What is field history worth for fertility? Field history was important to several trials in 2002. The Dordt College Agricultural Stewardship Center raised corn on ground that in 2001 had grown either oats alone or oats with a red clover underseeding. To some of the 2002 corn they applied 197 lbs of anhydrous ammonia nitrogen, and the rest of the corn received no additional N. This gave them four different treatments based on the combination of the clover possibilities and the two fertilizer levels: no clover and no fertilizer (the control treatment); clover but no fertilizer; fertilizer but no clover; and both clover and fertilizer. Table 3, shows yields and economics for these four treatments as well as for the clover factor and the fertilizer factor separately. When no nitrogen fertilizer was applied, the previous year’s red clover significantly increased yields and profitability. When nitrogen fertilizer was used, the history of red clover did not increase corn yields, but it increased fall corn stalk nitrate by 1,000 parts-per-million (ppm) nitrate -N, demonstrating that the red clover provided quantities of nitrogen to the following corn. The end-of-season stalk nitrate test is a tool that allows producers to balance fertilizer and other sources of N.
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