Effect of fertilizer application on growth and yield of soybean variety vnuad2 in winter season 2021 (khóa luận tốt nghiệp)

VIETNAM NATIONAL UNIVERSITY OF AGRICULTURE

FALCUTY OF AGRONOMY

UNDERGRADUATE THESIS
TITLE:
EFFECT OF FERTILIZER APPLICATION ON
GROWTH AND YIELD OF SOYBEAN VARIETY
VNUAD2 IN WINTER SEASON 2021
Student:

LE DUC HIEN

ID:

620010

Class:

K62KHCTT

Supervisor:

Senior lecturer, Dr. VU THI THUY HANG

Department: PLANT GENETICS AND BREEDING

HA NOI – March, 2021


DECLARATION

I hereby declare that this paper is my own work. All results and data in
this thesis are absolutely honest and have not been submitted before to any
institution for assessment purposes. All sources used in this paper were cited in
references.
Hanoi, 10th March 2022
Student

Lê Đức Hiền

i


ACKNOWLEDGEMENT

To complete this thesis, I am deeply indebted to people who have been
providing me with precious support and advice.
Firstly, I would like to send my gratitude to my supervisor, Dr. Vu Thi
Thuy Hang, Department of Plant Genetics and Breeding, Faculty of Agronomy,
Vietnam National University of Agriculture, for her enthusiastic support, helpful
advice and considerable encouragement in the completion of my thesis.
I would also like to express sincere thanks to the lecturers from the
Faculty of Agronomy in general and lecturers in the Department of Plant
Genetics and Breeding in particular, who taught and created best conditions for
students during learning process and research.
I would like to give special thanks to Dr. Vu Ngoc Thang, Ms. Phạm Thị
Ly and Mr. Hoàng Đức Nhật Linh for their helpful technical supports.
Last but not least, I want to express my sincere thanks to my family and
friends who have always been by my side, give me support and strength to
complete this graduation thesis.

ii


TABLE OF CONTENTS
DECLARATION ................................................................................................... i
ACKNOWLEDGEMENT .................................................................................... ii
TABLE OF CONTENTS ..................................................................................... iii
LIST OF TABLES ................................................................................................ v
LIST OF FIGURES .............................................................................................. vi
ABSTRACT ........................................................................................................ vii
CHAPTER 1. INTRODUCTION ......................................................................... 1
1.1. Background .................................................................................................... 1
1.2. Objective and requirements............................................................................ 2
1.2.1. Objective ..................................................................................................... 2
1.2.2. Requirements ............................................................................................... 2
PART II: LITERATURE REVIEW...................................................................... 3
2.1. Classification, origin of soybean .................................................................... 3
2.1.1. Origin of soybean ........................................................................................ 3
2.1.2. Classification of soybean ............................................................................ 4
2.2. Soybean production in the world ................................................................... 4
2.3. Soybean production in Vietnam ..................................................................... 8
2.4. Values of soybean ........................................................................................ 11
2.5. Fertilizer application in soybean production ................................................ 12
2.5.1. General principles of fertilizer application ............................................... 12
2.5.2. Research on fertilizer application for soybean in the world ..................... 14
2.5.3. Research on fertilizer application for soybean in Vietnam ....................... 17
CHAPTER III. MATERIALS AND METHOD ................................................. 21
3.1. Plant materials .............................................................................................. 21
3.2. Location and time ......................................................................................... 21
3.3. Experimental design ..................................................................................... 21

3.4. Cultural practices.......................................................................................... 23
3.5. Trait measurements ...................................................................................... 23
iii


3.5.1. Growth and development characters ......................................................... 23
3.5.2. Yield components and yield ...................................................................... 25
3.6. Evaluation of disease and pest damage and lodging resistance of
VNUAD2 .................................................................................................... 25
3.7. Data analysis ................................................................................................ 26
CHAPTER 4. RESULTS AND DISCUSSION .................................................. 27
4.1. Effects of fertilizers on growth of VNUAD2 variety in winter season 2021 .... 27
4.2 Effects of fertilizers on fresh weight of VNUAD2 variety in winter
season 2021 at different growth stages ....................................................... 29
4.3. Effects of fertilizer on dry weight of VNUAD2 variety in winter season
2021 at different growth stages ................................................................... 34
4.4. Effects of fertilizers on nodule formation of VNUAD2 variety in winter
season 2021 at different growth stages ....................................................... 38
4.5. Effects of fertilizer on leaf area and leaf area index of VNUAD2 variety
in winter season 2021 at different growth stages ........................................ 41
4.6. Effects of fertilizers on yield components of VNUAD2 variety in winter
season 2021 ................................................................................................. 43
4.7. Effect of fertilizers on individual yield and yield of VNUAD2 variety in
winter season 2021 ...................................................................................... 47
4.8. Effects of fertilizers on disease, pest damage and lodging resistance of
VNUAD2 variety in winter season 2021 .................................................... 49
CHAPTER 5. CONCLUSIONS AND SUGGESTIONS ................................... 51
5.1. Conclusions .................................................................................................. 51
5.2. Suggestion .................................................................................................... 51
REFERENCES .................................................................................................... 52

