Abstract: Five magnesium fertilizer rates were set to study the effect of Mg application on yield and magnesium fertilizer utilization rate of direct-sowing rapeseed（Brassica campestris L.）. The results showed that Mg application could significantly increase the yield of direct-sowing rape（P<0.05）, and the maximum yield was reached at 45 kg/hm² of MgO, and the yield increase was 387 kg/hm² compared with no Mg application, with a yield increase of 18.0%. Also, Mg application increased the biomass proportion of seeds and pods and decreased the proportion of stems. Mg application significantly increased the number of pods per plant and seeds per pod of rapeseed, reaching the maximum at 45 kg/hm² and 30 kg/hm² of MgO, respectively, which increased by 17.8% and 12.1% compared to the treatment without Mg application. Mg application increased Mg content and accumulation in all parts of rapeseed, and the increase of horn sell and grain was significantly greater than that of the stem. The apparent utilization rate of Mg fertilizer tended to increase first and then decrease, reaching a maximum of 21.4% at 30 kg/hm² of MgO, and the agronomic efficiency was greatest at 15 kg/hm² of MgO, which was 11.7 kg/kg. Comprehensively considering yield, nutrient absorption and utilization, Mg application should be emphasized in this area, and the appropriate MgO application rate was 40~45 kg/hm².

Key words: direct-sowing rapeseed（Brassica campestris L.）, magnesium fertilizer application rate, yield, Mg uptake, magnesium fertilizer utilization rate