In 2003, the Dordt College Ag Stewardship Center completed a trial begun the year before, when oats was seeded with and without red clover. In 2003, corn was planted on these plots, either with additional nitrogen fertilizer or without. Consequently the trial treatments made a 2×2 grid, (called a 2×2 “factorial”) consisting of the four combinations of nitrogen and clover.
The goal was to determine whether clover would supply sufficient N to the corn. Statistically speaking it did, because there was enough variability in the field that the 9 bushel spread among the treatments could not be distinguished from a random occurrence. Neither the nitrogen factor nor the clover one was significant. Even if the yield differences were “real,” their value would be less than the additional fertilizer and seed costs involved, even at current high grain prices. A similar trial by the Dordt College Ag Stewardship Center in 2000-2001 gave a similar result.