Assessment on Ecological Safety of Farmland Fertilization of China
Qinpu Liu1,a, Yuling Guo1,b, John P. Giesy2,3,4,5,c
1
Nanjing Xiaozhuang University, Nanjing 211171, China
Toxicology Centre and Department of Veterinary Biomedical Sciences, University of Saskatchewan,
Saskatoon, Saskatchewan, Canada
3
School of Biological Sciences, University of Hong Kong, Hong Kong, SAR, China
4
Department of Biology and Chemistry and State key Laboratory in Marine Pollution, City University of
Hong Kong, Hong Kong, SAR, China
5
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing
University, Nanjing, China
a
liuqinpu@163.com, bgyl600008871@163.com, cJGiesy@aol.com
2
Keywords: Fertilization intensity; Ecological safety assessment; Non-point source pollution;
China;
Abstract: Here is presented the concepts of Fertilization Ecological Hazard Index (FEHI) and
Fertilization Ecological Safety Threshold (FEST). These concepts have been used to develop
models that assess the hazards posed by fertilization with inorganic fertilizers on ecological
environments in China. Based on these models, there were 11 regions, most of which are located in
Western China, slightly at risk from over-fertilization, while 14 regions located in central or eastern
China were at a moderate hazard from overuse of fertilizers. Six regions in western China were
found at ecological safety of environment because of small amounts of fertilizers used in these
regions. Ecological safety of environment decreased along the gradient from northwest to southeast
by fertilization. There were several factors that influence FEHI. It is obligatory for local
governments to offer training to guide reasonable uses of fertilization. It would be prudent for China
to establish laws to protect soils, especially to regulate the use of fertilizers in agriculture.
Introduction
Globally, approximately 30% ~ 50% of surface waters were once affected by non-point source
pollution, especially from use of inorganic fertilizers in agriculture[1]. Non-point source pollution is
more serious in China. In order to improve the food production since the 1990s, fertilizers use has
been growing greater and greater. In China, the rapid increase of GDP has provided the fiscal means
for farmers to buy inorganic fertilizers to improve yields of crops. In 2011, the total amount of
fertilizers used by agriculture was 57.04 million tons [2], which is approximately a third of the
world's total consumption of chemical fertilizers. The mass of fertilizer used per unit area in China
is more than 3 times greater than the average of the world [3]. The rate of utilization of applied
fertilizer by plants in China is 30% ~ 35% for N, 15% ~ 20% for P, 35% ~ 50% for K. Unused
nutrients are fixed in soil, leached into waters, or are volatilized into the atmosphere. These releases
result in acidification of soils and eutrophication of surface waters and contribution of heavy metals,
such as copper (Cu), mercury (Hg), and cadmium (Cd). While several studies of non-point pollution
of surface waters focused on trace metals [4,5], little has been done relative to hazards posed by
chemical fertilizers. Here the concepts of Fertilization Ecological Hazard Index (FEHI) and
Fertilization Ecological Safety Threshold (FEST) are presented and used to evaluate ecological
1
safety of farmland fertilization in order to enhance the sustainable development of agriculture in
China.
Materials and methods
Data collected. Most of the information used in this assessment came from the 2012 China
Statistical Yearbook [2], which were compiled by the Bureau of statistics of the people's Republic of
China, and the document of Eco-county, Eco-city, Eco-province Construction Indexes (Revised
Draft) from State Environmental Protection Administration issued in 2007[6]. Some of the data
were compiled from the 2012 China Statistical yearbook.
Methods of assessment. Assessment of safety of environment refers to the evaluation on
the damage and threats to human health, economy, ecological system initiated from social economy
activities of human beings and natural disasters, and the decision of management. Here concept of
the FEHI for assessing effects of fertilizers on ecological environment is presented (Equations 1-2).
FEHI t  Wi  FEHI i
FEHI i 
FI i
FI i  FESTi
(i = N, P, K)
(1)
(i = N, P, K)
(2)
Where: FEHIt refers to the total Fertilization Ecological Hazard Index, which is the sum of
component hazard factors multiplied by weighting factors. FEHIi refers to single factor for an
individual constituent of fertilizers, such as N, P or K, Wi is the weight of each factor with values
between 0 and 1. FIi refers to the Fertilization Intensity (FI, kg/ha) of i factor, that is the mass of
fertilizer i applied on the per unit of cultivated land area. FESTi is the Fertilization Ecological
Safety Threshold (FEST) of a single factor, which is the maximum mass of a fertilizer applied to
soil to maximize productivity without adverse effects on the environment. The mass of N, P, or K
is the net volume in the forms of N, P2O5, K2O, respectively.
