Population's Effect

When it comes to corn silage there will always be a debate about which is most important, yield or quality. Let’s be real honest, the “crop” guys say yield and the “cow” guys say quality. The arguments go something like this… Yield is most important: you have to have something to feed. Quality is most important: you can’t just feed “trees”. The truth of the matter is that both are important. There are obvious aspects of both that make sense. Of the two, yield is the most controllable and least variable, so it is the easiest to deal with in a lot of ways. But what if there was one way to meet in the middle so to speak? Over the last two years we have looked at how planting population effects both yield and quality. Here is what we recorded.

In 2014 at Livingston, Wisconsin we planted, harvested, and analyzed two Masters Choice hybrids (MC527 and MC5250) planted at 5 different populations. (18,000, 24,000, 30,000, 36,000, and 42,000 plants per acre) As expected, the greater the population the higher the yield, except for the 42,000 population. It seems that the decrease in yield was an effect of the weather, there was little to no rain from the beginning of July till the end of August. Average yield went from 12 tons acre at 18,000, peaked at 32 tons at 36,000 and dropped off to 20 at 42,000. Quality was measured by milk per ton (MPT). As expected MPT decreased as population increased. The MPT ranged from 3596 at 24,000 to 2948 at 42,000 planting population.

In 2015 we repeated the same trail, but added 2 more hybrids, and broke quality down into two categories, fiber quality and starch quality. We took two samples of each hybrid at each population and averaged the analyses. Average yields followed the same trend as before ranging from 20.44 tons at 18,000 to 25.39 at 42,000. The quality data was more interesting. All the fiber digestibility measurements declined as the population increased. 30 hour NDFd was the most dramatic, ranging from 65.18 at 18,000 all the way down to 56.26 at 42,000. That could equate to a loss of over 5lbs of milk per cow per day.

It really seems to me that there is a happy medium in each case; the quality went down as yield increased, but there was a place where both yield and quality were more than adequate. It was somewhere between 30 and 36 thousand planting population on this farm. My suggestion is to consider why you are planting at the population you are used to. Could there be room to improve quality with out losing yield?