rows of corn crop on a sunny day

Welcome to the Corn DD50 Management Program.

The Corn DD50 program is designed to assist corn producers, consultants, and Extension personnel with management of corn in Arkansas. For more details on the DD50 program and how it works, please see the “About Corn DD50” section. This product was developed by the University of Arkansas System Division of Agriculture and the Arkansas Corn and Grain Sorghum Promotion Board. The purpose of the product is to provide assistance to Extension clientele that is consistent with corn production recommendations of the Arkansas Cooperative Extension Service. Information and predicted dates provided through this program should be used as a guide and does not replace the need for in-person inspection of the crop.

About the Corn DD50 Management Program

Dr. Jason Kelley, Corn Extension Agronomist

Corn growth and development is strongly correlated with air temperatures. Knowing accurate local daily high and low temperatures, corn development can accurately be predicted. The Corn DD50 program is a summary of the degree-day (DD) model (sometimes referred to heat units or growing degree days), which uses daily high and low air temperatures from a 24-hour period to predict corn development. Corn degree days are calculated by using the equation below:

dd50 equation dd50= daily maximum temperature plus daily minimum temperature divided by two minus 50

Maximum temperature = 86°F if maximum temperature is > 86°F
Minimum temperature = 50°F if minimum temperature is < 50°F

Using this equation, the maximum temperature for corn growth is set at 86°F as temperatures above 86°F do not result in more growth. Conversely, a minimum temperature of 50°F is used as corn growth ceases at temperatures at or below 50°F that are still above freezing.

Example 1: Daily high temperature was 85°F and the minimum daily temperature was 55°F. The accumulated Degree Days (DD) would be ((85+55)/2) – 50 = 20 Degree Days

Example 2: Daily high temperature was 95°F and the minimum daily temperature was 74°F. The accumulated Degree Days (DD) would be ((86+74)/2) – 50 = 30 Degree Days. In this example, since the high temperature was above 95°F, a base high temperature of 86°F was used.

Example 3: Daily high temperature was 70°F and the low temperature was 45°F. The accumulated Degree Days (DD) would be ((70+50)/2)-50 = 10 Degree Days. In this example since the low temperature was below the base temperature of 50°F for growth, 50°F was used for the calculations.

The Corn DD50 program uses a weather station network of over 30 sites across Arkansas by using the Applied Climate Information System (ACIS). The Applied Climate Information System (ACIS) is a system architecture developed, maintained, and operated by the NOAA Regional Climate Centers (RCCs). The weather data from the closest station to the field is used to account for weather differences among geographic locations, DD50 predictions are calculated based on temperature data collected from locations closest to the specific fields based on the county selected for the field.

How to Use the Corn DD50

The Corn DD50 program can be used by individual producers who manage their own crops, by consultants with multiple clients, or by county agents for producers within their county. To participate in the Corn DD50 management program, two options are available to producers or consultants. The first option is for producers or consultants to log onto the Cooperative Extension Service website and enter their fields directly at The second option is for producers to submit their planting date, hybrid, and location of each corn field to their local county Extension office to enter into the program and send the report to the producer. It is preferred that producers and consultants set up an account and enter their own fields so that they make check the program for updates as the season progresses and the information progresses throughout the season.

At the beginning of the season, the Corn DD50 operates using 30-year temperature averages for the field location. The Corn DD50 program is continually updated with the current year's weather data to improve accuracy. Daily temperatures and resulting accumulated Degree Day units vary considerably across years. Those with enrolled fields will be notified when current year temperature data significantly differs from the predictions based on 30-year average temperature data.

The Corn DD50 program is not intended to be a substitute for in-person field scouting, but another management tool to assist producers with timing of management decisions. Therefore, growers are encouraged to verify corn growth stages before making management decisions where growth stage is extremely important.

Uses of the Corn DD50

The Corn DD50 program assists growers with numerous management decisions based on estimated growth stages. Growth stages and estimated input timing includes anticipated emergence date, anticipated herbicide application cutoff dates, side-dress and pre-tassel nitrogen application times, time of greatest irrigation demand, silking dates, timing of foliar fungicides, irrigation cutoff times, maturity date, and estimated harvest date. The Corn DD50 program can be an important tool in planning harvest dates and how planting date or hybrid maturity differences may influence corn harvest date.

Explanation of the Corn DD50 Printout

The Corn DD50 provides numerous estimated dates for management practices. The following is an explanation of each management practice and the estimated dates. The date or range of dates estimated for each input should be used as a guideline. Since factors other than temperature can influence the rate of corn development (example, saturated or very dry soils), producers/consultants should check each field in random spots to ensure accuracy of the Corn DD50 program. The listing of a pesticide application window does not always mean that the pesticide is recommended by the University of Arkansas System Division of Agriculture or that these products are recommended over other suitable alternatives. Suggested timing for pesticides on the Corn DD50 assumes federal and state labeling. However, label revisions can occur at any time. Before using any pesticide, always read and follow the directions and precautions printed on the label. Refer to the MP44, Recommended Chemicals for Weed and Brush Control, for specific University recommendations.

