To understand if or how much uneven emergence of seedling corn effects overall yield of late emerging plants, a number of Universities and on-farm research have studied the effect.
A Crop Science Abstract study of Response of Corn Grain Yield to variability of even emergence and variability in plant spacing found:
- Compared with the uniformly early emerged plants, one out of six plants with a two- leaf stage delay in emergence reduced yield by 4%.
- One out of six plants with a four-leaf stage delay reduced yield by 8%.
“These results indicate that corn is more responsive to emergence variability than plant spacing variability.”
“Variation in plant emergence reduced yield, whereas variation in with-row spacing did not affect yield.”
Lori Abendroth, Iowa State University agronomist, wrote “when smaller corn plants compete with larger ones, they are at a significant disadvantage in the fight for sunlight, moisture and nutrients. Meanwhile, as the smaller plants battle for whatever resources they can grab, they drag down yields of the older plants. The result is the whole field suffers.”
“If one-fourth of the crop emerges just a week late, yields can drop about 6%. A two-week delay for half the plants sets up the crop for a 17% loss.”
Bob Nielsen, Purdue University: Uneven emergence is a problem that will haunt you the whole season.
University researchers from Wisconsin and Illinois have documented as much as a 15% decrease in yield when 25% of corn plants were delayed a week and a half.
Cousins Jason and Adam Watson of Villa Grove, Illinois reported on their own farm replicated research in Corn + Soybean Digest.
In 2013 and 2014 Jason flagged newly emerged seedings each day at noon, according to day of emergence. After hand harvesting the 40 foot row experiment they arranged the ears on the shop floor accordingly.
In 2013 the day one emergence (a population of 21,000 P/A) ears averaged 18 rows around 34-37 kernels long. This averaged 639 kernels per ear.
- All day 2 emerged plants (a population of 9,000 P/A) ears had 16 rows around and were 34-37 kernels long. This averaged 568 kernel ears.
- All day 3 emerged plants and later (a population of 5,000 P/A) lacked any ears at all or were “weeds”.
In 2014 weather conditions were much cooler after planting and the plants took 10 days longer to emerge.
- Day one emerged plants resulted in a population of only 5,000 plants per acre.
- Day 1 emerged plants the ears averaged 16.33 rows around 40.5 kernels long or 660 kernels per ear average.
- Day 2 emerged plants (a population of 21,000 P/A) averaged 18 rows around and 38.66 kernels long or 696 kernels per ear average.
- Day 3 emerged plants (a population of 7,500 P/A) averaged 11 rows around and 25.5 kernels long or 280.5 kernels per ear average.
The Watson cousins on farm research is something NuTech DSM’s, Dealers and customers could do on their own to evaluate how well their planters are setup for optimum emergence. Seed costs per acre are the same. But yields are an area for increasing or loosing dollars per acre!
The Progressive Farmer published an article in the April 2018 edition that also discusses this topic. Good read.
Suggestions to avoid uneven emergence:
Corn sometimes emerges unevenly because of environmental factors that growers can not control. Nevertheless, do what you can to manage what you can control.
- Wait until the field is ready
- Monitor both soil moisture, soil temperature and short term weather forecast. Soil temperature should be at least 50 degrees in the coolest soil types of the field.
- Avoid excessive tillage trips which dry or compact the seedbed.
- Tilling when soils are too wet can produce cloddy soils, a major cause for uneven stands.
- Monitor seed placement during planting to be sure there is uniform and good seed to soil contact. If not add seed firmers such as Keeton brand. Uniform seed depth is critical. Adjust seed openers, closing wheels and/or press wheel tension.
- Manage residue. If row cleaners are used to wipe away residue don’t be too aggressive but enough that allows for a good clean seed bed.
- Don’t plant any shallower than 1.5 inches. 2” to 2.5” is generally ideal.
- Agronomists agree that excessive planter speed is the biggest deterrent of uniform seedling depth and emergence.
- Checking seed to soil contact across different soil types in each field can increase your net income. After planting is too late for this year.