The estimates of N loads in percolation water from 100 cm were
3.46 to 5.82 kg N ha−1 (Table 2) during the three rice seasons. Based
on the current investigation and previous studies (Tian et al., 2007;
Zhao et al., 2009a; Zhu et al., 2000), it can be concluded that N
leaching from most flooded rice paddies in TLR may not be as high
as feared, because less than 6 kg N ha−1 was leached, and therefore
the effect on N pollution of groundwater might not necessarily be
higher than that of some other upland soil (Zhang et al., 2005).
One important reason for the low rate of N leaching might be the
puddled layer with low permeability at about 15–20 cm in depth.
The estimates of N loads in percolation water from 100 cm were3.46 to 5.82 kg N ha−1 (Table 2) during the three rice seasons. Basedon the current investigation and previous studies (Tian et al., 2007;Zhao et al., 2009a; Zhu et al., 2000), it can be concluded that Nleaching from most flooded rice paddies in TLR may not be as highas feared, because less than 6 kg N ha−1 was leached, and thereforethe effect on N pollution of groundwater might not necessarily behigher than that of some other upland soil (Zhang et al., 2005).One important reason for the low rate of N leaching might be thepuddled layer with low permeability at about 15–20 cm in depth.
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