The question of how far apart corn rows should be planted is not a new one. One has only to go to an equipment auction to see how row spacing recommendations have changed over the years. There is a whopping 82% difference in spacing between an old 36 in. planter and a modern unit with 15 in. rows.
But why is there so much variability in row spacing? Well, the fact of the matter is that corn is a very adaptable plant. It doesn’t need a specific row spacing to perform well. In fact, research has shown that even corn grown at 60 in. spacing can deliver decent yields if the plant population is maintained. Wide row corn research has mostly been focused on providing a solar corridor for interceded crops, but there has also been a recent resurgence in narrow row corn research and interest.
The theory behind narrow row corn is that, at any given plant population, the plants are more evenly distributed throughout the field and compete with each other a little bit less. This allows the crop to have better access to the total amount of sunlight, water, and nutrients available in the field. While this doesn’t necessarily affect forage quality much, in theory, it should mean more yield… and research in the northern latitudes has measured this to be a biomass increase of 0-10% across years and locations (twice as high as for grain). This equates to about a ton of wet forage/acre for most folks. If in-field biomass was worth about $50/ton to you, then you could theoretically get a return of $50,000 in additional corn over the first 1,000 acres of silage corn.
But the benefits of narrow row corn don’t end there. Farmers consistently report better weed control (due to faster canopy closure), reduced erosion, and improved standability. If improved standability is not that important to you, there is also the option to use the improved spacing to push for higher plant populations. This is not required, however, to see a yield benefit.
So, what’s the catch? Well, most silage growers probably don’t have a planter that is set up for 15 in. rows and modern equipment doesn’t come cheap. While the price for the extra row units might not be that overwhelming if you already need a new planter, a multi-directional chopper head may also be required. And then, you have to consider the additional wear and tear of maintaining double the row units over time.
My take is that a narrow row corn planter makes a lot of sense for those growing silage on less than ideal agricultural soils… like those we farm here in the North Country. The improved row spacing really seems to shine in cases where root development might be hindered for some reason, such as a big rock beneath the soil. On the flip side, higher plant populations could be planted in heavier soils that have ample water and nutrient reserves. A narrow row planter is also a great tool for those of us who are limited on land base. A 5% increase in yields means 5% more P removal from the soil. You get more forage, higher manure rates, and less of a chance your soil and nutrients are going to wash away on you!
— Allen Wilder