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- R.L. (Bob) Nielsen
Dept. of Agronomy
Purdue University
West Lafayette, Indiana
- Email: rnielsen@purdue.edu
- Web: www.kingcorn.org
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- Variable stands of corn are costly in terms of bushels and lost revenue.
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- Parable of the sower (Matthew 13:3-8)
- Seeds along path bird feed
- Seeds in rocky ground scorched,
withered
- Seeds within thorns choked
by weeds
- Seeds in good soil brought
forth grain
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- “The sins of planting will haunt you all season!”
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- “A young field of corn can look pretty darn uniform from the seat of
your pickup tooling down the blacktop at 60 mph.”
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- Plant spacing variability (PSV)
- How uniformly were the seeds distributed within the row by the planter?
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- Very crowded plants here and there...
- Typically caused by planter malfunction
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- Gaps between plants of various sizes caused by…
- Planter malfunction and/or
- Poor germination or survival of plants
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- Mixtures of crowded plants and gaps between plants caused by…
- Planter malfunction and/or
- Poor germination or survival of plants
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- No effect if surviving plant population is still within optimum range.
- For many soils, “optimum” final stand ranges from about 28 to 32,000
ppa.
- Lower grain yield if surviving plant population is less than optimum.
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- If targeted seeding rate is below the optimum threshold, doubles may
actually increase yield until that threshold is exceeded.
- E. Nafziger, J. Prod. Ag. 9:238-240 (1996)
- Yields or standability may decrease at some point beyond optimum
population threshold.
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- When variable plant spacing is a MIXTURE of gaps and doubles…
- Effect will usually be negative because the extra plants (doubles) and
the plants adjacent to the gaps cannot make up for the grain yield loss
caused by the missing plants.
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- First, I have to explain how you measure and quantify the plant spacing
problem.
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- Calculate a simple mathematical measure of variability called the standard
deviation.
- Large values equal large variability.
- Most computer spreadsheet programs will easily allow you to calculate
standard deviations from a list of values.
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- From my field research, 1987-93
- Yield levels from 95 bu/ac to 200 bu/ac
- Applicable to standard deviations between 2 and 12 inches
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- Pioneer™ researchers reported very similar yield loss rates from four
locations across the Midwest in 2000.
- Three different genetic families.
- Approximately 3.4 bushel decrease per inch increase in standard
deviation of plant spacing.
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- When measuring seed spacings, aim for a target standard deviation of
zero (0) inches.
- Hard to achieve, but make it your goal.
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- When measuring plant spacings, aim for a target standard deviation of
two (2) inches, rather than zero.
- For typical emergence percentages (90 to 95% of seeding rate), a
standard deviation among PLANT spacings of 2 inches may be equivalent
to perfect SEED spacing.
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- Germination of the seed (minor issue)
- Planter malfunction...
- Worn out planter parts
- Incorrect planter settings
and adjustments
- Operator error
- Otherwise known as that
“loose nut behind the wheel”
- So says Larry Cline (Deere & Co.)
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- Irregular patterns of plant death by hail, frost, insects, disease can
cause PSV.
- Make sure you diagnose the cause(s) of stand variability early to
determine whether to blame the planter or Mother Nature!
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- Variability for time of seedling emergence throughout the field
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- Delayed plants cannot compete with older, more established plants.
- At best, delayed emergers will contribute little to yield.
- Potential yield losses...
- 8 to 20 % loss if 25 % or more of stand is 2 or more leaf stages
“behind”
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- Variability in soil moisture
- Soil variability for texture and
natural or artificial drainage
- Uneven seeding depths
- Uneven distribution of crop residues
- Soil drying patterns due to tillage traffic
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- Variability in seedbed soil temperature
- Variable soil color and texture
- Variable seeding depths
- Variable distribution of crop residues
- Especially important when soil temps. are hovering around 50F (10C).
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- Uneven seed to soil contact
- Rough, cloddy seedbeds
- Uneven distribution of crop residues
- Coulter running too deep
- Incorrect furrow openers adjustment
- Incorrect furrow closers adjustment
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- With just a little effort and common sense on your part!
- Offseason care of planter
- Replacing worn parts
- Making planter adjustments and
operating the planter as soil &
weather conditions dictate
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- Take the time to inspect & service your planter on your own, or…
- Let your local planter dealer do it for you.
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- Clean planter inside and out.
- Remove all seed from hoppers and metering units.
- Don’t let it sit in the
hoppers and rot or
attract rodents for
months.
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- Remove seed discs from vacuum planter.
- Else rubber seals remain compressed and will fail sooner than
otherwise.
- Hang on wall, not stacked on workbench, to avoid warping.
- Store where temps remain above freezing.
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- Lubricate all chains and bearings.
- If practical, remove the chains and
soak in oil all winter.
- Protect the planter from the elements.
- Preferably inside.
- Or outside but protected.
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- Check and replace all worn out parts.
- Seed meter components, chain links, disc openers, hydraulic hoses, seed
tubes, etc.
