When it comes to producing crops, farmers can get competitive, always shooting for the next 10 bu. Have you ever considered you’re actually salvaging yield potential rather than maximizing it?

“Seed’s greatest potential yield exists while it’s still in the bag,” says Farm Journal Field Agronomist Ken Ferrie. “After you plant the crop, it adjusts its yield potential based on the elements and the environment. There’s only one way for yield potential to go—downward. So your job is to salvage as much yield as possible.”

If you do everything else right, weather sets the cap on yield. But you don’t know how the weather is going to shape up. “Your goal is to weatherproof the crop as much as possible to reduce negative effects of weather,” Ferrie explains.

With corn, the first eight growth stages, V1 through V8, have a major impact on yield potential. It’s as if the plants are negotiating with Mother Nature to see how many bushels the weather will let them produce. Here’s how you can bolster your plants:

1. Plant in the sweet spot. “Wait for soil temperature to get warm enough to trigger germination, which is above 50°F, as soon as possible after planting,” Ferrie says. He calls the ideal planting time the sweet spot.

“Hitting the sweet spot also means the soil has adequate moisture, and you’ll avoid sacrificing yield from late planting,” he adds.

The climate where you farm determines your sweet spot. “In northern regions, the issue might be getting the crop planted early enough for it to finish before frost,” Ferrie says. “In the south, it might be based on planting early enough to avoid pollination during excessively hot weather.”

2. Know how many days you have to actually plant your crop and when they occur.“The sweet spot usually is about a 10-day window,” Ferrie says.

If you farm various soil types that are ready to plant at different times, you have a wider sweet spot. Farming in an arid climate, with irrigation, widens the window as well because the weather is more consistent.

In many areas, though, especially the Midwest, there’s a good chance all your ground will be ready within a fairly short window, Ferrie says. So farmers in those areas have to be able to cover more acres in less time. If your area’s sweet spot is from April 15 to May 1, for example, it’s the same amount of time whether you farm 500 acres or 5,000. Each operator has to find a way to plant within that window.

In Ferrie’s experience, the farmers who are equipped to plant all their corn in five to seven days are usually more likely to finish within that window. In the Corn Belt, if it takes 10 to 20 days, you won’t often have that large of a window.

3. What if you can’t cover all your acres during the sweet spot? “In that case, you must start earlier or finish planting outside the sweet spot,” Ferrie says. “Mudding in seed means sacrificing yield right off the bat. Planting before the soil temperature is higher than 50°F means the seed will wait longer to germinate. The longer it waits, the higher the risk of insects and diseases.

“If you have to plant early, consider applying insecticide and fungicide seed treatments,” Ferrie says. “If a field has a history of seed-attacking insects or disease, plant that one in the sweet spot to reduce pest pressure.”

4. Don’t plant in cold soil, which could lead to seed chilling. “Chilling can happen anytime the seed imbibes water and the soil water temperature is at or below 50°F,” Ferrie explains.

After germination, symptoms of chilling include seeds containing a seed root with no sprout (or mesocotyl), or a sprout without a seed root. “More common,” Ferrie says, “is for the sprout to corkscrew and struggle to find its way to the surface.”

Reduced stands deal a serious hit  to yield potential. “A typical field in the Corn Belt sustains a 10% to 13% decrease from planted stand to ear count,” Ferrie says. “So if you plant 36,000 seeds per acre, you wind up with 32,500 ears. Good managers try to cut this loss in half, so the ear count will hang at 34,000.”

5. Count plants and ears. “I’ve seen a 25% drop from planted population to ear count, and the grower wasn’t aware of it,” Ferrie says. “Take detailed stand and ear counts for every field and every hybrid, and record the data. Review it and compare it with past years. If a field consistently falls outside a 5% to 6% drop from planted population to ear count, review all your practices, from preparing the field to scouting, to tighten the gap.”

6. Patience pays. “Sometimes missing the sweet spot results from a lack of patience, often by letting the neighbors, rather than field conditions, dictate when you plant,” Ferrie says.
 
