Overcoming Challenges to Plant the 2019 Corn Crop

Rainy weather since last fall has left many crop acres in precarious condition entering the 2019 planting season. Late harvest and wet soils prevented raised beds from being implemented last fall in many fields. Also, fields which were muddy during harvest were rutted and had little or no opportunity for subsequent tillage to repair and prepare fields for spring planting. Recent rains have further limited opportunity for field preparation prior to planting and could deteriorate seedbed condition of fields which were able to be prepared last fall.

Accordingly, 2019 planting conditions will likely be even more challenging than what is already difficult for Mississippi corn producers.  It is well documented that corn is very responsive to early planting, but we must also establish a uniform stand to fully achieve a productive crop. Although corn seedlings possess tremendous vigor, corn is inherently far less forgiving compared to other crops when stand establishment issues occur.

Of course, soil temperature and moisture are primary factors which affect corn seedling establishment. Soil temperature is the main factor influencing seedling growth rate. Therefore, you should always make sure temperatures are favorable for corn seedling growth before you begin planting. Cool soils will substantially hinder germination and seedling growth, which could create emergence disparity and distort development. Sluggish growth also makes seedlings more vulnerable to other issues, including wet, saturated soils, seedling pathogens, insect pests, and herbicide injury. We also know from recent years that soil saturation can limit aeration, stunt or kill corn seedlings, and restrict root development.

This could be even more challenging than normal this season, since many fields have not been bedded. Some have asked whether it is necessary to grow corn on raised beds, considering we won’t likely have much opportunity to implement them in advance of planting. Although it is certainly not necessary to grow corn on raised beds, they do help alleviate issues with soil saturation common in high-rainfall regions, and are necessary to facilitate our predominant furrow irrigation method in the Mid-South. Thus, for furrow-irrigated fields I recommend implementing raised beds prior to planting where practical, and pray we have opportunity to do so this spring.  A primary concern associated with establishing raised beds in the spring is that soils will likely be very prone to soil compaction due to abundant soil moisture. Compaction is a serious limitation to subsequent root development, which is critical to provide resources important to optimize productivity.

There are several management options we can use to improve our chances of achieving successful corn stands.

• Avoid tillage, bedding or planting fields while soils are marginally wet. Your goal associated with planting is to optimize precision and achieve uniform, vigorous stands. Planting wet soils will likely inhibit planter performance, create persistent issues and compound problems with abundant rainfall that hinder stands. Tire traffic from tractors and equipment produce soil compaction that inhibits root and plant growth. Seed furrow compaction can inhibit moisture imbibition by the seed as well as severely restricting seedling root growth.  You simply have to be patient enough to avoid these problems.

• Don’t knock down your beds any further than necessary. Raised beds are intended to provide relief to seedlings from saturated soils. Harrowing off several inches of bed height diminishes their effectiveness, while presenting a cooler environment for your seedlings. This is a no-win scenario.

• Plant well-drained soils first. Heavy-textured clay soils naturally stay wet longer, leading to more stand issues and failure, particularly when planting early.

• Measure soil temperature before you start planting. A reasonable goal for corn is at least 55 degrees F measured early in the morning 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 adverse conditions is asking for big trouble.

• Moderate planting depth may improve stand establishment. Corn seed should be planted at least 1 ½ inches deep to enable proper root development, and 1 ½ to 2 inches is normal. Deeper planting is not usually needed unless soils are really dry and you need to place seed deeper to reach moisture, which is rarely necessary in this region. Deep planting will delay emergence and may expose seeds to cooler and wetter soils which can lead to substantial stand problems, including emergence variability. Thus, keep planting depth moderate, particularly when planting early, when soil moisture is moist, and on heavy-textured clay soils. Where bird depredation is likely, I suggest using a repellent to deter damage, while retaining benefits associated with moderate planting depth.

• Deep seeding has little practical effect on roots. Corn possesses the biological ability to regulate its nodal root placement when planted deeper than 1.5.” This occurs because the shoot elongates upward from the seed until it senses light, indicating where crown development and the origin of nodal roots will occur under the soil surface. In other words, if corn is seeded deeper than normal, the mesocotyl will simply elongate further to ensure the nodal roots develop from a proper position. Nodal roots compromise the main corn root system and are fundamentally responsible for uptake of resources and affording stability. Brace roots are another part of the nodal root system which naturally develop from nodes above the soil surface much later (V12 to VT), which further enhance stability. Accordingly, there is little basis to assume that deep planting enhances root development, standability, or produce other benefits for corn, particularly in our moist, spring environment.

• Moderating planter ground speed should 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.” Increasing planter ground speed hinders planter performance, stand uniformity and corn yield. Although new technology and after-market equipment may improve seed metering performance, high ground speed still reduces stand uniformity achieved. Increasing speed increases inertia causing seeds to roll and/or bounce more during planting, creating poorer seed spacing and seeding depth variability. For instance, even at a slow speed of 4 mph, you are dropping about 15 seeds per second per planter unit – and each mile per hour increases distance covered by 18-inches per second, so achieving a picket fence stand is no simple task. Do your part to improve your outcome by slowing down.