A. Vietnamese references:................................................................................... 52
B. Foreign references: ......................................................................................... 53
SOME PICTURES ABOUT PROCESS CONDUCTED UNDERGRADUATE
THESIS ....................................................................................................... 55

iv


LIST OF TABLES
Table 2.1. Status of soybean production in the world in the period 20102020 ....................................................................................................... 5
Table 2.2. Area, yield and production of soybeans of some countries in the
period 2015-2020 .................................................................................. 7
Table 2.3. Area, yield and production of soybean in Vietnam during 20102020 ....................................................................................................... 9
Table 3.1. Measured traits for VNUAD2 in winter season 2021 ....................... 24
Table 3.2. Yield components and yield measurement for VNUAD2 in winter
season 2021 ......................................................................................... 25
Table 3.3. Evaluation of disease and pest damage and lodging resistance of
soybean................................................................................................ 26
Table 4.1. Effects of fertilizers on growth of VNUAD2 variety in winter
season 2021 ......................................................................................... 28
Table 4.2. Effects of fertilizers on fresh weight of VNUAD2 variety in
winter season 2021 at different growth stages .................................... 31
Table 4.3. Effects of fertilizer on dry weight of VNUAD2 variety in winter
season 2021 at different growth stages ............................................... 35
Table 4.4. Effects of fertilizer on nodules of VNUAD2 variety in winter
season 2021 at different growth stages ............................................... 39
Table 4.5. Effects of fertilizer on leaf area and leaf area index (LAI) of
VNUAD2 variety in winter season 2021 at different growth stages .. 42
Table 4.6. Effects of fertilizers on yield components of VNUAD2 variety in
winter season 2021 .............................................................................. 45

Table 4.7. Effects of fertilizers on individual yield and yield of VNUAD2
variety in winter season 2021 ............................................................. 48
Table 4.8. Effects of fertilizers on disease, pest damage and lodging
resistance of VNUAD2 variety in winter season 2021 ....................... 49

v


LIST OF FIGURES
Figure 4.1. Growth of VNUAD2 at different fertilizer treatment at podding
stage..................................................................................................... 33
Figure 4.2. Nodule formation of VNUAD2 at different fertilizer treatment ...... 41

vi


ABSTRACT

This study aimed to identify the most suitable levels of nitrogen and
potassium fertilizers for growth and yield of soybean variety VNUAD2. The
experiment design split plot design with 3 replications. Three levels of nitrogen
(40, 50 and 60 kg/ha) and four levels of potassium (60, 80, 100 and 120 kg/ha)
were applied. Plant density was of 50 plants/m², with 2 rows/plot and plot size
of 5 m2. Measured traits included growth characters such as plant height, height
of first pod insertion, number of leaves, nodes and primary branches on main
stem, dry and fresh weight of plants, nodule formation, yield components and
yield. Pest and disease resistance and lodging resistance were also recorded.
Results showed that the growth parameters were affected by different
fertilizer rates. The amount of nitrogen at the level of 50 kg/ha and the amount
of potassium at the level of 100 kg/ha resulted in higher plant height, first pod

insert height, number of nodes, number of leaves, and number of primary
branches. Different rates of nitrogen and potassium also affect fresh and dry
weight stem and roots, nodule characters and leaf areas at different growth
stages. The level of 50 kg/ha of nitrogen and 100 kg/ha of potassium provided
the higher values than other rates. Besides, the leaf area and leaf area index
reached the high values at the application of 60 kg/ha of nitrogen and 80 kg/ha
of potassium at the fruiting stage. Yield components were also affected by
different rates of fertilizer application. Individual yield and yield achieved
significantly high values when fertilizer was applied at 50 kg/ha for nitrogen and
at 100 kg/ha for potassium.

