NDAWN Corn Growing Degree Days Information (original) (raw)
For most plants, phenological development is strongly related to the accumulation of heat or temperature units above a threshold or base temperature below which little growth occurs. This lower threshold temperature varies with plant species. Scientists have determined the lower base temperature for corn is 50 °F (10 °C). In some plants there is also an upper threshold temperature, above which conditions are stressful to the plants. The upper limit for corn is 86 °F (30 °C). Although temperature is the most important factor controlling the rate of plant development, other factors such as water and light availability and daylight length may modify its effects.
The most common temperature index used to estimate plant development is growing degree days (GDD) which are calculated from the daily maximum and minimum air temperature. Growing degree days have proven useful for crop consultants, producers, and scientists who use them to predict plant development rate and growth stage. In certain crops this information is used to help plan crop management decisions such as irrigation or pesticide application timing, and for scheduling harvest.
Corn Growing Degree Day Calculation
Corn growing degree days (GDD) are calculated by subtracting the plant's lower base or threshold temperature of 50 °F (10 °C) from the average daily air temperature in °F or °C. Average daily air temperature is calculated by averaging the daily maximum and minimum air temperatures measured in any 24-hour period. All daily NDAWN data are based on a midnight to midnight (Central Standard Time) 24-hour calendar day.
In Formula Form
The Daily Average Temp (°F) = (Daily Max Temp °F + Daily Min Temp °F) / 2
and
Daily Corn GDD (°F) = Daily Average Temperature °F - 50 °F
Constraints on maximum and minimum temperatures are used to eliminate the effect of low or high temperatures that prevent or retard growth. For corn these constraints are:
If the daily Max and/or Min Temp < 50 °F (10 °C), it's set equal to 50 °F (10 °C).
and
If the daily Max Temperature > 86 °F (30 °C), it's set equal to 86 °F (30 °C)
Example 1:
Given: Daily maximum temperature = 80 °F and daily minimum temperature = 56 °F;
Then:
Daily average temperature = (80 °F + 56 °F) / 2 = 68 °F.
and
Daily Corn GDD (°F) = 68 °F - 50 °F = 18 GDD (°F).
Example 2:
Given: Daily maximum temperature = 66 °F and daily minimum temperature = 38 °F;
In this case:
The daily minimum temperature of 38 °F is replaced with 50 °F, according to the above constraint.
Then:
Daily average temperature = (66 °F + 50 °F) / 2 = 58 °F.
And,
Daily Corn GDD (°F) = 58 °F - 50 °F = 8 GDD (°F).
Example 3:
Given: Daily maximum temperature = 94 °F and daily minimum temperature = 73 °F;
In this case:
The daily maximum temperature of 94 °F is replaced with 86 °F, according to the above constraint.
Then:
Daily average temperature = (86 °F + 73 °F) / 2 = 79.5 °F.
And,
Daily Corn GDD (°F) = 79.5 °F - 50 °F = 29.5 GDD (°F).
Example 4:
Although unlikely it is possible for the minimum temperature to be < 50 °F and the maximum temperature to be > 86 °F on the same day. In this case both constraints are applied.
Corn Growth Stage Estimation Using Accumulated Growing Degree Days (GDD)
Daily Corn growing degree days (GDD) (°F or °C) are accumulated beginning with the day after your specified planting date and continue until yesterday or until a specified ending date. Planting date is used rather than emergence date because it is more readily available in producers records. Both the daily GDD and the accumulated GDD are displayed in tables for specified stations. Accumulated GDD provide information as to how rapidly the season is progressing, and allow comparisons with other years and to long term averages.
Corn growth stages are not currently estimated on NDAWN because the relationship between accumulated GDD and growth stages for the shorter season varieties grown in North Dakota have apparently not been established yet. If or when validated data become available corn phenological growth stages will be estimated.
Note that the time from planting to emergence varies somewhat because of variations in planting depth and seedbed conditions that affect soil temperature, soil water content, surface residue, and soil type. Because of this variation the number of GDD required from planting until emergence may vary somewhat from field to field.
Reasonable estimations of field conditions from GDD calculations also require that temperatures measured at NDAWN weather stations are similar to those experienced by plants in the field. Differences in temperatures between stations and fields can be due to the distance from an NDAWN station and differences in field elevation or relief, soil color, type, and water content, and surface residue.
Variable Definitions
Corn Growing Degree Days (Corn AGDD) (°F or °C)
Growing degree days GDD (°F or °C) for Corn are calculated as follows:
Daily Corn GDD (°F) = ((Daily Max Temp °F + Daily Min Temp °F) / 2) - 50 °F
or
Daily Corn GDD (°C) = ((Daily Max Temp °C + Daily Min Temp °C)/2) - 10 °C
With the following constraints:
If daily Max Temp > 86 °F (30 °C) it's set equal to 86°F (30 °C).
If daily Max or Min Temp < 50 °F (10 °C), it's set equal to 50°F (10°C).
For more information see GDD Calculation.
Corn Accumulated Growing Degree Days (Corn Accum AGDD) (°F or °C)
The Accumulated Corn GDD is the sum of all daily GDD that have occurred from the day after your specified planting date until the indicated date. Daily growing degree days (GDD) (°F or °C) for corn are accumulated beginning with the day after your specified planting date and continue until the current date or a specified ending date.
For more information see GDD Calculation.
