# Aggregate Indices Method in Soil Quality Evaluation Using the Relative Soil Quality Index

Authors: Ho Ngoc Pham; Hai Xuan Nguyen; Anh Ngoc Nguyen; Diep Ngoc Tran
Journal: Applied and Environmental Soil Science
 (2015)

---

## Abstract

This paper presents a new approach to assess the soil quality by aggregate indices using the Relative Soil Quality Index (RSQI) proposed by Ho Ngoc Pham. RSQI is integrated from the individual indices into a simple formula for overall assessment of the soil quality. RSQI is different from other approaches. Particularly, the individual indices and the weighting factors of Pham are calculated from the analytical laboratory data and the environmental standards, respectively, and not self-regulated as in methods of some other authors. In this paper, the authors applied the RSQI to assess the Soil Environmental Quality of rice intensive cultivation areas through a case study in Haiduong province in 2013. The RSQI is calculated for sampling points in 12 districts and simulated the Soil Environmental Quality on GIS map. The results show that the Soil Environmental Quality of rice intensive cultivation areas in Haiduong is predominantly divided into three levels: good, moderate, and poor. According to the report of General Statistics Office for Haiduong province, rice intensive cultivation areas in 2013 achieved a relatively high average rice yield of 5.90 tonnes per hectare; it means actual soil properties are in line with results of the research.


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## Body

## 1. Introduction

The assessment of soil degradation in the world is primarily based on single criteria to build the assessment thresholds for each group of total content of bioelements, content of available forms of bioelements, heavy metals, and so forth, in which each parameter in the group of total content of bioelements and the group of content of available forms of bioelements is categorized into three levels: high, medium, and low or rich, moderate, and poor, respectively, to serve for the degradation assessment of agricultural land and forestry. The environmental quality index (EQI) approach to assess air, water, and soil was first mentioned in the work of Ott [1], and afterwards, the application of EQI to assess the soil quality (SQ) is continuously developed and widely used [2–7].The soil degradation assessment in Vietnam has interested many scientists. Vietnamese scientists have made in-depth studies on the thresholds and the assessing scale for the group of total content of bioelements, content of available forms of bioelements and heavy metals, and so forth. In which, typical studies are of Nguyen [8], Le [9], Tran [10], Nguyen [11], Le and Tran [12], and the National Technical Standards on the soil environment for the heavy metals group [13]. However, the approach to assess soil degradation by aggregate indices in Vietnam is still new. Such approach was first mentioned in the dissertation of Nguyen in order to create an environmental land map at the provincial scale [14]. The author applied the Total Soil Quality Index (TSQI) proposed by Pham [15] to determine the Soil Environmental Quality for agricultural land (rice cultivated areas). Nevertheless, calculating the weighting factors of each group is complicated. Therefore, Pham developed the TSQI into the Relative Soil Quality Index (RSQI) which simplifies the calculation of the weighting factors of total content of bioelements, content of available forms of bioelements, pHKCl, and heavy metals group in reality [16]. Because of the paper’s scope, the authors only apply RSQI into aggregate assessment of the SQ of rice intensive areas in Haiduong province.


## 2. Materials and Method

### 2.1. Materials

(i) The research used the soil sample analysis data for 12 districts with rice intensive cultivation areas in Haiduong province [17].(ii) Research materials of Vietnamese authors [8–12] and Vietnam’s environmental regulations [13] were used to convert the categorized scale of individual index into the individual assessing scale of SQ which served for the calculation of the SQ assessment by aggregate indices, using RSQI.


### 2.2. Method

#### 2.2.1. Formula of Relative Soil Quality Index (RSQI)

RSQI is a new approach to assess the SQ by aggregate indices. It is based on the synthesis or integration of individual indexqi of n surveyed parameters in order to form a formula which simplifies the SQ assessment at each monitoring point. RSQI proposed by Pham is determined by the following formula [16]:(1)RSQI=1001-PkPn,where(2)Pk=∑i=1kWiqi-1,(3)Pm=∑i=1m1Wiqi+∑i=1m2Wi1-qi,(4)Pn=Pm+Pk,(5)n=m+k=m1+m2+k,where Pn is the common sum (sum of separate sums Pk and Pm); Pm includes m of numbers of qi with values ≤1; Pk includes k of numbers of qi with values >1; n is the number of monitored parameters.Noting. Formula (1) clearly shows that RSQI depends on the relative ratio Pk/Pn. The higher the value of the ratio is, the smaller the value of RSQI will be. Thus, the SQ is poorer.(i) Calculating Individual Index
q
i
(Subindex) of Each Parameter
i. To calculate RSQI in formula (1), we first need to calculate individual index as the following:(a)
The groups below in Vietnam’s environmental regulation (to the heavy metals group) are(6)qi=CiCi∗.There are three cases:(7)Case  1:  IfCi<Ci∗soqi<1Soil with good quality—nondegraded soil,Case  2:  IfCi=Ci∗soqi=1Soil with moderate quality—soil starting to degrade,Case  3:  IfCi>Ci∗soqi>1Soil with poor quality—degraded soil.(b)
The groups in the interval [a,b] in Vietnam’s environmental regulation (group of total content of bioelements, group of content of available forms of bioelements): (8)Case  1:  IfCi<asoqi=aCi>1Soil with poor quality—degraded soil,(9)Case  2:  Ifa≤Ci≤bsoqi=CiCi∗=1Soil with moderate quality—soil starting to degrade,(10)Case  3:  IfCi>bsoqi=bCi<1Soil with good quality—nondegraded soil.(ii) Calculating the Separate Sums
P
k, Pm,and the Common SumPnUsing Formulas (2) to (4). From (1) to (10),Ci is the actual monitoring value of parameter i,Ci∗,  a, and  b are the permitted limit values of parameter i,m1 is the number of parameters with qi=1 (as Ci=Ci∗),m2 is the number of parameters with qi<1,k is the number of parameters with qi>1.


#### 2.2.2. Calculating the Temporary Weighting FactorsWi′ and the Final Weighting Factors Wi

W
i is the final weighting factors of the parameter i; Wi accounts for the importance which presents the relation between each parameter i; and j is the number of parameters of each examination group. The final weighting factor Wi is determined through the temporary weighting factor Wi′ as follows.(a) Groups Below in Environmental Regulation (Heavy Metals Group). Wi′ is calculated by formula:(11)Wi′=1/j∑1jCi∗Ci∗=∑1jCi∗j×Ci∗,where Ci∗ is allowance limited value of parameter i and j is the number of parameters selected by the group for examination.(b) Groups in the Interval
[
a
,
b
]
in Environmental Regulations (Group of the Total Content of Bioelements, Group of the Content of Available Forms of Bioelements). Consider parameter groups in the intervals: a1,b1,a2,b2,a3,b3,…,[aj,bj].The formula to calculateWi′ of parameter i for each group is as below:(12)Wi′=∑i=1jbi-aij×bi-ai,where the environmental regulation value of parameter i in the interval [ai,bi] is (bi-ai) and j is the number of parameters of each group.Example. There are 2 parameters (j=2) given in [a1,b1], [a2,b2]. The environmental regulation values of [a1,b1] and [a2,b2] are (b1-a1) and (b2-a2), respectively. According to (12), we calculate(13)W1′=b1-a1+b2-a22×b1-a1;W2′=b1-a1+b2-a22×b2-a2.(c) Calculate the Final Weighting Factor of Parameter
i  (Wi). The final weighting factor of each parameter i of each group is identified by the following formula:(14)Wi=Wi′∑1jWi′(15)Obviously,∑1jWi=1,where j is the number of parameters selected by the group for examination.


