Corn yield is a factor of the number of ears and the number and size of kernels on each one in a field. The only way to increase bushels per ear is to document results and make changes next season, says Farm Journal Agronomist Ken Ferrie. The process involves scouting before and during harvest, analyzing results and drafting your plan.
Preharvest scouting
Review previous scouting reports, so scouts can check problem areas.
Perform stalk push-tests and test ear shanks for droppage, to determine which field to harvest next.
Count ears versus plant population, and log the locations for post-harvest analysis. “Because potential barren plants are visible from emergence through pollination, missing ears should not come as a surprise,” Ferrie says. “If they do, step up your in-season scouting next year.”
Record how ears performed next to gaps in the row to see how a hybrid responded to extra sunlight. “If the ears are mainly 14 rows around, but 16 or 18 rows next to the gap, the hybrid flexes in girth in relation to population,” Ferrie says. “If ears in the gap are longer, the hybrid flexes in length. If they are bigger but have the same number of kernels, the hybrid flexes in kernel depth.”
Scouting during harvest
“Besides continuing to prioritize fields for harvest, scouts should check behind combines to help operators prevent grain loss and spread residue uniformly,” Ferrie says. “Volunteer corn and areas of heavy residue will affect next year’s stand.”
If a combine operator sees a drastic yield drop on the monitor that no scouting report predicted, call the pest team and figure out what happened while plants are still present.
Postharvest Analysis
Meet with your team and have them bring maps and memories. Stress the importance of the process. “For example, you may know low yield resulted from barren stalks, but only the pest team’s early-season scouting reports will show the cause was late-emerging plants,” Ferrie says.
Do not send your yield maps to be analyzed by someone outside your operation. Only your team, including consultants involved with decision-making, know what really happened.
Yield maps must show yield spatial variability. Use raw data, not contoured maps, set up in seven to 10 ranges (yield increments) with equal points, whether the variation in a field is 15 bu. per acre or 50 bu. “A well-calibrated yield map will talk to you,” Ferrie says. “If combine operators are present when you analyze yield maps, they will understand the importance of getting good ones.”
Overlay soil type and topography on yield maps to identify the cause of many yield swings.
Compare the records your pest team collected about ear size with the same location on your yield maps. “Comparing ear count to actual yield will teach you a lot about hybrid flex, which can range from 4 bu. per thousand ears to 10 bu.,” Ferrie says. “In a dry year you will learn whether a hybrid holds a set amount of bushels per ear or dumps kernels under stress.”
Don’t stack years of map data to obtain average yields. Dry areas will yield higher in wet years and vice versa. “Averages don’t necessarily reveal management zones,” Ferrie says.
Create management zones, and manage the limiting factor in each one, with tools such as variable-rate population and nutrients, multiple hybrid planting and drainage.
“When low-yielding areas are linked only to the past season, find the cause, such as a missed spray application or spray drift,” Ferrie says.
Plan Ahead to Harvest Data
Collecting the data you need for effective postharvest analysis requires planning tasks and addressing manpower needs well before you fire up the combine, Ferrie says. Be sure to allow your combine operators the time, training and resources they need to calibrate yield monitors and produce useful maps.
Also check where compaction layers were found by scouts and where sprayer operators or drone images found ruts, and draft a tillage plan. Schedule lime or fertilizer applications that are required ahead of tillage.
