Where you place the treatment comparison, a product or practice that is compared with one or more other products or practices, is important. Productivity of a field can vary significantly from one edge to the other due to soil type, slope, previous history, etc. Figures 1-3 show how one treatment can have an advantage over another due to field variability.

In our example, field productivity increases from east to west as the soil improves and the slope decreases. Many producers like to split fields in half; however, with this variability, which treatment would you put on which half? A uniform treatment comparison site with the same moisture, soil, and slope would be ideal; however, this is hard to find. What may appear to be a uniform field may have unseen factors influencing variability. (The next section addresses methods for overcoming variability.)

Video: Identifying your question & selecting the site