Growth Stages and Management Inputs

Emergence: Days from planting to emergence can vary considerably based on soil and air temperature. Emergence can occur as quickly as 4 days under warm soil and air temperatures such as encountered during a very late planting date. With cool soil and air temperatures that are often encountered from early March plantings, emergence may take as long as 28 days some years. Estimated DD50’s to full emergence is 120 to 150 units. Soil crusting from rainfall after planting can delay emergence. High levels of crop residue such as in a no-till or cover crop production system may slow emergence on early planted corn.

Recommended Dates for Side-Dress Nitrogen Application: A majority of the side-dress nitrogen is applied between the V4 to V8 growth stages. Accumulated DD50’s from planting is approximately 450-800 units. There is broad window which side-dress nitrogen can be applied and still maintain maximum yields.

Atrazine Herbicide Cutoff: Atrazine herbicide can be applied postemergence over the top of corn until the corn reaches 12 inches in height. This typically corresponds to the V5 growth stage and 500 DD50’s accumulated since planting. Consult the MP44 for the latest herbicide recommendations.

Liberty Herbicide Cutoff: For Liberty tolerant Hybrids ONLY. Liberty herbicide cutoff for postemergence over-the top applications to corn is the V7 stage. Accumulated DD50’s since planting is approximately 700. Consult the MP44 for the latest herbicide recommendations.

Glyphosate Herbicide Cutoff: For Glyphosate Tolerant Hybrids ONLY. Glyphosate herbicide cutoff for broadcast application is 30-inch tall corn (measured to the whorl) or V8 growth stage, whichever is more restrictive. In early-planted corn, the V8 growth stage typically will not be 30 inches tall, while with later plantings at the V8 stage plants may be 30 inches or taller. Accumulated DD50’s from planting is approximately 800 units. Consult the MP44 for the latest herbicide recommendations.

Pre-tassel nitrogen application timing: Incorporating a planned pre-tassel nitrogen timing to spread nitrogen applications throughout the season and reduce the nitrogen loss potential is a good management practice for Arkansas corn. A 3-way nitrogen split with approximately 30-50 units of N at planting (30 for sandy and silt loams and 50 for clays), the bulk of nitrogen at the side-dress application, and 46 units of nitrogen applied during the 1-2 weeks prior to tassel is a common application program. Timing of the pre-tassel nitrogen application window is approximately 3 weeks, from as early as V10 to tassel/early silking. Accumulated DD50’s since planting is 1000-1500. Consider taking tissue samples (uppermost collared leaf or earleaf if present) at least 18-21 days after the sidedress application from the V10 stage to tassel to determine crop nitrogen status. Tissue samples showing greater than 3% nitrogen are less likely to respond to a pre-tassel nitrogen application and should produce maximal yield as it relates to nitrogen fertility.

Greatest Irrigation Demand: Greatest water usage occurs during the V10 to R4 stages and peaks near silking. Adequate rainfall or supplemental irrigation is needed to achieve maximum yields during these stages. Accumulated DD50’s from planting is approximately 1100-2100 units. Soil moisture sensors are an excellent way to verify adequate soil moisture.

Beginning of Silking: Silking is a critical crop stage and having adequate soil moisture is key for successful pollination. The tassel stage and early silking occur nearly simultaneous on many hybrids. Accumulated DD50’s from planting to silking varies by hybrid, but hybrids that are typically grown in Arkansas normally range from 1300-1500 units.

Scout for Foliar Diseases: Scout for Foliar Diseases: Foliar fungicide applications prior to silking will not provide season-long disease protection and are generally not advised. Scout to determine a need for a foliar fugicide application. University trials suggest applications after the R4 stage are unlikely to have a positive impact on yield and are not recommended.

R5 Growth Stage (Dent Stage): At the R5 growth stage, water consumption is slowing. With normal temperatures, maturity is 21-24 days away on most hybrids. Accumulated DD50’s from planting for most of our typical hybrids is approximately 2200 units.

Furrow Irrigation Termination: At growth stage R5.5 (50% starch line), corn is typically 10-12 days from maturity. If irrigation has just been completed and soil moisture is wet, adequate moisture should be present to reach maturity. Soil moisture sensors will aid in determining the timing and need of the last irrigation. Accumulated DD50’s from planting is approximately 2520 units for most hybrids grown in Arkansas.

Pivot Irrigation Termination: At growth stage R5.75 (75% starch line), corn is approximately 7 days from maturity. If irrigation has just been completed, adequate soil moisture should be present to reach maturity. Soil moisture sensors will aid in determining the need or timing of the last irrigation. Accumulated DD50’s from planting is approximately 2720 for most hybrids grown in Arkansas.

R6 Maturity (Black Layer): Corn has reached maturity and no additional inputs are needed. Grain moisture is approximately 30-35% moisture. Monitor stalk integrity and plan harvest accordingly. Accumulated DD50’s from planting varies by hybrid, but 2700 to 3000 units are typically needed to reach maturity for most hybrids grown in Arkansas.

Harvest Date (18% moisture grain): Harvest date can vary considerably depending on grain drying/storage capability. For producers with high capacity continuous flow dryers, harvest can begin as soon as maturity is reached. For those who let grain field dry, approximately 25 days after maturity is needed for grain to reach 18% moisture most years. Periods of rain or high humidity will delay drying of grain.