Planting Tips for Corn & Soybeans
Planting Tips for Corn and Soybeans
Planting corn and soybeans at the optimal planting date, planting depth and seeding rate can help get the crop off to a good start and maximize yield potential. Get planting tips and information on evaluating corn stands and making replant decisions.
|Critical Steps to Planting Success|
Early Corn Planting Considerations
Factors to Consider Before Planting Corn
- Soil temperature of at least 50º F at 2-inch depth and preferably a warming trend in the 3-5 day forecast.
- Germination and root development will not occur below 50º F (root growth will be extremely slow even in the low 50’s).
- Prolonged exposure to low temperatures reduces seed and plant metabolism and vigor and increases sensitivity to herbicides and seedling blights.
- The risk of chilling injury decreases incrementally as the soil temperature increases above 50º F during the initial imbibition (water uptake).
- Sustained temperatures of 20º to 25º F or below can penetrate the soil enough to damage the coleoptile, mesocotyl, or the growing point and cause plant death in seedlings that haven’t emerged from the soil.
Prolonged exposure to soil temperatures below 50º F promotes seed deterioration and seedling disease.
Soil temperature at planting is a key environmental component of stand establishment; however, soil conditions after planting are also critical.
- Minimum of 24-hours of rain-free following planting.
- When a dry seed imbibes cold water (typically 50º F or below), imbibitional chilling injury may result (causing corkscrewed shoots, fused coleoptiles, premature leaf emergence underground & other germination oddities).
- Cold water can also cause cell walls in the germinating seed to rupture. Ruptured cells can have ill-effects on developing seedlings and can also attract disease pathogens and insects.
Coleoptile injury from freezing temperatures.
- Avoid planting right before a period of large temperature swings.
- Even if the “average” soil temperatures are above optimum, seedlings can be adversely affected by wide swings in soil temperatures. Affected seedlings will have stunted and distorted leaves and may or may not emerge from the soil.
- Research has shown that a swing of soil temperatures of more than 27º F (soil high temperature minus soil low temperature > 27º F) may adversely affect mesocotyl growth.
- Sandier soils can often be planted earlier in the spring because they dry out faster than heavier soils; however, sandy soils tend to experience wider temperature fluctuations, especially on clear nights with cold air temperatures.
- The effect of adverse conditions can and does vary from seedling to seedling, causing erratic and uneven stands.
Cold-temperature induced “corkscrew” damage symptoms.
Corn Planting Depth & Spacing
Optimum Planting Depth
Planting corn to a depth of 1½ to 2 inches is optimum for nodal root development.
- 2 inches – best under normal conditions
- 1½ inches – may be favorable when planting early into cool soils
- Never plant shallower than 1½ inches
Determining Planting Depth
- Planting depth can easily be determined after seedling emergence.
- The nodal root area (crown or growing point) typically develops about ¾ of an inch beneath the soil surface regardless of the seed depth.
- Measure the mesocotyl length (the area between the seed and crown or growing point, then add ¾ inch to determine the planting depth.
Corn planted too shallow:
- Is less able to uptake water and nutrients through the roots. Shallow-rooted corn plants suffer dramatically during periods of summer drought.
- Can develop a condition called "rootless corn syndrome." Plants will fall over due to the lack of nodal root development in dry soil.
- Can expose corn seedlings to herbicide residues increasing the potential for herbicide injury.
- Late-season root lodging concerns are reduced with improved nodal root systems.
Symptoms of Irregular Planting Depth:
- Uneven emergence.
- Non-uniform mesocotyl length.
- Varying plant height.
- More severe root-lodging in summer wind events
Planting Depth Recommendations
- Set the planting depth in the field, with the planter being pulled at full operating speed
- Check for good seed-soil contact; strive for firm seedbeds that promote uniform emergence and stronger root systems.
- Slower planting speeds between 4 to 5 mph achieve more uniform planting depths.
- Utilize in-row residue management equipment where needed; especially in corn-following-corn rotations.
- Utilize a planter down-pressure control system.
Pioneer on-farm surveys have shown that uniform plant spacing maximizes yield.
Types of Non-Uniform Plant Spacing
- Misplaced plants due to worn planter parts
- Missing plants (skips)
- Extra plants (doubles)
- May decrease yield relative to a uniform stand
- Will decrease yield relative to a uniform stand
- Yield of adjacent plants will increase, but not enough to compensate for the missing plant
- May increase yield slightly if stand is below optimum
- Yield of doubled plants as well as adjacent plants will decrease, but the yield of the extra plant will compensate for this reduction
Grain yield of individual plants by position relative to skips and doubles (30,000 plants/acre)
Plant Position Plant yield (lbs) Next to skip 0.43 2nd from skip 0.40 Control 0.39 Next to double 0.35 Double 0.33
Nafzinger, E.D. 1996. Effects of missing and two-plant hills on corn grain yield. Journal of Production Agriculture 9:238-240.
Pioneer studies show that individual plant yield reaches a maximum level when plants are within 2-3 inches of perfect equidistant spacing.
- Make sure the target plant population is high enough to maximize profitability.
