The 2009 ASHS Annual Conference

The most appropriate way to compare mixed plantings to pure stands is a matter of debate, but a consensus has emerged that mixed plantings tend to be more productive. Few horticulture extension materials offer practical advice for designing mixed plantings. One exception, a popular series of gardening manuals promoting biointensive production, recommends that plant spacing in mixtures be set to the mean of monoculture spacing recommendations for component crops. In most cases this results in a lower plant density in mixtures than in segregated pure stands, reducing the likelihood of realizing a mixture yield advantage. An improved method for calculating mixture spacing is proposed that sets total plant density in mixed plantings equal to the combined density of segregated pure stands. This method is intended to allow meaningful comparisons of mixtures to pure stands, and increase the likelihood of realizing a yield advantage from mixed planting. The method derives mixture spacing recommendations from monoculture spacing and the proportion of the mixture accounted for by each crop. A mixture spacing calculator that uses the method is available online at http://organic.kysu.edu/CompanionSpacing.shtml.