Improvements in technology can sneak up on us. I was reminded of this recently while reviewing the results of the 2013 National Corn Growers Association Yield Contest, particularly the plant populations of the average entrant compared to the contest winners. Planting and harvest populations were measured for each entrant. Unsurprisingly, the winners had higher populations at both planting and harvest. Average planting population wasn’t much different than many farmers currently plant – about 32,000 seeds per acre – but the population for the winners was much higher: just over 39,000 seeds per acre. This would suggest that with intensive management on good soils, modern corn hybrids have the genetic capability to maximize yields, with at least 20 percent more plants per acre than most farmers use.
Planted versus harvested populations
The other interesting result was the difference between planted and harvested populations. Typically, we figure that about 10 percent of the seed we plant won’t survive due to nongermination, insects, diseases, etc. Back when we used planter box treatments for seed corn, we estimated seed losses at Miner Institute by counting the number of 80,000-kernel units of seed corn we planted, then measuring plant population when the plants were about a foot high.
For two years in a row we wound up with a 9 percent loss, which we thought was very acceptable. However, that was using planter box treatments that farmers mixed with their seed corn. These materials contained a combination of insecticide and fungicide, intended to protect the seed and seedling for the first few weeks after planting. While planter box treatments were fine for the plate-type planters that started to disappear from farms a generation ago, they weren’t designed for today’s plateless and air planters.
A land-grant university agricultural engineering department once did an evaluation of planter box treatments in modern planters and discovered that most of the treatment wasn’t on the seed by the time it was tucked into the furrow. Today’s seed company-applied treatments (Poncho, Cruiser Extreme and several others) adhere much better to the seed and therefore should be a big improvement, albeit one that most of us take for granted.
With this in mind, it was interesting to look at the survival rate for the NCGA yield contest: The average seed survival rate for all entrants was 96 percent, while for the winners it was an unbelievable 100 percent. The actual figures were 39,166 seeds planted per acre and 39,222 plants harvested, suggesting that somewhere during the season the field created some plants, which of course didn’t happen. This was the result of some counting or statistical “wiggle.”
The important point here is that by putting everything together – hybrids, seed treatments, corn planters, soil preparation and crop management – the best farmers have less than a 10 percent loss from planting to harvest, maybe much less.
Long ago, the plant manager of a large seed company told me that the germination percentage stated on the company’s seed tags was usually incorrect; the actual germination percentage was almost always higher. In fact, he said that the seed tags we were looking at were printed before the seed corn was germination-tested because they knew it would be higher than the 95 percent stated on the tag.
Another reason for better stands is modern seed treatments. For proof of this, examine the results of the corn hybrid trials done each year since 2008 by the University of Wisconsin, which include an organic trial with no seed treatment at all. Planted at a rate of 34,100 per acre, seed survival in the several trials where the seed was treated with an insecticide-fungicide averaged 91 percent, while the untreated seed in the organic trials averaged 82 percent survival.
I almost didn’t write this article. Why? Because many farmers leave some yield potential “in the bag” by not planting enough seeds per acre. In these cases their assumption of a 10 percent loss, while actual losses are often less, would probably be a plus. Also, we assume that the farmers entering a national yield contest are a cut above average and have other parts of their corn production program up to snuff. (Of course so do you – we’re referring to your neighbor!)
Seed companies often didn’t recommend a high enough population in their annual seed catalogs, at least not for corn harvested for silage in the northeastern U.S. While this isn’t as common now, I still see some population recommendations in seed catalogs that are lower than what research is showing to be ideal for most situations.
Check final stands this fall
You’ll soon be harvesting your corn, at least corn intended for silage, with grain corn harvest coming some weeks later. It’s a challenge to count plants after grain harvest, but it’s easy following silage harvest.
Assuming a 30-inch row spacing (charts are readily available for other row widths), measure off 17 feet 5 inches of row and count the number of plants in this distance. To make this quick and simple, use a measured piece of baler twine tied to two garden stakes or 20-penny nails. Add three zeros to the count for plant population per acre. Do this in enough places in the field so you’re comfortable that the average approximates the actual population. I recommend at least 10 counts, and more in larger fields. Hopefully there won’t be a lot of variability between counts; if there is, then something went wrong between planting and harvest.
For instance, if you have an average population of 32,000, most individual counts should be between 30 and 34, with only the occasional outlier. If average population is under 30,000, unless the corn is growing in sandy, droughty soils, you could probably increase yields next year by bumping up the population by several thousand plants per acre. Work with your crop consultant or other farm advisor on this.