Abstract: An investigation was made at a doublerice reddish paddy field established in 1982 to study the growth and development and grain yield of early rice and species and biomass of weeds after 30-year application of organic fertilizer, chemical fertilizer, organic and inorganic fertilizer at the same application rates of nitrogen (N), phosphorus (P), and potassium (K) contained in chemical fertilizer and organic fertilizer. The results showed that fertilization promoted the growth and significantly increased the yield of early rice. To some extent, increasing amount of fertilizers and balancing types of fertilizers and nutrients promoted the growth and yield of early rice. On the basis of applying organic fertilizer, applying nitrogen fertilizer in priority, followed by applying phosphate fertilizer, could increase early rice yield in reddish paddy soil. Among all the fertilization treatments, singleorganic fertilizer application had the best effect in increasing the density and promoting the growth of weeds; among all combined application of organic and inorganic fertilizer treatments, balanced combined application had the best effect in promoting the growth of weeds, in particular, suppressing the reproduction of malignant weeds. Compared with organic fertilizer or chemical fertilizer application alone, combined application of organic and inorganic fertilizers generally reduced the diversity, dominance and evenness of weed community in early rice field. Long-term application of chemical fertilizer, especially nitrogen fertilizer played a decisive role in the diversity, dominance and evenness of weed community on the basis of applying organic fertilizer. The weed biomass at the active tillering stage of early rice could represent early rice grain yield to a certain extent.

Key words: barnyardgrass, nitrogen level, physiological characteristic, rice, grain yield