- Establishing a desired corn stand is essential to maximizing yield potential and profitability.
- Factors such as soil conditions, soil fertility, weather, pests, and planting speed can play a role in stand establishment.
- Decisions made prior to and at planting in regards to equipment maintenance, weather, soil conditions, and monitoring planter accuracy can influence yield potential for the season.
Soil conditions at planting play an important role in stand establishment. Regardless of the amount of tillage planned (minimum tillage vs. conventional), the soil should be sufficiently dry for equipment passage to reduce compaction. When soil is compacted the soil particles have little pore space between them, resulting in poor root, moisture, and nutrient penetration. Sidewall compaction can occur in the seed furrow if the soil contains too much moisture at planting (Figure 1). This can prevent the primary root or seed radical from penetrating through the compaction into surrounding soil and nutrients. Ultimately, the seedling may die or become a “non-productive” plant.
Deep compaction into the root zone can cause issues later in the season as roots grow deeper into the soil profile. Root restriction can cause nutrient and moisture deficiencies.
Variable soil moisture and temperature in the seed zone can make a big difference in the amount of time it takes coleoptiles to emerge. When seeds have absorbed about 30% of their weight in water, germination begins.1
To help establish uniform emergence, seeds should be planted at a consistent depth into adequate moisture with good seed-to-soil contact. Normally, planting depth should be 1.5 to 2 inches. A depth of less than 1 inch will result in the nodal root system developing too near the soil surface, which can result in rootless corn syndrome. Shallow-planted seed is also subject to feeding by animals and birds. Planting depth and spacing should be checked regularly during planting to ensure proper placement. Emergence delays of about 10 days scattered throughout the field can result in yield losses up to 9%. Delays of about 21 days can result in yield losses up to 22%.2 An evaluation of 350 commercial corn fields for plant spacing variability suggested that yield may improve up to 6.5 bu/acre in 60% of the fields and more than 7.5 bu/acre in 24% of the fields by improving plant spacing uniformity within the rows.3
Role of Fertility
Precautions should be taken to avoid injury to seedling roots from applied fertilizers. Planting too quickly behind an anhydrous ammonia application could result in root burn. General recommendations are to wait approximately seven to ten days to plant after an anhydrous ammonia application.4 However, there is no definitive waiting period as injury has occurred from fall-applied anhydrous ammonia. Anhydrous applications should be applied diagonally across the field to avoid the potential of placing a corn row directly into a previous anhydrous knife slot. Anhydrous ammonia application into wet soils may result in soil smearing as the knives pass through the soil profile, which will not allow the ammonia to dissipate.
Pop-up fertilizers should be placed 2 inches below and 2 inches to the side (2 x 2) of the seed row to help avoid seed injury, especially under dry soil conditions on light or sandy soils. According to information from Pennsylvania State University, starter fertilizer rates should be below 10 pounds of nitrogen and potassium (K2O) per acre and must not contain urea or Diammonium phosphate (DAP).5
Role of Weather
Corn seed requires a soil temperature of at least 50° F for germination and uniform emergence. If soil conditions are dry, seeding depth should be deep enough to meet soil moisture. Uneven soil moisture can lead to uneven emergence. Wet soils with a temperature below 50° F may cause chilling injury during germination (Figure 2). Imbibitional chilling injury happens when a dry corn seed takes in cold water from rain or melting snow. As usual, the germinating corn seed takes in the water and swells. However, cold water can cause cell membranes to become rigid and rupture, which may result in aborted radicals, proliferation of seminal roots, and delayed seedling growth.
Utilizing a 4-inch long temperature probe around midday should provide a good idea of the temperature the soil will achieve for the day (Figure 3). In addition, short term weather forecasts can provide clues toward soil warmth. A forecast with warm air temperatures and sunny days can be favorable for planting. Conversely, cool cloudy days can result in unfavorable planting conditions, especially if freezing temperatures occur.
