Contrasting fertilizer nitrogen contribution rates for achieving maximum grain yield in double‐ and single‐cropped rice

The contribution rate of fertilizer nitrogen (N)—defined as the percentage of N uptake from fertilizer relative to total N uptake—is a fundamental parameter for establishing knowledge‐based fertilization recommendations in crop production. This study aimed to compare the fertilizer N contribution rate for achieving maximum grain yield between double‐ and single‐cropped rice ( Oryza sativa L.). Data from four field experiments conducted between 2014 and 2023 were used to analyze the relationships of fertilizer N contribution rate and grain yield with N application rate in both double‐ and single‐cropped rice, thereby estimating the fertilizer N contribution rate required to achieve maximum grain yield. The results showed that the fertilizer N contribution rate increased by 3.21%–3.58% and 1.92%–2.35% for each 10 kg ha −1 increase in N application rate in double‐ and single‐cropped rice, respectively. Maximum grain yields were achieved at N application rates of 190–208 kg ha −1 per crop for double‐cropped rice and 211–244 kg ha −1 for single‐cropped rice. Correspondingly, the fertilizer N contribution rates for achieving maximum grain yield ranged from 60.91% to 74.51% in double‐cropped rice and from 46.90% to 49.65% in single‐cropped rice. These results indicate that N fertilizers contribute more to grain yield in double‐ than in single‐cropped rice, underscoring the importance of developing N management strategies and policies tailored to specific rice cropping systems.