New corn growers must stress variety selection, seeding rate, nitrogen use

How well farmers fare with new or expanded acreages of corn may come down to three critical factors that have changed dramatically from growing corn a decade or more ago, according to North Carolina State Corn Specialist Ronnie Heiniger.

Selecting the right hybrid, choosing the optimum seeding rate and managing nitrogen are three factors critical to growing corn in the Southeast and are among production practices that have changed the most over the past 10-12 years.

Variety selection is always the first step in planting a crop and with corn hybrids changing so dramatically over the past few years, it will be a challenge for new growers to not only select the right variety, but find adequate seed in a specific variety.

Growers who bought seed back in February probably had no problems, but those who waited late to make the decision to go to corn or increase corn acreage may be in a position of planting hybrids not well suited to their land.

Today's hybrids have better drought tolerance, increased stay green ability and early maturity than varieties grown 10 years ago. If these characteristics are combined in hybrids that have the Bt gene to give some tolerance to corn ear worms and corn borers, the corn plant's ability to survive and thrive under greater stress will be increased, according to Heiniger.

These new more drought tolerant hybrids will help on marginal lands, but there is no way around the fact that corn needs water, Heiniger stresses. If a grower puts corn on land prone to drought stress or poor water utilization they should not expect high yields of corn — no matter what variety they plant.

With much of the additional corn acreage going in on marginal soils that are not ideal for corn production, choosing a hybrid with more stress tolerance is a first step in setting a grower up for success on these less than ideal soils. Much of this land was planted to cotton because it was a higher risk for corn. Since the onset of minimal-tillage and Roundup Ready varieties in the mid-1990s, and the subsequent increase in cotton acreage, significant advances have been made in corn hybrids.

A look at variety tests is a first good step in selecting the optimum hybrid for a particular farm. Then, look at varieties over the past three years which have been in the top 10 in yield and quality. Compare this to years in which you have had stress and determine which varieties did well under stress situations.

“By looking at variety performance over a period of years and in different locations a grower gets a couple of different perspectives on risk, because you are considering which hybrids performed well statewide, but you are also getting a better idea what the risk is in planting a particular variety in a particular place,” Heiniger explains.

Local information also can help in choosing the right hybrid. Some counties still have ag agents who conduct local tests. And, most seed companies have good information on specific varieties. There is plenty of information out there that is routinely used by corn growers, but may not be so evident to growers who haven't grown corn in recent years or ever, Heiniger says.

Once a grower selects a good hybrid, they are ready to position that hybrid to their best advantage. “By positioning, I mean putting it in a maximum plant population that your environment can sustain. This shift to higher plant populations, I believe, is the primary reason we have seen corn yields going up in recent years,” Heiniger says.

If a grower has been out of corn for a decade, the yield potential today would have been astronomical then, and the average would have been outstanding yields. If a grower made 150 bushels per acre, that was a big corn crop 10-15 years ago. Now, it's the national average.

In North Carolina, Heiniger points out the average corn yield has increased to 134 bushels per acre in 2006, and has increased by about three bushels per acre over the past few years.

Growers set up on 38-inch rows are limited to how far they can go with maximizing plant populations. The Rule of Intra Competition comes into play, Heiniger says. He explains, if corn plants are closer than four inches apart, root systems compete with each other and one plant will put on a smaller ear. On 38-inch rows, growers are limited to how many plants they can actually get out there before plants get into this intra competition, Heiniger stresses.

“I've talked to growers who have grown 4,000-5,000 acres of cotton, and they are taking half or more of that land out of cotton and planting corn. In cases like that, then it is economical to shift row spacing to 20-24 inches. A planter set up like that would work well with both corn and soybeans,” Heiniger says.

In some counties in southern North Carolina, where herbicide resistance is an issue, we are expecting to see 40-50 percent of cotton acreage go to other crops. Corn is the logical other crop, though soybeans and wheat also can be profitable,” Heiniger says.

“Under ideal soil conditions, with irrigation to assure adequate moisture, corn plants at 5-6 inch row spacings are set up for maximum growth and yield. On cotton land that is marginal for corn, the soil won't support closer plant spacings. For new growers, I recommend starting out with a plant population of 25,000 to 27,000 plants per acre, which is higher than they used to grow 10-15 years ago.

“Growers have to get their mind around this plant population issue. In cotton, plant population isn't so important. If a grower switches large acreage from cotton to corn, they have to look much more closely at plant populations, if they want to achieve high yields,” Heiniger says.

If a grower is used to planting corn as a rotation crop with cotton, hoping to break even, then plant population may not be so important. If a grower is looking at corn as a high income main crop, then he has to address the plant population issue. At better than $4 per bushel most farmers have elevated corn from second or third to first crop.

The price of corn has risen and stayed at near records, the price of nitrogen and other fossil-fuel-based fertilizers have increased even more dramatically.

Even at $4.20 per bushel, poor nitrogen management can quickly take corn from the black to the red side of the ledger. If a grower puts cotton on soil that is prone to stress, using a starter fertilizer increases root volume and root mass, which is critical to high yields on the more marginal soils.

“We like to see a one to one blend, something like a 10-10-10, what I call a good tobacco fertilizer,” Heiniger says. In areas where potassium is not an issue, a liquid fertilizer, like a 19-19-0 can work well, he says.

In most cases 25-50 pounds of nitrogen as a starter will pay big dividends. This can be 10-12 gallons of 19-19-0 or a couple hundred pounds of 10-10-10 right beside the row at planting will get the plant to grow off quick enough to establish a root system that is more drought tolerant, has better standability, and other characteristics you need to produce high yields, Heiniger says.

Corn planting started early in 2007, whether that will equate to good corn remains to be seen. Ideally, Heiniger says planting in April is the best bet. Hopefully, the increase in corn acreage will be accompanied by high yields and continued high prices. Taking care of hybrid selection, plant population and nitrogen management will go a long way to insuring a good yield for both old and new corn growers, Heiniger concludes.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.