The effects of waterlogging at germination stage on growth and yield of soybean genotypes in winter cropping season 2020

Plant height dynamic of soybean genotypes .... ABSTRACT The aims of the graduation thesis are evalution the effects of waterlogging at germination stage on growth and yield of soybean g

VIETNAM NATIONAL UNIVERSITY OF AGRICULTURE

COMMITMENT

I hereby declare that this is my own research, the data and research results

in this report are truthful and have not been used to defend a degree

I hereby certify that all assistance in the implementation of this graduate research project has been thanked and the information cited has been indicated

by the origin, name of the author, time of publication

Ha Noi, February 25th, 2021

Student

Nguyen Thi Hai Yen

me complete this graduation thesis

Secondly, I would like to send my gratitude to my instructor, Ph.D Nguyen Van Loc, Department of Food Crop, Faculty of Agronomy, Vietnam National University of Agriculture, for their enthusiastic support, helpful advice and considerable encouragement in the completion of my thesis

I would also like to express sincere thanks to M.S Tran Thi Minh Ngoc from Department of Food Crop and all the lectures from Faculty of Agronomy, who taught and created best conditions for students during learning process and research

Last but not the least, I would like to thank my family and my friends who have alwaay beens by my side, give me support and strength to complete this graduattion thesis

I sincerely thank you!

Hanoi, February 25th , 2021

Student

Nguyen Thi Hai Yen

CONTENTS

COMMITMENT i

ACKNOWLEDGEMENTS ii

CONTENTS iii

LIST OF ABBREVIATIONS vi

LIST OF TABLES vii

LIST OF PICTURES, FIGURES viii

ABSTRACT ix

CHAPTER 1: INTRODUCTION 1

1.1 Rationale 1

1.2 Aims and requirements 3

1.2.1 Aims 3

1.2.2 Requirements 3

CHAPTER 2: LITERATURE REVIEW 4

2.1 Origin and distribution of soybeans 4

2.2 Values of soybeans 4

2.2.1 The nutritional value 4

2.2.2 Value increase the crop, improve the agricultural environment 6

2.2.3 The industrial value 7

2.2.4 The medical value 7

2.3 Soybean production in the world and Vietnam 8

2.3.1 Soybean production in the world 8

2.3.2 Soybean production in Vietnam 10

2.4 Physiological requirements of soybean plants 12

2.4.1 Soil requirements 12

2.4.2 Humidity requirements 12

2.4.3 Temperature requirements 13

2.4.4 Light requirements 13

2.5 Soybean growth and development characteristics 14

2.5.1 Vegetative stage 15

2.5.2 Reproductive stage(R) 16

2.6 Overview of research on the effects of inundation on soybean yield in the country and in the world 17

2.6.1 Effects of inundation on soybean production 17

2.6.2 Research situation of the effect of the flood on the development of soybean plants in the world 18

2.6.3 Research situation of the effect of the flood on the development of soybean plants in Viet Nam 20

CHAPTER 3: MATERIALS AND METHODS 22

3.1.Plant materials 22

3.2 Experimental design 22

3.3 Cultural practices 23

3.4 Research content 24

3.5 Trait observation 24

3.5.1 Qualitative traits 25

3.5.2 Quantitative traits 25

3.6 Growth and development indicators 25

3.7 Productivity components 26

3.8 Data analysis 26

CHAPTER 4: RESULTS AND DISCUSSION 27

4.1 Germination rate of soybean genotypes in winter cropping system 2020 27

4.2 Vegetative traits of soybean genotypes 28

4.2.1 Plant height dynamic of soybean genotypes 28

4.2.2 The number of trifoliate leaves dynamic of soybean genotypes 31

4.2.3 The number of branches per plant dynamic of soybean genotypes 34

4.2.4 The number of node dynamics of soybean genotypes 36

4.2.5 Some growth characteristics of soybean genotypes 38

4.3 The dry matter of soybean varieties after harvesting 41

4.4.1 Components of productivity of soybean genotypes 43

4.4.2 Yield of soybean genotypes 47

CHAPTER 5: CONCLUSIONS AND SUGGESTIONS 54

5.1 Conclusions 54

5.2 Suggestions 55

REFERENCES 56

APPENDIX 59

LIST OF ABBREVIATIONS

CV : coefficient of variation LSD : Least significant difference

LIST OF TABLES

Table 2.1 Nutritional value per 100g soybean seeds 5

Table 2.2 Soybean production in Vietnam from 2014 to 2018 11

Table 2.3 Humidity and rainy requirements of soybean plant for each of stages 13

Table 2.4 Temperature requirements for each of soybean stages 13

Table 2.5 Impact of flooding stress on different growth stages of a soybean crop 19

Table 3.1 Soybean genotypes used for experiment in winter cropping systems 22

Table 4.1 Germination rate of soybean genotypes 27

Table 4.2 Plant height dynamic of soybean genotypes 29

Table 4.3 The number of trifoliate leaves dynamic of soybean genotypes 31

Table 4.4 The number of branches per plant dynamic of soybean genotypes 34

Table 4.5 The number of node dynamic of soybean genotypes 37

Table 4.6 Some growth characteristics of soybean genotypes 39

Table 4.7 The dry matter of soybean genotypes after harvesting 41

Table 4.8 Components of productivity of soybean genotypes 43

Table 4.9 Components of productivity of soybean genotypes 44

Table 4.10 Yield of soybean genotypes 48

LIST OF PICTURES, FIGURES

Picture 2.1 World soybean production from 2000-2020 8 Picture 2.2 Vegetative stage of soybean 15 Picture 2.3 Reproductive stages of soybean 16 Fig 3.1 Waterlogging and control treatment when soybeans were in germination

stage 23 Fig 4.1 Variation in the plant height of soybean genotypes under waterlogging

