Agronomic Traits, Nutrient Accumulation, and Their Correlations in Wheat, as Affected by Nitrogen Supply in Rainfed Coastal Saline Soils

How nitrogen (N) levels affect agronomic performance and the nutrient utilization process in wheat grown in rainfed coastal saline soils remains largely unknown. This study investigated the influence of three N supply treatments (0, 100, and 200 kg/ha) on the growth and accumulation of P, Ca, Mg, K, Na, Zn, Fe, and Se of eight wheat genotypes across two consecutive seasons (2020–2021, 2021–2022) in a rainfed coastal field. Both agronomic performance and nutrient accumulation were significantly affected by N supply and genotypic effects. The increased total accumulation of nutrients was mainly due to enhanced agronomic performance by N supply. Grain Zn and Fe concentrations increased, while the grain Se concentration decreased with the N supply increasing. Genotype “Jimai 775” exhibited both a higher grain yield and a higher nitrogen agronomic efficiency among the tested genotypes. The association among agronomic traits and nutrient accumulation was obviously modified by the N supply, as revealed by principal component analysis, correlation analysis, and stepwise multiple regression models. These findings suggest that both the N supply level and genotypic differences should be taken into consideration to enhance nutrient utilization in wheat cultivated in coastal saline soils.