vii


CHAPTER 1. INTRODUCTION
1.1. Background
Soybean (Glycine max (L). Merrill) is a short-term industrial crop with
multi-faceted effects. It is a plant of high economic value, occupies an important
position in the transformation of crop structure and diversity agricultural
products in our country towards commodity agricultural production and
sustainable agricultural development. In addition, soybean is also a plant with
the ability to fix nitrogen, increase soil fertility, and improve soil very well. Its
products are a source of food for humans, animal feed, raw materials for the
processing industry, and valuable export items. Therefore, soybean cultivation
has long been interesting and strongly developed in many countries around the
world, including Vietnam (Duong Hong Dat, 2012).
Soybean is one of the most important grain legumes in terms of its
use as food, animal feed, and industrial material, with seeds being characterized
by a high content of protein (30 – 48%) and oil (13 – 22%). Soybean is ranked
number one in the world oil production (48%) in the international trade markets

among the major crops, including cottonseed, peanut, sunflower seed, coconut
and palm kernel (Singh and Hymowitz 1999). In addition, soybean, as other
legume plays a critical and important role in ecosystems and sustainable
agriculture because of its ability to sequester C while enhancing soil quality and
tilth (Graham and Vance 2003). Its capacity for symbiotic nitrogen fixation with
compatible rhizobia (Graham and Vance 2003) provides essential and „free‟
nitrogen for use by the host plants or by associated or subsequent crops.
Soybean was domesticated from wild soybean, Glycine soja Sieb.
et Zucc in the cool, humid north-east of China (Hymowitz 1970). Then, the
soybean was disseminated to other Asian countries such as Korea, Japan,
Indonesia, the Philippines, India, Thailand, and Vietnam. By the 16th and 17th
centuries, the soybean was introduced to Europe and North America (Singh and
1


Hymowitz 1999). Since the crop improvements aimed soybean as a grain crop
started in the 1920s in well- irrigated areas of United States, soybean has
become a large commercial grain crop and has been breed for mechanized
agriculture (Hymowitz 1988). Nowadays, the soybean is a world crop, cultivated
widely in the USA, Brazil, Argentina, China and India.
Soybean production is affected by many factors including varieties,
agronomic practices, and climate conditions. Of which, agronomical practices
such as plant density, sowing time and fertilizer application are need to be
studied to find the most suitable practice for any new varieties. VNUAD2 is a
new soybean variety and its plant density of 40 – 50 plant/m2 was identified by
Vu et al. (2021). However, there have not been studies on fertilizer application
for it. Therefore, we conduct the “Effect of fertilizer application on growth and
yield of soybean variety VNUAD2.”
1.2. Objective and requirements
1.2.1. Objective

Identify the most suitable levels of nitrogen and potassium fertilizers
for growth and yield of soybean variety VNUAD2.
1.2.2. Requirements
VNUAD2 was grown in winter season 2021 in Gia Lam. Different
levels nitrogen and potassium fertilizer were applied to VNUAD2. The study
required evaluation of growth and yield of VNUAD2 for:
- Agronomical traits related to growth and development of VNUAD2
under different fertilizer application treatments
- Yield components and yield of VNUAD2 under different fertilizer
application
- Based on growth performance and yield of VNUAD2 to select the most
suitable level of fertilizer application

2


PART II: LITERATURE REVIEW

2.1. Classification, origin of soybean
2.1.1. Origin of soybean
The soybean (Glycine max (L). Merr.) is believed to be one of the oldest
food crops in the world. Some evidences that relate to history, geography and
archaeology all indicate that soybeans are native to Asia and originated in
China. The soybean was domesticated from its wild ancestor (called Glycine
soja) which was distributed throughout China, Japan, Korea, East Asia but its
distribution in China is most extensive the largest (Qiu and Chang, 2010). Based
on historical observations, both Fukuda (1933) and Hymowitz (1970) thought
that Northeast of China was the origin of soybean because various semi-wild
soybeans were distributed there and many soybean varieties carried primary
features in this region. However, many other theories are that soybean is

originated from the south of China (Wang, 1947; Ding et al., 2008) or from
other areas in China (Lu, 1978).
Soybean spread to Europe and America in the 18th century and was first
introduced to Africa in the early 19th century, through Southern Africa. The
immense economic values of soybeans were really approved in the 1920s. Only
when considered as seed crops and cultivated in favorable irrigation areas in the
US, has soybean become such a crop with great commercial values and selected
for mechanized agriculture (Hymowitz, 1988).
Some studies documented that soybean was cultivated in Vietnam during
Hung dynasty and even earlier than mung bean and black bean (Ngo The Dan et
al., 1999). Despite its very early appearance, soybean has been developed as a
potential crop with high nutrition values and made a great contribution to
Vietnam‟s economy over a few decades. However, both soybean cultivation area
and productivity are still much lower than these of other countries in the world.
3