#### 2.2.3. Hierarchy for Assessing SQ of RSQI Index [16]

See Table1.Table 1
Hierarchy for assessing SQ of RSQI =I index.
I
-
n is even
I
-
n is odd
SQ
Colour
5
0
2
n
-
1
n
<
I
≤
100
50
2
n
-
1
n
<
I
≤
100
Good/excellent (I=100) (no degradation)
Green
100
n
-
1
n
<
I
≤
50
2
n
-
1
n
100
n
-
1
n
<
I
≤
50
2
n
-
1
n
Moderate (start degradation)
Yellow
50
<
I
≤
100
n
-
1
n
50
n
-
1
n
<
I
≤
100
n
-
1
n
Poor (degradation)
Orange
100
n
<
I
≤
50
100
n
<
I
≤
50
n
-
1
n
Very poor (strong degradation)
Red
0
≤
I
≤
100
n
0
≤
I
≤
100
n
Hazardous (very strong degradation)
Brown
Note.
(i) Whenn=2, the levels poor, very poor, and hazardous are overlapped; therefore the hierarchy will consist of only 3 levels; when n=3, the levels very poor and hazardous are overlapped; therefore the hierarchy will consist of 4 levels.
(ii) WhenWi=1 in (2) and (3) formulas, RSQI does not have weighting factors.
(iii) Suggestions are the following:
(a) Good/excellent SQ does not need treatment.
(b) Moderate SQ needs to be monitored.
(c) Poor SQ needs to be properly fertilized.
(d) Very poor: hazardous SQ needs appropriate technological treatment for parameters significantly greater than acceptable standard.


#### 2.2.4. Converting Hierarchy for Assessing Criterion to Hierarchy for Assessing SQ

To apply (7)–(10) formulas, first, levels and hierarchy for assessing criterion need to be converted to levels and hierarchy for assessing soil quality (SQ) for each individual criterion.The conversion Tables2, 3, and 4 are based on the application of Vietnam research materials about criterion for assessing soil groups.Table 2
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for the group of total content of bioelements.
Parameter
Criterion (%)
Hierarchy
Reference
Hierarchy for SQ∈ [a, b] (%)
SQ
SOM
>2.5
High
>2.5
Good
1.25–2.5
Medium
Nguyen [8]
1.25–2.5
Moderate
<1.25
Low
<1.25
Poor
Total N
>0.2
Rich
>0.2
Good
0.1–0.2
Moderate
Nguyen [11]
0.1–0.2
Moderate
<0.1
Poor
<0.1
Poor
Total P
>0.1
Rich
>0.1
Good
0.06–0.1
Moderate
Le [9]
0.06–0.1
Moderate
<0.06
Poor
<0.06
Poor
Total K
>2
Rich
>2
Good
1-2
Moderate
Tran [10]
1-2
Moderate
<1
Poor
<1
PoorTable 3
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for the group of content of available forms of bioelements.
Parameter
Criterion (mg⋅kg−1)
Hierarchy
Reference
Hierarchy for SQ∈ [a, b] (mg⋅kg−1)
SQ
N bioavailable
>80
Rich
>80
Good
20–80
Moderate
Le and Tran [12]
20–80
Moderate
<20
Poor
<20
Poor
P bioavailable
>46
Rich
>46
Good
36–46
Moderate
Nguyen [11]
36–46
Moderate
<36
Poor
<36
Poor
K bioavailable
>150
Rich
>150
Good
100–150
Moderate
Tran [10]
100–150
Moderate
<100
Poor
<100
PoorTable 4
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for heavy metals (mg⋅kg−1, top soil).
Parameter
Land for agricultural purpose, reference(QCVN 03:2008/BTNMT) [9]
Hierarchy for SQ
SQ
(1) Cadmium (Cd)
<2
Good
2
=2
Moderate
>2
Poor
(2) Copper (Cu)
<50
Good
50
=50
Moderate
>50
Poor
(3) Lead (Pb)
<70
Good
70
=70
Moderate
>70
Poor


## 2.1. Materials

(i) The research used the soil sample analysis data for 12 districts with rice intensive cultivation areas in Haiduong province [17].(ii) Research materials of Vietnamese authors [8–12] and Vietnam’s environmental regulations [13] were used to convert the categorized scale of individual index into the individual assessing scale of SQ which served for the calculation of the SQ assessment by aggregate indices, using RSQI.


## 2.2. Method

### 2.2.1. Formula of Relative Soil Quality Index (RSQI)

RSQI is a new approach to assess the SQ by aggregate indices. It is based on the synthesis or integration of individual indexqi of n surveyed parameters in order to form a formula which simplifies the SQ assessment at each monitoring point. RSQI proposed by Pham is determined by the following formula [16]:(1)RSQI=1001-PkPn,where(2)Pk=∑i=1kWiqi-1,(3)Pm=∑i=1m1Wiqi+∑i=1m2Wi1-qi,(4)Pn=Pm+Pk,(5)n=m+k=m1+m2+k,where Pn is the common sum (sum of separate sums Pk and Pm); Pm includes m of numbers of qi with values ≤1; Pk includes k of numbers of qi with values >1; n is the number of monitored parameters.Noting. Formula (1) clearly shows that RSQI depends on the relative ratio Pk/Pn. The higher the value of the ratio is, the smaller the value of RSQI will be. Thus, the SQ is poorer.(i) Calculating Individual Index
q
i
(Subindex) of Each Parameter
i. To calculate RSQI in formula (1), we first need to calculate individual index as the following:(a)
The groups below in Vietnam’s environmental regulation (to the heavy metals group) are(6)qi=CiCi∗.There are three cases:(7)Case  1:  IfCi<Ci∗soqi<1Soil with good quality—nondegraded soil,Case  2:  IfCi=Ci∗soqi=1Soil with moderate quality—soil starting to degrade,Case  3:  IfCi>Ci∗soqi>1Soil with poor quality—degraded soil.(b)
The groups in the interval [a,b] in Vietnam’s environmental regulation (group of total content of bioelements, group of content of available forms of bioelements): (8)Case  1:  IfCi<asoqi=aCi>1Soil with poor quality—degraded soil,(9)Case  2:  Ifa≤Ci≤bsoqi=CiCi∗=1Soil with moderate quality—soil starting to degrade,(10)Case  3:  IfCi>bsoqi=bCi<1Soil with good quality—nondegraded soil.(ii) Calculating the Separate Sums
P
k, Pm,and the Common SumPnUsing Formulas (2) to (4). From (1) to (10),Ci is the actual monitoring value of parameter i,Ci∗,  a, and  b are the permitted limit values of parameter i,m1 is the number of parameters with qi=1 (as Ci=Ci∗),m2 is the number of parameters with qi<1,k is the number of parameters with qi>1.


