Effects of aerated irrigation and nitrogen fertilization on soil properties and water and nitrogen use efficiency in maize

To assess the synergistic effects of nitrogen (N) application rates on soil properties, maize yield, and water-N use efficiency under aerated irrigation in red loamy soils of Guangdong, a 3-year field experiment (2021–2023) was conducted with three N levels [150 (N1), 300 (N2), and 450 kg·hm −2 (N3)] and a control (CK). Results showed that N2 (300 kg·hm -2 ) and N3(450 kg·hm -2 ) treatments significantly reduced soil bulk density by 3.87% and 5.23% ( p < 0.05), and increased total porosity by 5.40% and 6.27%, respectively, compared to CK. Soil water storage and respiration were highest under N2 (300 kg·hm -2 ) during key growth stages (V6–VT, VT–R2). N application enhanced organic carbon (up to 59.6% in 300 kg·hm -2 ) and total nitrogen (up to 96.2% in 450 kg·hm -2 ), while decreasing C/N ratio and increasing microbial biomass (up to 78.9% higher in 300 kg·hm -2 vs. CK). N2 (300 kg·hm -2 ) significantly improved maize yield by 63.7%, WUE by 70.9%, and N use efficiency (agronomic efficiency: 25.1 kg·kg −1 ; recovery rate: 41.9%). A quadratic yield model indicated 250–300 kg·hm −2 N as optimal. These findings suggest that moderate N application 300 kg·hm -2 under aerated irrigation enhances soil structure, nutrient availability, and crop productivity, offering a sustainable approach for nitrogen-efficient maize production and red soil management in subtropical regions.