Can anybody introduce me the backgroud information about this paragraph "Sarah stayed two weeks at Sunnybrook Farm. There she learned to love old Farmer Franklin’s son, Walter. Farmers have been loved and wedded and turned out to grass in less time. But young Walter Franklin was a modern agriculturist. He had a telephone in his cow-house, and he could figure up exactly what effect next year’s Canada wheat crop would have on potatoes planted in the dark of the moon."-from Springtime à la Carte(by O.Henry)

Why did the author mention that "he could figure up exactly what effect next year’s Canada wheat crop would have on potatoes "?

What is the background behind this ?