### 2.2.2. Calculating the Temporary Weighting FactorsWi′ and the Final Weighting Factors Wi

W
i is the final weighting factors of the parameter i; Wi accounts for the importance which presents the relation between each parameter i; and j is the number of parameters of each examination group. The final weighting factor Wi is determined through the temporary weighting factor Wi′ as follows.(a) Groups Below in Environmental Regulation (Heavy Metals Group). Wi′ is calculated by formula:(11)Wi′=1/j∑1jCi∗Ci∗=∑1jCi∗j×Ci∗,where Ci∗ is allowance limited value of parameter i and j is the number of parameters selected by the group for examination.(b) Groups in the Interval
[
a
,
b
]
in Environmental Regulations (Group of the Total Content of Bioelements, Group of the Content of Available Forms of Bioelements). Consider parameter groups in the intervals: a1,b1,a2,b2,a3,b3,…,[aj,bj].The formula to calculateWi′ of parameter i for each group is as below:(12)Wi′=∑i=1jbi-aij×bi-ai,where the environmental regulation value of parameter i in the interval [ai,bi] is (bi-ai) and j is the number of parameters of each group.Example. There are 2 parameters (j=2) given in [a1,b1], [a2,b2]. The environmental regulation values of [a1,b1] and [a2,b2] are (b1-a1) and (b2-a2), respectively. According to (12), we calculate(13)W1′=b1-a1+b2-a22×b1-a1;W2′=b1-a1+b2-a22×b2-a2.(c) Calculate the Final Weighting Factor of Parameter
i  (Wi). The final weighting factor of each parameter i of each group is identified by the following formula:(14)Wi=Wi′∑1jWi′(15)Obviously,∑1jWi=1,where j is the number of parameters selected by the group for examination.


### 2.2.3. Hierarchy for Assessing SQ of RSQI Index [16]

See Table1.Table 1
Hierarchy for assessing SQ of RSQI =I index.
I
-
n is even
I
-
n is odd
SQ
Colour
5
0
2
n
-
1
n
<
I
≤
100
50
2
n
-
1
n
<
I
≤
100
Good/excellent (I=100) (no degradation)
Green
100
n
-
1
n
<
I
≤
50
2
n
-
1
n
100
n
-
1
n
<
I
≤
50
2
n
-
1
n
Moderate (start degradation)
Yellow
50
<
I
≤
100
n
-
1
n
50
n
-
1
n
<
I
≤
100
n
-
1
n
Poor (degradation)
Orange
100
n
<
I
≤
50
100
n
<
I
≤
50
n
-
1
n
Very poor (strong degradation)
Red
0
≤
I
≤
100
n
0
≤
I
≤
100
n
Hazardous (very strong degradation)
Brown
Note.
(i) Whenn=2, the levels poor, very poor, and hazardous are overlapped; therefore the hierarchy will consist of only 3 levels; when n=3, the levels very poor and hazardous are overlapped; therefore the hierarchy will consist of 4 levels.
(ii) WhenWi=1 in (2) and (3) formulas, RSQI does not have weighting factors.
(iii) Suggestions are the following:
(a) Good/excellent SQ does not need treatment.
(b) Moderate SQ needs to be monitored.
(c) Poor SQ needs to be properly fertilized.
(d) Very poor: hazardous SQ needs appropriate technological treatment for parameters significantly greater than acceptable standard.


### 2.2.4. Converting Hierarchy for Assessing Criterion to Hierarchy for Assessing SQ

To apply (7)–(10) formulas, first, levels and hierarchy for assessing criterion need to be converted to levels and hierarchy for assessing soil quality (SQ) for each individual criterion.The conversion Tables2, 3, and 4 are based on the application of Vietnam research materials about criterion for assessing soil groups.Table 2
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for the group of total content of bioelements.
Parameter
Criterion (%)
Hierarchy
Reference
Hierarchy for SQ∈ [a, b] (%)
SQ
SOM
>2.5
High
>2.5
Good
1.25–2.5
Medium
Nguyen [8]
1.25–2.5
Moderate
<1.25
Low
<1.25
Poor
Total N
>0.2
Rich
>0.2
Good
0.1–0.2
Moderate
Nguyen [11]
0.1–0.2
Moderate
<0.1
Poor
<0.1
Poor
Total P
>0.1
Rich
>0.1
Good
0.06–0.1
Moderate
Le [9]
0.06–0.1
Moderate
<0.06
Poor
<0.06
Poor
Total K
>2
Rich
>2
Good
1-2
Moderate
Tran [10]
1-2
Moderate
<1
Poor
<1
PoorTable 3
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for the group of content of available forms of bioelements.
Parameter
Criterion (mg⋅kg−1)
Hierarchy
Reference
Hierarchy for SQ∈ [a, b] (mg⋅kg−1)
SQ
N bioavailable
>80
Rich
>80
Good
20–80
Moderate
Le and Tran [12]
20–80
Moderate
<20
Poor
<20
Poor
P bioavailable
>46
Rich
>46
Good
36–46
Moderate
Nguyen [11]
36–46
Moderate
<36
Poor
<36
Poor
K bioavailable
>150
Rich
>150
Good
100–150
Moderate
Tran [10]
100–150
Moderate
<100
Poor
<100
PoorTable 4
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for heavy metals (mg⋅kg−1, top soil).
Parameter
Land for agricultural purpose, reference(QCVN 03:2008/BTNMT) [9]
Hierarchy for SQ
SQ
(1) Cadmium (Cd)
<2
Good
2
=2
Moderate
>2
Poor
(2) Copper (Cu)
<50
Good
50
=50
Moderate
>50
Poor
(3) Lead (Pb)
<70
Good
70
=70
Moderate
>70
Poor


