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 populations.

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 depth.

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 moist soil.

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.