Ever since man started breeding different varieties of crops and comparing them there’s been an effort to describe the differences between those varieties. Some of them might be on the taller side while others might flower earlier. The assessment of how long some varieties take to develop in comparison to others is now termed “relative maturity,” a rating that most every seed company attempts to report in some way.
Relative maturity is most often expressed in days (i.e. days to maturity) since that was historically the easiest way to measure differences in time. This can be a bit of a misnomer, however. On hearing “days to maturity,” most people assume that they can just go ahead and count the days from when they planted to see when they will be harvesting. While this may have worked at some place and at some time, the truth is that relative maturity almost never lines up perfectly with actual days to harvest. Depending on how “maturity” is defined and what the climate is like where the crop is grown, it might be way off.
In more recent years, corn breeders have started measuring corn maturity in “Growing Degree Days/units” rather than just days. You might see this written as GDD to black layer or some other point in crop development in seed catalogues. What makes this method better is that it accounts for how warm it is for each day that the plant is growing. This makes sense since plants don’t grow and develop as well when it is too cold/hot for them.
While the degree day method is better, it’s still far from perfect when it comes to actual crop development. As it turns out, plants are somewhat adaptable in the amount of heat units they need for development depending on how much light they are getting each day, how healthy they are, and how stressed they are. Thus, late-planted corn may be able to mature with fewer degree days than the same corn planted on time.
So, what’s the point of all this rambling about relative maturity in corn? The point is to not get too hung up on relative maturity when you buy your corn seed for next year. Yes, hybrids do differ in maturity relative to one another, but there are enough limitations in this number that it shouldn’t be held up as gospel truth. There is no universal standard for how relative maturity is assessed by seed companies. So, 100-day corn from one company is not necessarily going to mature with 100-day corn from another company. I can also tell you that most corn breeders are more focused on grain maturity than silage maturity. So, what looks like a 100-day corn from a grain standpoint might perform more like a 95-day corn if the stalk tends to dry down quickly.
When the rubber meets the road, the big questions that silage growers need to answer are: “How is the tonnage on my farm?” and “Is the quality (fiber, starch, moisture…) acceptable for the needs of the farm in most years?” The only way to truly assess this is to try different hybrids on your farm and to look at as much of the local silage trial data that you can get your hands on. Of course, seeing what’s working on your neighbor’s farm is a good strategy as well.
— Allen Wilder