Common Corn Planter Issues And What Can Be Done About Them
Aprli 25, 2002 9(6):43-44
Joe Lauer, Corn Agronomist
As we prepare for the 2002 corn planting season we need to keep a few things in
mind about the planting operation.
Row width: Narrower rows are better, especially 30-inch rows. Yields consistently
increase about 5% when rows are narrowed from 36- or 38-inches to 30-inches. As
row width continues to narrow, yield increases are not as consistent, but on average
increase another 2 to 3%. In narrower rows, the growing space of each plant is optimized
and plants canopy quicker, which theoretically should result in better moisture
retention, better weed control, and less chemical cost.
Planting speed: A 160-Acre field takes 11 hours to plant with a 15-foot six-row
planter driven at 8 mph with no stops. For that same field using the same planter,
but driven at 5 mph it would take 17.6 hours to plant. You would also need to factor
in filling stops. A 6-row, 15-foot planter seeding at 33,000 seeds/Acre with standard
1.6-bushel hoppers (total = 9.6 bushels; 1 bushel = 80,000 seeds/bushel) would require
at least 7 stops to refill the planter. Planter manufacturers usually recommend
planting speeds of 4.5 to 5 mph in order to maintain good seed spacing. As speeds
increase, seed spacing becomes more uneven. The optimum planting speed is dictated
by more than the machine metering and planting capabilities. Rocky situations, terraces,
steep hillsides, etc. may require slowing down to meet field conditions.
Seed Population: The Wisconsin recommended harvest plant population for corn
grown in 30-inch rows is 30,000 plants/Acre, and 26,000 plants/Acre on lighter soils.
For wider row spacing decrease plant population and for narrower sow spacing increase
plant population no more than 2,000 plant/Acre. For corn silage fields, harvested
plant populations should be about 2,000 plants/Acre greater. Typically about 10%
of the seed and plants in a field are lost during emergence and over the course
of the season, so seeding populations should be higher than recommended plant harvest
Metering: Most corn seed meters are singulated meters rather than volumetric
meters typically found for crops such as wheat, oats, rape and alfalfa. Important
things to look for in a meter are its ability to handle a wide variety of crop seed,
seed sizes (i.e. small, medium and large), and seed types (flat v. round). Meters
should also have the ability to use electronic seed monitors, allow fast clean out
and easy "plate" changes. Another emerging important trait is meter size,
which ultimately affects row spacing. Three general types of meters are available
on the market: 1) plate and wheel meters, 2) finger pick-up and brush meters, and
3) air and vacuum meters. Advantages and disadvantages exist for all types. Plate
and wheel meters need to "fit" the seed being planted. Warping and wear
areas on plates are difficult to detect and will affect performance. Finger pick-up
and brush meters require frequent maintenance and regular servicing. Both are sensitive
to wear, seed treatment, row unit vibration, speed, environmental conditions and
typically cannot be used for small seeds. Air and vacuum meters contain many hoses,
fans and seals and have the potential for pinhole leaks, which affects performance.
These meters are typically sensitive to field conditions such as high winds, steep
slopes and rough fields.
Seed Spacing: Many factors affect seed spacing including the type of meter
device, location of the meter above the ground, seed delivery and seed bounce. On
high-speed, high acreage planting equipment the best place for the meter is mounted
on the row unit, directly above the double disk openers. Singulating meters located
high above the row unit cannot maintain precise seed spacing in the bottom of the
seed furrow because seeds bump into the seed tubes and seed delivery elements in
the opener, changing drop speed and slightly altering direction. Guiding the seed
to the bottom of the seed furrow with a curved drop tube ensures that every seed
makes it to the bottom of the furrow and it greatly decreases the incidence of seed
contacting the disk opener. Using some sort of "seed firmer" helps eliminate
seed bounce in the bottom of the furrow. Plants themselves also have the ability
to compensate for variations in spacing. Typically most planters have seed spacing
variations of 2 inches or more.
Depth Control: Poor depth control results in uneven emergence and wasted
seed. Plants that emerge later often produce less and sometimes nothing at all.
In order to control seed depth, the double disk opener depth must be controlled.
This done by adjusting down pressure, properly setting side gauge wheels and/or
adjusting pressure on the trailing press wheel or closing wheels. Planting speed,
which affects planter vibration, seed delivery and seed bounce also influences seed
Sidewall Compaction: In wet field conditions, disk openers can slick soil
to the point that roots cannot penetrate the sidewalls. With slick hard sidewalls
on the seed furrow, roots will naturally grow along the path of least resistance
with the seed furrow and not penetrate deeper into the soil profile. The young plant
will not follow the moisture front into the soil under dry conditions and nutrient
uptake will be limited. A separate coulter in front of the double-disk opener helps
alleviate sidewall compaction problems.
Residue Management: In cold, wet planting conditions it is important to remove
residue from above the seed zone to promote fast soil warm-up and quicker and more
even germination. Moving residue to the area between rows may slow weed germination.
Residue must not interfere with the depth controlling system. Coulters and trash
whippers that clear residue away from the row allow side depth wheels or rear depth
controlling press wheels to run on the soil allowing even depth control. Decaying
residue should be kept away from the germinating seed to minimize diseases in certain
field conditions. As rows become narrower it becomes more difficult to place residue,
especially in heavy corn residue. In most field conditions the cutting coulter should
be run deeper than the disk openers allowing clean cutting of the residue. When
residue is not cleanly cut, but simply pushed into the ground "hairpinning"
occurs negatively affecting seed to soil contact, increasing disease problems and
on dry, windy days wicking away moisture. When soil conditions are soft it is difficult
to cut residue cleanly.
Moisture Retention: In dry conditions plant to moisture and apply enough
down pressure to remove air pockets and compact the soil around and above the seed
to seal in moisture. Avoid hairpinning and keep residue out of the area of the seed.
For good germination the seed must be placed in the bottom of the seed furrow in
Other Issues: Other management practices such as seedbed preparation (tillage),
soil compaction, planting date, and fertilizer placement often directly influence
planter performance. These topics and others such as crop rotation, hybrid selection,
fertilization and harvesting techniques affect crop productivity in general and
will be discussed in future articles.