Synergistic application of growth regulators and nitrogen is associated with improved maize yield under saline stress through optimized growth dynamics

Ensuring food security by expanding crop production into marginal lands faces the dual challenge of environmental stress and resource limitations. We fitted and evaluated a logistic growth model to quantify how growth regulator (GR) and nitrogen (N) fertilization were associated with maize growth dynamics, nitrogen use efficiency ( NUE ), and yield formation under saline-alkaline stress. Field experiments in southern Xinjiang, China, evaluated three GR concentrations (200-, 500-, and 800-fold dilutions; GR1, GR2, GR3) combined with four N rates (225, 300, 375, 450 kg ha −1 ; N1-N4) under resource-saving magnetoelectric-activated brackish water irrigation. The logistic model achieved close fit ( R 2 = 0.970–0.999) for plant height and dry matter accumulation dynamics. Within the current single-season dataset, GR2N3 increased maximum dry matter accumulation rate ( DMV max ) and average dry matter accumulation rate ( DMV avg ) by 59.34% and 57.50%, respectively, relative to CK, corresponding to a grain yield of 12.35 t ha −1 , which was 54.18% higher than that of CK. An exploratory multiple-regression model incorporating dry matter accumulation, DMV avg, and nitrogen use efficiency explained 97.5% of the yield variation within the current dataset. In addition, DMV avg alone was strongly associated with yield ( R 2 = 0.91). Response-surface analysis ( R 2 = 0.86) estimated a theoretical maximum DMV avg of 1.26 t ha −1 d −1 at a GR dilution of 750-fold and an N rate of 500 kg ha −1 ; because the estimated N rate exceeded the experimentally tested range, this result should be interpreted as a model-derived estimate rather than a validated recommendation. The results provide site-specific, model-based insights into growth–yield relationships under arid saline–alkaline conditions, rather than broadly applicable nitrogen recommendations. The model-derived growth parameters quantitatively demonstrated that yield improvement was primarily associated with coordinated enhancement of growth-rate dynamics, rather than with biomass accumulation alone. These findings provide a quantitative framework for precision maize management and offer an analytical basis for sustainable intensification and food security in saline–alkaline regions.