Table 1 Independent variables and emissions factor of farm inputs for rice, wheat, and maize production in China.
Indicators
|
Independent variables
|
Description of independent variables
|
Coefficient
|
GHGs emission (kgCO2-eq kg-1)
|
Active nitrogen emission (kgN-eq kg-1)
|
Resources Input
|
N
|
N-fertilizer application rate per unit area (kg ha-1)
|
1.53
|
0.89×10-3
|
|
P2O5
|
P2O5-fertilizer application rate per unit area (kg ha-1)
|
1.63
|
0.54×10-3
|
|
K2O
|
K2O-fertilizer application rate per unit area (kg ha-1)
|
0.65
|
0.03×10-3
|
|
Herbicides
|
Herbicides application rate per unit area (kg ha-1)
|
16.61
|
3.53×10-3
|
|
Insecticides
|
Insecticides application rate per unit area (kg ha-1)
|
10.15
|
4.49×10-3
|
|
Fungicides
|
Fungicides application rate per unit area (kg ha-1)
|
10.5
|
7.05×10-3
|
|
Diesel
|
Diesel consumption from machinery operation per unit area(kg ha-1)
|
4.99
|
4.66×10-3
|
|
Electricity
|
Power consumption from irrigation per unit area (kWh ha-1)
|
0.82
|
0.12×10-3
|
|
Film
|
Film application rate per unit area (kg ha-1)
|
22.72
|
12.03×10-3
|
|
Rice seed
|
Rice seed application rate per unit area (kg ha -1)
|
1.84
|
0.76×10-3
|
|
Wheat seed
|
Wheat seed application rate per unit area (kg ha-1)
|
0.58
|
0.24×10-3
|
|
Maize seed
|
Maize seed application rate per unit area (kg ha-1)
|
1.93
|
0.88×10-3
|
Expect output
|
Grain yield
|
Total crop yield per unit area (kg ha-1)
|
|
|
Undesired output
|
Global warming
|
Standardized global warming potential per unit area (kgCO2-eq ha-1)
|
|
|
|
Eutrophication pollution
|
Standardized eutrophication potentials per unit area (kgN-eq ha-1)
|
|
|
The conversion coefficients of CO2 equivalent for most of inputs were from the Chinese Life Cycle Database (CLCD v0.7, IKE Environmental Technology CO., Ltd, China), except those of pesticides and seeds which were from Ecoinvent v2.2 (Swiss Centre for Life Cycle Inventories, Switzerland). The Nr emission factors (Nn) from IKE eBalance v3.0 (IKE Environment Technology CO., Ltd, China).
Table 2
The life cycle inventory dataset of farm size, grain yield, agricultural inputs and fields of rice, wheat and maize production in the surveyed regions (mean ± S.E.)
Item
|
Rice
|
|
Wheat
|
|
Corn
|
Jiangxi
|
Hunan
|
|
Jiangsu
|
Anhui
|
|
Hebei
|
Jilin
|
Farm size (ha)
|
2.1±0.5
|
2.6±0.9
|
|
2.4±1.1
|
1.6±0.3
|
|
0.6+0.2
|
0.8+0.2
|
Grain yield (t ha-1)
|
6.0±0.4
|
5.4±0.5
|
|
5.7±0.8
|
6.0±0.7
|
|
6.7±0.6
|
7.7±0.7
|
Diesel oil (L ha-1)
|
107.1±27.1
|
95.2±33.4
|
|
131.9±31.4
|
103.0±29.0
|
|
104.1±19.2