Windy conditions can dry soil out around planted seed. Without moisture, the roots may not be able to continue growth and seedlings may die or become stunted.
Role of Pests
Soil insects such as wireworm, seedcorn maggot, white grub, and grape colaspis can feed on seed kernels and destroy germinating seeds. Seed treatments can not only help provide protection against these and other labeled soil insects, but also help protect seed from soil and seed borne diseases including Fusarium, Rhizoctonia, and Pythium. Additional seed treatments may be available to further help protect seed from black cutworm and corn nematode pressure after root development.
Role of Planting Speed
Planter speed may affect seed spacing accuracy. In a 2001 University of Nebraska study, seed spacing accuracy was reduced as planting speed was increased.6 The study measured spacing accuracy for speeds of 2, 4, and 6 mph. In this study, yield was not affected by increased speed. However, in another study at the University of Nebraska, yields were decreased as speeds increased from 5 mph to 7.5 mph. The study reported a profit loss of more than $20 an acre at $3.50/bu.7
In a 1993 planting trial, twenty-two farmers in Indiana, Illinois, and Iowa planted corn at 4, 5, 6, and 7 mph. The study was replicated on each farm 3 times. Results indicated a yield loss of 3 bu/acre at 6 and 7 mph compared to slower speeds of 4 and 5 mph.8 In the same study, 7 of the 21 planters showed yield decreases of 1.6 to 4.7 bu/acre for each 1 mph increase in planting speed. A 3 mph increase from 4 to 7 mph would provide per acre dollar losses of $19.20 and $56.40 with corn priced at $4.00/bu.
Role of Grower
The decisions of when to plant, when and how to apply fertilizer, herbicides, and insecticides, how deep to plant, speed of planting, and other decisions are ultimately determined by the grower. Establishing the desired stand is a factor of many interactions that can to some extent, be regulated through management. Overseeing equipment maintenance, checking weather forecasts, determining soil conditions, and ensuring timely checks of planting accuracy, are a few of the elements that growers can influence.
1Nielsen, R.L. 2000. Corn growth and development. What goes on from planting to harvest? Purdue University. AGRY-97-07. https://www.agry.purdue.edu/
2Carter, P.R., Nafziger, E.D., and Hicks, D.R. 1992. Effects of uneven seedling emergence in corn. National Corn Handbook. Purdue University. NCH-36. https://www.extension.purdue.edu/
3Nielsen, R.L. 2001. Stand establishment variability in corn. AGRY-91-01. Purdue University. https://www.agry.purdue.edu/
4Schwab, G. 2009. Avoiding anhydrous ammonia seedling injury. Corn & Soybean News. Volume 9, Issue 4. University of Kentucky. http://www.uky.edu/
5Beegle, D.B., Roth, G.W., and Lingenfelter, D.D. 2007. Starter fertilizer. Penn State Extension. Agronomy Facts 51. http://extension.psu.edu/
6Elmore, R. 2002. How does planter speed affect plant spacing? Iowa State University. Corn Production. http://www.agronext.iastate.edu/
7Jasa, P. 2007. Increased planting speed can cost yields. Nebraska crop production & pest management information. University of Nebraska. CropWatch. http://cropwatch.unl.edu/
8Nielsen, R.L. 1993. Planting speed effects on stand establishment and grain yield of corn. Purdue University. AGRY-94-02. https://www.agry.purdue.edu/
Sawyer, J.E. 2003. Ammonia burn hits cornfields. Integrated Crop Management. Iowa State University. IC-490(12). http://www.ipm.iastate.edu/
Nielsen, R.L. 2005. Planter maintenance: less down time, more yield. Purdue University. Corny News Network. http://www.agry.purdue.edu/
Larson, E. 2009. Corn planting suggestions. Mississippi State University. Grain Crops Update. http://msucares.com/
Elmore, R. 2012. Imbibitional chilling and variable emergence. Iowa State University.
Integrated Crop Management News. http://www.crops.extension.iastate.edu/
Web sources verified 12/04/15. 140404070134