Consequences of a Late Spring Frost on Maize Grain Yield and Plant-to-Plant Variability.

In 2015, southwestern Ontario experienced a late spring frost event on May 23^rd. The nature of the damage was highly variable across the fields, leading to undamaged, killed and frost-damaged maize seedlings adjacent to one another in the field. Triplet sets of plants were identified that differed in whether the plants had been frost-damaged (F), undamaged (U), or were missing (X), for a total of six treatments (FFF, FUF, UFU, UUU, XFX, and XUX), with all measurements being made on the middle plant of the triplet. This study examines the effects that frost damage in general and the resulting plant-to-plant variability have on flowering time, harvest index, grain yield and total plant biomass. Frost damage resulted in delays in flowering of 9-13 days, and significantly affected grain yield and the yield related traits. As expected, the outside plants in the triplet sets did impact the performance of the undamaged plants, with the trend being UUU < FUF < XUX for most of the traits followed in this study. However, in the frost-damaged triplets, there was no effect of the outside plants in the triplet sets, as UFU ≈ FFF ≈ XFX. Our results show that maize plants damaged by a late spring frost sustain substantial yield losses, and that the losses are due to reduced dry matter accumulation, rather than partitioning. Finally, unlike other types of stresses (e.g., plant density, variable emergence) the competitive ability of the frost-damaged plants is compromised.