Vertical bars indicate SEM 30 Fig 4.2 Variation in the number of trifoliate leaves of soybean genotypes under

waterlogging(A) and control condition (B) Vertical bars indicate SEM 33 Picture 4.1 Soybean genotypes under control(A), and waterlogging conditions(B) in

the flowering stage 34 Fig 4.3 Variation in the number of branches per plant of soybean genotypes under

waterlogging(A), and control conditions(B) Vertical bars indicate SEM 36 Fig 4.4 Variation in the number of node of soybean genotypes under waterlogging

Vertical bars indicate SEM 38 Fig 4.5 The dry matter of soybean genotypes after harvesting Bars genotypes are

significantly different at P<0.05 42 Picture 4.2 TT2(A), and D8(B) genotype when harvesting 47 Fig 4.6 The individual yield of soybean genotypes Bars genotypes are significantly

different at P<0.05 51 Fig 4.7 The actual yield of soybean genotypes Bars genotypes are significantly

different at P<0.05 52 Fig 4.8 The theoretical yield of soybean genotypes Bars genotypes are

significantly different at P<0.05 52

ABSTRACT

The aims of the graduation thesis are evalution the effects of waterlogging at germination stage on growth and yield of soybean genotypes in the winter cropping system 2020, and selecting varieties with good flood tolerance for research and plant breeding The experiment was arranged at the experimental field of the Faculty of Agronomy in VNUA Five soybean genotypes, including HSB0059, DT84, TT2, D8, LSB17-21-12-15 were used in this study The experimental design was got the result by 3 random plants in each genotype and 2 formula (waterlogging and control experiment), and RCD We planted 6 beds, 3 beds under waterlogging condition, and 3 beds under control condition Waterlogging conditions when soybeans were germinating The results of this study show that the germination rate under waterlogging conditions was greatly reduced by 25% However, compared to control conditions, vegetative traits and yield of soybean varieties under waterlogging conditions were reduced The actual yield under waterlogging conditions varied from 9.9 to 32.9 quintals/ha while it varied from 11.8 to 38.2 quintals/ha under control conditions HSB0059 variety had the highest

germination rate, and yield under two conditions Further experiments to evaluate

the inundation effects on soybean growth and yield under rice conditions in winter cropping systems should be further conducted to come to more accurate conclusions HSB0059, TT2, LSB17-1-12-15 had high germination rate and high yield and adapted under waterlogging conditions It is necessary to do more experiments to evaluate other criteria to put into production in production areas with unfavorable conditions in production

CHAPTER 1: INTRODUCTION

1.1 Rationale

Soybean Glycine max (L.) Merrill belongs to the legume family Soybean

has been grown for three millennia in Asia and more recently, has been successfully cultivated around the world Today, the world’s top producers of soybean are the United States, Brazil, Argentina, China and India

Soybean is a short-term industrial plant, which has many values in many aspects: supplying protein, vegetable oil for humans, animal feed, raw material for some industries, and improving soil fertility Soybean is an economically important legume seeds contain an average of 40% protein and 20% oil, and its plants enrich the soil by fixing nitrogen in symbiosis In the international world trade markets, soybean is ranked number one in the world among major oil crops ( Chung and Singh 2008) Moreover, soybean seed also contain iron, calcium, phosphorus and fiber components for digestion Vitamins in soybeans are abundant in group B such as vitamin B1, B2, B6 Soybean oil, used in food and industrial applications, is another product In the United States, the bulk of the harvest is solvent-extracted with hexane, and the “toasted” defatted soy meal (50% protein) then makes possible the raising of farm animals (e.g chicken, hog, turkey) on a large industrial scale Therefore, soybean has become one of the most important crops in agricultural production in many countries around the world

Soybean plant (Glycine max (L) Merrill), belonging to the legume family (Fabaceae) are able to fix the unused plant nitrogen molecule nitrogen into usable nitrogen form by the rhizobium in the roots In order to meet the need for high efficiency in soybean production, the first condition is that the seedling is good before planting, conditions that affect the germination of the seed such as

the important factor affecting the appearance and development of the seed (Pollock, 1972) Depending on the planting season, the seed may experience cool, sunny, or rainy weather after planting the seed is wet, or weather without proper water, in which case the seed may be submerged for a number of hours or several days Inundation or saturation of the soil can cause poor seed germination and planting and may decrease crop yields

