Effect of balanced application of boron and phosphorus fertilizers on soil bacterial community, seed yield and phosphorus use efficiency of Brassica napus

Highlights: • Balanced application of B and P fertilizers increases soil bacterial diversity. • Appropriate B and P combination has a positive synergistic effect on PUE and seed yield of rapeseed. • The positive synergistic effects differ among rapeseed cultivars. • About 1 Na₂B₄O₇·5H₂O: 10 P₂O₅ in the field experiments reported here improves seed yield of rapeseed. Rapeseed (Brassica napus L.) is extremely sensitive to both boron (B) and phosphorus (P) deficiencies. Application of chemical fertilizers is generally considered to be an effective agronomic practice to improve crop productivity, and it also affects soil bacterial community. However, there are few studies of the effects of balanced B and P fertilizer applications on crop yield and bacterial communities. In the present study, field experiments with five P application rates (0, 45, 90, 135 and 180 kg P₂O₅ ha⁻¹) and four B application rates (0, 4.5, 9 and 18 kg Na₂B₄O₇·5H₂O ha⁻¹) were conducted in 2016–2017 and 2017–2018 to investigate their effects on seed yield and P use efficiency (PUE) of B. napus. The smallest seed yields were obtained when B or P fertilizers were not applied (P₉₀B₀ or P₀B₉). Balanced B and P applications benefitted yields. The P₄₅B_4.5 treatment produced greater seed yield and PUE than the P₄₅B₁₈ treatment, and the P₁₈₀B₁₈ treatment produced greater seed yield and PUE than the P₁₈₀B_4.5 treatment. Sequencing of 16S rRNA genes revealed that the P₉₀B₉ treatment had greater soil bacterial diversity, and a different bacterial community composition, compared with the P₉₀B₀ or P₀B₉ treatments. Overall, our results underline the importance of balanced B and P nutrition for maximal seed yield of B. napus and the effects of B and P fertilizers on the soil bacterial community of B. napus.