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(-1)) 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(-1) than at 0 or 60 kg N ha(-1). 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. (c) 2021 Society of Chemical Industry.