Abstract: To explore the effect of preceding cover crops on winter oilseed rape (Brassica napus L.) in Guan⁃
zhong Plain in China, a 2-year completely randomized experiment was carried out to study the impact of preceding
cover crops. Soil nutrient content, aboveground dry matter accumulation and allocation, nitrogen and phosphorus ac⁃
cumulation, seed yield and its components of winter oilseed rape were investigated. The test consisted of 4 treat⁃
ments: SW (soybean as preceding cover crop), HW (hairy vetch as preceding cover crop), MW (maize as preceding
cover crop), FW (fallow without preceding cover crop, control). Results showed that the SW and HW treatments sig⁃
nificantly improved soil alkali hydrolyzed nitrogen, nitrate nitrogen, ammonium nitrogen and available phosphorous
content compared to FW. Among the leguminous treatments, SW treatment has the most obvious effect of increasing
soil nutrient content. The soil nutrients of MW were lower than those of FW treatment. In contrast to FW, SW and
HW significantly improved annual dry matter accumulation by 26.05%, 13.12%, nitrogen accumulation by 30.86%,
14.86% and phosphorus accumulation by 37.03%, 20.35% respectively, while MW was 2.74%, 12.76% and 3.48%
lower respectively. Compared to FW, SW and HW treatments significantly increased annual seed yield by 29.48%
and 17.77% respectively. MW treatment had no significant effect on seed yield. Correlation analysis showed that the
significant effect of improving seed yield of SW and HW treatments was due to the increase of soil nutrient, aboveg⁃
round dry matter accumulation, nitrogen accumulation, phosphorus accumulation as well as pods per plant. The
above results suggested that soybean and hairy vetch might be the reasonable choice of preceding crop for winter oil⁃
seed rape. Meanwhile, soybean could be recommended as the best feasible preceding crop to optimize seed yield, ni⁃
trogen and phosphorus accumulation for winter oilseed rape in Guanzhong Plain in China.

Key words: winter oilseed rape (Brassica napus L.), preceding cover crops, seed yield, dry matter accumulation, nutrient accumulation