目的:農民常常的這樣講:“任何好的稻種在一個地方種久了總會變壞。比如‘七擔種’的稻種,在這裏初種的兩三年內,都有五擔到六擔多的收量,但經過幾年後,便減到三擔至四擔了。” 無疑的,這是由於品種的“退化”所引起的滅收現象。值得注意的:這種現象不僅限於農民所栽培的土種,就是在同一地區內經久推廣的育成種也難例外。因此在全國的廣大的稻米產區中,這 PURPOSE: Farmers often say: “Any good paddy grows in one place for a long time and it will always get worse. For example, in the seven or three years, there are five burdens However, after a few years, it was reduced to three burdens to four burdens. ”There is no doubt that this is due to the phenomenon of“ degeneration ”caused by the breeds. It is noteworthy that this phenomenon is not limited to the soil cultivated by peasants, that is, it is no exception to the extended breeding in the same area. Therefore, in the vast rice producing areas in the country, this