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CÁC CÔNG TRÌNH KHOA HỌC ĐÃ CÔNG BỐ CỦA LUẬN ÁN

CÁC CÔNG TRÌNH KHOA HỌC ĐÃ CÔNG BỐ CỦA LUẬN ÁN

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HUE UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY



LE CONG NAM



RESEARCH ON MINERAL FERTILIZATION BY LEAF

NUTRITIONAL DIAGNOSIS FOR RUBBER TREES

IN QUANG TRI PROVINCE



AGRICULTURAL DISSERTATION OF PHILOSOPHY DOCTOR



HUE, 2018



HUE UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY



LE CONG NAM



RESEARCH ON MINERAL FERTILIZATION BY LEAF

NUTRITIONAL DIAGNOSIS FOR RUBBER TREES

IN QUANG TRI PROVINCE



AGRICULTURAL DISSERTATION OF PHILOSOPHY DOCTOR

Major: Crop Science

Code: 62.62.01.10

SCIENTIFIC SUPERVISORS

1. Assoc. Prof. Dr. NGUYEN MINH HIEU

2. Assoc. Prof. Dr. DUONG VIET TINH



HUE, 2018



The thesis has been completed at Faculty of Agronomy,

University of Agriculture and Forestry, Hue University



Scientific supervisors:

1. Assoc. Prof. Dr. NGUYEN MINH HIEU

2. Assoc. Prof. Dr. DUONG VIET TINH



Referee 1:

Referee 2:

Referee 3:



The defence will be held at Hue University of PhD council

on …... h …..., day …... month …….. in 2018



The thesis can be found at:

Vietnam National Library

Library of Hue University of Agriculture and Forestry



INTRODUCTION

1. Introducing

The trifoliate rubber tree (Hevea brasiliensis Muel. Arg.) belongs to genus of the

Euphobiaceae, which is a multi-purpose tree, with a great economic, social and ecological

role. Rubber has a lot of value, rubber latex becomes one of the four main raw materials of

the world's industries (behind iron and steel, coal and oil), rubber wood can be used in

industry. wood processing and construction, granular materials for cleaning, chemicals,

paint,...

World output of rubber increased by over 20%, from 9 million tons in 2010 to 12.3

million tons in 2015; World rubber demand will reach 30.5 million tons in 2015, forecast

2019 increased 3.9% compared to 2015 to 31.7 million tons.

In Vietnam, rubber is a key industry, one of ten major export items. In 2016, the area is

965 thousand hectares, Vietnam is the second largest in the world in terms of productivity

(1.7 tons/ha), third in output (1.1 million tons), fourth in export volume (1 million tons)

(ANRPC, 2016).

Quang Tri is a province with a relatively large land fund, and soil conditions are in line

with the growth and development of rubber trees. The province has 20,689 ha of rubber,

distributed mainly in 3 districts of Vinh Linh, Gio Linh, Cam Lo (accounting for 90%),

output of 12.3 thousand tons (Quang Tri Statistical Yearbook, 2016).

At present, in Quang Tri as well as the central region, low yielding rubber trees, poor

quality of garden, fertilizer use are spontaneous, lack of foundation and efficiency is not

high. Besides, fertilizing according to nutritional diagnosis is the progress of the science of

fertilizers, crop science. Fertilizing according to nutritional diagnosis to make balanced and

reasonable fertilizer application; harmonize the relationships between land, crops, climate.

However, in Vietnam there is only one study on nutritional diagnosis for rubber trees

but it is done in rubber plantations in the Southeast, research also proposed mineral nutrient

ladder, not applied. The system of diagnosis and recommendation system (DRIS) is not

perfect and difficult to apply to production.

Starting from the above issues, we conducted the study on the application of mineral

fertilizers according to the leaf nutritional diagnosis for rubber trees in Quang Tri.

2. Objectives of the project

2.1. General objectives

Contribute to improve the method of mineral fertilizers according to the leaf

nutritional diagnosis in the condition of using rubber latex for rubber business period in

Quang Tri province.