Around the world, research on the effects of waterlogging tolerance of the soybean plant is new research Research works are often focused mainly on evaluating the ability to grow and develop According to research by Sung (1995), soybean seeds that were submerged before germinating for 24 hours only reached 50% germination and did not soften after flooding for 48 hours In humid parts of the world, waterlogging is a major environment stress limiting soybean production (Kokubun etal., 2013) In inhibits growth and seed yield, leading to decreased root growth, nitrogen fixation, leaf chlorophyll content, and growth, and photosynthesis activity (Scott et al., 1989; Oosterhuit et al., 1990; Sung, 1993; Linkemer et al., 1998; Bacanamwo and Purcell, 1999; Pedo et al., 2015; Suematsu et al., 2017) Therefore, breeding varieties with strong waterlogging-tolerance is a desirable trait in countries with much rainfall(Van Nguyen et al., 2017)

In Vietnam, soybean is widely cultivated in all 7 ecological regions in the whole country In which, the Northern midlands and mountains are the largest sowing area Soybeans are very suitable in rotation, intercropping, pillow crop with many other crops contribute to increasing crop yield and improving land-use efficiency This issue is very implications for increased crop intensification

in our country Rainfall is one of the most significant factors required for the proper growth and development of crop plants, particularly in developing countries However, an excessive amount of rainfall has its impact in the form of flooding, which has severe impact on the growth of crop plants, including

soybean crops cultivated in rain-fed regions Flooding stress causes significant damage to the morphological and physiological features of soybean crops and hence reduces grain yield severely Soybeans often planted in winter cropping system are affected by rainfall than those conventional planted in spring-summer season in Northern Therefore, productivity and quality of soybean Viet Nam is low

Currently, our country is one of the most affected countries Climate change causes drought, soil salinity, and waterlogging - severely affecting plant growth, development, and productivity Therefore, the research on the tolerance

of inundation of plants in general and soybean, in particular, is urgent and has high applicability The results of this study serve as the basis for further studies and for the selection of soybean genotypes that are resistant to inundation So

that, to contribute to solving the above problem, we carried out the subject” The

effects of waterlogging at germination stage on growth and yield of soybean genotypes in winter cropping season 2020”

1.2 Aims and requirements

1.2.1 Aims

This study aims evaluate the effects of waterlogging at germination stage

on growth and yield of soybean genotypes in winter cropping season 2020

1.2.2 Requirements

- Evaluation of some morphological and agro-biological characteristics of soybean varieties in winter cropping

- Evaluate the growth and development of soybean

- Determine the factors constituting the yield and yield of the sample soybean variety

CHAPTER 2: LITERATURE REVIEW

2.1 Origin and distribution of soybeans

Soybean (Glycine max L Merr) belongs to the legume plant (Fabaceae),

originated from Northeast Asia (China), known for 5,000 years Soybean has been cultivated since 1,100 BC Soybean is widely distributed, from 480 North

to 300 South latitude, closely reacting to day length and is a typical short-day crop From the North of China, soybeans were developed to Japan, Korea, East, and South China, Southeast Asian countries including Vietnam In the 17th century, soybeans were introduced to Europe …

According to Le Quy Don's book "Van Dai loai ngu", Vietnam has a history of soybean cultivation from the 6th century, originally planted in the northern mountainous areas of Cao Bang and Lang Son Soybeans are used to make tofu, soy sauce, sauces, oils, milk, and flour in some foods and confectionery Before the August Revolution, the soybean area reached 30,000 hectares, the yield reached 4.1 quintals/ha After 1973, our country had only significant development in soybean production By 1983, the soybean area had increased to 106 thousand hectares, yield 5 - 9 quintals/ha

2.2 Values of soybeans

2.2.1 The nutritional value

- According to an analysis by the US Department of Agriculture (USDA)

Table 2.1 Nutritional value per 100g soybean seeds

Nutritional value per 100g soybean seeds

- According to other sources of analysis

In soybean seeds, there are chemical components: Protein (40%), lipid 25%), glucid (10-15%); There are mineral salts Ca, Fe, Mg, P, K, Na, S; vitamins

(12-A, B1, B2, D, E, F; enzymes, wax, resin, cellulose In soybean, there are enough basic amino acids such as isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan, valine In addition, soybeans are considered to be a complete protein source because they contain significant amounts of non-essential amino acids for the body

Soy-based foods are considered a type of "boneless meat" because they contain abundant plant protein, which can be substituted for protein from animal meat Even the amount of protein in 100 grams of soybeans can be equivalent to the amount of protein in 800 grams of beef

In countries such as Japan, China, 60% of the daily protein intake comes from soybeans The protein content of soybeans is much higher than the amount

of protein contained in other beans

2.2.2 Value increase the crop, improve the agricultural environment

Soybean plants have the ability to fix nitrogen from the air through the root nodule system, soybean roots are branched to make the soil more porous, improve the soil, and soybean leaf stalks make green manure Estimate per hectare, after planting, soybean remains in the soil about 30 kg, equivalent to urea nitrogen and 5-8 tons of organic matter In recent years, the growers of high-class fruit and ornamental plants have used a lot of soybean seeds and soybean meal to care and fertilize the plants with high results

Soybean rotation with other crops has the effect of balancing soil nutrients, contributing to cutting off pest lines in rotation, minimizing the use of harmful chemicals for the environment, leaving residues of toxic substances for agricultural products

Experienced farmers realize that after each crop, soybean yields higher yields, fewer pests and diseases, and saves 30% of fertilizer In the provinces of the Red River Delta, the rice yield here increased significantly compared to the formula of 2 rice crops + 1 winter corn crop, soil quality improved more clearly

