Abstract
Mustard is a high-nitrogen-sensitive leafy vegetable, whose growth and yield are highly susceptible to inappropriate nitrogen (N) availability. Conventional mustard production depends on frequent urea topdressing, which causes asynchronous N supply and crop uptake, low nitrogen use efficiency (NUE), nutrient leaching and high labor input, restricting simplified efficient cultivation. Controlled-release blended fertilizer (CRBF) combines fast-acting conventional urea and slow-release coated urea to match soil N release with crop N demand, wherein conventional urea satisfies seedling N requirements and coated urea sustains N supply throughout growing season. Single basal CRBF application serves as a promising labor-saving alternative to traditional split fertilization. Nevertheless, the optimal ratio of conventional urea to coated urea and comprehensive effects of single CRBF application on crop performance and soil microecology remain unclear. In this study, a field experiment was conducted with six treatments: no N (CK), conventional urea (U), and four CRBF ratios with coated urea proportions of 30% (CRU1), 50% (CRU2), 70% (CRU3), and 100% (CRU4). We evaluated crop physiology, soil properties, microbial community, NUE, yield and economic benefits. One-way ANOVA, PCoA, Mantel test and PLS-PM were used for statistical analysis. The results showed that CRU3 achieved the optimal comprehensive performance. Compared with split urea application (U), CRU3 significantly increased leaf stomatal conductance and transpiration rate, and elevated the activities of leaf NADH-GOGAT and GDH by 39.59% and 15.06% at most, which promoted vegetative growth of mustard. In terms of soil environment, CRU3 raised soil ammonium nitrogen, catalase and urease activities by 61.25%, 20.16% and 55.56%, respectively, increased the relative abundance of beneficial ammonia-oxidizing archaeon Crenarchaeota by 96.85%, and reduced the pathogenic fungus Olpidiomycota by 17.56%. Benefiting from improved crop physiology, soil nutrient supply and microecological conditions, CRU3 increased mustard yield, NUE and economic returns by 6.66%, 13.96%, and 8.11%. In conclusion, single application of CRBF with a 30:70 blending ratio of conventional urea to coated urea is an efficient and sustainable N management strategy for mustard cultivation. This practice coordinately improves crop productivity, nutrient use efficiency and soil microecological health, providing reliable technical basis for simplified, green and high-efficiency mustard production.