2.2. Specific objectives

- Assess the status of the orchard, use fertilizer and use latex stimulant for small rubber

plantation in Quang Tri.

- Assessment of nutrient content in soil, leaf and relationship to rubber productivity in

Quang Tri.

- Building a mineral nutrient ladder through leaves for the rubber business period in

Quang Tri.

- Identify integrated diagnostic and recommendation system (DRIS) for rubber

business period in Quang Tri.

- Establishment of fertilizer complexes for rubber business period in Quang Tri

according to leaf nutritional diagnosis in the condition of using latex stimulant.

1



3. Scientific and practical significance

3.1. Scientific significance

- The research results of the thesis will provide scientific data on the correlation of

mineral elements N, P, K in soil, in leaves with rubber yield in the business period, which is

the scientific basis. To evaluate the nutritional status through the content of mineral

nutrients in the leaves.

- To supplement and perfect the method of fertilizing according to the leaf nutrition

diagnosis for rubber trees in the business period, which shall serve as a basis for perfecting

the process of fertilizing the rubber trees, especially the rubber plantations.

- The research results of the project will be a valuable reference for teaching and

scientific research in the direction of proper fertilization based on leaf nutritional diagnosis

in terms of using latex stimulant not only for rubber trees but also for other crops.

3.2. Practical significance

- Introduce widely to farmers who are producing rubber latex an advanced method of

fertilization is the method of fertilization according to the nutritional diagnosis through the

leaf under the condition of simultaneous use of latex stimulant to increase productivity.

- Based on the leaf mineral nutrient level and the established DRIS index, farmers

have been able to adjust the dosage of fertilizer in the condition of using latex to develop a

rubber efficient and sustainable way.

4. Frame work of thesis

- The study focused on investigating the status of orchards, use of fertilizers, latex

stimulants, mineral nutrient assessments in soil, in rubber leaves to build mineral nutrient

ladder and high leaf index rubber businesses of RRIM 600 in the age of 10 - 20 are planted

on reddish brown basalt in hilly areas in 3 districts with rubber area accounting for nearly

90% of the rubber area of Vinh Linh, Gio Linh and Cam Lo of the Quang Tri province.

- The study was conducted for 4 years: 2013 - 2016.

5. New (Novel) contributions of the thesis

- Build up a mineral nutrient ladder through rubber leaves trading in Quang Tri

towards optimal nutrition to achieve yield of 1.5 - 2 tons of latex per hecta in the condition

of using latex stimulant with mean values of dry matter content in nitrogen leaf (xN ) of

3.25%, phosphorus (xP ) of 0.25%, potassium (xK ) of 1.00% and standard deviation the

concentration of nitrogen (δN) was 0.36, phosphorus (δP) was 0.04, potassium (δK) was 0.23,

the optimum level of nitrogen content in leaves was 3.56 - 3.91%, phosphorus 0.30-0.33%,

potassium 1.24 - 1.46%.

- Determine the DRIS index for rubber business in Quang Tri in the condition of using

latex stimulant, set up on three axes: N/P, N/K, K/P with the center of intersection of the N,

P, K content on the rubber leaves was optimized according to the average yield of the

highest yields on each axis, respectively, (xN/P ) was 11.99; (xN/K ) was 4.20; (xK/P ) is 2.85,

the reliable limits for the nutritional balance (normal threshold) of the N/P ratio are 10.19 –

13.79, N/K is 2.42 - 3.28, K/P is 3.57 - 4.83, contributing to improve the method of

fertilizing by nutritional diagnosis.

- Two fertilizer complexes for rubber production under the condition of using latex

stimulants in Quang Tri province were constructed: 100 kg N + 25 kg P 2O5 + 80 kg K2O / ha

and (120 kg N + 10 kg P2O5 + 80 kg K2O + 4,500 kg of organic fertilizer) / ha.