Values of FEHIt (or FEHIi) range from 0 to 1. When FEHIt is equal to 0.5, FIi is equal to FESTi,
where fertilization of cropland is at the critical point of environment ecological safety, which means
that the amount of fertilizer applied is at the upper limit for optimal productivity of crops without
causing adverse affects on the environment. When FEHIt is near 1.0, Fertilization Intensity (FIi) of
fertilizer greatly exceeds the fertilization ecological safety threshold (FESTi). That is, pollution
due to excess application of inoganic fertilizers would be extremely serious. When FEHIt
approaches 0, use of inorganic fertilizer is nearly 0 and FIi is much less than the FESTi, which is
referred to organic agriculture. The degree of safety or hazard can be assessed by magnitude of
deviation of the FEHIt from 0.5. By use of intervals of 0.15, environment ecological safety can be
classified into six categories ranging from very safe to extremely dangerous (Table 1).
Table 1 Catergories of environment ecological safety of fertilization.
Categories
of
FEHIt
Criteria
Serious hazard
> 0.80
Mass of fertilizers Greater than three times of FEST
Medium hazard
0.66-0.80
Mass of fertilizers between three times and twice of FEST
Light hazard
0.51-0.65
Mass of fertilizers between
Safety
0.36-0.50
Mass of fertilizers less than one FEST
Ecological safety
twice and one FEST
2
High safety
0.21-0.35
Mass of fertilizers less than half FEST
Absolute safety
< 0.20
Mass of fertilizers is much fewer
Results and Discussion
Calculation and Distribution of FEHI. Before calculation on the Fertilization Ecological
Hazard Indexes (FEHIt), the threshold FEST should be determined. Here 250 kg/ha is used as the
threshold FESTt because the Chinese government considers it to be the criteria for the safe
fertilization in China [6]. Values of Wi are considered as 0.3, 0.5, 0.2 for N, P, K, respectively,
according to their contribution to eutrophication. Using the models of ecological hazard,
fertilization intensities (FIi and FIt) and FEHTt were calculated for each region of China (Table 2).
The geographical distribution of hazards posed by fertilization in regions of China were ranked
by FEHIt from least to greatest (Table 2). Based on this ranking, six regions in the west of China
were classified as safety from fertilization, 11 regions, most of which were in the west of China
were classified as light hazard, while 14 regions, located in the central or east of China were
classified as medium hazard. This distribution is in accordance with the level of economic
development in the region, with more fertilizers used in more developed regions.
Table 2. The Fertilization Intensity (FIi and FIt ) of NPK, FEHIt and ecological safety assessment for each
provincial region of China in 2011.
Provincial
FIN
FIP
FIK
FIt
Regions
(kg/ha)
(kg/ha)
(kg/ha)
(kg/ha)a
Tibet
55.3
47.6
28.8
Qinghai
85.6
41.5
Guizhou
131.6
Gansu
FEHIt
Assessment
Location
131.63
0.37
Safety
West
25.3
152.38
0.38
Safety
West
42.3
35.8
209.76
0.43
Safety
West
99.7
54.8
32.8
187.26
0.44
Safety
West
Heilongjiang
87.1
59.3
46.7
193.1
0.45
Safety
North east
Inner Mongolia
136.5
65.2
43.8
245.6
0.49
Safety
West
Shanxi
135.5
86.3
60.7
282.47
0.54
Light hazard
West
Yunnan
196.3
75
58.9
330.15
0.55
Light hazard
West
Liaoning
211.8
70.8
71.4
354.05
0.56
Light hazard
North east
Jilin
189.1
76
87.6
352.69
0.57
Light hazard
North east
Ningxia
201.6
80.4
63.4
345.4
0.57
Light hazard
West
Chongqing
255.5
112.4
56.9
424.83
0.62
Light hazard
West
Shanghai
319.6
90
81
490.66
0.62
Light hazard
East
Sichuan
246.3
114.9
58.8
420.08
0.62
Light hazard
West
Zhejiang
305.4
98.7
75.2
479.32
0.63
Light hazard
East
Shaanxi
288.4
106.7
116.6
511.73
0.65
Light hazard
West
Xinjiang
239.8
144.6
60.9
445.33
0.65
Light hazard
West
Hebei
293.9
127.2
95.4
516.48
0.67
Medium hazard
East
Beijing
370.9
116.2
110.2
597.35
0.68
Medium hazard
East
Jiangxi
218
141.5
138.4
497.93
0.68
Medium hazard
Middle
Tianjin
313.9
144.8
94.2
552.95
0.68
Medium hazard
East
Guangxi
237.1
139.3
199.1
575.48
0.69
Medium hazard
West
Anhui
284.7
148.1
142.5
575.32
0.7
Medium hazard
Middle
Hunan
350.5
126.3
163.1
639.92
0.7
Medium hazard
Middle
3
a
Hainan
296.7
149.5
209.8
656.07
0.72
Medium hazard
East
Jiangsu
431.9
166.5
109.5
707.86
0.72
Medium hazard
East
Shandong
308.5
163.6
158.2
630.23
0.72
Medium hazard
East
Guangdong
441.8
159.9
250.7
852.43
0.75
Medium hazard
East
Hubei
412.2
210.9
137.8
760.89
0.75
Medium hazard
Middle
Fujian
437.6
207.5
264.2
909.19
0.78
Medium hazard
East
Henan
412.1
255.2
182.7
849.96
0.78
Medium hazard
Middle
FIt = FIN + FIP + FIK
Factors influencing distribution of FEHI. In order to ascertain reasons for the distribution
of FEHI, several factors (xi) were selected to be evaluated by use of correlation analyses with
Fertilization Intensity (y) (Table 3). These factors include multiple cropping index (x1), proportion
of land irrigated (x2), proportion of arable land (x3), income per farmer (x4), yield of grain per
hectare (x5), arable land per rural person (x6), rate of disasters (like flooding or draught) area
(percentage of natural disaster area affected to areas covered) (x7), proportion of population that is
rural (x8).