2.2.3 The industrial value

Soybean is the raw material of many different industries such as the processing of artificial rubber, paint, printing ink, soap, plastics, rayon, liquid fuels, lubricants in the aviation industry, but weak soybeans are used to squeeze oil Currently, in the world, soybean is the leading plant in supplying raw materials for oil press, soybean oil accounts for 50% of total vegetable oil Characteristics of soybean oil: slow drying, high iodine index: 120-127; Condensation at temperatures: - 15 to - 18 0 C From this oil, people make hundreds of other industrial products such as candles, soap, nylon, etc

2.2.4 The medical value

Soybean is one of the precious medicinal herbs Soybeans have long been known as a food with high nutritional value because of their higher protein content than any other agricultural product Moreover, soybeans also contain a lot of minerals, B vitamins, especially herbal chemicals that have the ability to prevent and treat diseases In recent years, soybeans have been transformed from food to medicine Soybeans and dishes made from soybeans also have preventive and curative values Soybean works to make the human body long, energetic, increase memory and regenerate tissues, harden bones, and increase the body's resistance In medicine, soybean meal (which has lost its smell by steam) is mixed with cereal flour, cocoa is used as food for babies, people with diabetes, people with rheumatism, gout, overworked workers

In the pharmaceutical industry, soybean meal is used to process antibiotic mold culture medium, and to process some amino acids such as arginine,

soybean herb has properties against cancer germs such as breast cancer, colon cancer, lung cancer, stomach cancer, prostate cancer

2.3 Soybean production in the world and Vietnam

2.3.1 Soybean production in the world

Soybean is a short-term crop that is widely grown and is one of the most nutritious and economical crops in the world Typically countries such as, America, Brazil, Argentina China, India Their soybean production accounts for 90-95% of world production, according to USAA’s 2008 US soybean output at 33%, followed by Brazil at 28% and Argentina at 21% Soybean all over the world Soybeans occupy the most important positions in eight of the world’s most important crops: soybean, peanut, cotton, sunflower, canola and coconut Soybean is grown in almost all countries in the world, with 73% in the American, followed by Asia (China, India), accounting for 23.15% In recent years, world soybean production has gradually increased and is shown in the following chart:

Picture 2.1 World soybean production from 2000-2020

According to the US Department of Agriculture (USDA), in May 2020, the world soybean production 2020/2021 is estimated to be 362.76 million tons

Soybean production last year (*) was 336.11 million tons, this year's 362.76 million tons estimated to increase by 26.64 million tons or 7.93% of global soybean production

In addition to the four countries (USA, Brazil, Argentina, China) that produce the world's largest soybeans, Japan is also a long-standing soybean producer The soybean plant was introduced to Japan about 200 BC, but it wasn't until 1960 that it started to develop (Nogato, 2000) In 1960, the soybean area of this country was only 340,000 ha, but by 1997 it reached 832,000 ha (Nguyen Van Luat, 2005)

Southeast Asia is a limited soybean production region but imports a lot of soybeans and increases each year (source USDA, 2010) In 2003, the region was the largest soybean importer with nearly 3.5 million tons of soybean meal and 3 million tons of soybeans In which, Indonesia produces about 800,000 tons/year

of soybeans and imports 1.4 to 1.5 million tons, Thailand produces 600,000 to 700,000 tons/year of soybeans In 2002, Thailand imported 1.3 million tons of soybeans and 1.9 million tons of soybean meal The Philippines has very little soybean production, but its three millers import about 350,000 tons of soybeans, and 1.25 million tons of meals are imported Vietnam also has a small local production, but its booming food industry imported 600,000 tons of soybean meal in 2002 Vietnam is the only country in the region to see the growing demand for two numbers

In general, the world's soybean production in recent years has developed strongly due to its nutritional and economic value The increase in yield and yield of soybeans is due to many factors, the most influencing factor is variety, which is the reason why people have been focused on developing soybean varieties from the past The application of technical advances, intensive farming

in production, and the use of advanced technical methods in soybean breeding

research have made soybean acreage, productivity, and yield increase gradually throughout the year

2.3.2 Soybean production in Vietnam

In Vietnam, soybean is a food plant with a long and important tradition, providing protein mainly for humans, and is an indispensable component of traditional and modern meals Before the 80s of the last century, soybean yield in Vietnam was still low due to the old breeds and outdated cultivation techniques Vietnam has a history of cultivating soybeans for thousands of years, but our soybean growing area accounts for only a very small part of the total cultivated area, about 1.5-1.6% (Pham Van Thieu, 2000) Previously, soybean production was concentrated in a small scale in the northern mountainous provinces such as Cao Bang, Lang Son, Before the August Revolution, the soybean area of the country was about 32200 ha; the yield is 4.1 quintals/ha After the August method, our State has paid attention to boost soybean production, but the result is not high Since 1973, soybean production began to have significant developments (Doan Thi Thanh Nhan et al., 1996) The national soybean area after reunification is 39,954 ha with a yield of 5.2 tons/ha (Ngo The Dan et al., 1999)

According to the Vietnam Institute of Agricultural Science and Technology, Vietnam's soybean area is not stable, domestic soybean production is only enough

to supply about 8–10% of demand, by 2017, soybean planting area all over the country reached about 100 thousand hectares, yield about 1.57 tons/ha, production reached 157 thousand tons In 2018, the country's soybean area reached 105 thousand hectares, the average yield of 1.6 tons/ha, the output of 168 thousand tons.(Table 2.2)