2



CHAPTER 1

OVERVIEW OF THE STUDY

1.1. Scientific basic overview of studied matters

1.1.1. Rubber tree and basic ecological requirements

1.1.2. Nutrition and fertilizer for plants

1.1.3. Scientific basis of nitrogen fertilization for rubber trees

1.1.4. Scientific basis of P fertilizer application for rubber trees

1.1.5. Scientific basis of potassium fertilization for rubber trees

1.1.6. Scientific basis of organic fertilizer application for rubber trees

1.1.7. The scientific basis for the use of latex stimulants for rubber trees

1.1.8. Scientific basis of fertilization according to nutritional diagnosis for rubber

1.2. Practical basis overview of studied matters

1.2.1. The development of natural rubber in the world and in Vietnam

1.2.2. Studies on N, P, K fertilization for rubber trees

1.2.3. Studies on organic fertilizers for rubber trees

1.2.4. Study on the use of Ethephon stimulant to increase the productivity of latex

1.2.5. Studies on fertilizing for rubber by leaf nutritional diagnosis

1.2.6. Basic conditions and situation of natural rubber production in Quang Tri province

1.2.7. Explain the reasons for choosing the problem and the study sites



3



CHAPTER 2

OBJECTS, CONTENT AND METHODOLOGY

2.1. Objects and materials

2.1.1. Research subjects

Research on rubber trees (Hevea brasilinesis Muel Arg.), a clone of the RRIM600

clonal plant in the 10-20 years of age, was planted on the FRs (Rhodic Ferralsols) - reddishbrown basaltic soil - in the hillsides of Quang Tri province.

2.1.2. Study materials

- Fertilizers: Nitrogen fertilizers: Use urea fertilizer containing 46% N. Phosphorus:

Use Super Phosphate containing 16% P2O5. Potassium: Use of MOP Kalichloride MOP

containing 60% K2O. Organic fertilizer (manure): Use cattle manure from the local

population (a mixture of manure produced by water, dung (straw, leafy green manure) and

leftover food of cattle containing 83.1% water, 0.29% N, 0.17% P 2O5, 1.00% K2O, 0.3%

CaO and 0.1% MgO.

- Latex Stimulatex, the trade name for the active ingredient (a.i.) Ethephon is 2.5%.

2.2. Research contents

Contents 1: Survey on the status of orchards, use of fertilizers and latex stimulants for

rubber plantations in Quang Tri.

Content 2: Assessment of nutrient content in soil, leaf and relationship with rubber

productivity in Quang Tri.

Content 3: Research on building a leaf nutrient ladder for rubber trees in Quang Tri.

Content 4: Research on determining integrated diagnostic and advisory system for

rubber business in Quang Tri.

Content 5: Fertilizer test on mineral leaf nutrition for rubber trees in Quang Tri.

2.3. Methodology

2.3.1. Evaluation of plantation status, use of fertilizers and latex stimulants for rubber

plantations in Quang Tri

- Methods of use:

+ Method of inheriting and analyzing documents

+ Field survey method (plot, standard plot, ...)

+ Methods of sociological investigation (using questionnaires, in-depth interviews,

participatory observation, ...)

- Collection criteria:

+ Actual gardening (planting year, area, density of density, current density).

+ The situation of fertilizer use in the business period (fertilizer, dosage, application

time).

+ The use of stimulant (drug, use, dosage, effect of drug).

+ Cost, income, efficiency of small rubber plantations.

+ Some difficulties exist in the production of rubber plantations (especially difficulties,

existing in fertilizing and using latex stimulants).

Surveyed in 3 communes in 3 districts, 35 households in each commune (105

households in total) represent the main rubber plantations in Quang Tri.

