Dan Fromme1, Beatrix Haggard2, Josh Lofton2, and Rick Mascagni3
Alexandria1, Winnsboro2, and St. Joseph3, respectively
Planting the 2014 corn crop is just around the corner and everyone is asking when we should plant. The goals to a successful corn establishment are a rapid and uniform stand emergence. To achieve this goal, make sure that soil temperatures are adequate. Consequences of planting too early are a delayed and non-uniform stand of corn. The time from planting to emergence varies widely with environmental conditions and to a lesser degree, with planting depth. During this stage, development is affected directly by soil temperature and indirectly by air temperatures.
Importance of Uniform Seedling Emergence
Uneven seedling emergence can cause grain yield losses. When 25% or more of a stand is made up of plants that emerged 7-10 days late, yield losses will approach seven percent. When 25 to 50% of a stand is made up of plants that emerged 21 days late, yield losses will approach 10 percent. When more than 50% of stand is made up of plants that emerged 21 days late, yield losses will approach 20 percent. Yield losses from delayed emergences are related to several factors. First, delayed emerging plants are at a disadvantage for light, water, and nutrients when surrounded by older, larger plants. Plants that emerge early reach the grand growth phase (about V5 or V6) sooner than delayed emerging plants. By the time the delayed emerging plants begin their rapid growth phase, the early emerging plants have leaped ahead of them in terms of overall plant growth. The critical differences in growth stages between early and delayed emerging plants are about two leaves (e.g., V4 versus V2). When the differences in growth stages are more than two, the delayed emerging plants become barren plants (i.e., no ears). Therefore, when delayed emerging plants compose a large percentage of a stand, yield loss is simply equivalent to that associated with late planting. Secondly, delayed emerging plants often silk and pollinate significantly later than the rest of the field. A small number of late tasseling plants scattered throughout the field may not provide adequate amounts of pollen for successful fertilization of the silks.
Three Requirements for Uniform Germination and Emergence in Corn
There are three requirements for a rapid and uniform germination and emergence in corn. First, an adequate and uniform soil temperature is needed. An adequate soil temperature for corn is simply defined as being greater than 50oF at the 2-inch depth. Corn will not germinate or emerge quickly and uniformly when soil temperatures are less than 50oF. Uneven or non-uniform soil temperatures can be caused by different soil types in the field, uneven residue cover in reduced tillage systems and uneven seeding depth control.
Second, adequate and uniform soil moisture is needed at the seed zone. Adequate moisture is when the soil is not too wet or dry. Uneven soil moisture in the seed zone can be caused by different soil types, tillage patterns, and uneven seeding depth control.
Third, an adequate and uniform seed to soil contact is critical. Soil must be firmed around the seed in order for it to imbibe water. When planting conditions are not optimum is when have seed to air contact, seed to clod contact, or seed to trash contact. Seed to air contact occurs when planting into wet soils which results into an open planter furrow. Kernels lying in this open environment are dependent on rainfall for germination and emergence to occur. Seed to clod contact results from planting into cloddy fields created by working the soil too wet. Seed to trash contact results from surface trash falling into the seed furrow during no till planting when soil and or trash are too wet for adequate coulter cutting action.
Influence of Soil Types and Tillage Systems
One management aspect that is often overlooked for planting date determination is tillage systems. It has been well documented in the literature that high residue tillage systems typically warm slower in the spring than those with the soil surface exposed. In addition to these production practices, soil color will also affect the speed at which the soil warms. Darker soils will typically warm faster if they have similar amount of moisture as a lighter colored soil.
Determining When to Plant for a Rapid and Uniform Plant Stand
Rapid and uniform corn emergence helps ensure a strong and vigorous stand establishment. Adequate soil temperature is most simply defined as being greater than 50F at the 2-inch depth. However, when soil temperatures warm to the mid-50’s or greater, emergence will occur in 7-10 days which will give you a better chance of having a rapid and uniform stand. Keep in mind, when average daily soil temperatures are less than or fluctuating about 50oF, corn emergence will occur much more slowly and less uniformly making the seedlings more susceptible to soil borne insects, pathogens, and herbicide injury.
Remember, we have had a cooler than normal winter, make sure soil temperatures are adequate for achieving a rapid and uniform stand. Consequences of planting too early are a delayed and non-uniform stand of corn.
For further questions or comments, please contact:
Dan Fromme, Corn and Cotton Specialist, 318-473-6522 or firstname.lastname@example.org
Josh Lofton, Field crop agronomist, 318-498-1934 or email@example.com