Table 2.2 Soybean production in Vietnam from 2014 to 2018

Currently, the country has formed 7 soybean production regions, of which 4 main regions are: the Southeast has the largest area, accounting for 26.2% of the country's soybean area, mountainous areas and Northern Midlands 24.7%, Red River Delta 17.5%, Mekong River Delta 12.4% The total area of these four regions accounts for 66.6% of the country's cultivated area, the rest is the coastal plains of Central Vietnam and the Central Highlands (Ngo The Dan et al., 1999)

In the four main production regions above, the Mekong River Delta, although small in area, has the highest productivity in the country, the average yield of the whole region is 18.8 quintals/ha, especially in some places in the country the area yielded 30 quintals/ha (Pham Van Bien et al, 1976) In the Southeast, soybeans are concentrated mainly on the red soil of Dong Nai province Although the cultivated area is not large, it accounts for 1/3 of the country's

regions: Red River Delta, Southeast, and Mekong River Delta account for more than 60% of the country's soybean production Soybean grown in spring crop accounts for 14.2% of the area, summer crop it was 2.68%, the Summer-Autumn season 31.3%, the Autumn-Winter crop 22.1%, and the Winter-Spring crop 29.7% (Ngo The Dan et al., 1999)

Overall, soybean production scale is still very small compared to other crops and much lower than domestic demand, as well as compared with the GoV's 2020 target outlined in " The plan for agricultural and rural development for the 2016–2020 period "is 265 thousand tons of soybeans on a cultivated area

of 166 thousand hectares The report estimates this lack of growth due to low yields, lack of expansion in growing areas, and poor competitiveness with other crops make farmers less salty Therefore, we must take measures to expand the planted area while improving the yield of soybean varieties to meet production and consumption needs

2.4 Physiological requirements of soybean plants

2.4.1 Soil requirements

- Soybean plants can be adapted to many different types of soil, but the best soil is loam, sandy soils, well-drained, weed-free, not suitable for sandy, rocky, acidic soils, poor drainage A pH of 5.2 - 6.5 is the most suitable for soybeans to grow

- According to Doan Thi Thanh Nhan et al (1996), soybeans can still be grown on basalt red soil, upland land, hilly land On heavy loam soil, soybeans are difficult to grow, but when they regrow, they are quite adaptive In sand soil, soybean yield is not stable

2.4.2 Humidity requirements

Although soybean is upland, water is also one of the important needs and also one of the major limiting factors to soybean production During the entire growing process from sowing to harvest, soybeans require between 350 and 400

mm to 600 mm of rain The water efficiency of soybean is 600 - 1000g water / 1g dry matter (Doan Thi Thanh Nhan et al., 1996)

Table 2.3 Humidity and rainy requirements of soybean plant for each of

stages

Stage Humidity and rainy requirements

Humidity (%) Amount of rain (mm)

Table 2.4 Temperature requirements for each of soybean stages

is necessary to take good care of the beans to quickly cover the soil, the plants can absorb maximum light Soybeans respond to day length, different varieties react to different day lengths

According to Doan Thi Thanh Nhan et al., 1996 light has a profound effect

on soybean morphology, it changes the flowering and ripe time, affects plant height, leaf area, and many other properties of the tree, including seed yield During all stages of true growth, flower bud formation is believed to be less susceptible to cyclic photosensitivity The first flower buds form both at 16 hours and at 10 hours However, later flower bud development is very slow under long-day conditions and the time to flower can be doubled First, the flower buds appear on the meristem at an axillary of the leaves on the stem and then towards the tip, base, and branch If the number of short days is not enough, the flowers show only a few segments on the main stem, while the remaining segments and the tip continue to proliferate In contrast, under continuous short-day (10-12 h) conditions, the flowers bloom very quickly within 7- 10 days, the tops of varieties with limited growth habit also flower In long-day conditions (14-16 h) the first flower buds appear as soon as the lighting time is 10-12h Day length also affects the fruiting rate and fruit growth rate Short days increase the rate of beans and speed of dry matter accumulation in the fruit After flowering, if having long-term conditions, high air temperature, soybeans lose fruit, few seeds In Vietnam, soybean varieties are divided into 3 groups: early ripening group, medium ripening group, and late-ripening group Early ripe varieties with little response to day length should be planted in all 3 seasons, while late ripe varieties have a clear response, so there must be a reasonable crop arrangement (Doan Thi Thanh Nhan et al., 1996)

2.5 Soybean growth and development characteristics

It is divided into two phases: vegetative (V) and reproductive (R) In the first stage is the growth of vegetative (roots, stems, leaves); in the second stage,

it is transformed to form reproductive stage and reserves such as flowers, fruits, seeds

2.5.1 Vegetative stage

Picture 2.2 Vegetative stage of soybean

VE: Vegetative emergence; VC: Vegetative cotyledon;

V1: Single leaf and true leaf bud (3-lobed leaves)

V2: First single leaf and 2 true leaves develop to full size

V3: The first single leaf and the first 3 real leaves grow to full size

V (n): Single leaf and full-grown (n) true leaves

 The period from sowing to growing (VE - VC):

