Keys To Success For Early Corn Planting

DR. ERICK LARSON

MISSISSIPPI STATE, MISSISSIPPI

It is now March and we have generally had a drier than normal winter, so anticipation of corn planting is high, if you haven’t already been in the field.  Corn is generally very responsive to early planting, but we often face challenges that can overwhelm the benefits. It is your responsibility to make sensible cropping decisions, execute timely and precise practices, and implement methods to enhance corn productivity or limit risk, setting the table for this season. This article will discuss strategies to optimize your stand, ultimately enhancing the productivity and profitability of your corn crop.

So if the opportunity arises, what constitutes an acceptable early planting date? Soil temperature and moisture primarily dictate seedling growth and survival and thus, are generally far more relevant than calendar dates. Germination and seedling emergence is a cumulative process dictated by temperature during which corn seedlings are particularly vulnerable to saturated soils from ever-present rainfall. Therefore, there is normally considerably more risk associated with adverse weather for  early plantings, compared to later in the spring.

Soil temperature is the primary factor regulating seedling germination with warmer temperatures increasing growth and likelihood of successful uniform emergence. Fortunately, you can measure soil temperature and watch the forecast to assess your chances. A reasonable goal for corn is at least 55 degrees F measured near dawn at planting depth. Corn will not germinate at temperatures below 50 degrees F, and its growth rate slows considerably with cool temperatures. Therefore, exposing your expensive seed to cool conditions is risky. On the other hand, if temperatures stay warm, then you can take advantage of the weather to plant your corn crop and hopefully reap the rewards, particularly for dryland producers. This is important because dryland corn is fully dependent on mid-summer environmental conditions, and early maturity nearly always produces higher yields.

In order to realize optimal yield potential, corn plants need to successfully achieve a good, uniform stand, which can be a difficult challenge in the Midsouth. Emergence disparity, poor seed spacing, soil compaction and other issues can all reduce corn yield potential as much as seedling mortality and overcome benefits of early planting. In fact, the highest corn yield produced in the state NCGA Yield Contest the past four years was planted the first week of May. Accordingly, planting conditions were much better than normal and produced huge dividends, despite the drawbacks of the crop maturing during the heat of the summer. However, there are several tactics which we can use to improve our stands with early corn plantings.

Best management practices for improving corn stand establishment include:

• A moderate 1 ½ to 2 inch planting depth should improve your likelihood of achieving a good stand. Deep planting will delay emergence and likely expose seeds to cooler and wetter soils, which can stunt seedling growth and often create problems in our environment, including emergence variability. Corn seed should be planted at least 1 ½ inches deep to enable proper root development, but deeper planting is not needed unless soil moisture is inadequate for germination, which is rarely necessary in this region. Accordingly, keep planting depth moderate, particularly when soil moisture is moist, and on heavy-textured clay soils. Where bird depredation is likely, use a repellent to deter damage, while retaining benefits associated with moderate planting depth.
• Raised beds are a proven method to help relieve seedlings from saturated soils and improve corn stand establishment. Accordingly, don’t knock your beds down any further than necessary to facilitate planting. Harrowing several inches of soil off the top of your beds diminishes their effectiveness, while presenting a cooler environment for your seedlings. This is a no-win scenario.

• Avoid planting or any field operations while soils are marginally wet, if possible. Your goal associated with planting is to optimize precision and achieve uniform, vigorous stands. Planting wet soils may inhibit planter performance, but more importantly create persistent soil issues. Tire traffic from tractors and equipment produce soil compaction that inhibits root and plant growth. Seed furrow compaction can inhibit moisture absorption by the seed which will hinder germination, as well as severely restrict root growth. You simply have to be patient enough to minimize these problems.
• Moderating planter ground speed can also enhance stand uniformity and corn yields. Top producers such as world record corn producer David Hula state, “Even spacing and emergence are critical to high corn yields.” Although new technology and after-market equipment may improve efficiency, high speed invariably presents issues which ultimately confound stand quality. Achieving a picket fence stand is no simple task, so do your part by slowing down.

Corn is generally quite responsive to planting rate, but numerous factors affect what constitutes an optimal plant density for your fields. Corn productivity normally responds positively to increasing plant population before leveling out and often diminishing as rates becomes excessive. This yield plateau occurs because ideal light interception has already been achieved, or other factors become more serious yield limitations. Therefore, your goal is to find this sweet spot which optimizes yield potential, but doesn’t surpass it and reduce your profitability. Excessive plant population also increases competition for resources, which stresses plants and compounds other limitations.

There are several factors that can affect what constitutes an optimal plant population for various fields on your farm:

• Irrigation normally improves corn response to plant population, because it allows you to manage a major yield limitation. Dryland producers cannot predict and have little control over soil moisture availability during June and July, when corn needs and sensitivity are high. Last summer’s drought definitely reminds us that dryland producers should use moderate planting rates to ensure healthy plants and respectable yields in case drought is severe. Accordingly, my standard dryland corn plant population goal is going to be around 28,000 plants/a, and about 34,000 plants/a for irrigated fields, dependent upon other factors noted below. Similarly, if your corn yields are historically modest, despite planting more than 30,000 plants/a, planting rate is not likely your limiting factor, so increasing rate is not going to be responsive or profitable.
• Narrow row width enhances corn response to planting rate because better spacing improves plants’ ability to intercept light, and obtain nutrients and water. For instance, corn grown in 30-inch rows at 38,000 plants/a has the same 5.5-inch in-row spacing as corn grown at 30,000 plants/a in 38-inch rows. This is why 30-inch rows are proven to be about 8-10% more productive, compared to 38 to 40-inch rows. Therefore, optimal seeding rate for wide rows is going to be several thousand plants per acre less than in 30-inch rows.
• Planting date is well-known to effect on corn productivity and growth, and thus, we should adjust rates when planting dates vary substantially. Corn planted early is generally more productive because critical reproductive stages occur when temperatures are cooler and generally more favorable. Also, early planted corn generally attains less leaf area and plant height, compared to later planting, because cooler spring temperatures limit vegetative growth. Both these factors enhance corn response to higher seeding rate. Conversely, late planted corn produces taller, leafier plants, which are exposed to higher summer temperatures and stress, limiting yield potential. Thus, planting rate can be trimmed as we progress into late-April and May. ∆
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DR. ERICK LARSON: State Extension Specialist, Mississippi State University