Getting a Good Corn Stand Starts With the Planter

Mike Rankin
Crops and Soils Agent - Fond du Lac County
University of Wisconsin - Extension

    The corn planter is one of the most expensive implements that a farmer can own. Not that it necessarily has the highest initial cost, but from the fact it only accomplishes one function (planting corn) and thus is only used on a limited number of acres per year. This makes the per acre cost of ownership very high compared to many other implements.

    Although the corn planter only performs one function, it is an extremely important one and for this reason the planter deserves careful attention to maintenance. This will help insure good stand establishment and protect your investment.

    During the past growing season, a research project was initiated in Fond du Lac County to evaluate the impact of corn stand uniformity on grain yields. To establish stands with variable plant to plant spacings, corn was planted at 4, 6, and 8 miles per hour and replicated three times on several different farms.

    Plant to plant spacings were measured in each of the field plots after corn had emerged. As expected, the number of seed doubles and row gaps increased as planting speed increased. Grain yields decreased by about 5 percent as planting speed increased from 4 to 8 miles per hour. This yield loss amounted to 10 bushels per acre on one farm and 8 bushels per acre on another.

    I think most corn producers realize that 8 miles per hour is too fast to plant corn. However, there are factors other than speed that can cause variable stands and the magnitude of yield loss that was seen in the research trial. In fact, I measured stand uniformity in seventeen Fond du Lac County fields in 1998 and noted a wide variation in stands. These were all fields where emergence was excellent and actual plant populations were close to what was planted.

    Now is the time to make sure your planter is ready for spring. Although seeding rate doesn't relate to stand uniformity, it is still a good first step to insure that corn is planted at an optimum density (28,000 to 32,000 seeds per acre in most cases) and you are actually planting the intended amount of seed. The operator's manual contains the information needed to determine the seeding rate for various sprocket combinations and row spacings. This is based on a particular tire size and pressure. If your tire size or pressure are different than those listed in the manual, seeding rates will also be different. Many planter manufacturers will also check planter unit function as a service to their customers.

    As previously mentioned, uniform seed placement within the row is also important to obtain maximum yields. Corn plants next to a gap in the row may produce larger ears to help compensate for missing plants, however, these plants cannot make-up for those that are crowded as seed doubles or triples growing within one or two inches of each other. Plants placed too closely together in a row will compete ineffectively for sunlight, water, and nutrients. Crowding results in barren plants or ears too small to be harvested.

    Plant spacing variability is often related to misadjusted or malfunctioning planter mechanisms. With finger-pickup style planters, double or triple drops may occur from worn finger-pickup mechanisms, misadjusted finger tension, worn knockoff brushes, or from driving too fast.

    Another important planter component to check before hitting the fields this spring is the disk furrow openers. For double disk arrangements, the two disks should have about two inches of contact at the point they enter the soil during operation. If the length of contact is less or if they do not touch at all, the "V" shaped seed furrow will be replaced by a "W" furrow. This will impact seeding depth and seed-soil contact. In no-till conditions, it will also reduce penetration into the soil crust. Regardless of what make or model of planter you operate, it will likely need service before the planting season.

    Finally, once planting time arrives, make sure to operate the planter within the specified speed range. As research has demonstrated, planting too fast can cause even the best-adjusted planter to perform below optimum in terms of seeding depth, placement, and uniformity.

    Insects, diseases, soil conditions, and weather can all cause corn emergence and stand uniformity problems in a given year. Make sure your planter and its operation aren’t added to this list in 1999.

For more information contact Mike Rankin