Nowadays, Vietnam still imports a large quantity of soybean and its processed
products from US, China and other countries.
2.1.2. Classification of soybean
Soybean is polyploidy origin due to high chromosome number; it includes
diploid and tetraploid nature (2n = 40 or 4n = 40) in the family Leguminosae, the
subfamily Papilionoideae, the tribe Phaseoleae and the genus Glycine and,
scientific name is Glycine max (L.) Merrill.
There are many different classifications, but so far, the system of
classification was mainly relied on morphological characteristics, geographical
distribution and the number of chromosomes.
Glycine genus is subdivided into 26 perennial wild indigenous species of
Australia with perennial crops in Australia, the South Pacific Island, the
Philippines, Taiwan and Southeast China. The genomes of 2n, 4n genes and

multiple deflates (40, 80, 38, 78) (Chung and Singh, 2008; Orf, 2010).
Hybridisation between the species in this sub-family is very unsuccessful,
except for Glycine canescense grown for animal feed. Thus, in vitro culture in
pre-embryo stage will be obtained in order to obtain some ripening fruit between
the diploid species of this subspecies and Glycine max. Some crosses between
G. max and tetraploid species, G. tomentella, can produce hybrid and F1 seeds,
but the F1 plants are ineffective (Nguyen Van Hien, 2000).
The areas where soybeans are mainly grown range from cold temperateclimate regions (Northern U.S. and Canada) to tropical regions (Indonesia).
Temperatures between 22 and 35°C are required for its growing season, and can
affect its flowering dates.
2.2. Soybean production in the world
Soybeans are the most important oilseed crops in the world, ranking
fourth after wheat, rice and maize. Due to its wide adaptability, it has been
cultivated in about 70 countries but is concentrated in the Americas more than
4


70%, followed by Asia (Hartman et al., 2016). Currently, soybean genetic
resources in the world are stored mainly in 15 countries including Taiwan,
Australia, China, France, Nigeria, India, Indonesia, Japan, Korea, South Africa,
Sweden, Thailand, USA and Russia with 45,038 varieties (Tran Dinh Long,
2002).
Soybean production situation in the world in recent years is shown in
table 2.1.
Table 2.1. Status of soybean production in the world in the period
2010-2020
Year

Area
(million ha)

Yield
(ton/ha)

2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020

102.8
103.8
105.4
111.1
117.7
120.9
121.6
123.9
124.9
122.4
127.6

2.6
2.5

2.3
2.5
2.6
2.7
2.8
2.8
2.8
2.8
2.9

Production
quantity
(million ton)
265.1
261.6
241.3
277.7
306.3
323.3
335.6
353.0
348.7
336.6
368.5

(Source: Faostat, 2021; />
Soybean production in the world has increased significantly over the
years. The area from 102.8 million hectares (2010) increased to 122.4 million
hectares (2019), an increase of 19.6 million hectares. The yield increases
substantially from 2.6 tons/ha (2010) and to 2.8 tons/ha (2019). During the years

2010 - 2019, the production quantity tends to increase over years due to
increased acreage and productivity with almost 265.1 million ha in 2010 and
336.6 million ha in 2020. In recent years, the demand for products made from

5


soybean is increasing but the world soybean production area is decreasing.
Perhaps the cause is an outbreak of some animal diseases and a reduction in the
need for raw materials for animal feed, especially in China.
Forecast in 2020, the area for soybean in the world was 127.6 million ha,
the yield was 2.9 ton/ha and production were 368.5 million tons. The largest
areas of soybean production in the world are in the Americas, followed by Asia,
Europe and Africa. The Americas provides 87.1% of global soybean production.
America, Brazil, Argentina, India, and China are the leading countries in
soybean production and their soybean production accounts for 90-95% of the
world production. Among major producing countries, the Brazil is the top
producer during the year 2015-2020, (38.6 million ha and 133.0 tons) in terms of
area and production in 2020, followed by USA (33.3million ha and 116.2 tons),
Argentina (17.3 million ha and 53.5 tons) and China (9.3million ha and 17.5
tons), respectively (Table 2.2). This is the result of the application of techniques,
mechanization in agricultural production, high yield transgenic and pest
resistance varieties. In addition, in the development strategy, countries also
increase the soybean acreage by replacing other crops such as sunflower (in
Argentina), cotton (in the US), using grasslands (in Argentina and Brazil) or
replacing native plants (in Brazil) (Masuda and Goldsmith, 2009).

