Bhuiyan and Tabbal, as referenced in Pingali et a/., 1997). In other areas, water availability is threatened by degrading water quality caused by industrial pollution. Water in the Agno River in Pangasinan Province is polluted with sediments and chemicals from mining activities upstream (Castaneda and Bhuiyan, 1993). Postel (1997) listed examples of competition between industry and agricultural for India.
1.2 Justification
Therefore, the study was conducted in order determine the critical stages of growth of paddy that was mostly affected with the occurrence of water stress. There were three targeted critical stages of growth of paddy such as active tillering stage, panicle initiation and heading stage. The occurrence of water shortage at the stage of growth of paddy that was susceptible to water stress caused declination of growth and yield of paddy variety TR8 while the occurrence of water shortage at the stage of growth of paddy that was more tolerant to water stress will not cause a massive reduction to the growth and yield of paddy variety TR8. Conditions that lead to water stress was shown by figure 1.2 (i) and 1.2 (ii) [Appendix I].
In conclusion, water shortage should be prevented especially during the vulnerable stage of growth of paddy to ensure a normal growth of paddy and avoid great loss in yield.
1.3 Significant of Study
The significant of this study is to help the farmers especially the small farmers in Sabah who are managing paddy field to identify the critical growth stages of paddy that requires water the most. Rice can be grown under irrigated (lowland) or rainfed
(upland or lowland) conditions. Rainfed rice occupies about 45% of the global rice area and accounts for about 25% of the rice production. Drought has been identified as one of the main constraints for improving yield, which presently averages 2.3 t ha-1. According to Garrity eta/., (1986), 50% of rainfed lowland and all rainfed uplands are drought prone. Therefore, this study determined which ciritical stages of growth of paddy variety TR8 that was more tolerant or susceptible to the occurrence of water stress. These three targeted stages of growth of paddy were including active tillering, panicle initiation and heading. By the way, the identifications of effects of water stress were focused on the growth and yield of paddy variety TR8.
Thus, this study can eventually help the farmers to minimize the effect of water stress on the growth and yield of paddy when they have to deal with water shortage problem. This study is able to help the farmers identifying when is the most crucial time of paddy that requires water and when is the most tolerant growth stage of paddy towards shortage of water. Thus, they can reduce the supply of water at the tolerant growth stage of paddy towards water stress if they need to save water during drought session. Therefore, they can prevent great loss of yield during the occurrence of water shortage. This important knowledge can save the farmers from wasting water during the more tolerant growth stage of paddy in order to irrigate the paddy field especially when they have to manage a large area of paddy field.
Hopefully, the knowledge about water stress and their effects on growth and yield of paddy variety TR8 may help the farmers to increase their income by
systematically and economically managing the water level in the paddy field.
1.4 Objectives
The objectives of this research were:
1. To investigate the effect of water stress at different critical growth stages of paddy on the growth and yield of paddy variety TR8.
2. To determine the most susceptible critical growth stage of paddy varietuy TR8 towards water stress.
1.5 Hypothesis
1. Ho : There is no significant difference on the growth and yield of paddy variety TR8 due to water stress at different critical growth stages of paddy.
Ha : There is significant difference on the growth and yield of paddy variety TR8 due to water stress at different critical growth stages of paddy.
2. Ho : There is no significant difference in term of susceptibility of different critical growth stages of paddy variety TR8 towards water stress.
Ha : There is significant difference in term of susceptibility of different critical growth stages of paddy variety TR8 towards water stress.
CHAPTER 2
LITERATURE REVIEW
2.1 Rice
Rice belongs to the Poaceae family and Oryzeae tribe. There are 12 genera within the Oryzeae tribe. Meanwhile, the Oryza genus is comprised of approximately 22 species of which 20 are wild species and two species are cultivated. The cultivated species of Oryza genus are Oryza saliva and Oryza giabemima (Vaughan, 1994). But, Oryza saliva is the most widely grown compared to another cultivated species of Oryza genus, Oryza giaberrima. Oryza satrva species is grown worldwide, including in Asian, North and South American, European Union, Middle Eastern and African countries while Oryza giaberrima species is grown solely in West African countries. Thus, O, saliva and glaberrima saliva hybrids are replacing O. giabemrma in many parts of Africa due to higher yields (Unares 2002). By the way, Oryza sab/va species can even be further classified into three sub-species which are indica rice, japonica rice and javanica rice (Vaughan 2003). The differences between the three sub-species was shown in Table 2.1 (Appendix II).
