A critical analysis of "harvest index"
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The many ways in which harvest index ratio (HI) can be used are discussed. A selection of published values for HI are given. Attention is drawn to the confusion in calculating the HI such that some present methods of assessing HI may distort the results. Despite the claims made for HI, and its widespread use throughout much of the literature, its use in some cases is superfluous and may obscure some kinds of information. As a ratio, it is subject to error in both components, and is most unlikely to be normallly distributed, so that normal analysis of variance will not be valid. A farmer needs to know the probability of achieving a given margin of returns over costs rather than unnecessarily knowing or quoting a HI. Suggestions are made as to when and where to use the HI. Emphasis is placed on adopting percentage increase of response between yields rather than using HI.