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Evaluation of Growth Indicator Differences Among Study Cells in Tien Ky Town


Table 3.6. Evaluation of the difference in growth indicators between the studied OTCs in Tien Ky town


Growth index

D 1.3

(cm)

D t (m)

H vn (m)

Length (m )

Standard cell TK01

Medium

13.18

2.71

9.62

4.18

Standard error (S)

3.38

0.81

0.70

1.24

Variance (S 2 )

11.43

0.65

0.49

1.53

Coefficient of variation (S%)

25.65

29.89

7.28

29.60

Standard cell TK02

Medium

12.35

2.41

9.99

4.59

Standard error (S)

1.92

0.29

0.59

0.89

Variance (S 2 )

3.67

0.09

0.34

0.79

Coefficient of variation (S%)

15.52

12.20

5.87

19.33

Standard cell TK03

Medium

13.42

2.43

10.08

4.76

Standard error (S)

1.79

0.30

0.52

0.69

Variance (S 2 )

3.21

0.09

0.27

0.48

Coefficient of variation (S%)

13.36

12.52

5.18

14.56

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Evaluation of Growth Indicator Differences Among Study Cells in Tien Ky Town


U TK12 | (OTC TK01 and TK02)

1.17

1.89

2.24

1.47

|U TK13 | (OTC TK01 and TK03)

0.34

1.75

2.91

2.23

|U TK23 | (OTC TK02 and TK03)

2.23

0.26

0.63

0.81


In Tien Ky town area, the difference in size of Do Bau in the three standard plots is not as obvious as in Tien Canh, but the difference is larger than that of Do Bau in Tien Hiep commune. Regarding the diameter at breast height (D 1.3 ) between


There is a clear difference between plots 02 and 03 (|U| = 2.23 > 1.96). Regarding tree height: between plots 01 and 02, plots 01 and 03 there is a clear difference. Comparing the height below the branches of Do Bau in plot 01 with plot 03 shows that there is also a clear difference (see figure 3.4).


Figure 3.4. Comparison of growth characteristics of Do Bau in three standard plots in Tien Ky town

3.2. Results of investigation on basic soil characteristics in the study area

3.2.1. Physical characteristics of soil in the study area

Soil factors, soil thickness is one of the site factors, it is the space for distributing the root system of plants, is the storehouse of nutrients, is the source of moisture for plants. Soil thickness reflects the weathering process of materials (parent rocks, minerals and soil formation process), it reflects the level of soil erosion, vegetation living on it. Researching the influence of soil type, soil thickness... on the growth of Do Bau trees is the basis for determining suitable site conditions.

According to research results, the soil for growing Aquilaria crassna is 50 - 100 cm thick. Some other physical characteristics are shown in Table 3.7.


Table 3.7. Soil mechanical composition in the study area



Mechanical composition according to FAO %

Classify

OTC

< 0.002

0.002-0.02

0.02-2

A

Tien Ky area


TK01

25.25

48.54

26.21

TB Clay

TK02

30.37

42.87

26.76

TB Clay

TK03

33.89

44.30

21.81

TB Clay

B

Tien Hiep commune area


TH01

29.02

45.87

25.11

TB Clay

TH02

26.46

46.21

27.33

TB Clay

TH03

24.31

43.79

30.90

TB Clay

C

Tien Canh commune area


TC01

27.13

42.26

30.61

TB Clay

TC02

31.42

47.66

20.92

TB Clay

TC03

28.71

46.35

24.94

TB Clay

Soil mechanical composition factors between study areas did not show clear differences.

In TC01 area, trees grow on bare ground with flat terrain. In TC02 area, trees are grown on terrain with a fairly small slope < 5. In TC 03 area, trees are grown on hills with a slope > 10. In both areas, the vegetation grows strongly with many types of grasses and shrubs.

The soil in Tien Hiep commune has a brown surface, areas TK02 and TK03 have high humidity, the ground cover is strongly developed with many types of shrubs. Area TK01 has no ground cover so the soil is mixed with rocks and gravel.

In Tien Ky town area, all 3 research standard plots have Do Bau trees planted on bare ground without the growth of vegetation. The soil is brown and mixed with gravel.


3.2.2. Chemical characteristics of soil in the study area

Humus or organic matter in the soil is an important indicator of soil fertility, it has a decisive effect on the physical, chemical and biological properties of the soil. According to the results of soil analysis of the research areas, it can be assessed that the humus content in the soil in the forests planted with Aquilaria trees is at an average level (in areas TK01, TK01, TK03, TC01, TC02) or quite good (in areas TH01, TH02, TH03, TC03).

Total nitrogen content is average. However, available nitrogen (including mineral nitrogen and some easily decomposable organic nitrogen that plants can absorb) is only at a poor level of <4mg/100g of soil.

Total Phosphorus content in different areas shows clear differentiation. In Tien Ky area, total available Phosphorus is only poor (%P2O5 0.03 -0.06) to average (%P2O5 0.06 - 0.1). Meanwhile, soil in Tien Canh has rich total Phosphorus content (%P2O5>0.1). In Tien Hiep area, total Phosphorus level of Tien Hiep area has quite large difference at the research sites.

The content of easily digestible phosphorus in Tien Ky town area is very low <5mg/100g. While in Tien Canh it is quite high >10mg/100g.



