Rock and Roll Agronomy

The Cornerstones of High Yielding Corn

Some are choosing to plant corn with an air seeder. Whatever the planting method, plant population, seed spacing, and uniform emergence are critical

by Jason Hanson, Certified Crop Advisor
jlhanson@agriliance.com

Planting equipment is vastly improved these days, with better no-till seeding ability and fertilizer placement. So it’s not surprising for me to hear that some growers are going to plant corn through some of the latest one-pass type drills or air-seeders.

Still, just because we can doesn’t necessarily mean we should. “A person will pay all season for the sins of planting,” as the saying goes. So what are some of the finer points of corn stand establishment that we need to be mindful of? Let’s look at some data.

The three main components in achieving uniform plant stands in corn – accurate population, uniform seed spacing and uniform emergence – are just so critical for high yielding corn. Corn just cannot recover from a poor stand, which can be defined as one that has a high number of skips or doubles, inter-plant spacing issues, and variable emergence (due to seed/soil contact, soil conditions etc).

Fix the seed skips and doubles
Dropping 24,000 seeds per acre doesn’t really mean much if that stand has too many skips, doubles or even triples. These things are impacted by seeding equipment speed, planter condition and seed size.

The cost of doubles comes two fold. Usually if you can keep the doubles to fewer than 10% then it won’t affect yield much, but it does reduce your population, which might affect fixed type corn more than a flex type corn. The main cost of doubles is additional seed cost. A general guide is that if planter speed is too slow, you encounter more skips; too fast and you run into doubles.

One of the first things to have done is getting a planter – new or used – into good seeding condition. Get worn parts replaced and planter units calibrated . That way, the potential for skips and doubles is reduced.

Air seeder versus planter
One measurement of stand evaluation is your final corn population’s standard deviation, which measures the variability in that stand.  Our field of 24,000 on 30” spacing should have a plant every 8.75” apart, and deviating from that means deviating from our yield potential.

Research at Purdue University shows that for every 1” in standard deviation, there is a 2.5 bu/ac yield loss. In their evaluation of 350 corn fields, the best fields were losing 5 bu/ac and the worst fields up to 21 bu/ac.

So if that’s the deviation we’re getting with a planter, how will it be for an air seeder?  As already noted, seeding equipment is better today than even five years ago. And there are observations and anecdotes of growers using air seeders to plant corn, although we don’t know how the air-seeded corn would compare with corn using a planter without a side-by-side comparison.  Sure, the air-seeded corn might have yielded 100 bu/ac, but by using a row planter, would that same field have yielded 130 bu/ac?

I did some digging on the Web, and did find some observations pertaining to seeding corn. One study involved planting silage corn with both air seeder and planter. The thing that stood out was that when you are planting high populations for silage, the final tonnage wasn’t much different with either piece of equipment. The standard deviation was much higher with the air seeder (11.9 to 14.4”) than the planter (2.1-3.5”). This translated into an estimated yield loss of 25.8 bu for air-seeded corn compared to planter (Penn State, G. Roth, M. Antle and S. Harkcom).

Work conducted at Kansas State University in 1998 used an air seeder that was seeding corn in 7.5” spacing, 15” spacing and two rows planted 7.5” apart on 30” spacing. Here too the issue was intermittent plant spacing and erratic plant stands. Corn planted with the air seeder on 15” spacing averaged 20 bu/ac less than corn planted on 15” spacing with a planter.

When the paired rows with the air seeder were compared to 30-inch planter spacing, the air seeder averaged 9 bu/ac less yield. It was noted that corn planted in either 7.5” or 15” spacing produced yields similar to 30” rows when the population for the air seeder was increased 10,000 plants per acre . The other noteworthy item from the K-State study was the seed-to-soil contact and covering of the seed; stands were 10-20% less.

Uniform emergence is key
The photo at right illustrates the effect of a poor stand. A uniform stand is so important to corn from a yield standpoint. This can’t be stressed enough.

One of the single most important decisions at planting time will be seed depth. We can spend all winter talking about what to do – plant to moisture , plant population, etc – but  it comes down to the settings and adjustments on planting day that matter. That 1.5-2” seeding depth is the most ideal. Some issues with planting too shallow can be slow water absorption and poor nodal root development. Planting too deep can delay emergence and reduce vigor.

Again, make sure that equipment is ready and set to go this spring. Watch for worn openers, make sure residue managers are doing their job and gauge wheels are set.

We really have to watch when planting into heavy wheat residue in no-till situations. A study was done in Ontario comparing vacuum planters, finger planters and an air seeder under different tillage systems. The results were that planter maintenance and mechanisms were more critical when in no-till conditions and when operating speeds were increased.

Planting speed is very critical indeed to uniform emergence, as it affects final depth and the impact our climate conditions will have during planting (see graphic, effect of speed on seed depth). Uniform emergence with the vacuum or finger type planters wasn’t an issue as it was with the air seeder.  An appropriate planting speed can translate into better yield for air seeders as well as planters.   So watch your planting speed, as the temptation to push and “get’er done” can ultimately hurt emergence.

How much maintenance will planting equipment get before it hits the ground?  Will the seed-to-soil contact and planting depth affect our final stands? With more acres going in, will farmers push planting speeds? Will they match up genetics to changing field conditions? Come next October, these might be bigger questions than whether you’re using an air seeder or a planter with corn. 

Hanson is a certified crop advisor, and rocks and rolls near Devils Lake, N.D. as regional agronomist with Agriliance/Croplan Genetics.