Adjusted growing degree day accumulation is a more accurate measurement of maturity than days after planting.
This year’s peanut seeds may have just gone into the ground, but it’s never too early to take steps to maximize your crop’s yield and grade. Making sure peanuts are harvested at optimum maturity is one of the crucial steps.
To take this step, you must effectively track the crops maturity. While days after planting is commonly used to quantify peanut maturity, it is not the most accurate unit of measure available. It should not be the sole criteria used to determine harvest date.
Many Factors Affect Maturity Rate
Environmental factors, primarily temperature and moisture availability, not the calendar, drive how fast a peanut crop matures. Adjusted growing degree day (aGDD) is a unit that accounts for these factors. Depending on environmental conditions, a field will accumulate aGDDs at a different rate each calendar day and at a different rate than other fields experiencing different environmental conditions. A peanut crop will fully mature with approximately 2,500 aGDDs. Tracking the number of aGDDs accumulated by a specific field allows you to effectively track its maturity.
- Tracking maturity with aGDDs is important as shown in these examples:
Planting date can affect how fast aGDDs are accumulated shortly after planting. Lower air and soil temperatures associated with early plantings slow the accumulation compared to fields planted later in the season. - Even slight drought stress slows the accumulation of aGDDs. The frequency of rainfall or irrigation and soil type can affect how fast the crop matures. This situation can become very evident in rain-fed fields when summer showers are hit and miss.
To illustrate how aGDDs accumulate throughout the season and to provide growers with an approximation of how their fields should be progressing, the Florida peanut team will be sharing an aGDD tracker throughout the season. The aGDD tracker is essentially a table that shows the accumulation of aGDDs for a wide range of planting dates at locations across the peanut-producing region of the state.
Another Use For PeanutFARM
The aGDDs shown on the aGDD tracker are calculated by the Peanut Field Agronomic Resource Manager or PeanutFARM found at peanutfarm.org. The weather data, daily upper and lower temperature, and rainfall used in the aGDD calculation is generated by the corresponding Florida Automated Weather Network station.
Growers are urged to set up their own fields in PeanutFARM to allow more accurate calculation of aGDD for each field. This will enable them to enter their own field-specific information, rainfall and/or irrigation data. Temperature data is provided by the FAWN station closest to the field. Start soon to stay on top of the rainfall/irrigation data.
PeanutFARM is also a valuable irrigation scheduling tool. There is no cost to use it. If you need assistance getting started with PeanutFARM, contact your county’s agriculture Extension agent.
Pod Blasting Still Recommended
Just like DAP should not be the only factor to determine harvest, aGDDs calculated by PeanutFARM should not be the deciding factor either. Once the aGDD tracker reaches 2,300, samples of peanuts should be collected and tested with pod blasting to help determine the crops actual physiological maturity. This final step will provide a recommendation of days to harvest. Most Extension offices in peanut-producing counties offer pod-blasting services.
Article by Mark Mauldin, Washington County, Florida, agriculture and natural resources Extension agent.
