Multiple applications of N fertilizer on corn (Zea mays L.), with the last application as late as tasseling (VT) or early reproductive stages, is regarded as having potential to lower N requirements or to increase yields, or both. To test this, we conducted trials with N rates ranging from 0 to 280 kg N ha⁻¹, applied at or near planting (early), or with 56 kg N ha⁻¹ retained and dribbled near the row at VT stage (late split). Averaged across eight trials with corn following soybean [Glycine max (L.) Merr.], economically optimum nitrogen rate (EONR) values were 159 and 169 kg N ha⁻¹ for early and late‐split N, and predicted yields at the economically optimum nitrogen rate (Y_EONR) were identical, at 14.8 Mg ha⁻¹. The net return to nitrogen (RTN) at the EONR averaged $537 ha⁻¹ for early N and $525 ha⁻¹ for late‐split N. Averaged over six trials with corn following corn, EONR values were 171 and 170 kg N ha⁻¹, Y_EONR values were 14.1 and 14.0 Mg ha⁻¹, and RTN values were $745 and $731 ha⁻¹ for early and late‐split N, respectively. Within each set of trials, t tests revealed no significant differences due to N timing on EONR, Y_EONR, or RTN. With little or no agronomic benefit and added costs for late application, applying late‐split N is unlikely to be profitable in productive Corn Belt soils.

中文翻译：

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玉米对后期氮肥的产量响应

在玉米（玉米（Zea mays L.））上多次施用氮肥，最后一次施用是在抽穗期（VT）或生殖早期，这有可能降低氮需求量或提高产量，或两者兼而有之。为了测试这一点，我们进行了氮肥施用量介于0到280 kg N ha ^-1的试验，在种植时或临近种植时（早）施用，或者在VT阶段保留和浇灌56 kg N ha ^-1并排在行附近（后期分裂）。 ）。在大豆之后的八项玉米试验中平均得出[ Glycine max（L.）Merr。]，早期和后期分裂氮的经济最优氮率（EONR）值分别为159和169 kg N ha ^-1，并预测经济上的单产最佳氮率（Y _EONR）是相同的，在14.8 Mg ha ^-1。EONR早期氮的净氮净回报（RTN）平均为537 ha ^-1，后期分裂N的平均净氮为525 ha ^-1。在玉米之后的六个玉米试验中，EONR的平均值为171和170 kg N ha ^-1，早期分裂N和晚期分裂N的Y _EONR值分别为14.1和14.0 Mg ha ^-1，RTN值分别为$ 745和$ 731 ha ^-1。在每组试验中，t检验均未显示由于EONR，Y _EONR上的N个计时而造成的显着差异或RTN。由于几乎没有农艺效益，也没有增加后期施用的成本，因此，后期分裂施用N在生产性玉米带土壤上不太可能有利可图。