[Objective] Understanding of the restrictive factors that can reduce rapeseed (Brassica napus L.) yield and the reasonable direct sowing density of later sown rapeseed is the key for optimizing rapeseed cultivation and management under the condition of no-tillage. [Method] A field experiment was conducted to study the differences in condition of soil compaction and weed growth between no-tillage and conventional tillage and the effect of tillage methods on rapeseed growth, nutrients uptake and yield. At the same time the effect of different direct sowing densities on growth and nutrients utilization of rapeseed were also studied.[Result] The soil bulk density of no-tillage was significantly higher than conventional tillage. In the whole growth period of rapeseed, the soil bulk density of no-tillage was 0.11 g.cm-3 higher than conventional tillage, averagely. Compared with conventional tillage treatment, no-tillage was in favor of weed development, the N, P, K nutrient rates absorbed by weeds in no-ti11age treatment were, respectively, 1.9, 2.4 and 2.5 times as that of conventional treatment. Compared with conventional tillage treatment, dry matter accumulation rates and N, P, K uptake rates of rapeseed of no-tillage treatment decreased averagely by 18.2％, 17.1％, 16.4％ and 20.2％ in the whole growth period, respectively, the yield of no-tillage treatment decreased by 10.7％, and the difference was significant. The result of direct sowing density experiment showed that compared with low sowing density treatment, total weed amount and dry matter rates of weeds of high sowing density treatment decreased by 40.5％ and 56.4％, respectively; while dry matter accumulation rates and N, P, K uptake rates of rapeseed of high sowing density increased averagely by 55.3％, 46.7％, 53.6％ and 50.2％ in the whole growth period, respectively, and the yield of high sowing density increased by 43.1％. [Conclusion] It is concluded that under the condition of no-tillage, soil compaction and too many weeds are two serious problems, which led to decrease of rapeseed yield. Increasing direct sowing density of rapeseed under the condition of no-tillage is a very effective method to increase yield when direct sowing date is later, while in this experiment the most reasonable direct sowing density was 6×l05 plant/hm2.%[目的]研究免耕对油菜生长的影响,并初步了解导致免耕油菜产量降低的障碍因素,同时探讨晚播条件下免耕直播油菜的适宜直播密度.[方法]采用大田试验,比较免耕和翻耕条件下土壤紧实状况及杂草发生情况的差异,以及耕作方式对油菜生长,养分吸收和产量的影响,同时探讨免耕油菜在不同种植密度下的生长特点及其养分利用状况.[结果]免耕条件下土壤容重明显高于翻耕,整个生育期二者平均相差0.11 g·cm-3.与翻耕相比,免耕油菜田杂草生长量大,导致养分竞争加剧,杂草对氮、磷、钾的吸收量分别为翻耕处理的1.9、2.4和2.5倍.免耕条件下整个生育期油菜的干物质积累量及氮、磷、钾养分吸收量分别比翻耕处理降低了18.2%、17.1%、16.4%和20.2%.在种植密度为30万株/hm2时,与翻耕相比,免耕处理油菜籽减产10.7%.密度试验的结果表明,与低密度处理(30万株/hm2)相比,高密度处理(60万株/hm2)的杂草数量及干物质积累量分别降低了40.5%和56.4%,而整个生育期油菜干物质积累量及氮、磷、钾的养分吸收量则分别平均增加了55.3%、46.7%、53.6%和50.2%,油菜籽产量也提高了43.1%.[结论]油菜在免耕条件下会出现土壤紧实度大、根系生长和养分吸收受抑以及杂草过多竞争养分的现象,从而导致了产量降低.而在晚播条件下增加直播油菜的种植密度是提高油菜籽产量的有效途径,本研究中适宜的直播密度为60万株/hm2.
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