Normal Corn Growing Degree Days (Normal Corn GDD) (°F or °C)
The Normal Corn Growing Degree Days (GDD) for a specific date is the 30-year (1991-2020) average GDD. It is calculated by taking the average of all the GDD for the same date over 30 years, 1991-2020. For example, to obtain the Normal Corn GDD's for June 6, the number of Corn Growing Degree Days calculated for each June 6th during the 1991-2020 period (that is, June 6, 1991; June 6, 1992; June 6, 1993; ... ; June 6, 2019; June 6, 2020) are all averaged. This average is the Normal Corn GDD for June 6. This calculation procedure is repeated for every day of the growing season.Go here for more info on Climatic Normals.
Normal Corn Accumulated Growing Degree Days (Normal Corn AGDD) (°F or °C)
Normal Corn Growing Degree Days (GDD) (°F or °C) are accumulated or summed for a specified time period. The Corn AGDD is the total of the daily GDD for the period beginning with the day after planting and ending yesterday or on your specified end date. It is calculated exactly the same way as the Corn AGDD, except the daily normal GDD values are accumulated instead of the daily GDD's for a specific year. The purpose of this accumulation is to provide a comparison between the Corn AGDD's for a specific year and the Normal Corn AGDD's for the same time period. Go here for more info on Climatic Normals.
Departure from Normal Corn Accumulated Growing Degree Days (AGDD) (Dep Fr Nml Corn AGDD) (°F or °C)
The Departure from normal (Dep Nml) Corn Accumulated Growing Degree Days (AGDD) is a comparison between the Corn AGDD during a current or specified year and the Corn Normal AGDD. It is calculated after both the corn AGDD and the Normal Corn AGDD have been calculated for the same specified planting and end dates.
The Dep Nml Corn AGDD is calculated by subtracting the Normal Corn AGDD for a given date from the corn AGDD for the same date of the specified year. If the Corn AGDD total for that date is less than the normal AGDD total, the Dep Nml is negative.
For example, assume corn planted on May 1, 2005 has accumulated 585 GDD's by May 31, 2005 which means the Corn AGDD = 585. During the same time period, the Normal Corn AGDD = 655.
Dep Nml Corn AGDD (On May 31)
= 2005 Corn AGDD - Normal Corn AGDD
= 585 - 655
= -70
A negative Dep Nml Corn AGDD means that at this location temperatures during May, 2005 were lower than normal so fewer GDD's were accumulated, and crop growth is probably slower or less advanced than it would be if average or normal temperatures had occurred. If the Dep Nml is positive it means that the temperatures during the specified growing season were higher and the crop is probably more advanced than average development.
Go here for more info on Climatic Normals.
Departure from a Previous Year Corn Accumulated Growing Degree Days (AGDD) (Dep Fr yyyy Corn AGDD) (°F or °C)
The Departure from a previous year (Dep yyyy) Corn Accumulated Growing Degree Days (AGDD) is a comparison between the Corn AGDD during a current year and the Corn AGDD for a user selected previous year. Any year may be chosen for comparison to the current year as long as the selected station has data available for that year. If no data are available the departure from a previous year column will be blank. It is calculated after both the corn AGDD for the current year and the Corn AGDD for the previous year have been calculated for the same specified planting and end dates.
The Dep yyyy Corn AGDD is calculated by subtracting the previous year's total Corn AGDD for a given date from the current year's corn AGDD for the same date. If the current year's Corn AGDD total for that date is greater than the previous year's AGDD total, the Dep Prev yyyy Corn AGDD is positive.
For example, assume corn planted on May 1, 2005 has accumulated 950 GDD's by June 6, 2005 which means the current year, 2005 Corn AGDD = 950. During the same time period, the selected previous year's, 2004 Corn AGDD = 854.
Dep 2004 Corn AGDD (On June 6)
= 2005 Corn AGDD - 2004 Corn AGDD
= 950 GDD - 854 GDD
= 96 GDD
A positive Dep from 2004 Corn AGDD means that at this location temperatures during May 2 - June 6, 2005 were greater than those during the same period in 2004 so more GDD's were accumulated, and the crop is probably more advanced than it was in 2004. If the Dep from Prev yyyy is negative it means that the temperatures during the current growing season were lower than the previous year and the crop is probably less advanced than it was in the previous year.
Go here for more info on Climatic Normals.
Departure from 5-Year Average Corn Accumulated Growing Degree Days (AGDD) (Dep Fr 5-yr Avg AGDD) (°F or °C)
The Departure from a 5-year Average Corn AGDD (Dep 5-yr Avg AGDD) is a comparison between the Corn AGDD for a specified period during the current year, and the average AGDD for the past 5 years for the same period. The departure from a 5-year average Corn AGDD is available only when the selected NDAWN station(s) has at least 5 complete years of data available.
The Dep from 5-yr Average Corn AGDD is calculated by subtracting the 5-year average Corn AGDD for a given date from the current year's corn AGDD for the same date. If the current year Corn AGDD total is less than the 5-year average AGDD total, the Dep from 5-yr Avg AGDD is negative.
For example, assume corn planted on May 1, 2005 has accumulated 585 GDD's by May 31, 2005 which means the 2005 Corn AGDD = 585. For the same time period the 5-year, 2000-2004, average Corn AGDD = 655.
Dep from 5-yr Avg AGDD (On May 31)
= 2005 Corn AGDD - 5-yr Avg Corn AGDD
= 585 - 655
= -70
A negative Dep 5-yr Avg AGDD means that at this location temperatures during May, 2005 were lower than the past 5-year average so fewer GDD's were accumulated, and crop growth is probably slower or less advanced than it would have been if average temperatures had occurred. If the Dep 5-yr Avg AGDD is positive it means that the temperatures during the specified growing season were higher and the crop is probably more advanced than average development.