2.3.2. Method of sampling, treatment and analysis of soil samples and leaf samples to

evaluate nutrient status in soil, in rubber leaves

- Acres:

+ Get and process samples:

4



Land sample taken and treated in accordance with Vietnamese Standard TCVN 7538:

2006 - Soil quality - Sampling [4] by diagonal method in the cultivation layer (0 - 20 cm)

for 5 sites / study area rescue from 5 cross points in the garden, at each point along the edge

of the rubber canopy, dig a hole 30 cm deep, then use a knife to scrape a thin layer of soil

from top to bottom vertically, take about 200g. Land is sampled from 5 points mixed into 1

acre sample of land representing the garden for analysis. Avoid getting the soil under the

tree in the garden. Do not take in newly fertilized sites. After harvesting, remove the roots,

impurities, dried in air, dried, then milled through 1 mm sieve.

In order to assess the mineral nutrient status in soil, in leaves, the relationship between

them and yield, as the basis for the development of mineral nutrient levels and the DRIS

index, soil samples (with leaf samples) Three types of orchard: good garden with yield of

1.5 tons/ha, average orchard with yield from 1.0 - 1.5 tons/ha and bad garden with

productivity of less than 1.0 tons/ha, Choose 3 districts with the largest area of rubber for

sampling: Vinh Linh (for Vinh Tan commune), Gio Linh (Gio An commune), Cam Lo (Cam

Chinh commune) good form (10 samples), medium (10 samples), bad (10 samples). The

sample size is 3 types x 3 districts x 10 samples / district = 90 samples.

+ Analysis of research indicators: Total protein content: Analysis by Kjendahl method

improved [10 BC 377-99]. Total P 2O5 content and easy digestibility: Analysis by

colorimetric methods and Oniani [TCVN 8940: 2011]. Total K 2O content and easy

digestibility: Analysis by flame optical method (TCVN 8660: 2011) Organic carbon:

Wakley black method [TCVN 8940: 2011] pH KCl: Determination by measuring method pH

meter [10TCN 381-99].

- Leaf pattern:

Collection and processing of samples: Comply with Vietnamese Standards TCVN

8551: 2010 - Plants - Sampling and preparation methods [5] and Process of Vietnam Rubber

Industry Group 2012 [39]. A leaf sample is a composite of 30 trees, each of which is tripleleafed (each leaf has 3 single leaves), each leaf sample is equal to 270 leaves. The leaves are

collected from the lower branches of the canopy. In the shade, the leaves are placed on the

last leaf of the branch, mature leaves (about 90 to 150 days old) with the shoots stable. The

leaf sampler was representative of the sampling orchard, RRIM600 asexual clone, the same

basalt, shaved, no pest, far from the main road, far away from the floodplain, far from the

edge of the plot. Samples were dried in air, dried at 70 0C in a ventilated oven until dry, then

milled through a 1 mm sieve. Number of leaf samples to be taken, analysis was 90 samples,

leaf samples were taken at the same location with soil samples.

+ Analysis of research indicators: Using sulfuric acid sulfuric acid and hydroperoxide

(H2O2) as a substance to decompose samples, soak samples overnight and then decompose

at 2250C, let cool and conduct analysis according to the rules. process (determine N:

distillation, P: color comparison, K: flame photometer).

2.3.3. Method of building mineral nutrient ladder through rubber leaves

The main nutrient content values N, P, K analyzed from leaf samples (90 samples)

were calculated as meansx = ∑ xi / n and standard deviation (δ)

δ=

∑(x -x)2

(n-1)

Establishing mineral nutrient ladders on rubber leaves at levels: Very deficient: <x 2δ, deficient:x - 2δ →x - δ, medium:x - δ →x + δ, optimal:x + δ →x + 2δ, excess: >x

+ 2δ.

5



2.3.4. Determination of DRIS for rubber business

According to the Integrated Diagnosis and Recommendation Integrated Systems

(DRIS), DRIS is based on three axes: N/P, N/K, and K/P. The average value of the subset of

the highest productivity (according to Vu Huu Yem, 2012). Concentric circles are

considered reliable limits. The inner circle is placed in a variable displacement position with

an average of ± 15%, the outer circle placed in a fluctuating position relative to the average

of ± 30%. The two circles and three axes make up the area containing the arrow symbols, in

which the area in the inner circle has arrows (

) denotes a balanced nutritional state; The

arrows (

) in the areas between two circles indicate an imbalance trend (slightly lacking,

excess); The arrow (

) is outside of the 2 rounds showing the nutritional imbalance

(missing, excess).

