Ultra‐High Plant Populations and Nitrogen Fertility Effects on Corn in the Mississippi Valley

Abstract

Populations for high yield and low mycotoxin levels in furrow‐irrigated corn (Zea mays L.) have yet to be firmly established for the Midsouth USA. Preplant N applications compared with a split application and the effects on yield, yield components, and mycotoxin levels were also examined. Experiments were conducted at Site WR (102‐cm‐wide rows, Beulah fine sandy loam) and Site NR (76‐cm‐wide rows, Dundee silty clay). Plant densities of 71760, 82160, 92560, and 102960 plants ha−1 were grown in eight‐row plots, 9.1 m long at both sites. The N fertility treatments were 112 kg N ha−1 preplant, 224 kg N ha−1 preplant, and 112 kg N ha−1 preplant + 112 kg N ha−1 sidedressed at V6 (six leaves). Yields at Site WR did not differ among populations. Maximum yields at Site NR were at 71760 plants ha−1 (10.3 Mg ha−1) and then declined (b = −0.5065). Kernels per ear declined (b = −40.09 and b = −42.69), kernel weights declined (b = −0.4328 and b = −0.8172), and stalk lodging increased (b = 0.0103 and b = 0.0251) with increased populations for Sites WR and NR, respectively. These and previous data place the maximum population for corn in the Midsouth at about 70000 plants ha−1. No differences in yield occurred between the 224 kg N ha−1 preplant treatment and the split application of N. Yields were generally less with 112 kg N ha−1 per‐plant only. Aflatoxin and fumonisin levels at both sites were unaffected by plant population of N fertility.