Inorganic N accumulation in soil
Table 2 shows the amounts of accumulated soil inorganic N
(NO3
− N and NH4
+ N) at jointing and maturity stages. Our results
showed that NH4
+ N accumulation did not differ at jointing and
maturity stages among soil layers perhaps due to the rapid nitrification
(Liu et al., 2003) (Table 2).
At jointing stage, NO3
− N accumulation increased with soil
depth, as did the basal N rate in all soil layers, which was highest
in the 40–60 cm soil layer in all treatments except for N0. Thus,
soil NO3
− N leached fast and deep as the basal N rate increased.
However, NO3
− N mainly remained in the 0–40 cm soil layer at
maturity. The high accumulation of NO3
− N in the upper soil would
be beneficial to crop later growth, but with risks to leaching.