This pot experiment investigated the distribution of fertilizer nitrogen (N) and agronomic effects in a paddy soil-rice system using five treatments: control (C), urea (U), urea + straw (US), urea + urease + nitrification inhibitor (UI), and urea + urease + nitrification inhibitor + straw (UIS). Straw addition (US and UIS) significantly increased soil and urea-derived microbial biomass N, highlighting the role of biotic processes in N retention. Around 10% of urea-N was recovered as fixed ammonium (FA), subsequently released at tillering and maturation. US decreased rice yield and N uptake compared to U, while UIS mitigated this reduction. UIS is suggested as the optimal management strategy in Northeast China paddy soils, but economic and field-scale validations are needed.
