Delaying the application of N to corn (Zea mays L.) may help to match N supply to N uptake, but may also increase the risk of yield loss if N is applied too late or N uptake is delayed. In a 3-yr study with corn following soybean [Glycine max (L.) Merr.] (SC) and corn following corn (CC), N application was either split, with half (112 kg N ha^–1) at planting and the rest at stages ranging from V3 to R3; or with the entire increment (224 kg N ha^–1) applied at these stages. In SC, there was no yield loss from delaying application of the second increment of N to as late as R3, but yields declined as the full increment of N was delayed, by 5% at V9 to 34% at R3. In CC, delaying the second N increment to stage R2 or R3 lowered yield by 5% compared to application at V3, and delaying the full increment of N increasingly lowered yield, by 8% at V6 to 40% at R3. Corn able to recover leaf chlorophyll content (SPAD) following delayed N application produced full yields, and cumulative N deficiency (CND, ΔSPAD × delay expressed as modified growing degree days over periods with ΔSPAD>0, SPAD-MGGD) was linearly correlated with yield loss. With half of the N at planting, the remainder could be delayed to R1 or later without yield loss, but without N at planting, N needed to be applied before stage V9 in SC and before stage V6 in CC in order to assure maximum yield.

中文翻译：

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延迟施氮导致的缺氮和玉米产量

延迟向玉米（Zea mays L.）施氮可能有助于使氮供应与氮吸收相匹配，但如果施氮过晚或氮吸收延迟，也可能增加产量损失的风险。在一项为期 3 年的玉米跟随大豆 [ Glycine max (L.) Merr.] (SC) 和玉米跟随玉米 (CC) 的研究中，施氮是分开的，一半（112 kg N ha ^–1）在种植和其余的阶段从 V3 到 R3；或整个增量 (224 kg N ha ^–1) 应用于这些阶段。在 SC 中，延迟第二次施氮至 R3 没有造成产量损失，但随着 N 完全增量的延迟，产量下降，从 V9 的 5% 到 R3 的 34%。在 CC 中，与 V3 阶段的施用相比，延迟第二次 N 增量到阶段 R2 或 R3 使产量降低了 5%，并且延迟 N 的完全增量会逐渐降低产量，从 V6 的 8% 到 R3 的 40%。在延迟施氮后能够恢复叶片叶绿素含量 (SPAD) 的玉米可实现全产，累积 N 缺乏（CND、ΔSPAD × 延迟表示为 ΔSPAD>0 期间修正的生长期天数，SPAD-MGGD）与产量线性相关损失。播种时施入一半的氮，其余的可以推迟到 R1 或更晚，而不会造成产量损失，但播种时没有施氮，