## 2.2.1. Formula of Relative Soil Quality Index (RSQI)

RSQI is a new approach to assess the SQ by aggregate indices. It is based on the synthesis or integration of individual indexqi of n surveyed parameters in order to form a formula which simplifies the SQ assessment at each monitoring point. RSQI proposed by Pham is determined by the following formula [16]:(1)RSQI=1001-PkPn,where(2)Pk=∑i=1kWiqi-1,(3)Pm=∑i=1m1Wiqi+∑i=1m2Wi1-qi,(4)Pn=Pm+Pk,(5)n=m+k=m1+m2+k,where Pn is the common sum (sum of separate sums Pk and Pm); Pm includes m of numbers of qi with values ≤1; Pk includes k of numbers of qi with values >1; n is the number of monitored parameters.Noting. Formula (1) clearly shows that RSQI depends on the relative ratio Pk/Pn. The higher the value of the ratio is, the smaller the value of RSQI will be. Thus, the SQ is poorer.(i) Calculating Individual Index
q
i
(Subindex) of Each Parameter
i. To calculate RSQI in formula (1), we first need to calculate individual index as the following:(a)
The groups below in Vietnam’s environmental regulation (to the heavy metals group) are(6)qi=CiCi∗.There are three cases:(7)Case  1:  IfCi<Ci∗soqi<1Soil with good quality—nondegraded soil,Case  2:  IfCi=Ci∗soqi=1Soil with moderate quality—soil starting to degrade,Case  3:  IfCi>Ci∗soqi>1Soil with poor quality—degraded soil.(b)
The groups in the interval [a,b] in Vietnam’s environmental regulation (group of total content of bioelements, group of content of available forms of bioelements): (8)Case  1:  IfCi<asoqi=aCi>1Soil with poor quality—degraded soil,(9)Case  2:  Ifa≤Ci≤bsoqi=CiCi∗=1Soil with moderate quality—soil starting to degrade,(10)Case  3:  IfCi>bsoqi=bCi<1Soil with good quality—nondegraded soil.(ii) Calculating the Separate Sums
P
k, Pm,and the Common SumPnUsing Formulas (2) to (4). From (1) to (10),Ci is the actual monitoring value of parameter i,Ci∗,  a, and  b are the permitted limit values of parameter i,m1 is the number of parameters with qi=1 (as Ci=Ci∗),m2 is the number of parameters with qi<1,k is the number of parameters with qi>1.


## 2.2.2. Calculating the Temporary Weighting FactorsWi′ and the Final Weighting Factors Wi

W
i is the final weighting factors of the parameter i; Wi accounts for the importance which presents the relation between each parameter i; and j is the number of parameters of each examination group. The final weighting factor Wi is determined through the temporary weighting factor Wi′ as follows.(a) Groups Below in Environmental Regulation (Heavy Metals Group). Wi′ is calculated by formula:(11)Wi′=1/j∑1jCi∗Ci∗=∑1jCi∗j×Ci∗,where Ci∗ is allowance limited value of parameter i and j is the number of parameters selected by the group for examination.(b) Groups in the Interval
[
a
,
b
]
in Environmental Regulations (Group of the Total Content of Bioelements, Group of the Content of Available Forms of Bioelements). Consider parameter groups in the intervals: a1,b1,a2,b2,a3,b3,…,[aj,bj].The formula to calculateWi′ of parameter i for each group is as below:(12)Wi′=∑i=1jbi-aij×bi-ai,where the environmental regulation value of parameter i in the interval [ai,bi] is (bi-ai) and j is the number of parameters of each group.Example. There are 2 parameters (j=2) given in [a1,b1], [a2,b2]. The environmental regulation values of [a1,b1] and [a2,b2] are (b1-a1) and (b2-a2), respectively. According to (12), we calculate(13)W1′=b1-a1+b2-a22×b1-a1;W2′=b1-a1+b2-a22×b2-a2.(c) Calculate the Final Weighting Factor of Parameter
i  (Wi). The final weighting factor of each parameter i of each group is identified by the following formula:(14)Wi=Wi′∑1jWi′(15)Obviously,∑1jWi=1,where j is the number of parameters selected by the group for examination.


## 2.2.3. Hierarchy for Assessing SQ of RSQI Index [16]

See Table1.Table 1
Hierarchy for assessing SQ of RSQI =I index.
I
-
n is even
I
-
n is odd
SQ
Colour
5
0
2
n
-
1
n
<
I
≤
100
50
2
n
-
1
n
<
I
≤
100
Good/excellent (I=100) (no degradation)
Green
100
n
-
1
n
<
I
≤
50
2
n
-
1
n
100
n
-
1
n
<
I
≤
50
2
n
-
1
n
Moderate (start degradation)
Yellow
50
<
I
≤
100
n
-
1
n
50
n
-
1
n
<
I
≤
100
n
-
1
n
Poor (degradation)
Orange
100
n
<
I
≤
50
100
n
<
I
≤
50
n
-
1
n
Very poor (strong degradation)
Red
0
≤
I
≤
100
n
0
≤
I
≤
100
n
Hazardous (very strong degradation)
Brown
Note.
(i) Whenn=2, the levels poor, very poor, and hazardous are overlapped; therefore the hierarchy will consist of only 3 levels; when n=3, the levels very poor and hazardous are overlapped; therefore the hierarchy will consist of 4 levels.
(ii) WhenWi=1 in (2) and (3) formulas, RSQI does not have weighting factors.
(iii) Suggestions are the following:
(a) Good/excellent SQ does not need treatment.
(b) Moderate SQ needs to be monitored.
(c) Poor SQ needs to be properly fertilized.
(d) Very poor: hazardous SQ needs appropriate technological treatment for parameters significantly greater than acceptable standard.


## 2.2.4. Converting Hierarchy for Assessing Criterion to Hierarchy for Assessing SQ

To apply (7)–(10) formulas, first, levels and hierarchy for assessing criterion need to be converted to levels and hierarchy for assessing soil quality (SQ) for each individual criterion.The conversion Tables2, 3, and 4 are based on the application of Vietnam research materials about criterion for assessing soil groups.Table 2
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for the group of total content of bioelements.
Parameter
Criterion (%)
Hierarchy
Reference
Hierarchy for SQ∈ [a, b] (%)
SQ
SOM
>2.5
High
>2.5
Good
1.25–2.5
Medium
Nguyen [8]
1.25–2.5
Moderate
<1.25
Low
<1.25
Poor
Total N
>0.2
Rich
>0.2
Good
0.1–0.2
Moderate
Nguyen [11]
0.1–0.2
Moderate
<0.1
Poor
<0.1
Poor
Total P
>0.1
Rich
>0.1
Good
0.06–0.1
Moderate
Le [9]
0.06–0.1
Moderate
<0.06
Poor
<0.06
Poor
Total K
>2
Rich
>2
Good
1-2
Moderate
Tran [10]
1-2
Moderate
<1
Poor
<1
PoorTable 3
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for the group of content of available forms of bioelements.
Parameter
Criterion (mg⋅kg−1)
Hierarchy
Reference
Hierarchy for SQ∈ [a, b] (mg⋅kg−1)
SQ
N bioavailable
>80
Rich
>80
Good
20–80
Moderate
Le and Tran [12]
20–80
Moderate
<20
Poor
<20
Poor
P bioavailable
>46
Rich
>46
Good
36–46
Moderate
Nguyen [11]
36–46
Moderate
<36
Poor
<36
Poor
K bioavailable
>150
Rich
>150
Good
100–150
Moderate
Tran [10]
100–150
Moderate
<100
Poor
<100
PoorTable 4
Converting hierarchy for assessing criterion to hierarchy for assessing SQ for heavy metals (mg⋅kg−1, top soil).
Parameter
Land for agricultural purpose, reference(QCVN 03:2008/BTNMT) [9]
Hierarchy for SQ
SQ
(1) Cadmium (Cd)
<2
Good
2
=2
Moderate
>2
Poor
(2) Copper (Cu)
<50
Good
50
=50
Moderate
>50
Poor
(3) Lead (Pb)
<70
Good
70
=70
Moderate
>70
Poor