- Ensure that coulters and disc openers are aligned accurately.
- Proper alignment improves accuracy of seed furrow opening.
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- Ensure disc openers and furrow
closers are aligned accurately.
- Affects furrow closing efficiency.
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- Adjust or replace worn disc openers.
- Worn openers cut “W” furrows rather than “V”.
- Closing wheels may not completely firm soil around seed.
- Adjust shims so that bottoms touch.
- Replace openers when no longer possible.
- Some say replace when 1 inch of wear occurs.
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- For finger-pickup type planters.
- Check seed meter backplates.
- Rust buildup
- Seed treatment residues
- Worn down ‘dimples’
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- Check condition of seed conveyor belt.
- Age + seed treatment = brittleness
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- Inflate tires to correct pressure.
- Clean seed tubes and monitor sensors .
- Replace seed tubes if excessively worn at bottom.
- CALIBRATE THE PLANTER!
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- For air or vacuum planters:
- Calculate & record the seed weight for each seed lot you intend to
plant.
- Identify & record the correct pressure (air or vacuum) for the
calculated seed weight.
- Identify & record the correct seed disc (or drum) for the
calculated seed weight.
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- Calibrate the radar.
- Ensures accurate speed and distance measurement.
- Identify the correct transmission setting for the desired seeding rate.
- Use the operators manual.
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- Calibrate actual seed drop with...
- Planter transmission settings
- Planter monitor readouts
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- Calibrate at normal planting speeds and seeding rates in as close to
field conditions as possible.
- Don’t calibrate the planter in the farm lane.
- Else cannot account for wheel slippage and row unit bounce.
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- Calibrate pesticide and fertilizer planter attachments at same time…
- Application rates can easily change from year to year.
- Also check position of attachments relative to planter unit itself.
- Especially starter fertilizer attachments.
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- Check that the planter units are parallel or level to the ground when
the planter is in operation, because that affects...
- Disc opener depth
- Press wheel efficiency
- Seed to soil contact
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- Remember that excessive down pressure at the parallel linkages can lift
the planter frame AND the drive wheels.
- i.e., heavy-duty no-till springs
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- Remember that rapid and uniform corn germination and emergence will not
occur at soil temperatures less than 50o F.
- Seedling establishment will also not occur rapidly & uniformly if
soil temperatures remain cold.
- Cool soils especially likely when planting early and/or in no-till with
heavy surface trash.
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- Adjust air or vacuum planters according to seed size or weight.
- Seed plates, discs, or drums
- Air or vacuum pressure
- Remember to re-adjust as necessary when you switch hybrids or seed lots.
- Failure to do so can cost you dearly at harvest!
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- Remember graphite with finger-pickup meters: 1 tablespoon per bushel of
seed.
- If you discover that seed treatment is building up on the fingers or
backplate, then use more graphite.
- Remember talc with vacuum meters:
1 cup per bushel to prevent sticky seed.
- More under humid conditions.
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- Choose an appropriate seeding depth.
- Depends on field conditions & weather.
- Aim for a depth that will ensure uniform availability of soil moisture
for germination.
- No less than 1 ½ inches.
- As deep as 2 or 3 inches
if necessary to reach
adequate soil moisture.
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- Check the actual depth of seeding frequently from field to field or day
to day.
- Actual seeding depth can vary from targeted planter setting as soil
conditions change.
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- Adjust the depth and tension of no-till coulters from field to field,
day to day.
- Do not cut deeper with the coulter (in line with the disc opener) than
the depth of seeding.
- Avoid trapping old trash inside the furrow.
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- Adjust the tension of the furrow closing wheels according to the
conditions of the soil.
- Remember, excessive pressure
can compact the soil above the
seed and restrict emergence.
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- Planting speed should not exceed the manufacturer’s recommendations.
- Generally, the optimum range of speeds is 5 to 6 miles per hour.
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- A form of operator error that…
- Diminishes the capability of the metering unit to singulate individual
kernels.
- Interferes with the seed travel to the furrow when row units bounce
excessively.
- Often results in uneven seed to soil contact.
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- Yield losses can approach 2 to 5 bushels per acre for every 1 mph
increase.
- Based on my on-farm research with 22 farmers across Indiana, Illinois
and Iowa in 1993.
- The severity of the yield loss likely depends on the condition
(maintenance) of planter.
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- Diligently lubricate the chains and bearings.
- Best done at the end of a planting day when the chains and bearings are
warm.
- Use multi-purpose spray lubricant, not chain lube or old motor oil.
- Dries better, less sticky
- Less of a dirt magnet
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- The Bad News…
- The loss in yield potential from uneven stand establishment in corn
begins as early as the day you plant the field!
- The loss in yield potential can easily be as great as 7 to 15 bushels
per acre.
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- The Good News…
- Adjustments and repairs to planters plus the proper operation of the
planter can easily prevent these losses from occurring!
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- “Farming is a kind of continual miracle wrought by the hand of God.”
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Notes