3.3. Relationship between some basic characteristics of soil and Aquilaria tree

3.3.1. Relationship between soil and growth and development of Aquilaria crassna

Table 3.8. Results of soil analysis for growing Aquilaria crassna


Area

Humus (%)

Total Phosphorus mg/kg

Available phosphorus P 2 O 5 (mg/kg)

Total Nitrogen

%N

Nitrogen is readily available.

mg/100g

A. Tien Ky Town

TK01

2.66

145.69

61.0

0.111

1.61

TK02

2.98

194.59

31.1

0.111

1.12

TK03

1.86

279.46

44.1

0.103

1.89

TB_TK

2.50

206.58

45.40

0.11

1.54

B. Tien Hiep Commune

TH01

3.27

848.33

118.4

0.145

2.31

TH02

3.42

329.35

58.5

0.142

1.89

TH03

4.57

147.45

44.1

0.150

1.54

TB_TH

3.75

441.71

51.29

0.15

1.72

C. Tien Canh Commune

TC01

2.65

0.00

132.9

0.125

2.10

TC02

2.68

461.80

293.2

0.117

1.33

TC03

3.79

436.54

91.5

0.139

0.91

TB_TC

3.04

299.44

172.54

0.13

1.45


3.3.1.1. Effect of humus content on the growth of Aquilaria crassna

Data related to humus content and growth characteristics of Aquilaria crassna are shown in Table 3.9.



Table 3.9 shows: Humus content in standard plots ranges from 1.86% (standard plot TK03 - Tien Ky town) to 4.57% (standard plot TH03 - Tien Hiep commune). On average, humus content on Do Bau land in Tien Ky town is lowest (2.50%), in Tien Hiep commune is highest (3.57%). Difference

This deviation is considered to be negligible. Preliminary observation of two related data series

Table 3.9. Humus content and growth characteristics of Do Bau tree



OTC

D 1.3

(cm)

D t (m)

H vn (m)

Length (m )

Body number


Humus (%)

A. Tien Ky Town

TK01

13.18

2.71

9.62

4.18

1

2.66

TK02

12.35

2.41

9.99

4.59

1

2.98

TK03

13.42

2.43

10.1

4.76

1

1.86

TB_TK

13

2.5

9.9

4.5

1

2.50

B. Tien Hiep Commune

TH01

13.6

2.3

8.5

3.9

1

3.27

TH02

11.9

2.3

8.1

4

1

3.42

TH03

12.0

2.4

8.3

4

1

4.57

TB_TH

12.5

2.3

8.3

4

1

3.75

C. Tien Canh Commune

TC01

23.2

5.3

13.1

4.9

1

2.65

TC02

19.1

3.8

12.5

4.4

1

2.68

TC03

19.3

3.7

12.5

4.2

1

3.79

TB_TC

20.6

4.2

12.7

4.5

1

3.04


to diameter at breast height (D1.3), and humus content showed that there seemed to be an inverse relationship. However, statistical testing showed that there was no correlation between humus content and growth parameters such as tree diameter and height.


Relationship

R

R2

F

Humus – D 1.3

0.196480518

0.038604594

0.281083263

Humus – D canopy

0.188850923

0.035664671

0.258885775

Humus – H vn

0.332720491

0.110702925

0.871385389

Humus – H dc

0.686367125

0.47109983

6,235011814

There is a first-order correlation between humus content and branch height (H dc ): H dc = - 0.313647068 * %Humidity + 5.297167712

with R = 0.69 (R 2 = 0.47, F = 6.24).

3.3.1.2 Effect of phosphorus on the growth of Aquilaria crassna

A. Total phosphorus

Three parameters related to the “total phosphorus” index were determined: phosphorus content in mg/kg, total phosphorus percentage and phosphorus percentage as P 2 O 5 . The data are shown in Table 3.10

Table 3.10. Growth characteristics of Do Bau and total phosphorus of the varieties

standard plots in the study area



OTC

D 1.3

D t

H vn

H dc

Total Phosphorus

(cm)

(m)

(m)

(m)

mg/kg

A. Tien Ky Town

TK01

13.18

2.71

9.62

4.18

145.69

TK02

12.35

2.41

9.99

4.59

194.59

TK03

13.42

2.43

10.08

4.76

279.46

TB_TK

13

2.5

9.9

4.5

206.58

B. Tien Hiep Commune

TH01

13.6

2.3

8.5

3.9

848.33

TH02

11.9

2.3

8.1

4

329.35


TH03

12

2.4

8.3

4

147.45

TB_TH

12.5

2.3

8.3

4

441.71

C. Tien Canh Commune

TC01

23.2

5.3

13.1

4.9

0.00

TC02

19.1

3.8

12.5

4.4

461.80

TC03

19.3

3.7

12.5

4.2

436.54

TB_TC

20.6

4.2

12.7

4.5

299.44


Examination of the relationship of total phosphorus parameters with plant growth characteristics showed no clear relationship.

Total Relationship P

R

R2

F

mg/kg - D 1.3

0.130807329

0.017110557

0.121858976

mg/kg - D

0.324773261

0.105477671

0.825405555

mg/kg - H vn

0.204439159

0.04179537

0.305328924

mg/kg - H dc

0.541980423

0.293742779

2.911403086

As in the case of humus content, there is a relatively close correlation between total phosphorus (mg/kg) and branch height:

H dc = - 0.000781446 * P (mg/kg) + 4.572423766

B. Easily digestible phosphorus

Available phosphorus exists in the form of P-PO 4 3 - (mg/kg) and P 2 O 5 (mg/kg) and the growth characteristics of Aquilaria are shown in Table 3.11. Observing the data, it can be seen that the higher the amount of available phosphorus, the better the plant grows. Therefore, it is necessary to check the correlation between phosphorus and the growth of Aquilaria.

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