Microbially mediated nitrogen conservation and loss in low and high nitrogen input rice paddies

Abstract

High rates of fertilizer nitrogen (N) application in rice paddies is a common practice in the majority of the rice-producing countries. However, more than 60% of the applied fertilizer-N is lost to the atmosphere and other terrestrial ecosystems. This causes serious environmental pollution and economic loss. On the other hand, un-fertilized rice paddies have shown maintained soil N status and stable N supply to the rice plant for hundreds of years. Microbial N2 fixation is known to contribute N to un-fertilized rice paddies. However, N2 fixation alone cannot fully explain the maintained N nutrition in rice paddies, where favourable conditions for N loss by denitrification exist. In largely a..