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

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 PO ha) and four B application rates (0, 4.5, 9 and 18 kg NaBO·5HO ha) 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 (PB or PB). Balanced B and P applications benefitted yields. The PB treatment produced greater seed yield and PUE than the PB treatment, and the PB treatment produced greater seed yield and PUE than the PB treatment. Sequencing of 16S rRNA genes revealed that the PB treatment had greater soil bacterial diversity, and a different bacterial community composition, compared with the PB or PB 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.