Rice plant may be characterized as an annual grass, with round, hollow, jointed culms, rather flat, sessile leaf blades, and a terminal panicle. Under favourable conditions, the plant may grow more than one year. Rice is a unique plant as they can grow in aquatic habitat as other taxa in the tribe Oryzeae. Rice is a semi-aquatic plant due to the structure of leaf sheaths, stems and roots that contain a large number of air spaces. The existence of air spaces is because it has a series of air-conducting aerenchymatous tissues in the leaf sheaths, stems and roots. These spaces can ensure the continuous penetration of oxygen to the cells of roots growing in the absence of
oxygen. Besides, the roots of rice plant are usually very shallow that enable them take up the oxygen which diffuses into the water surface. Moreover, during the continuous flooding, rice plant is capable to respire by anaerobic respiration.
2.2 Morphology of rice
Rice is a typical grass, forming a fibrous root system bearing erect culms and developing long flat leaves. It has a semi-aquatic lifestyle, requiring water particularly during the reproductive growth phase. It forms multiple tillers, consisting of a culm and
leaves, with or without a panicle. The panicle emerges on the uppermost node of a culm, from within a flag-leaf sheath and bears the flowers in spikelets. The culm consists of a number of nodes and hollow intemodes that increase in length and decrease in diameter up the length of the culm. Primary tillers emerge from nodes near the base of the main culm and secondary and tertiary tillers emerge sequentially from these. Single leaves develop alternately on the culm, consisting of a sheath, which encloses the culm and a flat leaf blade. The leaf forms a collar or junctura between the sheath and blade and a ligule and two auricles develop on the inside of the junctura and base of the leaf blade respectively. Cultivars can vary widely in the length, width, colour and pubescence of the leaves.
The panicle emerges from the flag-leaf sheath and consists of a central rachis with up to four primary branches at each node. Primary and secondary branches bear the flower spikelets. Each spikelet has a single floret and two glumes. It is enclosed by a rigid, keeled lemma, which is sometimes extended to form an awn and partially envelops the smaller palea. The floret contains six stamens and a single plumose ovary with two branches. At anthesis, two lodules at the base of the floret swell and force the lemma and palea apart as the stamens elongate and emerge. The stigma is sometimes exposed as well.
The fertilised ovary is a caryopsis, meaning a small, single-seeded dry fruit with the pericarp and seed coat fused. It is commonly called a grain. The grain consists of an embryo, endosperm, pericarp and testa, surrounded by the husk or hull (the lemma and palea). Grain length varies with cultivar between 5 and 7 mm, and grains can be round, bold or slender. The following description is based on McDonald (1979) and OECD (1999).
2.2.1 Stage of growth of rice
There are three main developmental stages in rice. These are germination or vegetative growth, reproductive development, and grain ripening. By the way, the descriptions below are based on those published by the International Rice Research Institution (International Rice Research Institute, 2002). Commonly, in the tropical area, a 120 days variety rice plant use up around 60 days in the vegetative stage, 30 days in the reproductive stage along with 30 days in the ripening stage.