This period begins from when the water-absorbent seed swells until the plant has two cotyledons This time depends on external conditions such as temperature, soil moisture, and grain quality The summer crop in this period is about 4-5 days in the right humidity conditions If the temperature is low, making this time longer can be up to 7-10 days The suitable temperature for this period is 260 - 300C If the temperature is higher than 400, it affects seedlings and if the temperature is lower than 80 will cause the seed to grow longer The growing period must be sufficiently humid, require moisture in this period from

75% - 80% This is the decisive period of tree density per unit area and seedling health

 The period from emergence to flowering (V1 - Vn)

This is the period of the vegetative stage In the first stage, the plant grows slowly and is influenced by temperature and humidity When it comes time to bud, the flower grows rapidly This is a key period for the body to grow, burn short, and root deeply This period is the best drought-tolerant plants, the growth time of this period depends on the genetic characteristics of the variety

2.5.2 Reproductive stage(R)

Picture 2.3 Reproductive stages of soybean

At flowering, soybeans continue to develop stems, leaves, and roots This period requires great nutrition Soybean flowers usually bloom in the morning, but if the weather is overcast, the temperature is low, the flowering time is later After pollination forms fruit (5-7 days), when the fruit develops at its maximum, the seeds will develop The dry matter accumulation rate of the seed increases rapidly until the seed is firm Moisture in this period has a great influence on the growth rate of fruit and seeds The seeds reach their physiological maturity when the seeds are solid, the seed coat has the color of the variety, the pods turn ash yellow or gray-black, the leaves are yellowed and shed

Especially during this period, soybeans are often damaged by insects and stinks, and if heavy, their yield will be reduced Therefore, it is necessary to have control measures (using pesticides to eradicate with appropriate doses when the insects first develop)

2.6 Overview of research on the effects of inundation on soybean yield in the country and in the world

2.6.1 Effects of inundation on soybean production

Inundation is an adverse environmental factor that affects soybean production in tropical regions, where rainfall exceeds 1000mm (Fernandez and Shanmugasundaram, 1988) Soybean is usually grown in low-lying soils (bare ground, high altitude), the land often shows an excess of negative after heavy rains Inundation occurred severely affected soybean production Flooding limits plant growth such as reducing the amount of dry matter accumulated by roots and stems (Ahmad et al, 2002), and photosynthesis (Islam et al, 2010), reducing nitrogen fixation (Matsunami et ai, 2005), and causing soybean leaf yellowing (Kumar et at, 2013) The effects of inundation on soybean to reduce the growth and development of this plant are affecting soybean yield (Singh and Singh, 2011; Ahmad et al, 2002, Ahmad et ai, 2003 )

The lack of oxygen in the root zone is considered the major factor in wetland environments The reason is that the solubility of oxygen is reduced by

10 times in submerged versus normal conditions (Armstrong, 1980; Armstrong and Drew, 2002) The amount of oxygen decreases rapidly in the wetlands due

to its use in the respiration of the plant and of the plank In legumes, with prolonged flooding, plants often produce uncertain roots and form oxygen-free vacuoles that provide oxygen for growth and development (Shimamura et

al, 2003, 2010; Thomas et al, 2005) Root growth is related to the ground components, and therefore all parts are affected by the flooding condition

above-2.6.2 Research situation of the effect of the flood on the development of soybean plants in the world

Flooding is a natural phenomenon that greatly affects crop growth and development and significantly reduces crop yields in major growing regions of the world Flooding puts selective pressure on plants because large excess water

in the habitat can cause loss of oxygen, CO2, and light

According to Agronomy Journal, in the Southern USA, soybean was continuously flooded 3 cm above the soil surface at either the V4 or R2 growth stage for 2, 4, 7, or 14 days Flood duration effects on the soybean plant were manifested in yellowing and abscission of leaves at the lower nodes, stunting, and reduced dry weight and seed yield Canopy height and dry weight decreased linearly with the duration of the flood at both growth stages The growth rates were 25 to 35% less when soybean was flooded at R2 than at V4 The additional

4 weeks of vegetative growth after flooding allowed the soybean flooded at V4

to recover to a greater extent than the cultivars flooded at R2 A linear relation was found between seed yield and monthly average crop growth rates for the 4 week following flooding A linear decrease in seed yield with flood duration was also found On the Sharkey clay, rates of yield reduction were 157 and 124

kg ha−1 d−1 of the flood for the soybean flooded at R2 and V4, respectively On the Crowley silt loam, yield reduction rates were 101 and 53 kg ha−1 d−1 of the flood duration for the soybean flooded at R2 and V4, respectively

In one study, soybean seed germination was not processed in the field When the flooding treatment time was extended, the rate of seed bounce significantly decreased with longer flooding time After 6 hours of inundation, the germination rate decreased significantly by 12.1% and continued to decrease

to 51.8% after 1 day of inundation After 2 days of inundation, the germination rate decreased to below 10% and most of the eyes were able to germinate in the field Similarly, the study also showed that different inundation times also had a

great effect on the germination of soybean-treated seeds: the germination rate was also significantly reduced when pulled a long time for flood treatment After only 6 hours of inundation, the germination rate decreased significantly by 10.1% and continued to decrease to 50.0% after 1 day of flooding After the 2-day flood, the germination rate dropped to below 10% and there was almost no germination in the field (ChengJun Wu, 2017)

