Effects of phosphorus side dressing on the phosphorus uptake and utilization and yield of different Brassica napus cultivars

Objectives Reveals the response and differences of different Brassica napus cultivars to the heterogeneous distribution of soil available phosphorus (P) could provide theoretical support for improving the P use efficiency.

Methods Two Brassica napus cultivars, Zhongshuang11 (ZS11) and Shengguang168 (SG168), were used as test materials. Rhizotron and field experiments were conducted from 2019 to 2020 in Wuhan and Wuxue City of Hubei Province, respectively. The tested soil Olsen-P content in rhizotron experiment was 2.75 mg/kg; the field experiments were carried out at a low P fertility field (LP field) and a high P fertility field (HP field), with soil Olsen-P content of 8.65 mg/kg and 17.63 mg/kg, respectively, and the P fertilizer was applied in band. There were three treatments in all the experiments, including no P application (0P/0P), P side-dressing (1P/0P) and homogenous P supply (1P/1P). The plant height, branch number, silique number, 1000-seed weight, seed yield, dry matter accumulation, seed P accumulation and P partial factor productivity were measured at the mature stage.

Results SG168 showed higher plant height, branch number, silique number, seed yield, dry matter accumulation of each organ, seed P accumulation and P fertilizer partial productivity than ZS11 at the treatment of 0P/0P in both rhizotron and field experiments. SG168 showed higher plant height, branch number, seed yield and P fertilizer partial productivity than ZS11 under the same P treatment whether by rhizotron or by field experiments. Additionally, compared with 1P/1P treatment, 1P/0P treatment significantly improved P fertilizer partial productivity of Brassica napus, and the increase of P fertilizer partial productivity of HP field was higher than that of LP field. Compared with 1P/1P treatment, 1P/0P treatment significantly reduced the seed yield of two Brassica napus cultivars in LP field of field experiments. Compared with 1P/1P treatment, 1P/0P treatment significantly reduced the seed yield of ZS11 but had no significant effect on seed yield of SG168 under HP field of field experiments.

Conclusions Heterogeneous P supply could enhance the absorption and utilization of soil phosphorus by Brassica napus, improve contribution rate of soil fertility and P fertilizer partial productivity. SG168 has higher and more stable yield, and higher adaptability to low P than ZS11. The yield-increasing effect of heterogeneous P supply is better in high P fertility field than that in low P fertility field in this study. In high P fertility field of this study, SG168 could maintain seed yield at the half rate of regular P application through local P supply.