2.3.5. Method of experimental arrangement

2.3.5.1. Formulation of experimental fertilizer

- Experiment 1: Mineral fertilizers for rubber planted according to nutritional

diagnosis in Gio Linh district:

FI: 80 kg N + 35 kg P2O5 + 80 kg K2O / ha (by Process 2012 - Control)

FII: 40 kg N + 18 kg P2O5 + 40 kg K2O / ha (equal to ½ Process 2012)

FIII: 120 kg N + 53 kg P2O5 + 120 kg K2O / ha (equal to 1.5 times Process 2012)

FIV: 100 kg N + 25 kg P2O5 + 80 kg K2O / ha (based on nutritional diagnosis)

- Experiment 2: Applying organic fertilizers (manure) for rubber trees according to

nutritional diagnosis in Cam Lo district:

FI: 80 kg N + 35 kg P2O5 + 80 kg K2O + 4.500 kg manure / ha

FII: 40 kg N + 18 kg P2O5 + 40 kg K2O + 4,500 kg manure / ha

FIII: 120 kg N + 53 kg P2O5 + 120 kg K2O + 4,500 kg manure / ha

FIV: 120 kg N + 10 kg P2O5 + 80 kg K2O + 4,500 kg manure / ha

The experimental formulas were combined with 2.5% latex stimulant with the

following formula: S/2D d3 10m/12. ET2.5% Pa4/y (half shaved, one shave for 2 rests,

shaved for 10 months for 1 year, use 2.5% latex stimulant in four times (June, August,

September, October) for 1 year.

2.3.5.2. Placement method and experiment scale

Two randomized complete block design (RCBD) experiments were carried out, each

with 4 formulas and 3 replicates to 12 baselines (each replicate of one formula). Each cell

consists of 10 rubber trees, the total number of trees per experiment is 120 rubber trees, and

two experiments are 240 rubber trees.

2.3.5.3. Indicators of land monitoring, growth, development and productivity

- Content and percentage of major nutrients in soil before and after experiment. Carry

out sample processing and analysis of indicators.

- Content, ratio of macromolecular elements (N, P, K) in the leaves of the trees in the

experiment before and after the experiment. Carry out sample processing and analysis of

indicators.

- Latex productivity of the experimental plants:

The latex was collected from all plants in the plots, taken directly in accordance with

the Rubber Industry Group's 2012 procedure [39], determining the DCR (%) to calculate the

yield of the experiment.

+ Productivity g/tree/shave: (g/c/c)

Productivity of fresh latex (g/c/c)

6



Σ [NS1 + NS2 + NS3 + … + NSn]

x 1000

N

Of which:

NS1, NS2 .....NSn: Productivity of tree 1, 2, ... n

n: Total rubber trees in shavings

Productivity of dried latex (g/c/c)

[Latex (g) x DCR%] + [Potholes (g) x 50%]

Individual Productivity =

x 1000

N

Of which:

- DCR% is the content of dry latex

- N is the total number of trees monitored (number of shaved trees)

Determination of DCR (%) by means of "rapid-heating" method:

Weigh 5 grams of water (using weighing cups), treat with a special chemical mixture,

remove the impurities, then boil in the pan for 3 - 5 minutes, squeeze serum and cold rolled

until dry. Clean the impurities, take the amount of dried latex in the pan to achieve the

weight of dry pus (X)

X × 100

DRC (%) =

5

+ Average annual productivity (g/c/c):

Individual productivity

∑ [g/c/c (monthly average) x number of slices/month]

=

(annual average) (g/c/c)

Total shaves per year

Average yield per year (kg/ha/year):

Output

g/c/c (average year) x number of shaved trees/ha x Total shaved per year

=

(kg/ha/year)

1000

2.3.6. Methods of analyzing and processing information and data

2.3.6.1. Method of calculating indicators of economic efficiency

- Profit = Total revenue - Total expenditure. Inside:

+ Total = yield x selling price by time of harvest.

