What is in this article?:
- Odd field patterns help identify yield variation at plant level
- Plant height variation losses
- Mirrors old Purdue research
- Aerial images that show visual patterns in a field can be the first step in discovering problems that affect yields. Follow that up with detailed plant-by-plant analysis on the ground to verify the impact of the problem in yields and more objectively zero in on the problem.
- Aerial photos early or late in the day produce shadows that point out subtle plant height variations; plant height within a field correlates with ear size and yield.
- A close look at plant spacing and projected yields from single ears in a 17-foot, 5-inch span (1/1,000 acre in 30-inch rows) vividly shows planter skips and barren plants are yield killers.
Plant height variation losses
Recker’s client investigations have shown overall good yields on average, but variable emergence, compaction, uneven fertilization and varying seed placement have cut yields overall, often by as much as 20 bushels an acre. “In one instance, a field had a 188-bushel per acre average--that’s not bad. But the single plant variation ranged from 115 bushels an acre to 234 bushels an acre across the planter width,” Recker says. “To me, that says we can do better, if we go to the plant by plant level and determine what caused that inconsistency.”
In one of his investigations this year, Recker noticed plant-height variations on a diagonal pattern across the field as he flew across it. He took photos in early September and the farmer was not surprised at the variation—he had seen streaks in the field from early plant-height variations and even applied twice as much N at sidedress as he had planned to try to even out plant growth.
The farmer had applied manure in mid-April at an angle to the rows when it was really wet. He’d also done some light tillage when the soil was wet, but the tillage was at the opposite angle of the manure application. “The manure-application angle matched the aerial photo, so I figured height variations were related to the manure application. The operator first thought it was some kind of nozzle plugging,” Recker says. “So he told me to go ahead and see what I could find on the ground, even though he didn’t expect to learn a lot.
“He liked the idea that I get right down to the ear, and can pick up a pattern ear by ear. His combine yield monitor told him he gets from 220 to 240 bushels to the acre on this field. But he really understands now that the combine can’t pick up on this individual plant variation—he was surprised to see so much variation in ear size,” Recker says.
They will test further, but the operator no longer thinks it’s a fertilizer issue. “More likely, (the yield hit) is related to compaction of some kind—the pattern seems to match the dual tires of the tractor used for the manure application,” Recker says. “The farmer might consider using tank applicators that drive with the row instead of across it. ”
Recker’s plant-by-plant investigation suggests a lot of potential for higher yields on that field. “It’s yielding well, but it’s crying out for consistent emergence and consistent plant heights that could be producing 300 bushels an acre yields,” Recker says.