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End of Season Irrigation for Peanuts

End of Season Irrigation for Peanuts
By Wesley Porter, Extension Precision Ag and Irrigation Specialist, UGA &
David Hall, Extension Water Educator, UGA
It’s safe to say that the 2021 growing season has received its share of rainfall. From May
1st to August 24th Midville has received 16.23 inches, Tifton 21.95 inches, Attapulgus 19/84
inches and Jeffersonville located in the middle of the state has received 22.5 inches of rain.
Most farmers agree that this year will go down as one where pivots were started up very few
times. Weather patterns can turn around in a blink of an eye as we focus on the tropics closely
this time of year. An ill-timed and slow-moving storm from the gulf can be devasting. As I
finalize this report, Hurricane Ida is sitting in the middle of Mississippi, something we do not
need our way this time of year. Hopefully we all will be spared from such hardships.
August 2020 started out brutal at Stripling Research Park with maximum temperatures ranging
from 94-99 degrees the first 10 days of the month. To make matters worse, we had 2 & 4 inch
soil temperatures ranging anywhere from 88-95 degrees on those days with ET rates of up to
0.24 inches per day. This year temps are averaging a solid 5 degrees cooler, both air and ground
temperatures. The humidity has been oppressive though. Dr. Kemerait has been sounding the
horn weekly that the conditions are conducive for costly diseases. With peanut water needs
winding down towards the homestretch, the last thing a producer would want to do is schedule
irrigation without boots on the ground or moisture sensors relaying real time data, risking
increased disease outbreaks or soil drying out. During peak water demand and dry weather, it is
fairly simple to schedule irrigation events. This time of the season water demand begins to fall
off quickly and we have been receiving ample rainfall. Do not let your guard down if we enter a
dry period with dry hot west winds. (We prefer those conditions after digging!) Sandy soils can
dry out fast and we are looking at what appears to be a great crop. Remember, heavy
downpours that exceed the soil water holding capacities basically become run off. We have
received much of that this year. Hopefully, digging and harvest time will bring favorable
weather. In the meantime, if in doubt about moisture these last few weeks, walk your fields,
review moisture data, watch the weather closely and consult your UGA Extension County Agent
if you would like a second opinion. Keep a close check on your peanuts with peanut maturity
boards. They can help indicate if you will be digging early, on time or later than expected. This
tool can help you tremendously in irrigation scheduling.
The month of September is when the majority of our peanuts are dug and most of them are
now well past the peak water demand and need less than an inch of water per week. However,
there are still plenty of later planted peanuts due to wet conditions at planting and increased
price support for peanuts. Peanuts that were planted in early June that are still near peak
demand, so do not get behind on water on your later planted peanuts! Now is a good time to
start thinking about irrigation termination for earlier planted peanuts planted in mid-April to
early May.
Unlike corn and cotton, we do not have a physiological irrigation termination trigger for
peanuts. Once you reach 140 DAP or 2500 GDD’s, digging should be considered based on
maturity board checks. One of the biggest concerns with digging peanuts is that too much
moisture can cause excessive soil on the shell, especially in heavier soils and too little moisture
can making digging difficult. Keep in mind the timing of harvest, your soil type and how much
available moisture is actually in the soil if irrigation is needed to aid in the digging of peanuts. In
clay type soils you are much more apt to applying too much water and end up having to park
the digger for a day, totally defeating the purpose of irrigating to prepare the soil for proper
digging when you are ready.
Please refer to Figure 1 for irrigation requirements, and when to start thinking about
terminating irrigation.
Figure 1. Peanut water requirements, with considerations on irrigation termination.