RELIABILITY OF THE KERNEL MILKLINE METHOD FOR TIMING CORN-SILAGE HARVEST IN OHIO

The position of the kernel milkline (ML) has been recommended as a rel iable guide for determining the optimal time to harvest corn (Zea mays L.) for silage, This method has not been tested adequately in the cen tral and eastern Corn Belt, and the effect of planting date on variati on in whole plant dry matter (DM) content at different ML stages is un known. The objective of this research was to determine the variation i n whole plant DM content at different kernel ML stages of corn grown i n Ohio. Three hybrids representing early, mid, and full season maturit ies for central Ohio were planted on or about 1 May, 21 May, and 10 Ju ne 1992 and 1993, Kernel ML stage and whole plant DM content were dete rmined every 3 to 7 d beginning at full dent (FD) stage until ML disap pearance. Kernel ML stage and whole plant DM content were positively c orrelated (r = 0.89), On average, the kernel ML would have been an exc ellent indicator of when to harvest corn for silage; however, we found considerable variation in plant DM content within a given ML stage fo r individual sampling dates from all hybrids and environments, Variati on in DM content was present regardless of year, planting date, or hyb rid. Although corn was more likely to be at an ensilable DM content at certain stages than others, the variation in plant DM content within a stage was sufficient to raise concern over the reliability of the ke rnel ML method for determining when to harvest a particular field for silage in Ohio, Gravimetric determinations of plant DM content should he used to confirm when corn is at the optimal DM content for ensiling , Corn silage growers in Ohio should begin making gravimetric determin ations of plant DM content at FD for conventional tower or bunker silo s, and 1/4 ML for sealed (oxygen-limited) tower silos.