The factors, multiple cropping index, proportion of land irrigated, proportion of arable land,
income per farmer, yield of grain per hectare were significantly and positively correlated with FI,
but amount of arable land per rural person was negatively associated with FI. The relationship was
consistent with current natural and economic conditions of China. In central and eastern China,
densities of human habitation and rates of irrigation are greater than in the west, large areas are
suitable for agriculture, especially for multiple cropping, so farmers put more fertilizers onto arable
land in these regions. Because of overuse of fertilizers, the problems of non-point pollution were
more serious in these areas.
Table 3 Correlation coefficients (r) between Fertilization Intensity (FI) and factors
y
sig.(p)
(2-tailed)
x1
x2
x3
x4
x5
x6
x7
x8
0.727
0.482
0.394
0.377
0.355
-0.467
-0.324
-0.32
0.000
0.006
0.028
0.036
0.05
0.008
0.075
0.079
Effects of overuse of chemical fertilizers on the environment. Overuse of fertilizers is
not only detrimental to aquatic environments but also can damage crops and result in lesser
production of grains. Excess fertilization can cause deterioration of soil, pollution of air and water
and low quality agricultural products, eventually, and in some cases result in adverse effects on
health of people, such as methemoglobanemia caused by nitrite (NO2-). Approximately 13% ~ 28%
of N applied to crops as ammonia nitrogen (NH3-NH4+) escapes to the atmosphere. Nitrogen
fertilizer in soil can release N2O by nitrification and denitrification [7,8]. On a molar basis, the
potential of N2O to cause global warming is 200 times greater than that of CO2. Excess nitrogen in
surface and ground water mainly originates from farmland, on which excess inorganic N-containing
fertilizers are applied. Specifically 51% of anthropogenic N in the surface water is from farmland.
One reason for the outbreak of cyanobacteria (blue-green algae) observed in Tai Lake, Jiangsu
Province, during 2007 was non-point pollution from agriculture[9,10] (Ge et al., 2008, Li et al.,
2012). In the China environmental state bulletin of 2011 it was reported that the overall national
surface water was mildly polluted, 53.8% of 26 lakes (reservoirs) monitored exhibited
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eutrophication and among 200 cities monitored, 55.0% had poor quality ground water [11].
Conclusion
For the first time, models of evaluating the ecological safety of fertilization were proposed and
applied to assess China agricultural environment. Fertilizers are found to be over-used in most
regions. There were 11 regions, most of them are located in the west, being slightly at risk due to
over use of fertilizers; 14 regions, located in the central or east, were moderately at risk due to
overuse of fertilizers, and 6 regions, located in the west of China, were found not being affected by
use of inorganic fertilizers. Ecological risk caused by fertilization increased along a gradient from
northwest to Southeast. This trend was consistent with trends of distributions of natural and
economic factors. Because there were more than half of lakes in China eutrophied, excessive
fertilization was a significant environmental problem in China.
There were several factors which influenced the distribution of fertilization intensity. Regions
with greater GDP and more developed agriculture were determined to be more at hazard due to
over-use of inorganic fertilizers. So it is obligatory for local government to offer many kinds of
training programs to farmers. As farmers learn when, how and what fertilization to use, they will
make themselves involved in the environment protection.
Acknowledgements
The project was supported by Jiangsu Ecology Key Discipline Construction Project; Nanjing
Environmental Science Key Discipline Construction Project. Prof. Giesy was supported by the
Canada Research Chair program, 2012 program of "High Level Foreign Experts"
(#GDW20123200120) funded by the State Administration of Foreign Experts Affairs, the P.R.
China to Nanjing University, the Einstein Professor Program of the Chinese Academy of Sciences,
and a Distinguished Visiting at the Department of Biology and Chemistry and State Key Laboratory
in Marine Pollution, City University of Hong Kong.
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