Abstract
The effects of green manure fertilization (Chinese milkvetch) and pesticide application on the grain yield of early maturing rice variety were examined for 17 successive years in the paddy field of Shizuoka University. Green manure without pesticide (only weeds were removed with a weeder and by hand ;GM) were applied from 1993 to 2009, green manure and pesticide (GMP) from 1999 to 2009, chemical fertilizer and pesticide (CFP) from 1993 to 2009. According to weather fluctuation and the damage by rice stem borer from 1993 to 2000, the average rice grain yield in the GM plot during this period was 409 g m-2, while that during the nine years after 2001 was 466 g m-2, which was the same as that in the GMP plot (468 g m-2). On the other hand, the average rice grain yield in the CFP plot was 517 g m-2 from 1993 to 2000 and 539 g m-2 after 2001. The biomass yield of Chinese milkvetch was decreased by the feeding by the exotic insect in the GMP and GM plot in 2006, 2007 and 2009. Thus, the average biomass yield in the GM plot during those three years was 414 g m-2, although that in the other years was 493 g m-2 which was 93% of that in the CFP plot. A close positive correlation was observed between the amount of Chinese milkvetch applied and the rice grain yield. Therefore, the effect of the application of Chinese milkvetch was retarding of early growth of rice.
