Genotypic differences in the synergistic effect of nitrogen and boron on the seed yield and nitrogen use efficiency of Brassica napus.

Background: Rapeseed (Brassica napus) is highly sensitive to nitrogen (N) and boron (B) deficiency; however, the synergistic effects of these elements on rapeseed production are poorly understood. The aim of this study was to investigate the effects of co-application of N and B on seed yield, N uptake and N use efficiency (NUE) of rapeseed. Three rapeseed cultivars (W10, ZS11 and HG) were treated with different N and B application rates, and the seed yield, N uptake and NUE were examined in 2-year field experiments.

Results: The application of B fertilizer (4.5, 9 kg borax ha ) improved N uptake, NUE and seed yield. However, the magnitude of increase in seed yield by B fertilization was dependent upon the rate of N supply and genotype. The benefit of B was much greater at 180 kg N ha than at 0 or 60 kg N ha . The combination of N and B also improved N remobilization from sources (stems and husks) to sinks (seeds) and increased N recovery efficiency (NRE). Compared with the B-inefficient cultivar W10, the B-efficient cultivars ZS11 and HG were superior in growth, seed yield, N uptake and NUE on B deficient soils. Furthermore, B-efficient cultivars showed great potential in saving N input, and the yield increased by more than 40% under B deficiency conditions.

Conclusion: This study highlights a markedly synergistic effect of N and B nutrition on rapeseed NUE and yield production and shows that B-efficient genotypes can increase yield and reduce N inputs under B-deficient conditions. © 2021 Society of Chemical Industry.