Field experiments were carried out to study the effect of potassium application on winter rapeseed in the Yangtze River Valley and further to explore approaches of increasing rapeseed yield and improving potassium use efficiency.Data from 72 field experiments were collected across 10 main rapeseed production provinces in the period of 2004/2005~2006/2007 in this paper.The yield increasement by potassium application and yield increase rate,partial factor productivity,agronomic efficiency,physiological efficiency and apparent recovery efficiency were calculated in order to provide basis for the increase.The results indicated that application of potassium fertilizer increased winter rapeseed yield significantly.Average seed yield increment would reach to 349 kg·hm-2 compared with no potassium treatment,with the yield increased rate of 19.8%.However,there were 20.8% of the experiments showed little yield increase (i.e.,yield increase rate lower than 5%) with potassium fertilization.The study showed that yield increase rate declined with the increase of soil available potassium content.Apparently,soil potassium accumulation rose with potassium fertilization,with an increase of 38.1% as compared with the treatment with no potassium fertilization.The results also showed that the mean values of PFP,AE,PE and RE by potassium fertilization were 21.1 kg·kg-1,2.9 kg·kg-1,8.5 kg·kg-1 and 46.7%,respectively.The results suggest that applying potassium fertilizers would improve aboveground biomass of winter rapeseed and potassium accumulation,thus increase the seed yield significantly.Therefore,both soil fertility and the regular pattern of demand for potassium should be considered in the regional fertilization strategy.