|
88±10.3
|
Electricity for irrigation (kW h ha-1)
|
27.3±8.5
|
33.2±7.1
|
|
-
|
-
|
|
91.8±14.4
|
80.1±10.9
|
Seeds (kg ha-1)
|
78.6±14.0
|
36.0±17.8
|
|
44.2±9.7
|
55.5±6.6
|
|
44.6±7.6
|
35.5±5.1
|
Films (kg ha-1)
|
7.4±1.1
|
7.0±1.5
|
|
-
|
-
|
|
-
|
-
|
Herbicides (kg ha-1)
|
0.3±0.1
|
0.3±0.2
|
|
0.5±0.2
|
0.3±0.1
|
|
1.9±0.4
|
1.4±0.7
|
Insecticides (kg ha-1)
|
0.4±0.2
|
0.3±0.2
|
|
0.6±0.2
|
0.5±0.1
|
|
0.7±0.2
|
0.6±0.3
|
Fungicides (kg ha-1)
|
1.1±0.4
|
0.8±0.5
|
|
1.1±0.5
|
1.0±0.4
|
|
0.3±0.1
|
0.2±0.1
|
N fertilizers (kg ha-1)
|
363.2±97.4
|
217.0±96.3
|
|
272.4±83.1
|
197.3±57.1
|
|
172.8±31.1
|
200.3±37.0
|
P2O5 fertilizers (kg ha-1)
|
31.5±14.1
|
36.1±7.8
|
|
25.1±9.7
|
35.2±9.7
|
|
93.7±30.1
|
107.6±39.7
|
K2O fertilizers (kg ha-1)
|
67.0±23.0
|
86.9±30.0
|
|
56.2±18.6
|
78.1±25.7
|
|
63.86±16.7
|
91.1±26.7
|
CH4 (kg ha-1)
|
131.3±19.5
|
121.1±29.5
|
|
-
|
-
|
|
-
|
-
|
N2O (kg ha-1)
|
1.9±0.5
|
1.2±0.5
|
|
2.0±0.4
|
1.4±0.3
|
|
1.3±0.2
|
1.5+0.3
|
NH3 (kg ha-1)
|
149.04±39.5
|
89.07±40.0
|
|
90.9±34.1
|
65.9±23.1
|
|
47.2±13.2
|
55±21.2
|
NO3- (kg ha-1)
|
4.9±0.5
|
2.9±0.9
|
|
7.3±1.0
|
5.3±0.7
|
|
1.4±0.1
|
1.6±0.2
|
NH4+ (kg ha-1)
|
1.6±0.4
|
1.0±0.5
|
|
0.7±0.01
|
0.5±0.01
|
|
0.1±0.02
|
0.1±0.03
|
Table 3
The average hidden greenhouse gases (GHGs) and reactive nitrogen (Nr) emissions from agricultural inputs of grain crop production in China (mean ± S.E.)
Input
|
GHGs emission (kg CO2-eq ha-1)
|
|
Nr emission (g N-eq ha−1)
|
Rice
|
Wheat
|
Corn
|
|
Rice
|
Wheat
|
Corn
|
Diesel oil
|
504.7±134.1
|
451.3±149.7
|
479.3±134.1
|
|
471.4±139.8
|
547.3±140.1
|
447.6±77.1
|
Electricity for irrigation
|
24.8±6.6
|
-
|
70.7±13.1
|
|
3.6±0.9
|
-
|
10.3±1.8
|
Seeds
|
105.4±25.8
|
28.9±4.6
|
77.3±11.6
|
|
43.5±10.6
|
12.0±1.9
|
35.2±5.8
|
Films
|
163.6±23.8
|
-
|
-
|
|
86.6±11.8
|
-
|
-
|
Herbicides
|
5.0±1.7
|
6.6±3.1
|
27.4±8.3
|
|
1.1±0.4
|
1.4±0.7
|
5.8±1.8
|
Insecticides
|
3.6±1.6
|
5.6±1.1
|
6.6±2.1
|
|
1.6±0.8
|
2.5±0.6
|
2.9±1.2
|
Fungicides
|
10.0±5.0
|
11.0±4.8
|
2.6±1.2
|
|
6.7±2.1
|
7.4±2.8
|
1.8±0.8
|
N fertilizers
|
443.9±144.4
|
359.3±107.1
|
285.4±52.2
|
|
258.2±86.3
|
209.0±62.3
|
166.0±30.6
|
P2O5 fertilizers
|
55.1±17.1
|
49.1±5.2
|
164.1±18.9
|
|
18.3±6.1
|
16.3±1.6
|
54.4±6.6
|
K2O fertilizers
|
50.0±17.1
|
43.6±14.3
|
50.4±14.1
|
|
2.3±0.8
|
2.0±0.7
|
2.3±0.7
|
Totals
|
1366.0±234.1
|
955.6±194.4
|
1163.8±224.1
|
|
893.2±187.2
|
797.9±104.7
|
726.4±100.7
|
Table 4
Variation of product carbon footprint and nitrogen footprint with farm size classes (Mean ± S.E.).