+ Total expenditure = Input costs (fertilizer + other materials) + labor.

- The VCR (value added by fertilizer) is calculated by the formula:

Gross revenue increased by fertilizer application

VCR =

Total expenditure increased by fertilizer application

* Note: If VCR> 2: Fertilizer investment is profitable;

If VCR> 3: Farmer accepts fertilizer investment.

2.3.6.2. Methods of analyzing and processing information and data

Analysis and processing of information and data is done by statistical methods of

description, comparison of observation patterns, statistical analysis, logical analysis by

specialized software programs SPSS 10.0, Statgraphic, Microsoft Excel, Minitab combined

with Geographic Information System (GIS).

Productivity of fresh latex =



7



CHAPTER 3

RESULTS AND DISCUSSION

3.1. The status of orchards, use of fertilizers and latex stimulants for rubber

plantations in Quang Tri

3.1.1. Scale and quality of rubber plantations at household in Quang Tri

3.1.1.1. Scale of rubber plantation business at household in Quang Tri

Table 3.1. Scale of rubber plantation business at household in Quang Tri

Scale of rubber plantation (N0 of households /%)

Number of

Average area

District

2 ha/hh <

2 - 4 ha/hh

> 4 ha/hh

households (ha/household)

Vinh Linh

35

0.89±0.31

35 / 100.00

Gio Linh

35

1.53±1.24

26 / 74.28

7 / 20.00

2 / 5.71

Cam Lo

35

1.25±0.93

30 / 85.71

4 / 11.43

1 / 2.86

Whole province

105

1.22±0.90

91 / 86.66 11 / 10.48 3 / 2.86

Rubber plantations at household in Quang Tri mainly grow on small scale; There are

86.66% of type A households (less than 2 ha / household), 10.48% of type B households (2 4 ha) and only 2.86% of households type C (over 4 hectares).

3.1.1.2. Quality of rubber plantation business at household in Quang Tri

Table 3.2. Quality of rubber plantation business at household in Quang Tri

Average tree Average shade Rate of

House

Uniformity

District

density

density

trees

holds

of tree

(trees/ha)

(trees/ha)

(%)

Vinh Linh

35

403±42

363±40

89.94

Avg

Gio Linh

35

449±35

397±39

88.37

Bad

Cam Lo

35

455±19

410±22

90.17

Avg

Whole province

105

436±33

390±34

89.48

The density of rubber trees remaining at the time of survey was high (over 70%),

however, due to being planted at different times leading to the status of plants in uneven

lots, In the three districts, approximately 90%, but due to the pressure on income and

employment of people, many plants have not met the standards are still in operation.

3.1.2. Current status of fertilizer use and rubber plantation production in Quang Tri

Table 3.3. + 3.4. + 3.5. Situation of using fertilizer and rubber productivity in Quang Tri

Apply organic fertilizer Capacity

Apply mineral fertilizer N, P, K

(tons /

House

N

P2O5

K2 O

House Quantity

Rate of N:P:K

ha)

holds (kg/ha) (kg/ha)

(kg/ha)

holds (tons/ha)

Vinh Linh

1:0,5:0,7

33/35

81

38

54

33/35

4.8

1.3

Gio Linh

1:0,45:1,1

30/35

73

33

79

17/35

4.3

1.5

Cam Lo

1:0,9:0,9

33/35

52

45

47

23/35

4.6

1.4

Whole province



96/10

73/10

1:0,6:0,9

5

69

39

40

5

4.6

1.4

In addition to 9 households (8.6%), no fertilizer application, only organic fertilizers, 58

households (55.2%) mixed fertilizer N, P, K mixed with the rate of 1:1:1 (21 households,

8



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