Crop rotation and planting date are the two most important factors for increasing yield in corn production. But to really bump corn production higher — into the 200-bushel to 300-bushel range — will require a critical change in philosophy, according to Mississippi Extension corn specialist Erick Larson.

The keys include planting precision, weed resistance management, intensive scouting and irrigation scheduling.

Planting precision can help bump yield by improving stand uniformity, Larson told attendees of the Conservation Systems Cotton and Rice Conference in Baton Rouge, La. “Corn is a determinate plant. If a corn plant comes up a week later than its neighbor, you’re going to see a two- to three-leaf disparity in terms of growth that the smaller plant is not going to make up during the season. It will be at a competitive disadvantage. You want to avoid that at all costs.”

Producers can impact plant spacing by planting speed, according to Larson. “Yield contest winners routinely plant at 4 miles per hour or less to ensure seeds are planted in the bottom of the seed furrow, and that they are more evenly distributed out of the planter and stay put when delivered into the soil.”

Planting when optimum conditions exist across a field is also important, Larson said. “We don’t want to be planting into muddy conditions on one side of the field while it’s okay on the other.”

Larson says to calibrate planters to individual seed size when changing hybrids, plant seed 1.5 to 2 inches deep and maintain equipment to ensure it’s working properly.

Research data conducted in Mississippi showed that variability in plant spacing can have a significant effect on ear size, and yield, according to Larson. “In research in which plant population was very similar in plots, we had a 19 percent yield difference between uneven spacing and even spacing — 184 bushels an acre to 229 bushels an acre, a 44 bushel per acre response to uniform plant spacing. If we can improve plant spacing, we can gain a tremendous amount of yield.”

Herbicide-resistant Italian ryegrass is also becoming a bigger problem for corn producers in Mississippi, noted Larson. “We have 12 counties in the Delta with documented glyphosate-resistant Italian ryegrass. We also have 14 counties with ALS-resistant populations of Italian ryegrass, so we’re not having the same amount of success controlling it as we have in the past.”

Larson noted that in one verification field, the combination of early-season competition from resistant Italian ryegrass, “showed extreme competitiveness from ryegrass in March-April, when the corn is not growing as quickly as the ryegrass can. We saw a tremendous amount of early-season competition.”

Comparison of yield between weed-infested and clean areas “was even more substantial than the differences we saw due to uniform planting,” Larson said. “Hand harvesting of the areas indicated a 27 percent yield increase in yield (65 bushels) where we had no ryegrass competition. And this wasn’t a lot of ryegrass competition. We had one ryegrass plant per 7 square feet.”

When glyphosate-resistant Italian ryegrass populations are also ALS-resistant, this makes burndown extremely important for corn producers, according to Larson. “We don’t have the tools to go back and clean this up in the corn field post-emergence. This is probably the most threatening resistant weed control problem that we have in corn production.”

Irrigation scheduluing

Irrigation scheduling is also important for corn yields, noted Larson. “We need to look at what the corn crop needs and try to get away from just watering based on other crops, or irrigating on a certain day of the week. We’ve seen cases in the past where we overwater corn during certain times of the year and underwater during certain times of the year. Both can be damaging.”

Row width can also influence corn yield, Larson notes. Data show that 30-inch rows perform better than wide rows, while twin-row planting falls somewhere in between.

Other factors include hybrid selection, which could result in a 5 percent to 8 percent increase over a lesser choice, and using a starter fertilizer in furrow, which shows a moderate yield response of about 4 percent. “Supplemental insecticide seed treatments can also impact yield, as the standard (250) level seed treatments don’t always provide the adequate control we would expect,” Larson said.

As you intensify your management of corn, it is important to remember that “thorough crop scouting can greatly improve results and profitability,” Larson said.

While plant population and nitrogen rate do impact corn yield, growers don’t always see a yield impact when either population or nitrogen is increased from what is considered optimum, Larson says.

“Research we’ve conducted at Mississippi State on these two variables indicates that once you get to an optimum level, or what the Extension Service recommends, there’s not a lot of enhancement in yield beyond that point. We see a significant increase up to a certain point, then the yield levels off. There’s not as much to gain if you’re already planting at recommended plant populations and nitrogen rates.”