6

Table 2.2. Area, yield and production of soybeans of some countries in the
period 2015-2020
Year

USA

Brazil

Argentina

China

2015

33.12

32.18

19.35

6.51

2016

33.47

33.18

19.50

7.09

Area

2017

36.24

33.96

17.34

7.35

(million ha)

2018

35.66

34.77

16.32

7.97

2019

30.33

36.90

16.70

9.30

2020

33.30

38.60

17.30

9.30

2015

32.3

30.3

31.8

18.1

2016

34.9

29.1

30.1

18.0

Yield

2017

33.1

33.8

31.7

17.9

(quintal/ha)

2018

34.7

33.9

23.2

17.8

2019

31.9

34.1

29.3

19.5

2020

34.9

34.5

30.9

18.8

2015

106.9

97.5

61.4

11.7

2016

116.9

96.4

58.8

12.8

2017

120.0

114.7

55.0

13.1

2018

123.7

117.9

37.8

14.2

2019

96.7

126.0

49.0

18.1

2020

116.2

133.0

53.5

17.5

Production
(million
ton)

(Source: Faostat, 2021; />
Due to the selection methods, mutagenicity and hybrid, the United States
has created and breeding new soybean varieties. Varieties with high yield used
as breeding sources in breeding programs. Studies in soybean breeding by
mutant methods in the United States also achieved many results. Especially after
many years of testing thousands of soybean varieties, the United States has

7


found soybean allergy-free varieties. Today, most of development of soybean
varieties are conducted by private sector. However, public-sector breeders still
have an important role. In addition to variety development, public sector
breeders place emphasis on germplasm enhancement, breeding methodology
and molecular technology development. In the future, the productivity of
modern agriculture will depend largely on the ability to breed new varieties
adaptable to changing environmental conditions and management strategies.
China is a neighboring country of Vietnam and has similar farming
practices. Currently, China is the 4th largest country in the world in soybean
production. China has applied scientific advances in hybrid and imported
varieties. In addition, China has a number of programs to improve soybean
varieties with resistance to pests and weeds, suitable to the sub-regional climate.
These typical varieties are CN001, CN002 and YAT12. In recent years, China
has also developed many new varieties by mutation such as Tiefeng 18 resistant
to high alum, good lodging resistance, high productivity and good quality (Ngo
The Dan, 1994).
In general, the world's soybean production in recent years has thrived due
to its nutritional and economic value. The increase in yield and yield of
soybeans was due to several factors, the most influencing being variety.
Forecasts also show that the annual world soybean production will increase by
2.2% to about 371.3 million tons by 2030. However, the reality shows that the
production or demand for soybeans increases but the area of cultivated land
seems to decrease. That requires investment in research to improve seed yield
(Masuda and Goldsmith, 2009).
2.3. Soybean production in Vietnam
Soybean was grown in Vietnam very early and used to process for

familiar products such as soy sauce, tofu, cooking oil...

8


Soybean planting area in our country reached the highest level in 2010
and decreased year by year (Table 2.3). If in 2010, our country's soybean
growing area still reached 197.8 thousand hectares, then by 2017 it was only
68.5 thousand hectares, down 65.4% compared to 2010. Therefore, the annual
soybean production 2017 was only 101.7 thousand tons, down 65.9% compared
to 2010 (298.6 thousand tons). Thus, although the average soybean yield in our
country is relatively stable at about 15 quintals/ha, it is only approximately 1/2
of that of the world and the country's total soybean production can only meet
1/10 domestic soybean demand. This means that we have had to import a large
amount of soybeans over the years. In 2014 we imported 1,564 thousand tons,
worth 913.2 million USD, preliminary to August 2017 we imported 918.72
thousand tons, worth 391.93 million USD, the purpose is to serve feed
processing industry, a very small part of which is used to process daily feed
products such as milk, tofu or cooking oil (General Department of Customs, 2018).
Table 2.3. Area, yield and production of soybean in Vietnam during
2010-2020
2012

Year

2013

2014

2015

2016

2017

2018

2019

2020

Area
(thousand

119,2 117,2 109,4 100,8 99,60 68,40 53,30 49,40 41,60

ha)
Yield
(tons/ha)