## 3. Results and Discussion

### 3.1. Results

#### 3.1.1. Hierarchy for Assessing SQ of RSQI

The hierarchical scale for aggregate assessing soil quality of RSQI corresponding ton=10 parameters in Table 1 is shown in Table 5.Table 5
Hierarchy for assessing SQ of RSQI =I with n=10 parameters (Cd, Cu, Pb, SOM, Nt, Pt, Kt, Nav, Pav, and Kav).
RSQI
SQ
Colour
96–100
Good/excellent (I=100) (no degradation)
Green
91–95
Moderate(start degradation)
Yellow
51–90
Poor(degradation)
Orange
11–50
Very poor(strong degradation)
Red
0–10
Hazardous(very strong degradation)
Brown


#### 3.1.2. Calculating the Temporary Weighting FactorsWi′ and the Final Weighting Factors Wi

(i) Calculating the Temporary Weighting FactorsWi′ is as follows:The group of heavy metals (formula (11)):(16)WCd′=2+50+703×2=20.33;WCu′=2+50+703×50=0.81;WPb′=2+50+703×70=0.58.The group of the total content of bioelements (formula (12)):(17)WOM′=2.5-1.25+0.2-0.1+0.1-0.06+2-14×2.5-1.25=2.395=0.48;WNt′=2.394×0.2-0.1=5.98;WP2O5t′=2.394×0.1-0.06=14.94;WK2Ot′=2.394×2-1=0.60.The group of the content of available forms of bioelements (formula (12)):(18)WNav′=8-2+4.6-3.6+15-103×8-2=1218=0.67;WP2O5av′=123×4.6-3.6=4;WK2Oav′=123×15-10=0.8.(ii) Calculating the Final Weighting FactorsWi (formula (14)) is as follows:(19)WCd=20.3320.33+0.81+0.58=20.3321.72=0.93;WCu=0.8121.72=0.04;WPb=0.5821.72=0.03.The final weighting factors of other parameters of total content of bioelements group and content of available forms of bioelements group are calculated, respectively, and results are shown in Table 6.Table 6
The temporary weighting factorsWi′ and the final weighting factors Wi of 10 surveyed parameters.
Parameters
Heavy metals
Total content of bioelements
Content of available forms of bioelements
Cd
Cu
Pb
P
t
SOM
N
t
K
t
N
av
P
av
K
av
i
1
2
3
4
5
6
7
8
9
10
W
i
′
20.33
0.81
0.58
14.94
0.48
5.98
0.60
0.67
4
0.80
W
i
0.93
0.04
0.03
0.68
0.02
0.27
0.03
0.12
0.73
0.15
∑
W
i
1
1
1


#### 3.1.3. Calculatingqi, Pm1, Pm2, Pk, Pn, and RSQI

Based on the research materials mentioned in Section2.1, this research calculated individual parameter qi using formulas (7)–(10), calculated Pk and Pn using formulas (2)–(4), and calculated the RSQI index using formula (1) for soil samples.Because of the large sample size of the rice intensive cultivation areas surveyed in Haiduong including relatively high, medium, and low plains, we present how to calculate individual indexqi, the separate sums Pm1, Pm2, and Pk, and the common sum Pn (n=10 parameters) in order to determine the RSQI of a particular soil sample S1 (Table 7). Thus, only result of other samples is shown in Table 8:(20)Pm1=∑i=13Wiqi=0.02×1+0.27×1+0.12×1=0.41;Pm2=∑i=15Wi1-qi=0.93×1-0.01+0.04×1-0.19+0.03×1-0.26+0.68×1-0.6+0.73×1-0.3=1.76;Pm=Pm1+Pm2=0.41+1.76=2.17;Pk=∑i=12Wiqi-1=0.03×1.64-1+0.15×2.5-1=0.24;Pn=Pm+Pk=2.17+0.24=2.41;RSQI=100×1-PkPn=100×1-0.242.41=90.04—Moderateaccording to Table  5.Table 7
Calculating RSQI for a particular soil sample S1 withCi, monitoring values.
Parameters
Heavy metals
Total content of bioelements
Content of available forms of bioelements
Cd
Cu
Pb
P
t
SOM
N
t
K
t
N
av
P
av
K
av
i
1
2
3
4
5
6
7
8
9
10
S1-Ci
0.01
9.55
18.58
0.17
1.64
0.18
0.61
61.60
155.60
40
q
i
0.01
0.19
0.26
0.60
1
1
1.64
1
0.30
2.50
W
i
0.93
0.04
0.03
0.68
0.02
0.27
0.03
0.12
0.73
0.15Table 8
Results of calculation of RSQI based on monitoring data.
Soil samples
P
m
P
k
P
n
RSQI
SQ
(a) Relatively high plains
S1
2.17
0.24
2.41
90.04
Moderate (starting degradation)
S3
1.93
0
1.93
100
Excellent (nondegraded)
S5
2.02
0.03
2.05
98.54
Good (nondegraded)
S7
2.03
0.12
2.15
94.42
Moderate (starting degradation)
S9
1.73
0.08
1.81
95.58
Good (nondegraded)
S11
2.30
0.16
2.46
93.50
Moderate (starting degradation)
S13
2.24
0.17
2.41
92.95
Moderate (starting degradation)
S15
2.01
0.23
2.24
89.73
Poor (degradation)
S17
1.94
0.15
2.09
92.82
Moderate (starting degradation)
S19
2.11
0.21
2.32
90.95
Moderate (starting degradation)
S21
1.95
0.22
2.17
89.86
Poor (degradation)
S23
2.05
0.20
2.25
91.11
Moderate (starting degradation)
S25
2.40
0.15
2.55
94.12
Moderate (starting degradation)
S27
2.21
0.09
2.30
96.09
Good (nondegraded)
S29
2.26
0.07
2.33
96.99
Good (nondegraded)
S31
2
0.66
2.66
75.19
Poor (degradation)
(b) Medium plains
S57
1.82
0.22
2.04
89.22
Poor (degradation)
S59
1.72
0.08
1.80
95.56
Good (nondegraded)
S61
2.09
0.07
2.16
96.76
Good (nondegraded)
S63
2.04
0.45
2.49
81.93
Poor (degradation)
S65
2.03
0.40
2.43
83.54
Poor (degradation)
S67
2.32
0
2.32
100
Excellent (nondegraded)
S69
2.42
0
2.42
100
Excellent (nondegraded)
(c) Low plains
S73
2.26
0.27
2.53
89.33
Poor (degradation)
S75
2.22
0.37
2.59
85.71
Poor (degradation)
S77
2.25
0.07
2.32
96.98
Good (nondegraded)
S79
1.64
0.03
1.67
98.20
Good (nondegraded)
S81
1.30
0.01
1.31
99.24
Good (nondegraded)
S83
2.04
0.37
2.41
84.65
Poor (degradation)
S85
2.33
0.16
2.49
93.57
Moderate (starting degradation)
S87
2.08
0.35
2.43
85.60
Poor (degradation)
S89
1.70
0.28
1.98
85.86
Poor (degradation)
S91
1.91
0.09
2.00
95.50
Good (nondegraded)
S93
1.93
0.14
2.07
93.24
Moderate (starting degradation)
S95
2.24
0.21
2.45
91.43
Moderate (starting degradation)
S97
2.12
0.11
2.23
95.07
Good (nondegraded)


