A Great Plains Yield-Pro planter was used to plant four AgriGold hybrids in two row spacings and three populations. The plot also included two nitrogen rates.
Farm Journal Test Plots measure yield potential for flex and fixed ear hybrids based on water, sunlight and nutrients
The goal of planting variable hybrids is recognizing that a field is not created equal from one end to the other and responding accordingly to maximize yield potential. For on-the-go hybrid changes to become a reality, two obstacles have to be conquered—mechanically making that possible and agronomically placing the correct hybrid in the correct zone.
In 2013, Farm Journal Field Agronomist Ken Ferrie worked with farmers to prove it’s mechanically possible to vary hybrids on the go before the machines are commercially available. He also led an effort in the Farm Journal Test Plots to look at what it could mean to a farmer’s bottom line to plant different hybrids in different management zones.
Yield factor. "There is a lot of excitement around variable hybrid technologies," Ferrie says. "That’s because hybrid choice is the No. 1 factor that shows up in a yield map. We know using management zones to vary population is one way to manage a field’s variability. Varying hybrids expands on getting the most out of the zones because variable-rate population only manages for water-holding capacities."
The three big components of yield—water, sunlight and nutrients—all interact with hybrid characteristics. Maximum yield is achieved as soon as one of those components becomes the limiting factor.
"When sunlight hits the ground and when water is lost to evaporation instead of transpiration, those basically become somewhat wasted resources," Ferrie explains.
In its second year, the test plot was again located in DeWitt County, Ill., through a partnership with Great Plains Manufacturing and AgriGold Hybrids. A Yield-Pro planter was used to plant the two row spacings—30" and twin rows. AgriGold provided four hybrids—a fixed ear with upright leaf style, a fixed ear with pendulum leaf style, a flex ear with upright leaf style and a flex ear with pendulum leaf style.
To verify yield results, every Farm Journal Test Plot is harvested with a calibrated yield monitor, and every treatment pass is weighed using grain carts that are equipped with scales.
"We’ve done test plots with ear types since 2009 and have learned that all hybrids flex, but true flex hybrids carry the biggest risk under stress to go backward in yield," Ferrie explains. "To maximize yield with determinant hybrids, populations need to be pushed. Semi-flex hybrids are somewhere in between. In 2012, we added leaf style to the plot protocol to see what effect that characteristic had."
In all, each of the four hybrids were planted in two row spacings, three populations and two nitrogen rates.
"From previous plots, we’ve learned that as population increases, it’s important to support that higher plant density with more nitrogen," Ferrie says. "This is particularly important in the true flex genetics. Roughly, you should increase 8 lb. to 10 lb. of nitrogen for every 1,000 plants you add."
Leaf style and population directly affect how the hybrid manages water and sunlight.
"How quickly a canopy closes affects the amount of sunlight harvested, as well as water management," Ferrie says. "It depends on the year—which is more important.
"For example in 2012, using thermal maps of the test plot, I could label the hybrids by leaf type. The upright leaf styles did not canopy and therefore had more scorching and were noticeably hotter based on remote sensing technology," Ferrie says.
In the first year of the plot, the flex ear floppy leaf hybrid at the lower population was the highest yielding hybrid in 30" rows. That same hybrid was the overall yield winner in the plot when planted to twin rows at the lowest population.
"Leaf style, row spacing and population can be used together," Ferrie says. "In 2012, when water was limited, the narrow rows, lower population and floppy leaf captured maximum sunlight using the least amount of water. The flex ear flexed out to make up for the lower ear count. Once all the sunlight was captured, it didn’t help to push the population because that only increased water and nutrient demands."
In this 2013 test plot, both hybrids had a floppy leaf type, which can maximize water management. However, when put under stress at higher population, flex ear types carry more risk in flexing backward in yield, whereas determinate hybrids increase. This data is from a management zone with silt loam soil.
Adjust accordingly. In 2013, water wasn’t the limiting factor. More often than not, it was nitrogen or sunlight. The flex ear floppy leaf hybrid yielded 100 bu. higher than the year before. Again, the lowest population and highest nitrogen rate yielded best and was among the top entries in the plot. In the end, adding population did not add up to more bushels.
Using 2013 data, Ferrie found a wide swing in yield potential across the different treatments—and several lessons to be learned.
"In light silt loam soils, water is a concern, and we were able to add 40 bu. by changing the hybrid and nitrogen compared with the other entries at the same population," Ferrie explains. "In heavy clay soil, by changing the hybrid, population and nitrogen rate, we varied yield by 50 bu. Both of those examples are at the same row spacing, and we saw even more variance when we also factored in the two row spacings."
Ferrie reports that if hybrids all cost the same per bag of seed, in the net dollar return, the right population and nitrogen combination ranged from $160 to $260 in 30" rows. In twin rows, the range was $222 to $363.
"When a hybrid does not respond to higher populations, that is more tied to ear type," Ferrie says. "Where a flex ear, floppy leaf hybrid does best at lower populations, a determinant needs to be pushed."
Field findings. After several years of researching this topic in the Farm Journal Test Plots, Ferrie shares a few more of his observations. Flex eared hybrids can’t take the stress created by overplanting or underfertilizing.
In reviewing the test plot yield data, Farm Journal Field Agronomist Ken Ferrie notes that the best-yielding entry was twin rows planted at the low populations with a determinate ear, floppy leaf hybrid. These results are from a management zone with silty clay loam soil.
Determinate ear hybrids need to be pushed to maximize yield and can handle more stress. If a hybrid is a semi-flex, it falls in the middle of stress tolerance.
"Whether a hybrid is fixed or flex, once it maximizes sunlight at 96% light capture, that yield ceiling is set. One way we use twin rows is to harvest water and sunlight at lower populations. But in the zones with greater water-holding capacity, we’ll want to step up population," Ferrie says.
The value of this plot is that the hybrid characteristics are all being compared in the same field only a few passes from each other.
"In our experiences, we’ve seen upright leaf structures harvest more sunlight and respond in yield if that is the limiting factor," he explains. "Floppy leaf hybrids maximize light capture at much lower populations than upright hybrids. Semi-upright hybrids usually split the middle."
When water-holding capacity is a concern, lower the population to reduce water usage.
"At lower populations, flex eared hybrids will make up for the lower ear count, and a floppy leaf structure will canopy quicker," Ferrie says. "If you narrow the row spacing, light capture will peak even quicker to harvest more light by the plants."
In fields with high amounts of variability going from surplus water to droughty soils, Ferrie recommends farmers use a semi-flex ear type hybrid and variable-rate planting to mitigate risk. A semi-upright leaf structure will maximize sunlight and provide some drought protection. If a farmer were to narrow the rows that would help manage both water and sunlight.
"As we approach the ability to vary hybrids in the field, we need to know even more about how hybrids will behave," he says. "There are things you can look at in the characteristics of hybrid selection to minimize the guessing. But most importantly, farmers need to commit themselves to picking their hybrids with purpose."
He advocates that farmers focus on the entire system. "Compaction is a deal breaker—water and roots have to go down. If a farmer is using variable populations, he’s counting on depth of root," Ferrie says.
"Know the weakness of your hybrid, and then manage for that weakness," he adds. "For example, you may select a hybrid for its ear and leaf type but still need to scout if it has poor gray leaf spot scores. Or if it doesn’t have a strong package against Goss’s Wilt, you have to rethink its placement."
- Early Spring 2014