1,45

1,44

1,43

1,45

1,61

1,49

1,52

1,56

1,57

173,5 168,2 156,5 146,4 160,7 101,7 80,8

77,3

65,4

Production
(thousand
tons)
Source: General Statistics Office, 2021

9


In 2012, the soybean growing area of our country was 119.2 thousand
hectares, decreasing gradually over the years. By 2020, the area will be reduced
to 41.60 thousand hectares, a decrease of 65.10% compared to 2012.
In 2012, the average yield of the whole country reached 1.45 tons/ha,
increased continuously over the years and reached the highest level in 2016 at
1.61 tons/ha, then tended to decrease slightly over the years. By 2020, our
country's soybean yield will reach 1.57 tons/ha.
Due to the gradual decrease in area and productivity, our country's

soybean production has also decreased over the years. In 2012, the total soybean
production of the country reached 173.5 thousand tons. By 2016 it will decrease
to 160.7 thousand tons and soybean production will decrease the most in 2020 at
65.4 thousand tons.
According to Pham Dong Quang et al. (2005), currently, soybeans are
grown mainly in 27 provinces. According to statistics, soybean growing area is
mainly in the Northern provinces, about 100 thousand hectares (accounting for
more than 80% of the total area of the country). More than 60% of soybeans are
grown in highland areas. The Northern Midlands and Mountainous region have
the largest soybean growing area in the country with 49.7 thousand hectares
(accounting for 45.1% of the total area of the country) and the production is 62.2
thousand tons (accounting for 39.4% of the total area of the country). Next is the
Red River Delta with the second-largest soybean area, accounting for 36.5% of
the total area (40.2 thousand ha) but the leading products in the country,
accounting for 40.2% of the total production. (63.5 thousand tons).
Vietnam is ranked 6th in soybean production in Asia (after China, India,
Indonesia, Korea and Thailand). Over 40% of our country's soybean products
are used to produce vegetable oil, the rest is used for human food, animal feed
processing and breeding. Currently, Vietnam's soybean production only meets
more than 10% of domestic demand. Therefore, for many years, our country has
10


had to import soybeans in large quantities and most of them are used for the
purpose of processing animal feed.
2.4. Values of soybean
Soybean is a short-term crop with high economic value. It is hard to find a
plant that is as multifaceted as soybean. Its products are used as food for
humans, feed for livestock, raw materials for the processing industry, export
goods and as a soil improvement crop.

- Food value: Soybean seeds have high nutritional content, average
protein content is about 40-50%, lipid is 13-24%, carbohydrate is 22-35%. In
soybean seeds, there are quite a lot of vitamins, especially vitamin B1 and B2
content, in addition, there are vitamins PP, A, E, K, D, C... Especially in
germinating soybean seeds. The amount of vitamins has increased much,
especially vitamin C. Currently, from soybean seeds, people have processed
over 600 different products, of which more than 300 types of food are processed
by both ancient methods. Traditional, handcrafted and modern forms of fresh,
dried and fermented... such as bean sprouts, tofu, soy sauce, soy sauce... to other
premium products such as coffee beans, confectionery and meat fillings.
Soybean is also a medicine to cure diseases, especially black soybean, which has
good effects on the heart, liver, kidneys, stomach and intestines. Soybean is a
good food for people with diabetes, rheumatism, nervous breakdown and
malnutrition.
- Industrial value: Soybean is the raw material of many different
industries such as processing artificial rubber, paint, printing ink, soap, plastic,
rayon, liquid fuel, lubricating oil lubricants in the aviation industry, but mainly
soybeans are used for pressing oil. Currently in the world soybean is the leading
plant providing raw materials for oil pressing, soybean oil accounts for 50% of
the total amount of vegetable oil. Characteristics of soybean oil: slow drying,
high iodine index: 120-127; Condensation at temperature: -15 to -18oC. From
11


this oil people make hundreds of other industrial products such as candles, soap,
nylon...
- Agricultural values:
+ As fodder for livestock: Soybean is a good source of fodder for
livestock. 1 kg of pea is equivalent to 1.38 units of animal feed. The whole
soybean plant (stem, leaves, fruit, seeds) has a high protein content, so byproducts such as fresh leaves and stems can be very good fodder for livestock,

or dried as a general feed for livestock cattle. Industrial by-products such as
oilseed meals have quite high nutritional content: N: 6.2%, P2O5: 0.7%, K2O:
2.4%, so they make very good fodder for livestock (Ngo The Dan et al., 1999).
+ Soil improvement: soybean plants have the ability to fix atmospheric
nitrogen through root nodules. Soybean roots are deeply branched, making the
soil porous. Soybean is a valuable crop for soil improvement. Soybean leaves
are very good for making green manure. In the humid tropical conditions of our
country, soybean is a short-term crop that is easy to put into the system of crop
rotation, increased cropping, and intercropping. It is the first plant that gives the
effect to the next plant.
2.5. Fertilizer application in soybean production
2.5.1. General principles of fertilizer application
Fertilizer is an important factor determining the yield of crops. Therefore,
it is necessary to have a basis for reasonable fertilization to achieve the highest
yield. In addition to determining the nutritional needs of plants, it is necessary to
pay attention to factors such as the ability of the soil to provide nutrients,
determine the nutritional needs that the plants need, from which there are
appropriate fertilization methods.
Fertilization is to compensate for the amount of mineral nutrients for the
soil to help plants absorb more nutrients, develop better, plant roots go deeper,
nutrients from deep layers are mobilized more, more biomass and root biomass
12


