Exogenous plant growth retardants (PGRs) increase yield by reducing lodging occurrence but lower yield if lodging is absent in maize (Zea mays L.). It is hypothesized that PGRs can increase maize yield as well as improve lodging resistance by optimizing application timing. A two-year field experiment was conducted in 2018–2019 using plant growth regulator “Jindele” with active ingredients of ethephon and cycocel (EC; w/w=3:1), lodging susceptible (LS) and resistant (LR) maize hybrids, two plant densities of 60 000 and 90 000 plants ha⁻¹, and four EC application treatments. EC was sprayed at the 8-leaf stage T(8), 15-leaf stage T(15), and both stages T(8 +15), respectively, and no EC application was regarded as control CK. On average, T(8) and T(8 +15) significantly reduced lodging percent compared with T(15) and control due to the optimized morphology and strength of stem and root. Both T(15) and T(8 +15) resulted in a higher kernel number per ear (KN ear⁻¹) than T(8) and CK. In non-lodging conditions, T(15) yielded significantly better than CK, especially for LS hybrid in high plant density of 90 000 plants ha⁻¹ (13,417.4 vs 11,219.2 kg ha⁻¹), mainly as a result of increased kernel number. The increases in yield and kernel number were higher in LS hybrid than in LR hybrid. Both KN ear⁻¹ and KN m⁻² were significantly negatively correlated with internode length. The reduced internode length facilitated assimilate partitioning from leaves to the ear in T(8 +15) and T(15), thus increasing kernel number and weight. Ear-plant height ratio was considered an important parameter to evaluate lodging resistance and yield. The optimal ear-plant height ratios were estimated to be 36.6% for KN ear⁻¹, 39.4% for KN m⁻², and 38.4% for yield. The optimal range of ear-plant height ratio (36.60%39.43%) should be taken into account when breeding or selecting lodging-resistant and high-yielding hybrids as well as developing crop management to cope with lodging in practice.

外源植物生长抑制剂 (PGR) 通过减少倒伏发生来增加产量，但如果玉米 ( Zea mays L.)没有倒伏，则产量会降低。假设 PGR 可以通过优化施用时间来增加玉米产量并改善抗倒伏性。2018-2019 年进行了为期两年的田间试验，使用植物生长调节剂“金得乐”，活性成分为乙烯利和 cycocel (EC; w/w=3:1)，抗倒伏 (LS) 和抗性 (LR) 玉米杂交种，60 000 和 90 000 株 ha ^{-1 的}两种植物密度，以及四种 EC 应用处理。EC分别在8叶期T(8)、15叶期T(15)和T(8+ 15)期喷施，不喷EC作为对照CK。平均而言，与 T(15) 和对照相比，T(8) 和 T(8 +15) 显着降低了倒伏百分比，这是由于茎和根的形态和强度得到了优化。T(15) 和 T(8 +15) 导致每只耳朵的核数 (KNear ^-1 ) 高于 T(8) 和 CK。在非倒伏条件下，T(15) 的产量显着优于 CK，特别是对于 LS 杂种，在 90 000 株高密度的植物 ha ^-1 (13,417.4 vs 11,219.2 kg ha ^-1 ) 中，主要是由于籽粒数量增加。LS 杂种的产量和籽粒数量的增加高于 LR 杂种。KN 耳朵^-1和 KN m ^-2与节间长度呈显着负相关。节间长度的减少促进了 T(8 +15) 和 T(15) 中从叶子到耳朵的同化分配，从而增加了内核数量和重量。穗株高比被认为是评价抗倒伏性和产量的重要参数。估计最佳穗株高比对于 KN 穗^-1为 36.6% ，对于 KN m ^-2为 39.4%，对于产量为 38.4%。应考虑穗株高比的最佳范围（36.60% 39.43%），在实践中应考虑抗倒伏高产杂交种的选育或选育以及应对倒伏的作物管理。