- Typical seed corn germination is about 95%. Overplant by at least 5% to reduce the effects of germination-induced skips.
- Overplant for expected reductions due to insects and more stressful soil conditions (cold and wet).
- Be sure to check that the planter is properly adjusted and calibrated by digging behind the planter in every field.
Soybean Stand Establishment & Seeding Rates
Because there are many factors that affect soybean stand establishment, optimum seeding rates vary by region, cropping practice and field. Get tips on how to adjust seeding rates to compensate for common losses of stands. Stands that emerge uniformly with no large gaps or skips have the highest yield potential.
Corn Stand Evaluation
Many different stress factors are capable of reducing corn stands, such as:
- cold or wet soils
- insect feeding
- unfavorable weather conditions
Taking Stand Counts
- Take several sample counts to represent the field.
- Sample a length of row equal to 1/1000th of an acre.
- Measure off the distance appropriate for your row width, count the number of live plants and multiply by 1,000 to obtain an estimate of plants/acre.
Row Width Length of Row 38 inches 13 ft 9 in 36 inches 14 ft 6 in 30 inches 17 ft 5 in 22 inches 23 ft 9 in 20 inches 26 ft 2 in 15 inches 34 ft 10 in
When an injury event such as frost or hail occurs it is best to wait a few days to perform a stand assessment, as it will allow a better determination of whether or not plants will recover.
Stand counts should be taken randomly across the entire area of a field being considered for replant; this may include the entire field or a limited area where damage occurred.
Growth of green tissue near the growing point indicates that this plant would have recovered.
Soft translucent tissue near the growing point indicates that this plant will not recover.
Other Factors to Evaluate
- Stand uniformity - An uneven stand will yield less than a relatively even stand with the same number of plants.
- Plant health - Plants that are severely injured or defoliated will have reduced photosynthetic capability and a lower yield potential.
This plant was defoliated by hail. New green tissue indicates that it is recovering, but its yield potential has been reduced.
Corn yield is influenced by stand density as well as stand uniformity:
- Variation in plant size can have a negative impact on yield
- Uneven emergence timing leads to uneven plant size
Several Factors That May Lead To Uneven Emergence:
- Variation in soil moisture
- Poor seed- to- soil contact due to working or planting into wet soil
- Variation in soil temperature caused by uneven crop residue distribution
- Soil crusting
- Insects or disease
Late-emerging plants are at a competitive disadvantage with larger plants in the stand and will have reduced leaf area, biomass, and yield.
Impact of Uneven Emergence on Yield
Corn Replant Considerations
When corn stand loss occurs, replanting should be considered if the resulting yield increase will more than cover the cost.
Factors to Consider in Replant Decision-Making
- Plant density of the current stand
- Uniformity and health of the current stand
- Date of original planting and potential replanting
- Costs associated with replanting
- Crop insurance provisions
- In situations such as flooding damage, only a portion of the field may need to be considered for replant
- Frost or hail can damage a wide area. In this case plant density and health should be assessed across the entire field
Replant Yield Potential
- The expected yield from the current stand should be compared to expected replant yield.
- The table below shows yield potential for a range of planting dates and final plant populations.*
* Replant yield data was interpolated from University of Illinois population response data (E. Nafziger, E. Adee, and L. Paul) and University of Minnesota planting date response data (Hicks et al.).
Replanted areas in a field that experienced severe flooding damage in 2008.
Profitability of Replant
Even if replanting will increase yield, the yield increase must be sufficient to pay for all of the costs associated with replant such as:
- Extra herbicide or tillage costs
- Planting costs
- Increased grain drying costs
Also consider these factors when making a replant decision:
- Probability of an autumn freeze prior to physiological maturity of replanted corn
- Increased susceptibility of late-planted corn to summer drought or disease and insect pests such as gray leaf spot and European corn borer.
Hybrid Maturity for Replant
- The chart below shows the relative profitability of full-season, mid-maturity, and early maturity hybrids in 29 north-central Corn Belt environments over 17 years of DuPont Pioneer research.
- Results indicate that a grower may consider using a mid-maturity hybrid if replanting after May 17 and an early maturity hybrid if replanting after June 5.
Replanting to soybeans may be preferable after mid-June, but this will depend on soil-applied corn herbicides that were used.
Carter, P.R., E.D. Nafziger, and J.G. Lauer. Uneven Emergence in Corn. North Central Regional Extension Publication No. 344
Hicks, D.R., S.L. Naeve, J.M. Bennett, and N.B. Bennett. The Corn Growers Field Guide for Evaluating Crop Damage and Replant Options. Univ. of Minnesota.
Lauer, J.G. 1997. Corn Replant/Late-Plant Decisions in Wisconsin (A3353). Univ. of Wisconsin-Extension.
Delayed Corn Planting Considerations
When rainfall significantly delays field and planting operations, switching to early maturity hybrids may be considered. However, results from more than 18 years of Pioneer planting date studies indicate that growers should plant full-season hybrids until late May.
Central (red), north-central (orange), northern (green), and far-northern (blue) research sites for DuPont Pioneer planting date studies from 1987-2004.