were formed. Leaving a greater mass of roots and other bioaccumulation in the
soil every year, helping to provide more humus to the soil, making the soil more
porous, better absorptive capacity and soil fertility. Farmers can save more
fertilizer not only because nutrients from organic matter are returned to the soil
but also because the fertilizer utilization ratio is increased.
For effective fertilization, soil properties should be analyzed before

application. Soils with heavy or light mechanical composition must be given
priority to organic fertilizers. Applying organic fertilizer for soil with heavy
mechanical composition, bury shallowly, while for soil with light mechanical
composition, it must be deeply buried and heavy soil can be applied a lot,
concentrated fertilizer, while light soil must be fertilized a little. , fertilize
several times and apply close to the requirements of the plant.
Fertilizer for plants should be applied according to the needs of the plant.
There are plants that need a lot of nitrogen (plants for leaves), there are types
that need a lot of potassium (trees for tubers, fruit trees, trees for sugar). Seeds
that are fertilized with a lot of phosphorus will have bright seeds, good seed
quality, and sown with seeds that have more phosphorus, more vitality, and
higher yields. Oil crops, legumes, and spices need an adequate supply of sulfur.
Each growth stage of each plant also has different requirements. The first
stage plants need a lot of phosphorus and nitrogen, the later stages need a lot of
nitrogen, potassium and trace elements... Any stage should not over-fertilize the
plant's needs and every stage must provide it. nutrients in a balanced manner.
Fertilizer for plants, but the growth of plants is directly affected by
weather conditions and climate, so it may be necessary to adjust the fertilizer
application to suit the weather situation. Plants that stop growing in the northeast
monsoon should not be fertilized with nitrogen because it can reduce the cold
tolerance of the plant, so they may be planning to fertilize but have to step back
and sometimes have to fertilize earlier because the tree grows early. On sloping
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land, fertilizing must be based on weather conditions (rain and wind), sometimes
you have to wait for the sky to clear and clear before applying to avoid washing
away the fertilizer, but sometimes you also have to wait for the raindrops to
dissolve the fertilizer. Fertilization to the deep layer of the roots is more
favorable.

In summary, in agricultural production, the use of fertilizers must aim to
maximize the efficiency of fertilizer use, to make plants able to absorb the most
nutrients from fertilizers. Determining the right type of nutrients, the plant needs
is mentioned first, followed by the amount the plant needs, next is the time the
plant needs to provide and one thing that cannot be ignored is how to fertilize it
to ensure the most favorable for the absorption of nutrients by the plant and
minimize the loss of nutrients in the manure.
From that determination, there will be reasonable fertilization methods.
The basis of building a reasonable fertilizer regime is based on the nutritional
needs of the plant and the supply capacity of the soil. At each growth stage,
plants need different nutrients with different amounts of fertilizer. Therefore, it
is necessary to distribute the amount of nutrients required by the plant in
different stages. There are two periods that need to be prioritized to feed the
tree: the period of crisis and the period of high performance.
The crisis period of a nutrient element is the period in which the lack of
that element will have the worst effect on growth and yield. The period of high
yield is the period when the nutrient element has the best effect on yield, the
least amount of nutrients is needed for a unit of harvested product, so the
fertilizer investment has the highest efficiency. In manufacturing, periods of
high efficiency do not coincide with times of crisis.
2.5.2. Research on fertilizer application for soybean in the world
Besides research on varieties, many studies have been conducted on
application of various fertilizers for soybean. It is very important to study the
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fertilizer regime, planting mode, and care for the plants to grow well and
promote the full potential of the variety.
Nitrogen requirement is the most important factor for soybean plants. The
nitrogen requirements of soybean at different growth stages are different.