#### 3.1.4. Creating the Soil Environmental Quality Map

From the Table8, GIS technology with the spatial interpolation is applied to develop a simulated map of the SEQ assessment at the research area (Figure 1).Figure 1
The SEQ map of rice intensive cultivation areas in Haiduong province in 2013 developed from the aggregate SQ assessment approach by using RSQI. (The map is scaled from a map with the scale of 1 : 100,000.)


### 3.2. Discussion

(i) From Table8, the SQ of rice intensive cultivation areas in Haiduong is good (nondegraded soil), moderate (soil starting degradation), and poor (degraded).(ii) From the SQ map (Figure1), incorporation with digital land use map (Haiduong DoNRE, 2013 [18]) will calculate the area of rice intensive cultivation for 12 districts in hectare that consists of 3 groups: good (nondegraded), moderate (starting degradation), and poor (degradation) Soil Environmental Quality. Particularly, the nondegraded area of the province is 25,106.85 ha (36.29%), the area which starts to degrade is 28,821.69 ha (41.66%), and the degraded area is 15,254.33 ha (22.05%). To districts in the provinces with the moderate and poor soil quality, the soil with moderate and poor quality needs to be monitored and fertilized properly.(iii) According to the General Statistics Office (2013) [19], rice intensive cultivation areas in Haiduong province 2013 reached a relatively high average yield of 5.90 tonnes/ha. Because the RSQI approach shows results of the soil with good quality (nondegraded), the soil with moderate quality (start degraded), and the soil with poor quality (degraded), in which the degraded soil area accounts for only 22.05%, the soil quality of rice intensive cultivation areas is considered fairly good. Therefore, results of the research are in line with the relatively high yield in reality.


## 3.1. Results

### 3.1.1. Hierarchy for Assessing SQ of RSQI

The hierarchical scale for aggregate assessing soil quality of RSQI corresponding ton=10 parameters in Table 1 is shown in Table 5.Table 5
Hierarchy for assessing SQ of RSQI =I with n=10 parameters (Cd, Cu, Pb, SOM, Nt, Pt, Kt, Nav, Pav, and Kav).
RSQI
SQ
Colour
96–100
Good/excellent (I=100) (no degradation)
Green
91–95
Moderate(start degradation)
Yellow
51–90
Poor(degradation)
Orange
11–50
Very poor(strong degradation)
Red
0–10
Hazardous(very strong degradation)
Brown


### 3.1.2. Calculating the Temporary Weighting FactorsWi′ and the Final Weighting Factors Wi

(i) Calculating the Temporary Weighting FactorsWi′ is as follows:The group of heavy metals (formula (11)):(16)WCd′=2+50+703×2=20.33;WCu′=2+50+703×50=0.81;WPb′=2+50+703×70=0.58.The group of the total content of bioelements (formula (12)):(17)WOM′=2.5-1.25+0.2-0.1+0.1-0.06+2-14×2.5-1.25=2.395=0.48;WNt′=2.394×0.2-0.1=5.98;WP2O5t′=2.394×0.1-0.06=14.94;WK2Ot′=2.394×2-1=0.60.The group of the content of available forms of bioelements (formula (12)):(18)WNav′=8-2+4.6-3.6+15-103×8-2=1218=0.67;WP2O5av′=123×4.6-3.6=4;WK2Oav′=123×15-10=0.8.(ii) Calculating the Final Weighting FactorsWi (formula (14)) is as follows:(19)WCd=20.3320.33+0.81+0.58=20.3321.72=0.93;WCu=0.8121.72=0.04;WPb=0.5821.72=0.03.The final weighting factors of other parameters of total content of bioelements group and content of available forms of bioelements group are calculated, respectively, and results are shown in Table 6.Table 6
The temporary weighting factorsWi′ and the final weighting factors Wi of 10 surveyed parameters.
Parameters
Heavy metals
Total content of bioelements
Content of available forms of bioelements
Cd
Cu
Pb
P
t
SOM
N
t
K
t
N
av
P
av
K
av
i
1
2
3
4
5
6
7
8
9
10
W
i
′
20.33
0.81
0.58
14.94
0.48
5.98
0.60
0.67
4
0.80
W
i
0.93
0.04
0.03
0.68
0.02
0.27
0.03
0.12
0.73
0.15
∑
W
i
1
1
1


