Effects of N application and simulated rainfall pH value on NO3-N leaching loss from canopy of maize

In order to find out the effect of acid rain on corn canopy, a simulated rainfall experiment was conducted to investigate the influence of N application and rainfall pH on nitrate leaching loss from the potted maize canopy as well as its changes over the growing season. The results showed that the amount of nitrate (NO3--N) leaching from maize canopy was mainly influenced by canopy N content which closely related with N application when rainfall pH was above 5.0. N application significantly increased the amount of canopy NO3--N leaching loss, nevertheless, when rainfall pH was 4.0, both rainfall pH and canopy N content had significant influence on NO3--N leaching loss. The change characteristics of NO3--N leaching loss with decreasing rainfall pH varied at different growth stages, rainfall pH had more significant influence on NO3--N leaching in early growth stage than in later growth stage. Under the same pH rainfall condition, the amount of canopy NO3--N leaching loss decreased with maize growing: 11-leaf period >spinning period > grain-filling period, and the amount of leaching loss in early growth stage was obviously higher than in later stage. In conclusion, both canopy N content and rainfall pH could influence NO3--N leaching loss, but the canopy N content was the comparatively main factor, the maize canopy NO3--N could be significantly leached by simulated rainfall, especially in early growth stage, thus the amount of NO3--N leaching from canopy should be taken into account in study of canopy N cycle, flux and losses.