carbon, soil pH, and temperature (Bouwman 1996; Bouwman et al. 1993, Freney
1997; Hayatsu et al. 2008; Thomson et al. 2012).
Among the main flow pathways that contribute to N losses from agricultural
systems is N runoff and leaching. The characteristics of soil type, organic matter, and
particle-size distribution can affect the amount of N runoff from soils (Dreelin et al.
2006; Ouyang et al. 2010; Zhang et al. 2012b). Factors such as the terrain condition,
rainfall intensity, vegetation fraction, and soil moisture content can also affect the N
runoff (Bakhsh et al. 2005; B ouldin et al. 2004; Udawatta et al. 2006). Moreover,
the N loss through runoff can be affected by fertilization (Liu et al. 2014a). Similarly,
the amount of N leaching from agricultural systems also depends on the soil
characteristics, crop type, climatic conditions that dominated leaching, fertilizer
application rate, and field management practices (Goulding 2000; Schepers et al.
1995; Westermann et al. 1988).
With a large amount of N input, aboveground crop N uptake from croplands of
China increased from 8.1 to 16.9 Tg N year
À1 from 1980 to 2010 (Yan et al. 2014),
which accounts for less than 50% of the total N input. Therefore, decades of fertilizer
N overuse have caused a large amount of N to be lost to the soil, water, and air. N
loss from volatilization and denitrification increased from 3.1 Æ 1.0 to 7.6 Æ 2.5 and
from 3.1 Æ 1.3 to 7.3 Æ 3.0 Tg N year
À1 from 1980 to 2010. Approximately 2.1 and
2.4 Tg N year
À1 was lost through leaching and surface runoff, as well as
7.5 Æ 4.9 Tg N year
À1 accumulated in the soil. N surplus in croplands in China
increased 1.4 times (86.3–226.9 kg N ha
À1 year
À1 ) in the same period (Gu et al.
2017).
For major crops, Cui et al. (2014b) indicated that the average loss of N 2 O from
rice, wheat, and maize in China was 0.70%, 0.53%, and 0.86% of N fertilizer
application, respectively. The loss from leaching was accounted for 2.98%, 10.1%,
and 22.2% of the N application. NH 3 volatilization from the aforementioned crops
was as high as 17%, 14%, and 24% of the total N input from rice, wheat, and maize,
respectively. Furthermore, given the intensive crop rotations and high N application
rates, approximately 0.32, 0.02, and 0.86 Tg N year
À1 were lost through leaching,
NH 3 emission, and nitrification and denitrification, respectively, from the Chinese
greenhouse vegetable cropping system. However, the amounts of N losses from the
open-air vegetable cropping system were much higher than those from the greenhouse vegetable cropping system (Ti et al. 2015).
The overuse of N fertilizer has contributed to environmental pollution and costly
damage in China. For example, N losses through NH 3 and N 2 O emissions are
responsible for the heavy N deposition and air pollution in China (Liu et al. 2013;
Reis et al. 2009). Ti and Yan (2013) pointed out that 22–57% of the total nonpoint N
originated from cropland fertilizer runoff transported in large river basins in China
causing water pollution. Moreover, a life-cycle analysis of the three major crop
productions in China showed that the total damage costs of GHG emission and Nr N
loss were equal to 1.44% of the Chinese GDP (Xia et al. 2016).
13 Nitrogen Regulation in China’s Agricultural Systems
303
1997; Hayatsu et al. 2008; Thomson et al. 2012).
Among the main flow pathways that contribute to N losses from agricultural
systems is N runoff and leaching. The characteristics of soil type, organic matter, and
particle-size distribution can affect the amount of N runoff from soils (Dreelin et al.
2006; Ouyang et al. 2010; Zhang et al. 2012b). Factors such as the terrain condition,
rainfall intensity, vegetation fraction, and soil moisture content can also affect the N
runoff (Bakhsh et al. 2005; B ouldin et al. 2004; Udawatta et al. 2006). Moreover,
the N loss through runoff can be affected by fertilization (Liu et al. 2014a). Similarly,
the amount of N leaching from agricultural systems also depends on the soil
characteristics, crop type, climatic conditions that dominated leaching, fertilizer
application rate, and field management practices (Goulding 2000; Schepers et al.
1995; Westermann et al. 1988).
With a large amount of N input, aboveground crop N uptake from croplands of
China increased from 8.1 to 16.9 Tg N year
À1 from 1980 to 2010 (Yan et al. 2014),
which accounts for less than 50% of the total N input. Therefore, decades of fertilizer
N overuse have caused a large amount of N to be lost to the soil, water, and air. N
loss from volatilization and denitrification increased from 3.1 Æ 1.0 to 7.6 Æ 2.5 and
from 3.1 Æ 1.3 to 7.3 Æ 3.0 Tg N year
À1 from 1980 to 2010. Approximately 2.1 and
2.4 Tg N year
À1 was lost through leaching and surface runoff, as well as
7.5 Æ 4.9 Tg N year
À1 accumulated in the soil. N surplus in croplands in China
increased 1.4 times (86.3–226.9 kg N ha
À1 year
À1 ) in the same period (Gu et al.
2017).
For major crops, Cui et al. (2014b) indicated that the average loss of N 2 O from
rice, wheat, and maize in China was 0.70%, 0.53%, and 0.86% of N fertilizer
application, respectively. The loss from leaching was accounted for 2.98%, 10.1%,
and 22.2% of the N application. NH 3 volatilization from the aforementioned crops
was as high as 17%, 14%, and 24% of the total N input from rice, wheat, and maize,
respectively. Furthermore, given the intensive crop rotations and high N application
rates, approximately 0.32, 0.02, and 0.86 Tg N year
À1 were lost through leaching,
NH 3 emission, and nitrification and denitrification, respectively, from the Chinese
greenhouse vegetable cropping system. However, the amounts of N losses from the
open-air vegetable cropping system were much higher than those from the greenhouse vegetable cropping system (Ti et al. 2015).
The overuse of N fertilizer has contributed to environmental pollution and costly
damage in China. For example, N losses through NH 3 and N 2 O emissions are
responsible for the heavy N deposition and air pollution in China (Liu et al. 2013;
Reis et al. 2009). Ti and Yan (2013) pointed out that 22–57% of the total nonpoint N
originated from cropland fertilizer runoff transported in large river basins in China
causing water pollution. Moreover, a life-cycle analysis of the three major crop
productions in China showed that the total damage costs of GHG emission and Nr N
loss were equal to 1.44% of the Chinese GDP (Xia et al. 2016).
13 Nitrogen Regulation in China’s Agricultural Systems
303