### 3.1.3. Calculatingqi, Pm1, Pm2, Pk, Pn, and RSQI

Based on the research materials mentioned in Section2.1, this research calculated individual parameter qi using formulas (7)–(10), calculated Pk and Pn using formulas (2)–(4), and calculated the RSQI index using formula (1) for soil samples.Because of the large sample size of the rice intensive cultivation areas surveyed in Haiduong including relatively high, medium, and low plains, we present how to calculate individual indexqi, the separate sums Pm1, Pm2, and Pk, and the common sum Pn (n=10 parameters) in order to determine the RSQI of a particular soil sample S1 (Table 7). Thus, only result of other samples is shown in Table 8:(20)Pm1=∑i=13Wiqi=0.02×1+0.27×1+0.12×1=0.41;Pm2=∑i=15Wi1-qi=0.93×1-0.01+0.04×1-0.19+0.03×1-0.26+0.68×1-0.6+0.73×1-0.3=1.76;Pm=Pm1+Pm2=0.41+1.76=2.17;Pk=∑i=12Wiqi-1=0.03×1.64-1+0.15×2.5-1=0.24;Pn=Pm+Pk=2.17+0.24=2.41;RSQI=100×1-PkPn=100×1-0.242.41=90.04—Moderateaccording to Table  5.Table 7
Calculating RSQI for a particular soil sample S1 withCi, monitoring values.
Parameters
Heavy metals
Total content of bioelements
Content of available forms of bioelements
Cd
Cu
Pb
P
t
SOM
N
t
K
t
N
av
P
av
K
av
i
1
2
3
4
5
6
7
8
9
10
S1-Ci
0.01
9.55
18.58
0.17
1.64
0.18
0.61
61.60
155.60
40
q
i
0.01
0.19
0.26
0.60
1
1
1.64
1
0.30
2.50
W
i
0.93
0.04
0.03
0.68
0.02
0.27
0.03
0.12
0.73
0.15Table 8
Results of calculation of RSQI based on monitoring data.
Soil samples
P
m
P
k
P
n
RSQI
SQ
(a) Relatively high plains
S1
2.17
0.24
2.41
90.04
Moderate (starting degradation)
S3
1.93
0
1.93
100
Excellent (nondegraded)
S5
2.02
0.03
2.05
98.54
Good (nondegraded)
S7
2.03
0.12
2.15
94.42
Moderate (starting degradation)
S9
1.73
0.08
1.81
95.58
Good (nondegraded)
S11
2.30
0.16
2.46
93.50
Moderate (starting degradation)
S13
2.24
0.17
2.41
92.95
Moderate (starting degradation)
S15
2.01
0.23
2.24
89.73
Poor (degradation)
S17
1.94
0.15
2.09
92.82
Moderate (starting degradation)
S19
2.11
0.21
2.32
90.95
Moderate (starting degradation)
S21
1.95
0.22
2.17
89.86
Poor (degradation)
S23
2.05
0.20
2.25
91.11
Moderate (starting degradation)
S25
2.40
0.15
2.55
94.12
Moderate (starting degradation)
S27
2.21
0.09
2.30
96.09
Good (nondegraded)
S29
2.26
0.07
2.33
96.99
Good (nondegraded)
S31
2
0.66
2.66
75.19
Poor (degradation)
(b) Medium plains
S57
1.82
0.22
2.04
89.22
Poor (degradation)
S59
1.72
0.08
1.80
95.56
Good (nondegraded)
S61
2.09
0.07
2.16
96.76
Good (nondegraded)
S63
2.04
0.45
2.49
81.93
Poor (degradation)
S65
2.03
0.40
2.43
83.54
Poor (degradation)
S67
2.32
0
2.32
100
Excellent (nondegraded)
S69
2.42
0
2.42
100
Excellent (nondegraded)
(c) Low plains
S73
2.26
0.27
2.53
89.33
Poor (degradation)
S75
2.22
0.37
2.59
85.71
Poor (degradation)
S77
2.25
0.07
2.32
96.98
Good (nondegraded)
S79
1.64
0.03
1.67
98.20
Good (nondegraded)
S81
1.30
0.01
1.31
99.24
Good (nondegraded)
S83
2.04
0.37
2.41
84.65
Poor (degradation)
S85
2.33
0.16
2.49
93.57
Moderate (starting degradation)
S87
2.08
0.35
2.43
85.60
Poor (degradation)
S89
1.70
0.28
1.98
85.86
Poor (degradation)
S91
1.91
0.09
2.00
95.50
Good (nondegraded)
S93
1.93
0.14
2.07
93.24
Moderate (starting degradation)
S95
2.24
0.21
2.45
91.43
Moderate (starting degradation)
S97
2.12
0.11
2.23
95.07
Good (nondegraded)


### 3.1.4. Creating the Soil Environmental Quality Map

From the Table8, GIS technology with the spatial interpolation is applied to develop a simulated map of the SEQ assessment at the research area (Figure 1).Figure 1
The SEQ map of rice intensive cultivation areas in Haiduong province in 2013 developed from the aggregate SQ assessment approach by using RSQI. (The map is scaled from a map with the scale of 1 : 100,000.)


## 3.1.1. Hierarchy for Assessing SQ of RSQI

The hierarchical scale for aggregate assessing soil quality of RSQI corresponding ton=10 parameters in Table 1 is shown in Table 5.Table 5
Hierarchy for assessing SQ of RSQI =I with n=10 parameters (Cd, Cu, Pb, SOM, Nt, Pt, Kt, Nav, Pav, and Kav).
RSQI
SQ
Colour
96–100
Good/excellent (I=100) (no degradation)
Green
91–95
Moderate(start degradation)
Yellow
51–90
Poor(degradation)
Orange
11–50
Very poor(strong degradation)
Red
0–10
Hazardous(very strong degradation)
Brown


## 3.1.2. Calculating the Temporary Weighting FactorsWi′ and the Final Weighting Factors Wi

(i) Calculating the Temporary Weighting FactorsWi′ is as follows:The group of heavy metals (formula (11)):(16)WCd′=2+50+703×2=20.33;WCu′=2+50+703×50=0.81;WPb′=2+50+703×70=0.58.The group of the total content of bioelements (formula (12)):(17)WOM′=2.5-1.25+0.2-0.1+0.1-0.06+2-14×2.5-1.25=2.395=0.48;WNt′=2.394×0.2-0.1=5.98;WP2O5t′=2.394×0.1-0.06=14.94;WK2Ot′=2.394×2-1=0.60.The group of the content of available forms of bioelements (formula (12)):(18)WNav′=8-2+4.6-3.6+15-103×8-2=1218=0.67;WP2O5av′=123×4.6-3.6=4;WK2Oav′=123×15-10=0.8.(ii) Calculating the Final Weighting FactorsWi (formula (14)) is as follows:(19)WCd=20.3320.33+0.81+0.58=20.3321.72=0.93;WCu=0.8121.72=0.04;WPb=0.5821.72=0.03.The final weighting factors of other parameters of total content of bioelements group and content of available forms of bioelements group are calculated, respectively, and results are shown in Table 6.Table 6
The temporary weighting factorsWi′ and the final weighting factors Wi of 10 surveyed parameters.
Parameters
Heavy metals
Total content of bioelements
Content of available forms of bioelements
Cd
Cu
Pb
P
t
SOM
N
t
K
t
N
av
P
av
K
av
i
1
2
3
4
5
6
7
8
9
10
W
i
′
20.33
0.81
0.58
14.94
0.48
5.98
0.60
0.67
4
0.80
W
i
0.93
0.04
0.03
0.68
0.02
0.27
0.03
0.12
0.73
0.15
∑
W
i
1
1
1