7. Have big enough equipment and enough help. “Other times, missing the sweet spot comes down to how many acres can be planted in a day,” Ferrie says. “Say your area’s sweet spot is a 10-day window. If it takes you 15 days to plant, you will never hit the sweet spot in a good year, let alone a bad one when the weather goes against you.”

Having enough planting capacity has gotten a little easier with the advent of high-speed planters, Ferrie notes. But there are other factors to consider, such as the trend to earlier planted soybeans. “If you decide to plant soybeans when you normally plant corn, it changes the window,” Ferrie says. “Consider what size equipment and how much labor you will need to get both crops planted.”

Soybeans are much less concerned with the sweet spot than corn. “I’ve seen growers plant soybeans instead of corn, when conditions were not in the sweet spot, and improve yield in both,” Ferrie says.

8. Plant high-quality seed. “Seed quality is always important, but it’s essential when planting in poor conditions,” Ferrie says. “Seed with severe pericarp damage and poor saturated cold scores fares worse if chilled.”

9. Never let seed get hungry. “Once a stand is established, it must have access to nutrients to carry it through the first leg of the growing season, until it’s knee-high,” Ferrie says. “Seed carries its own supply of food, but it picks up nutrients from the soil as soon as roots appear.”

Applying phosphorus at planting weatherproofs corn when temperatures hang in the 50°F to 65°F range for a couple weeks. “As long as the soil temperature is below 65°F, it won’t release much phosphorus,” Ferrie says. “And phosphorus is the nutrient that drives cell elongation and division (or growth).

“Phosphorus won’t start to show up in high enough quantities for plant growth until the soil reaches 65°F, even if the soil test value is high,” Ferrie continues. “But you can get a lot of corn growth while soil temperature is between 50°F and 65°F, if you supplement the supply of phosphorus to the plant by applying some with the planter. Starter fertilizer is not sensitive to temperature, so roots will pick it up if they can reach it.”

10. Manage the carbon penalty. When soil warms up, the burgeoning microbial population can immobilize nitrogen, phosphorus and sulfur, making them temporarily unavailable (they become available again later in the season). “This is called the carbon penalty, which is related to how much and what kind of carbon is in the soil,” Ferrie says. “Planning your fertilizer program to manage around the carbon penalty is part of weatherproofing the crop.

“Applying nitrogen, phosphorus, sulfur, potassium and micronutrients with the planter is the most effective way to match fertilizer timing and placement to the needs of the crop. Applying nitrogen and sulfur as part of a weed-and-feed herbicide application is another option to reduce the effect of the carbon penalty.”

The larger volume of crop residue in continuous corn increases the challenge of managing the carbon penalty, compared with a corn-soybean rotation, Ferrie adds.

11. Keep feeding nitrogen. “Once past the carbon penalty stage, you must have enough nitrogen available in the soil to get corn knee high,” Ferrie says. “Nitrogen can be applied in strip-till operations, during a row-warming pass or with a weed-and-feed application. This nitrogen is for vegetative growth, which exerts a high demand during the plants’ rapid growth stage.”

12. Evaluate your fertilizer program. If you’re not sure your current program is meeting fertility needs through the V8 growth stage, Ferrie recommends putting out test strips. “If you’re applying phosphorus with the planter, turn it off and on for a few rounds,” he advises. “If the soil is meeting all the plant’s needs, you will see no visual difference where the starter is being applied. If you see a difference, it means the corn would grow faster if it had more phosphorus.

“To evaluate your nitrogen strategy, apply strips of various rates above and below your current rate. If you see strips of greener, taller corn early in the season, it means the plants would grow faster if they had more nitrogen. If a section in the field has zero,
30 lb., 60 lb. and up to 120 lb. of nitrogen per acre, the point where you no longer see a difference is where you applied enough nitrogen to offset the carbon penalty.”

You might call this your 12-step strategy to weatherproof corn. Weatherproofing is never more important than early in the season when plants decide how much of their potential yield they’ll actually deliver. 

Too dry, too wet and everything in between. This story is the fifth in an eight-part series on weatherproofing your crops. Follow along at bit.ly/weatherproof-crops