The vegetative stage involve several phase such as the germination, seedling growth and tillering. During this stage, the rice plant has active tillering, gradual increase in plant height and leaf emergence at regular intervals. Vegetative stage starts after the imbibition of the seed. Germination begins with the emergence of the coleorhiza and coleoptile from the pericarp. The radicle gives rise to the seminal root system, which has limited branching. According to Moldenhauer and Gibbons (2003), germination can occur under aerobic or anaerobic conditions. They observed that under anaerobic conditions, the coleoptile emerges first, as it is the only part of the embryo that can grow under energy derived solely from fermentation. Meanwhile, the fibrous roots develop from underground nodes. McDonald (1979) has observed that when the coleoptile elongates along with the epicotyls and reaches the soil or water surface, it splits open and the primary leaf emerges. Moldenhauer and Gibbons (2003) have studied that during this early phase of development, the plant can produce a leaf every four to five days as the primary culm develops. As the rice plant grows, primary tillers begin to emerge from the axial nodes of the lower leaves. These give rise to the secondary tillers, from which tertiary tillers can also develop. The intemodes begin to elongate at, or near, panicle initiation
Meanwhile, McDonald, 1979 evaluated that the reproductive stage involves culm elongation, declining in the tiller number, emergence of the flag leaf, followed by the booting, heading and flowering of the spikelets. But, vegetative stage of rice plant begins with panicle initiation. The timing of this may be linked to specific photoperiods and is highly cultivar-dependent. Besides, Moldenhauer and Gibbons (2003) discovered that panicle initiation occurs at the growing tip of the tiller. Based on their observation, panicle initiation takes about twenty-five days before the heading. As the panicle grows inside the flag-leaf sheath, senescence of the lower leaves begins. A further three
leaves develop before heading (panicle emergence) occurs. By the way, heading period takes about ten to fourteen days due to variation in panicle exertion among tillers of the same plant and among the plants in the same field. The panicle may emerge
partially or fully, and greater emergence is selected for in cultivars as a means of decreasing disease occurrence. Flowering typically begins one day after heading and continues down the panicle for approximately seven days until all florets on the panicle
have opened. Anthesis begins with the opening of the florets followed by stamen elongation and generally lasts 1.2 to 2.5 hrs between 9 am and 2 pm. However, this is temperature dependent and can take longer and occur later on cooler or cloudy days. Oka, 1988 stated that as pollen shedding generally occurs within nine minutes of floret opening, pollen is usually shed onto the florets of the same panicle, resulting in self- fertilisation. Fertilisation is completed within six hours. This is the stage when rice is most sensitive to cold temperatures (McDonald, 1979).
Once the florets are fertilised, the ovaries begin to develop into grains. This indicates that the grain ripening stage of rice plant has begun. The ripening duration takes about 15 days to 40 days depending on the variety. Initially, the grain fills with a white, milky fluid as starch deposits begin to form. The panicle remains green at this stage and begins to bend downwards. Leaf senescence continues from the base of the tillers but the flag-leaf and next two lower leaves remain photosynthetically active. The grain then begins to harden into the soft dough stage. Husks begin to turn from green to yellow and senescence of the leaves and tillers is at an advanced stage. During the final stage the grain matures, becoming hard and dry. The entire plant begins to yellow and dry out, at which point the grain can be harvested. At this point, the rice
plant has reached harvesting maturity. The summary of the growth stages of paddy was shown in the figure 2.2.1 below.
Initial/ _ Peak/ > Harvesting seedling Often takes 60 to 100 days maximum Often takes 30 stage
stage depending on the variety greenness days stage
h a 0
..
Vegetative stage Reproductive stage Growing stages Figure 2.2.1 The different growth stages of paddy Source: IRRI photo, 2014
2.3 Paddy variety TR8
Ripening stage
Paddy variety Sri Aman (TR8) is one of the paddy varieties that had been launched since 2009 by the chief minister of Sabah, Datuk Seri Musa haji Aman. It has high disease resistance at the same time it can produce high yield that can reach up to seven tons per hectare. It was found that the agronomy properties of this variety make it suitable to be planted in several main paddy growing districts in Sabah. This variety has been released by the Tuaran Agriculture Research Centre in a way to increase the rice production in our country for self-sufficiency. Therefore, farmers are encouraged to grow this rice variety as it also has good eating quality.
The rice variety is expected to reach a harvested yield up to 10 tons in one hectare of land under proper utilization of agriculture technology. Hence, it can aid in increasing the yield of the paddy farmers in Sabah where they can only reach a yield of 3.5 tons per hectare compared to previous yield that is around one ton per hectare (Utusan Sabah Online, 2009). In addition, this helps the Sabah government to reach the self-sufficiency in the production of rice in the future as the self-sufficiency in Sabah is currently at around 30 percent. Table 2.3 (Appendix II) shows the agronomy characteristics of paddy variety TR8.
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