In the past, the industry standard for collecting field scale performance data was that the company would hand out free product for producers to try on their farms and hope it gets taken to harvest. All too often, the producer was under a time crunch at harvest, which resulted in the field being harvested together. The outcome was that there was no data for the company.
More times than not producers will split a field in half to compare treatments. There are many factors that make this an unfair comparison. Leaving everything the same, there can be major yield differences from one side of a field to the other due to soil texture, topography, field history etc.