However, the nitrogen requirement of soybean is not high because the roots are
in symbiosis with the bacterium Rhizobium japonicum, so the plant has the
ability to fix nitrogen and provide the soil with a large amount of nitrogen.
According to Imsande (1992), the most nitrogen crisis stage in soybean is
the seed making and firming stage (R5 – R6). Lack of nitrogen at this stage
leaves will fall prematurely because nitrogen in the leaves is inherited for seed
development. The authors Ashour and Thalooth (1983) concluded that foliar
nitrogen supplementation at the seed making and firming stage (R5 – R6) has
the effect of increasing grain yield and increasing biomass yield.
According to Watanabe et al. (1986), to achieve a high seed yield (3
tons/ha) soybean needs to accumulate 300 kg N/ha. From the results of field
experiments, the author showed that applying 60 kg N/ha and 120 kgN/ha at
flowering increased soybean yield up to a saturated N content of 180 kg N/ha.
According to Sinha (1987), Borkert & Sfredo (1994) to achieve high soybean
yield, it is necessary to fertilize soybean with a significant amount of N at about
150 kg/ha.
Research by Bona et al. (1998) on the effect of late N for soybean
indicated that adding N fertilizer at the rate of 150 kg/ha at the beginning of the
fruiting period for soybean varieties with finite growth behavior has the effect of
increased seed yield and harvest coefficient, but has no effect on varieties that
grow indefinitely, but only causes the plant to continue vegetative growth.
Harper (1974) found that N2 immobilization and the use of nitrate (NO3)
are important for maximum yield. He found that an excess of NO3- was harmful
to yield because then N2 fixation was inhibited. Excessive nitrogen fertilization
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or improper fertilization will inhibit the formation, growth, and activity of
nodule bacteria. Nitrogen fertilization will not increase soybean yield if soil
nutrients already supply the plant's NO3 requirements (Porter et al., 1981).

However, if the soil is poor in organic matter and poorly drained, nitrogen
fertilization with the amount of 50-110 kg/ha has the effect of increasing yield.
In addition, phosphate is a very significant factor for soybean. When
plants are provided with adequate phosphorus, the rate of flower and fruit drop
will be reduced, the fruit set rate is increased, the rate of firmness will increase
significantly. According to Dickson et al. (1987), low soil availability of P is the
most important factor causing low yield in many Asian countries. According to
Tiaranan et al. (1987), in Thailand, many soybean production areas have easily
digestible P content in the soil from 1-5 ppm, when phosphate fertilizer
application has doubled yield, the author thinks that the phosphorus crisis of
soybean is about 8 ppm.
In Australia, Dickson et al. (1987) conducted experiments on phosphate
fertilization of fields in Queensland and showed that soybean yield was
significantly increased when phosphate was applied, the soybean's susceptibility
to secondary phosphorus fertilizers was significantly increased. It depends on
soil acidity, organic matter content and soil mechanical composition.
In Indonesia, fertilizing soil with easily digestible nutrients below 18 ppm
has significantly increased soybean yield, lack of easily digestible phosphorus is
often associated with soil, and high Al, Fe, and Mn content hinders bio growth
and productivity formation (Salesh & Sumarno, 1993).
In acidic soil, the ability to retain phosphorus is often high because the
ratio of Fe and Al is high, causing severe phosphorus deficiency, limiting the
ability of soybean to absorb nutrients. The application of lime will increase soil
pH, thereby increasing the easily digestible phosphorus content to help plants

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absorb phosphorus easily. In addition, it is necessary to combine N, P and
organic fertilizers to improve the efficiency of phosphate fertilizer use.

Potassium affects the growth, development, yield and quality of soybean
seeds. Research by Smit (1998) on the response of soybean to potassium
application showed that K application on leaves does not replace K application
before planting. The author also concluded that the protein content in seeds was
negatively correlated with the amount of potassium fertilizer (both KCl and
K2SO4) applied to the soil, while the oil content was positively correlated with
the amount of K fertilizer applied to the soil.
Nigeria (1990-1991) research on the effectiveness of the combination of
mineral fertilizers N, P, K has concluded that economic efficiency is highest in
the formula 60 tons of manure + 200 kg of N, P, K (15:15:15)/ha and applied
during the branching period of soybean.
2.5.3. Research on fertilizer application for soybean in Vietnam
With each crop, the nutritional needs of different crops are different.
When provided with adequate nutrients, crops in general and soybean plants in
particular will promote their yield potential. In the technical measures of
intensive farming to improve soybean yield, fertilizer plays a very important
role. Therefore, in addition to determining the appropriate set of varieties for
each region and each production season, it is necessary to research and perfect
the fertilizer application process to improve yield for each variety in each season
and different soil conditions necessary power.
Nitrogen fertilizer plays an important role in the growth, development and
yield of soybean. The source of nitrogen for soybeans is from fertilizers, soil and
the ability to fix atmospheric nitrogen by nodulation bacteria. Each stage of
soybean growth requires different amounts of nitrogen. Nitrogen is used in the
following forms: NH4NO3, HNO3, NH4OH and urea nitrogen CO(NH2)2.

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