Long−term excessive nitrogen fertilizer input has resulted in several environmental problems, including an increase in N₂O emissions and the aggravation of nitrate leaching; monitoring nitrogen fertilizer is crucial for maize with high yield. This study aimed to optimize the amount of nitrogen applied to maize by Climate−Smart Agriculture (CSA) so as to continuously improve agricultural productivity and reduce or eliminate N₂O emissions as much as possible. Field experiments with a completely randomized design were conducted to examine the effects of six nitrogen treatments (N application levels of 0, 120, 180, 240, 300, 360 kg·ha⁻¹, respectively) on N₂O emissions, residual concentration of nitrate and ammonium nitrogen, maize yield, and nitrogen utilization efficiency in 2018 and 2019. The results indicated that the residual concentration of nitrate nitrogen (${\mathrm{NO}}_3^{-}$−N) in the two seasons significantly increased; N₂O emissions significantly increased, and the nitrogen fertilizer agronomic efficiency and partial productivity of maize fell dramatically as the nitrogen application rate increased. The maize grain yield rose when the N application amount was raised (N application amount 300 kg·ha⁻¹. An increase in the nitrogen application rate can decrease nitrogen use efficiency, increase soil ${\mathrm{NO}}_3^{-}$−N residual, and N₂O emissions. Reasonable nitrogen application can increase maize yield and reduce N₂O emissions and be conducive to improving nitrogen use efficiency. By considering summer maize yield, nitrogen use efficiency, and farmland ecological environment, 173.94~178.34 kg N kg·ha⁻¹ could be utilized as the nitrogen threshold for summer maize in the North China Plain.

Maintaining stable male sterility is fundamental for ensuring the genetic purity and productivity of two-line hybrid wheat. However, unexpected heat events during the fertility-sensitive period can induce fertility restoration in photo-thermo-sensitive male sterile (PTMS) lines, posing a major threat to hybrid seed production. In this study, we identified two BS-type PTMS lines, BS166 and BS192, that consistently maintained sterility under heat stress in a seed-production environment, indicating strong heat-tolerant sterility. To uncover the molecular basis underlying this stability, we compared four BS-type PTMS lines exhibiting contrasting heat responses through field assessments, controlled heat treatments, transcriptome sequencing, and weighted gene co-expression network analysis (WGCNA). A total of 19,105 differentially expressed genes were identified, with the bisque4 module showing a significant correlation with seed setting rate. KEGG enrichment analysis revealed that starch and sucrose metabolism, cutin, suberin, and wax biosynthesis, fatty acid biosynthesis, and plant hormone signal transduction pathways were highly associated with heat-tolerant sterility. Core genes within these pathways displayed transcriptional stability in BS166 and BS192 but were strongly induced in heat-sensitive lines. In situ hybridization and RT-qPCR further confirmed tapetum-specific expression of TaBGLU32 and TaLACS1. Based on these findings, we propose a regulatory model explaining how PTMS lines maintain sterility stability under heat stress.