Rain clouds move toward ripening peanut field. Photo: Andrew Sawyer, University of Georgia
Green (unripe) peanuts are already being harvested for cooking, and high school football game previews were in the news this morning – a busy summer has almost entirely passed without my posting one aGDD tracker. Sorry for my lateness, but in this case I think better late than never.
While we are fast approaching harvest time for some of our earliest planted peanuts, for the majority of the harvest it is time to closely monitor maturity in order to plan the harvest to maximize yield and quality.
The tracker below shows the number of Average Growing Days (aGDDs) accumulated from 88 fictitious fields (8 sites x 11 planting dates) as of 08/19/22. Real-world temperature and precipitation data from the sites are used, as well as common soil types for the areas (Jay – loamy sand, Marianna – sandy loam, Marianna irrigated – sand, Monticello – sandy loam, Live Oak, and Bronson – sand).
Use the tracker to estimate the progress of your fields by following the fields on tracker most similar to you in terms of planting date, location and watering status. For more accurate tracking of your fields, you must PeanutFARM.org and set up your fields in the system.
You can enter field-specific rainfall/irrigation data and soil type. Temperature data is from the nearest FAWN weather station. If you’re interested in setting up your own fields on PeanutFARM.org, don’t hesitate to contact me for assistance.
The aGDD Tracker is compiled from data generated by PeanutFARM.org. The dark blue bars in the cells with the aGDD values show the progress towards 2500 aGDDs. The bar extends to the right as aGDDs are accumulated. The entire cell will turn dark blue and the text will be orange when a field has accumulated 2500 aGDDs.
It is recommended that fields be sampled and exact days to harvest determined by pod blasting once a field reaches 2300 aGDD; Text is yellow for fields that are between 2300 and 2500 aGDDs.
If you have fields approaching 2300 aGDD, contact your county extension office and make arrangements to have samples analyzed. At this point in the season with good moisture the fields will accumulate around 150 aGDD each week so plan accordingly – there will be a lot more orange and yellow in the fields tracker next week.
Remember that the information generated by the blast is only as good as the sample provided. Collect a good representative sample; Dig up (do not pull) crops in several places in the field, avoiding field edges and the ends of rows. Below is a link to a document detailing the entire maturity assessment process.
Methods for Assessing Peanut Maturity for Optimum Seed Quality and Yield
A few “nerd notes” from the Tracker:
Based on the current numbers, we see the expected trend of the later planting dates with on average more accumulated aGDDs per number of calendar days after planting than the earlier planting dates. This is to be expected as the fields planted later had only a few days when air or soil temperatures limited growth.
Both the planting dates on 6.6. as well as on 13.6. are an average of 20.5 aGDD per calendar day, while the planting dates on 4.4. and on 11.4. an average of 17.3 and 17.9 aGDD per calendar day. Again, the difference is caused by cooler temperatures experienced by the early planted fields in the early growing season.
At this point in the season temperature doesn’t matter – we have a lot of heat and assuming reasonable humidity all fields will accumulate about the same amount of aGDD.
Also, as expected, irrigated fields lag behind rain-fed fields. For the irrigated fields shown on the Tracker, PeanutFARM counts aGDDs as they would accumulate without drought stress. Because the fields are fictional and we don’t have to pay to run an imaginary pivot, our imaginary peanuts get every drop of water they want, on demand.
In this scenario, our irrigated fields average 21.0 aGDDs per calendar day across all locations and planting dates compared to the rain-fed fields, which average 17.9 aGDDs per calendar day. Real life irrigation management may not result in this essential difference.
Back in the world of computer models, the later planted, irrigated fields (no drought stress and lots of heat since planting) have an average of 22.4 aGDDs per calendar day. This accumulation rate would allow a peanut crop to mature in 112 days.
Before you run to hook up the excavator, remember that this is a “perfect world” scenario, disease and insect infestations, among other things, can slow down peanuts even when moisture and heat are plentiful. The best approach is that tracker Tell you when your fields should be near 2300 aGDD, then pull samples and create harvest plans based on the pod bursting results.