A field experiment was conducted to assess the impact of cow manure and its vermicompost on the improvement of rice grain yield and quality in Rasht, Iran in 2015 and 2016. The experimental factors were devoted to cow manure (0, 10 and 20 t ha -1 ) and vermicompost (0, 5 and 10 t ha -1 ). The results revealed that the application of cow manure and vermicompost increased leaf chlorophyll and grain yield components such as the number of fertile tillers and the number of grain, but, it decreased

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... 1000-grain weight. The highest grain yield was obtained from the application of 30 t ha -1 cow manure + 10 t ha -1 vermicompost in the first year (3537 kg ha -1 ) and in the second year (3958 kg ha -1 ). In addition, the application of cow manure and vermicompost increased the grain's N, P and K content by 8-20%, 22-23% and 20-33%, but decreased the starch content by 3-7%. Although the combined application of various rates of cow manure and vermicompost improved plant growth and nutrient uptake, the influence of vermicompost on the grain yield and quality of gain was much stronger. In poor areas of the world that experience reduction in rice yield mainly due to lack of soil organic matter, and the farmers cannot buy vermicompost to improve soil fertility, we recommend the combined application of manure and vermicompost, which leads to increased grain qualitative traits and milling percentage, resulting in higher nutritional value of grains and higher grain yield.