There were many researches about impacting of flooding stress on different growth stages of a soybean crop The results summarized in the table below

Table 2.5 Impact of flooding stress on different growth stages of a soybean

References

V 1 One unrolled trifoliate Reduced weightOosterhuis et al (1990)

V 6 Early flowering stageChlorosis and stunted Griffin and Saxton symptoms; dimin-(1988)

ished plant growth Reproductive Stages

R Beginning flowering Decreased shoot and Youn et al (2008)

stage dry matter

flowering stage

Reduced biomass

Oosterhuis et al (1990)

pod stage

Reduced seed yield

Van Toai et al (1994)

stage

Reduced grain mass

Schöffel et al (2001)

R 5 Grain filling

stage

Reduced seed yield

Singh and Singh (1995)

2.6.3 Research situation of the effect of the flood on the development of soybean plants in Viet Nam

In Vietnam, soybean is being grown very popularly in many growing regions across the country Research to find the lines (varieties) with high yield, good resistance to the climatic conditions of each growing area is interesting, but studies of soybean flood tolerance little

Soybean plant's flood tolerance studies T Van Toai, conducted in the Mekong Delta region of Vietnam The study used two varieties of soybean in Southeast Asia, the effect of inundation reduced soybean yield by an average of 52.5% The study showed that all the control plants in all three experiments survived, while the plants that were inundated for two weeks had the survival rate of the plants decreased to 51.8%, 69.1% and 58.9% (Tara T Van Toai, 2010)

Research of the Center for Scientific Research Support & amp; The mission was about the physiological change of soybean seedlings and seedlings under low-temperature conditions The study showed that when the temperature is lowered, the germination rate of soybean seeds decreased significantly When

the temperature was 25 ° C, the germination rate was 97.23% (like DT2008) and 96.11% (like DT84) when the temperature dropped to 16 ° C, the germination rate dropped to 57.22% the same DT2008 and 55.0% with the same DT84 In particular, at 8 ° C, the germination rate of soybeans in the two studied varieties dropped to 22.22 (Ong Xuan Phong, 2014)

Rain is the main water source for the production of upland crops in the world in general as well as the upland crops in Vietnam in particular, only a few regions can actively irrigate water resources Meanwhile, the rainfall in our country is often unevenly distributed between regions and months of the year Therefore, in dry crops, rain can be encountered, causing flooding in certain stages of growth, especially in the rainy season Prolonged rain made plants, are resistant to excess water, excess moisture, and oxygen deficiency during respiration Therefore, it is necessary to evaluate the growth and productivity of soybean varieties in flooding conditions, especially in winter

CHAPTER 3: MATERIALS AND METHODS

2021 Experiment design was got result by 3 random plants in each varieties and

2 formula (waterlogging and control experiment), and RCR We planted 6 beds, including 3 beds under waterlogging, and 3 beds under control conditions

Waterlogging experiment was provided water by rain Three beds under waterlogging were covered at both ends of irrigation drainage After raining, we didn’t cover at both ends of irrigation drainage Waterlogging exposed 2 days

We observed that it was rain when soybean was in the germination stage

Waterlogging treatment Control treatment

Fig 3.1 Waterlogging and control treatment when soybeans were at

- Fertilizer application per ha was as follows: Song Gianh microbiological

fertilizer: 250kg/ha; N:80kg/ha; P2O5 : 300kh/ha; K2O : 80kg/ha Fertilizer

application was applied 3 times:

+ Basal fertilizing: all fertilizer and phosphate fertilizers

+ The second time: apply a half of nitrogen and potassium fertilizer when the plant had 2-3 real leaves, apply 3cm from the original

+ The third time: applying when plant before flowering with the rest of

nitrogen and potassium fertilizers

-Soil was mix and cleaned weeds first time when the plant had 2-3 true leaves, combined with fertilizer application The second time was before flowering -Watering: Ensure adequate moisture for plants to grow and develop well

Depending on the weather and reasonable irrigation measures, pay attention to avoid flooding, if drought is to irrigate

-Pests and diseases prevention: Regularly check fields for pest and diseases

prevention and prevention in time

3.4 Research content

We have to research growth and growth indicators consists of growth: plant height dynamic, trifoliate leaf dynamic, internode dynamic, branches per plant dynamic, number of effective internode

In this subject, we have to research components of productivity yield, types

of yield

3.5 Trait observation

Traits were evaluated according to QCVN 01-58: 2011/BNNPTNT by Ministry of Agriculture and Rural Development for soybean

flushes had ceased and only sporadic flowering persisted) and physiological

maturity (recorded when &gt; 95% of the pods had ripened) For pod development, two flowers per plant were tagged, and records made of dates when the flowers fully opened and when the pods were mature (i.e the pod lost chlorophyll and

darkened)

-Morphological and yield related traits

Measurements were recorded for 5 plants/ variety Various vegetative traits were recorded such as plant height (cm), internode length (mm), number of leaves and nodes on main stem To determine internode length (mm), the length between the 5 th and 6 th nodes was measured and the average length per node was calculated These traits were measured on week 8 after sowing Other traits including numbers of main branches per plant, number of nodes on the stem were recorded at physiological maturity

3.6 Growth and development indicators

- Germination rate:

Germination rate (%)=𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑔𝑒𝑟𝑚𝑖𝑛𝑎𝑡𝑒𝑑 𝑠𝑒𝑒𝑑𝑠

Number of sowed seeds ×100 Some factors we have to calculate are: time to flowering, growth time,

3.7 Productivity components

Each variety will be followed 5 plants at harvest

- Count the total number of primary branches / main stems

- Number of effective node / main stems

- Count the total number of pods / plant

- Calculate the ratio of fill pods (%)

- Calculate the ratio of pod 1, 2, 3 seeds (%)

- Determine the weight of 1000 seeds(g)

- Individual yield(g / plant) = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 10 𝑝𝑙𝑎𝑛𝑡𝑠

10

- Theoretical yield(quintal/ha)= 𝑃1000 𝑠𝑒𝑒𝑑𝑠×𝑁𝑜.

𝑝𝑜𝑑𝑠 𝑝𝑙𝑎𝑛𝑡 ×𝑁𝑜.𝑠𝑒𝑒𝑑/𝑝𝑜𝑑×𝑑𝑒𝑛𝑠𝑖𝑡𝑦 10000

- Actual yield (quintal / ha) = 𝑡𝑜𝑡𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑝𝑙𝑎𝑛𝑡𝑠 𝑖𝑛 𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑏𝑜𝑥

Area of experimental box × 10000

3.8 Data analysis

The data collected during the experiment was synthesized and processed statistically according by EXCEL 2013 program and IRRISTAT

CHAPTER 4: RESULTS AND DISCUSSION

4.1 Germination rate of soybean genotypes in winter cropping season

2020

There are several reports that account for the negative correlation between germination percentage and flooding stress (Yaklich and Abdul-Baki, 1975; Maryam and Nasreen, 2012) When soy seeds are planted under non stress conditions (optimum conditions), they start to absorb water, imbibe, swell, and germinate within 1 or 2 days But the germination of seeds is delayed when fields are sometimes saturated with water from heavy rains and poor drainage Flooding causes mechanical damage on the soybean seeds and prohibits germination Wuebker et al (2001) reported

The result of germination rate of soybean genotypes in winter cropping season 2020 was presented in table 4.1

Table 4.1 Germination rate of soybean genotypes

The given table shows the germination rate of soybean genotypes in the winter cropping system 2020 The germination rates of varieties were different under all treatments We found that genotypes(G), waterlogging treatment(T), and their interaction(G×T) had a significant effect on germination rate From table 4.1, the mean germination rate under waterlogging stress of all varieties was lower from 48.3%(D8) to 71.1%(HSB0059) Besides, the mean germination rate under control conditions ranged from 59.4 to 94.5% Compare to the control, the mean GR under waterlogging stress was reduced from 25%(LSB17-1-12-15, HSB0059) to 30%(D8) HSB0059 was the best germination rate The germination rate of DT84, D8 under two conditions were low because the flooding tolerance ability of us was poor, or the seed quality of DT 84 and D8 was not good under control condition (approximate 70%)

Based on the germination rate, the genotypes were categorized into two groups, including a tolerant( HSB0059, TT2, LSB 17-1-12-15) and a sensitive group( DT84, D8) We should grow three genotypes: HSB0059, TT2, LSB1-1-12-15) in the field

In conclusion, the obtained results showed that the germination rate under waterlogging conditions was greatly decreased because when it was rain, stagnant water in the soil can cause seed germination (Narsai et al., 2015) Therefore, seed germination will decrease under low oxygen content condition

4.2 Vegetative traits of soybean genotypes

4.2.1 Plant height dynamic of soybean genotypes

Plant height reflects the growth and development of the varieties grown under certain conditions and the lodging resistance Soybean plants began to grow strongly in height when they entered the stage with 2—3 trifoliate leaves The growth of the main stem is also associated with various qualitative traits such as number of leaves, number of branches, numbers of effective nodes, and number of pods…, flower differentiates in a plant

Table 4.2 Plant height dynamic of soybean genotypes (unit: cm)

Genotypes

14 days after sowing

28 days after sowing

42 days after sowing

56 days after sowing

Compare control condition, the plant height of all genotypes in waterlogging treatment was reduced Plant growth is generally affected by changes in soil water content The oxygen content can be altered by flooding stress A hypoxic situation

minerals, nutrients, and hormones This insufficiency in nutrient and water uptake further leads to shooting damage (Vartapetian and Jackson, 1997; Jackson and Ricard, 2003) Hence flooding stress causes the damage of both root length and shoots length in soybean crops The symptoms of flooding stress, which appear on soybean shoots, are wilting of the leaves (Kramer, 1951) According to Sullivan et al.(2001), they accounted for a reduction in plant height for 3, 5, and 7-day floods

at early vegetative growth stages They also stated that a reduction in soybeans ranged from 20–93% after 6 days of flooding Several workers reported a reduction

in soybean yields on flooding, ranging in duration from 24 hours to 14 days (Scott

et al., 1989; Singh and Singh, 1995) In this study, plant height was reduced about 10% under waterlogging stress at 56 days after sowing

The below figure shows clearly the plant height dynamic under waterlogging conditions

Fig 4.1 Variation in the plant height of soybean genotypes under

waterlogging Vertical bars indicate SEM

0 10