Response of Corn to Uneven Emergence

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Abstract
Uneven emergence of corn (Zea mays L.) may occur when soils are dry at the time of planting. This research was conducted in seven environments in Illinois and Wisconsin during a 2‐yr period to measure the effect of uneven emergence on grain yield. Two hybrids (Pioneer Brand 3732 and 3615), chosen to represent differing responses to plant density, were hand planted in early May (E), 10 to 12 after E (M), and 21 to 27 d after E (L) to produce various patterns of among‐row and within‐row unevenness. There was no consistent interaction of hybrid with emergence patten, and responses were quite consistent among environments. Across environments, uniform E, M, and L plantings produced 11.8, 11.1, and 10.4 Mg ha−l, respectively. Uniform E rows bordered by M rows [E(M)] produced 11.4 Mg ha−l, while the other among‐row treatments E(L), M(E), L(E), and M(L) produced 12.2, 10.5, 7.9, and 11.8 Mg ha−l, respectively. The within‐row, repeating patterns of 3E:1M, 1E:1M, 3E:3M, and 1E:3M produced yields of 11.0, 10.7, 10.9, and 10.9 Mg ha−l, respectively, while the 3E:1L, 1E:1L, 3E:3L, and 1E:3L treatments produced grain yields of 10.5, 9.2, 9.4, and 9.1 Mg ha−l, respectively. Comparison of uneven within‐row patterns with incomplete stands showed that in no case did the presence of late‐emerging plants cause yield loss. While uneven emergence decreased yields, these data do not show a yield benefit to replanting in order to attain uniformity, with the possible exception of cases where one‐half or more of the plants are delayed in their emergence by at least 3 wk.

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