## 3.1.3. Calculatingqi, Pm1, Pm2, Pk, Pn, and RSQI

Based on the research materials mentioned in Section2.1, this research calculated individual parameter qi using formulas (7)–(10), calculated Pk and Pn using formulas (2)–(4), and calculated the RSQI index using formula (1) for soil samples.Because of the large sample size of the rice intensive cultivation areas surveyed in Haiduong including relatively high, medium, and low plains, we present how to calculate individual indexqi, the separate sums Pm1, Pm2, and Pk, and the common sum Pn (n=10 parameters) in order to determine the RSQI of a particular soil sample S1 (Table 7). Thus, only result of other samples is shown in Table 8:(20)Pm1=∑i=13Wiqi=0.02×1+0.27×1+0.12×1=0.41;Pm2=∑i=15Wi1-qi=0.93×1-0.01+0.04×1-0.19+0.03×1-0.26+0.68×1-0.6+0.73×1-0.3=1.76;Pm=Pm1+Pm2=0.41+1.76=2.17;Pk=∑i=12Wiqi-1=0.03×1.64-1+0.15×2.5-1=0.24;Pn=Pm+Pk=2.17+0.24=2.41;RSQI=100×1-PkPn=100×1-0.242.41=90.04—Moderateaccording to Table  5.Table 7
Calculating RSQI for a particular soil sample S1 withCi, monitoring values.
Parameters
Heavy metals
Total content of bioelements
Content of available forms of bioelements
Cd
Cu
Pb
P
t
SOM
N
t
K
t
N
av
P
av
K
av
i
1
2
3
4
5
6
7
8
9
10
S1-Ci
0.01
9.55
18.58
0.17
1.64
0.18
0.61
61.60
155.60
40
q
i
0.01
0.19
0.26
0.60
1
1
1.64
1
0.30
2.50
W
i
0.93
0.04
0.03
0.68
0.02
0.27
0.03
0.12
0.73
0.15Table 8
Results of calculation of RSQI based on monitoring data.
Soil samples
P
m
P
k
P
n
RSQI
SQ
(a) Relatively high plains
S1
2.17
0.24
2.41
90.04
Moderate (starting degradation)
S3
1.93
0
1.93
100
Excellent (nondegraded)
S5
2.02
0.03
2.05
98.54
Good (nondegraded)
S7
2.03
0.12
2.15
94.42
Moderate (starting degradation)
S9
1.73
0.08
1.81
95.58
Good (nondegraded)
S11
2.30
0.16
2.46
93.50
Moderate (starting degradation)
S13
2.24
0.17
2.41
92.95
Moderate (starting degradation)
S15
2.01
0.23
2.24
89.73
Poor (degradation)
S17
1.94
0.15
2.09
92.82
Moderate (starting degradation)
S19
2.11
0.21
2.32
90.95
Moderate (starting degradation)
S21
1.95
0.22
2.17
89.86
Poor (degradation)
S23
2.05
0.20
2.25
91.11
Moderate (starting degradation)
S25
2.40
0.15
2.55
94.12
Moderate (starting degradation)
S27
2.21
0.09
2.30
96.09
Good (nondegraded)
S29
2.26
0.07
2.33
96.99
Good (nondegraded)
S31
2
0.66
2.66
75.19
Poor (degradation)
(b) Medium plains
S57
1.82
0.22
2.04
89.22
Poor (degradation)
S59
1.72
0.08
1.80
95.56
Good (nondegraded)
S61
2.09
0.07
2.16
96.76
Good (nondegraded)
S63
2.04
0.45
2.49
81.93
Poor (degradation)
S65
2.03
0.40
2.43
83.54
Poor (degradation)
S67
2.32
0
2.32
100
Excellent (nondegraded)
S69
2.42
0
2.42
100
Excellent (nondegraded)
(c) Low plains
S73
2.26
0.27
2.53
89.33
Poor (degradation)
S75
2.22
0.37
2.59
85.71
Poor (degradation)
S77
2.25
0.07
2.32
96.98
Good (nondegraded)
S79
1.64
0.03
1.67
98.20
Good (nondegraded)
S81
1.30
0.01
1.31
99.24
Good (nondegraded)
S83
2.04
0.37
2.41
84.65
Poor (degradation)
S85
2.33
0.16
2.49
93.57
Moderate (starting degradation)
S87
2.08
0.35
2.43
85.60
Poor (degradation)
S89
1.70
0.28
1.98
85.86
Poor (degradation)
S91
1.91
0.09
2.00
95.50
Good (nondegraded)
S93
1.93
0.14
2.07
93.24
Moderate (starting degradation)
S95
2.24
0.21
2.45
91.43
Moderate (starting degradation)
S97
2.12
0.11
2.23
95.07
Good (nondegraded)


## 3.1.4. Creating the Soil Environmental Quality Map

From the Table8, GIS technology with the spatial interpolation is applied to develop a simulated map of the SEQ assessment at the research area (Figure 1).Figure 1
The SEQ map of rice intensive cultivation areas in Haiduong province in 2013 developed from the aggregate SQ assessment approach by using RSQI. (The map is scaled from a map with the scale of 1 : 100,000.)


## 3.2. Discussion

(i) From Table8, the SQ of rice intensive cultivation areas in Haiduong is good (nondegraded soil), moderate (soil starting degradation), and poor (degraded).(ii) From the SQ map (Figure1), incorporation with digital land use map (Haiduong DoNRE, 2013 [18]) will calculate the area of rice intensive cultivation for 12 districts in hectare that consists of 3 groups: good (nondegraded), moderate (starting degradation), and poor (degradation) Soil Environmental Quality. Particularly, the nondegraded area of the province is 25,106.85 ha (36.29%), the area which starts to degrade is 28,821.69 ha (41.66%), and the degraded area is 15,254.33 ha (22.05%). To districts in the provinces with the moderate and poor soil quality, the soil with moderate and poor quality needs to be monitored and fertilized properly.(iii) According to the General Statistics Office (2013) [19], rice intensive cultivation areas in Haiduong province 2013 reached a relatively high average yield of 5.90 tonnes/ha. Because the RSQI approach shows results of the soil with good quality (nondegraded), the soil with moderate quality (start degraded), and the soil with poor quality (degraded), in which the degraded soil area accounts for only 22.05%, the soil quality of rice intensive cultivation areas is considered fairly good. Therefore, results of the research are in line with the relatively high yield in reality.


## 4. Conclusion

The research used the soil sample analysis data for twelve districts in Haiduong province to calculate individual indices for 10 parameters. The selected basic parameters are Cd, Cu, and Pb;Pt, SOM, Nt, and Kt; Nav, Pav, and Kav. The separate sum Pm is integrated from parameters group with qi≤1 whereas the separate sum Pk is integrated from parameters group with qi>1. The common sum Pn equals Pm plus Pk. Using these sums, we calculated the RSQI values for 36 soil samples (16 samples in relatively high plains; 7 samples in medium plains; and 13 samples in low plains).The results of calculations show that the soil sample with good quality (qi<1) accounts for 14/36=38.88%; the proportions of soil sample with medium quality (qi=1) and poor quality (qi>1) are equal; both of them account for 11/36=30.56%.Based on the hierarchical scale of soil quality of RSQI, the soil quality of rice intensive cultivation areas in Haiduong is predominantly divided into three levels: good (nondegraded soil), moderate (soil starting degradation), and poor (degraded soil), corresponding to 3 levels which were assessed by individual index.The RSQI values are simulated on digital land use map by GIS technology. Each area has the same level described by the same colour on the map. Based on this map, calculating the area of each level (good, moderate, and poor) in hectare, the nondegraded area of the province is 25,106.85 ha (36.29%), the area which starts to degrade is 28,821.69 ha (41.66%), and the degraded area is 15,254.33 ha (22.05%). The map which is developed from the aggregate SQ assessment approach by using RSQI provides local managers an overview of the level of soil degradation before promptly taking appropriate measures to prevent or reduce pollution.In summary, our results are consistent with the reality. Therefore, the calculation method using individual indicesqi and the aggregate index RSQI has a scientific basis and high accuracy; the method could be applied in warning service and environmental management at the provincial scale.



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*Source: 253729-2015-11-25.xml*