Hybrid and plant density effects on nitrogen response in corn
The development of corn (Zea mays) hybrids that may be improved for nitrogen use efficiency along with the emphasis on higher plant density for maximum yields of modern hybrids have raised questions about interactions between N rate and plant density for different hybrids. Four corn hybrids (Pioneer 33D49, 33K44, 33W84, and 34F07), chosen to represent a range of responses to N rate and plant density (flex-ear vs. fixed-ear), were planted corn following corn for two years (2011 and 2012) at four sites in Illinois using combinations of three densities (44,460, 83,980, and 123,500 plants/ha) and four N rates (0, 90, 179, and 269 kg N/ha). Weather conditions and grain yields led us to group the data into two sets, consisting of three low-stress and three high-stress environments. Across the three sites that experienced substantial drought stress (Urbana 2011 and 2012, DeKalb 2012), the two lower densities (44,460 and 83,980 plants/ha) produced greater yields (7.4 and 7.0 Mg/ha) than did the highest density (5.2 Mg/ha) across all N rates. There was little yield response to N rates above 90 kg N/ha at the low and high densities, as there was a curvilinear increase until yield plateau at the low density (8.1 Mg/ha at 133 kg N/ha) and the high density (5.9 Mg/ha at 102 kg N/ha). Response to N was greatest at the middle density, as there was a quadratic response with maximum yield at 188 kg N/ha (8.7 Mg/ha). Hybrids responded to density as anticipated, with flex-ear hybrids yielding more than fixed-ear hybrids at the lowest density, and less at the highest density. Across the low-stress environments (DeKalb-2011, Monmouth-2011, and Monmouth-2012), the lowest density (44,460 plants/ha) responded little (+0.3 Mg/ha) to N rates above 90 kg N/ha, while there was greater response to N rates at the middle density (13.5 Mg/ha at 162 kg N/ha) and the high density (13.4 Mg/ha at 174 kg N/ha). Flex-ear hybrids generated greater yields than fixed-ear hybrids at the low density, and produced greater yields overall, while fixed-ear hybrids better maintained yields between the middle and high densities. No support was found for the idea that increasing corn yields requires increases in both plant density and N rate above rates typically used. These results advance our understanding of N rate-plant density interaction within contrasting environmental conditions, but understanding the complexities of hybrid interactions with N rate and plant density will require additional work.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign