Spacing uniformity — Yield effects and in-field measurement

Trials were done to investigate the effects of spacing uniformity on crop yield, and to assess a method of measuring spacing uniformity without the need to calculate the coefficient of variation. Spacing uniformities ranged from perfect to the worst observed in a previous field survey. Improved spacing uniformity gave increased marketable yields, with an improvement of 10% in gross return over the worst uniformity treatment. Such improvements are possible in commercial situations with proper attention to equipment maintenance and calibration and uniformity of seed piece size. Spacing uniformity is often measured by the coefficient of variation, which is derived from the mean and standard deviation of measured seed piece or plant spacings. This is not the best method to use, since the measure of uniformity is referenced to the actual spacing, not the desired or target spacing. The alternative method of assessing spacing uniformity involved counting the number of spaces that lie in a pre-determined “acceptable range” and calculating the percentage of “acceptable spaces”. The necessary calculations are easy if a suitable number (e.g. 40 or 50) of seed piece spaces are used.