4.四水平以上试验的设计4.1多水平正交表的特性和使用施肥量与作物产量一般都不是直线关系。要比较准确地描绘出两者的数量联系,往往需要设置四个、五个或更多水平。常用的四水平正交表有L_(16)(4~5)、L_(32)(4~9)、L_(61)(4~(21));五水平正交表有L_(25)(5~6)、L_(50)(5~(11))等。用 4. The design of more than four levels of testing 4.1 The characteristics and use of multi-level orthogonal table The amount of fertilizer and crop yield are generally not a straight line. To more accurately describe the quantitative relationship between the two, often need to set four, five or more levels. Commonly used four horizontal orthogonal tables have L_ (16) (4 ~ 5), L_ (32) (4 ~ 9) and L_ (61) (4 ~ 21) (5 ~ 6), L_ (50) (5 ~ (11)) and so on. use