The concentration of NO−3 in the lower portion of cornstalks at physiological maturity has been proposed as the basis for evaluating the N status of corn (Zea mays L.). Here we refine estimates of the optimal range in NO−3 concentrations for this test by using relevant economic scenarios that include 900 plot‐years of new data as well as 450 plot‐years reported earlier. The results showed that rainfall had little effect on concentrations of NO−3 identified as being optimal. However, calculations showed that optimal concentrations of NO−3 in stalks were influenced by prices of corn and fertilizer. For prices that have prevailed in the Corn Belt during the past decade, an optimal range of 0.7 to 2.0 g NO−3‐N kg−1 was shown to be more appropriate than the range originally reported. When this optimal range is used, the tissue test can be used to identify deficiencies of N as well as excesses of N. Overall, the results show that the end‐of‐season cornstalk test deserves attention as a tool for providing feedback that can be used to compare and refine systems for making N fertilizer recommendations.

Information from the northern Corn Belt comparing tillage systems and corn (Zea mays L.)/soybean [Glycine max. (L.) Merr.] rotations over years is limited. Field studies were conducted near Arlington, WI for 3 yr (1987–1989) on a Plano silt loam soil (fine‐silty, mixed, mesic Typic Argiudoll). The objectives were to determine the influence of tillage, N fertilizer level, and hybrid/cultivar on growth and grain yield of corn and soybean grown in various rotation sequences. Yields of both corn and soybean declined with consecutive years of monocropping, but only soybean had 15% lower yields with annually alternating corn and soybean than for the 1st yr of production following several years of the other crop. For the least “monocropping‐sensitive” hybrid (Pioneer 3737) or cultivar (BSR 101) evaluated and for either corn hybrid under conventional tillage (CT), the yield benefit of 1st yr compared to continuous cropping was similar for corn and soybean at about 15%. But with corn hybrid DeKalb 524 under no‐till (NT), and the brown stem rot (BSR) (caused by Phialophora gregata) susceptible soybean cultivar in 1987 and 1989, yields were more than 25% higher for 1st yr crop production. Average NT yields were similar to CT for both crops with 1st yr or alternate corn and soybean, but yields were usually lower under NT with monocropping.

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