Killing a weed isn’t as simple as spraying herbicide on it when you consider the unintended consequences in agricultural systems. While the herbicide may kill the weed as intended, it also may contaminate ground and surface waters or kill field edge vegetation that is beneficial in creating a barrier against invading plants. Considering multiple variables and effects of agricultural practices leads to better management decisions. 

The current issue of the journal Weed Technology introduces the spider plot—a graphical approach for evaluating multiple variables and tradeoffs in agriculture. The authors of the article also discuss applying this tool in the case study exercise of an educational workshop. 

Unintended effects of an agricultural method—weed control, tillage, rotation of crops, or planting of cover crops, for example—can be difficult to measure. These effects might manifest at a later time or at another site. Multiple variables make a decision less straightforward than it might seem. 

If the variables are considered beforehand, better decisions can be made or tradeoffs can be found that minimize potential impacts. Tools that facilitate the conceptualization, evaluation, and visualization of multiple variables can assist in learning. One such visual representation is the spider plot. 

A spider plot contains three or more axes, each representing a variable and sharing a common origin. Data are plotted on the axes, and data points are connected with a line. The size and symmetry of the resulting spider web indicates the relative magnitude of each variable and the overall performance of the system. 

The spider plot was introduced at an educational field-day workshop attended by farmers, agriculture professionals, and students. The activity was designed to illustrate the multifunctionality of cover crops planted to suppress weeds or improve soil quality, showing participants that further variables, such as the type of cover crop, might play a role. The authors suggest the spider plot as a useful tool for weed science education and extension programs.

Full text of the article, “Assessing and Visualizing Agricultural Management Practices: A Multivariable Hands-On Approach for Education and Extension,” Weed Technology, Vol. 25, No. 4, 2011, is available at