You'll have to read the book to get the whole fascinating story of Magruder and the research plots. Despite a number of significant hurdles, amazingly the research is today still being conducted on the same soil Magruder plowed up in the late 1890s, and agronomists at Oklahoma State are still comparing yields of the original "check" plot to new treatments that have been added over the years to study the effects of adding manure or various "synthetic" fertilizers. Here's a modern-day photo of the plot, which as you can see, is now a federal historic landmark.