Crop
|
Region
|
Carbon Footprint (kgCO2-eq kg-1)
|
|
Nitrogen footprint (gN-eq kg-1)
|
LZF
|
MZF
|
SZF
|
|
LZF
|
MZF
|
SZF
|
Rice
|
Jiangxi
|
0.80±0.12b
|
0.89±0.15b
|
1.12±0.07a
|
|
17.47±3.11b
|
20.44±1.31b
|
24.07±2.01a
|
|
Hunan
|
0.78±0.11a
|
0.82±0.13a
|
0.98±0.14a
|
|
12.05±2.11a
|
13.85±3.08a
|
16.03±3.21a
|
Wheat
|
Jiangsu
|
0.26±0.04c
|
0.35±0.01b
|
0.40±0.02a
|
|
14.17±2.01c
|
17.01±1.41b
|
19.12±1.11a
|
|
Anhui
|
0.22±0.04c
|
0.28±0.01b
|
0.31±0.01a
|
|
9.88±3.22c
|
11.64±1.42b
|
15.87±1.33a
|
Corn
|
Hebei
|
0.25±0.02a
|
0.27±0.02a
|
0.30±0.02a
|
|
5.96±2.37a
|
6.86±1.41a
|
8.61±2.13a
|
|
Jilin
|
0.20±0.03b
|
0.24±0.02b
|
0.29±0.01a
|
|
5.46±0.67b
|
6.84±0.44b
|
7.94±0.53a
|
Household farms were divided into two categories of small sized (SZF, <0.7 ha), middle sized (MZF, 2-7 ha) and large sized household farms (LZF, >20 ha) according to the farm size data obtained in the survey. Different letters indicate significant differences between farm size classes at p < 0.05.
Table 5
The eco-efficiency and redundancy rate of grain crop production on province levels in China (mean ± S.E.)
Item
|
Rice
|
|
Wheat
|
|
Corn
|
Jiangxi
|
Hunan
|
|
Jiangsu
|
Anhui
|
|
Hebei
|
Jilin
|
Eco-efficiency
|
|
0.55±0.15
|
0.51±0.13
|
|
0.69±0.24
|
0.62±0.21
|
|
0.87±0.15
|
0.91±0.13
|
Undesired yield redundancy rate
|
Labor
|
0.4%
|
0.3%
|
|
-0.2%
|
-2.6%
|
|
-1.1%
|
2.0%
|
Seeds
|
-7.3%
|
-5.7%
|
|
-8.8%
|
-9.3%
|
|
-10.4%
|
-10.9%
|
Tillage
|
-10.6%
|
-12.0%
|
|
-10.0%
|
-15.4%
|
|
-9.9%
|
-14.5%
|
Sowing
|
-2.8%
|
-5.4%
|
|
-1.9%
|
-6.1%
|
|
-7.9%
|
-4.5%
|
Harvest
|
-17.7%
|
-19.9%
|
|
-17.4%
|
-16.8%
|
|
-7.9%
|
-4.5%
|
Electricity for irrigation
|
-17.9%
|
-15.0%
|
|
|
|
|
-7.7%
|
-4.6%
|
Herbicides
|
-8.7%
|
-4.3%
|
|
-12.5%
|
-14.1%
|
|
-16.8%
|
-23.3%
|
Insecticides
|
-8.1%
|
-4.2%
|
|
-1.3%
|
-1.7%
|
|
-19.1%
|
-15.3%
|
Fungicides
|
-0.2%
|
-0.6%
|
|
-2.9%
|
-9.9%
|
|
-2.7%
|
-9.2%
|
N fertilizers
|
-17.9%
|
-20.9%
|
|
-24.6%
|
-32.9%
|
|
-31.7%
|
-31.3%
|
P2O5 fertilizers
|
-3.9%
|
-2.0%
|
|
6.8%
|
-0.5%
|
|
-7.9%
|
-3.4%
|
K2O fertilizers
|
-2.6%
|
-4.9%
|
|
4.0%
|
-0.7%
|
|
-11.0%
|
-5.5%
|
Grain yield
|
-0.4%
|
-0.1%
|
|
-1.3%
|
-2.7%
|
|
-3.4%
|
-1.1%
|
GWP
|
-25.1%
|
-22.7%
|
|
-12.5%
|
-13.1%
|
|
-14.0%
|
-13.5%
|
Nr
|
-17.9%
|
-10.9%
|
|
-24.5%
|
-23.0%
|
|
-20.2%
|
-20.6%
|