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Published 12 May 2006
Take Time to Evaluate Corn Stand Establishment
R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address:
ith
the majority of Indiana's corn crop planted, the next phase of the growing season
is stand establishment. Growers intuitively strive for fields of corn with evenly
spaced plants that emerge quickly and uniformly.
Uneven emergence can be caused by spatial variability for seeding depth, seed-to-soil
coverage, seedbed moisture, seedbed temperature, or damage from soil-borne insects
and diseases. Uneven plant spacing within the row is most commonly due to problems
related to the planter, including worn seed meter components, poorly lubricated
chains and fittings, mismatch of seed size with seed meters, and excessive planting
speed. Stand losses due to pests or weather often result not only in lower plant
densities, but also in unevenly spaced survivors. Corn that initially emerges
and develops uniformly through early leaf stages can take a turn for the worse
around the three- to four-leaf stage if the kernel or mesocotyl is damaged by
insect or disease prior to the successful development of nodal roots from the
crown area of the plant.
Take time over the next few weeks to assess the uniformity of stand establishment
in fields as plants emerge and develop through their early leaf stages. Identify
the cause(s) of uneven stands before the evidence disappears and determine whether
changes in your planting operation or agronomic decisions may improve the odds
of uniform stand establishment in the future.
- Early-planted corn remains at risk for the development of seedling diseases
given the recent onset of cool, wet conditions plus the fact that seed-applied
fungicides begin to lose their effectiveness 2 to 3 weeks after planting.
Brownish or otherwise discolored seed roots, kernel tissue, or mesocotyls
are symptoms of seedling disease and can have devastating effects on young
plants prior to successful development of nodal roots from the crown area.
- Some early-planted fields were also "nipped" by light frost in recent weeks
at the time that the seedlings were just beginning to emerge from the soil.
Frost injury to coleoptiles may hinder the normal splitting of the coleoptile
tip and emergence of true leaves; resulting in a "laddered" or "knotted" appearance
as the true leaves rupture through the sides of discolored and injured coleoptiles.
- Fields planted more recently and not yet emerged are at risk of damage from
cold, saturated soils and/or subsequent development of hard soil crusts once
fields begin to dry. Be prepared with the rotary hoe if we experience a quick
return to sunny warm days before the crop emerges. Bare soil temperatures
have dropped by as much as 10 degrees F since the mid-week onset of the rains.
Water-logged soils translate to soil oxygen deficits that can be detrimental
to germination and early seedling development. Germination and emergence will
occur at a slow pace until temperatures rise to normal levels or beyond. Slow
seedling development further aggravates their susceptibility to disease, insect,
and weather stresses.
- Uneven plant spacing within the row can be measured and quantified by simply
measuring plant spacings within a set length of row. The simplest measuring
technique requires a 25-ft tape measure with large easy-to-read numbers, a
pad of paper and pencil (or handheld PDA), a good pair of walking shoes (and/or
hip waders), and a computer with a spreadsheet program like Microsoft® Excel.
Record consecutive plant spacings (inches) within 25ft of row (for each row
unit of the planter if you want) at several locations within a field. Enter
the numbers in columns on a computer spreadsheet and calculate the standard
deviation for each list of plant spacings using Excel's built-in mathematical
formula (=stdev). My research suggests that corn grain yield may decrease
up to 2.5 bu/ac per inch increase in standard deviation of plant spacing within
a standard deviation range of 2 to 8 inches.
Related References
Nielsen, R.L. 2001. Stand Establishment Variability
in Corn (AGRY-91-01). Purdue Univ. Online at http://www.agry.purdue.edu/ext/pubs/AGRY-91-01_v5.pdf
[URL verified 5/12/06].
Nielsen, R.L. 2006. Effect of Plant Spacing Variability
on Corn Grain Yield: 2005 Research Update. Purdue Univ. Online at http://www.kingcorn.org/research/psv/Report2005.pdf
[URL verified 5/12/06].
For other information about corn, take a look at the Corn Growers' Guidebook
at http://www.kingcorn.org.
© 2006
, Purdue University, an equal
access, equal opportunity university. This material may be available in alternative formats. If you have trouble accessing this page because of a disability, please contact RLNielsen at rnielsen@purdue.edu.
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