Commodities: Fieldcrops: Peanuts: 2007 Peanut Update
Irrigation Strategies
John P. Beasley, Jr.
Providing supplemental water during times of stress in a growing season is critical to producing a high yielding, top quality peanut crop. Not all producers have the luxury to irrigate their peanut crop on an as need basis. The key, however, is not if you can irrigate, but how you irrigate. The amount of water to be applied and the timing in which it is applied are the critical factors in maximizing return on investment when irrigating.
The chart above is the weekly water use by peanut. The total amount of water that is required from planting to harvest is about 22 inches. The time period of greatest water requirement in a peanut growing season is the 50 – 110 days after planting. For a peanut field planted on May 1st the critical water requirement period would start in early June and go through the month of August. Based on the water curve in the chart above, the crop would need nearly 19 inches of water during the 90-day period of June, July, and August. In most years we do not receive that much rainfall so supplemental irrigation is needed.
What is the best method to determine when to irrigate? Many producers are now using Irrigator Pro, a program developed by scientists with the USDA National Peanut Research Lab (NPRL) in Dawson. It comes as part of the Farm Suite program available from the NPRL. There are several programs in the Farm Suite software. Irrigator Pro requires a computer to run the program, a rain gauge, and a soil thermometer to measure the 2-inch soil temperature. Training is available to any producer interested in using Irrigator Pro to schedule irrigation applications.
Another irrigation scheduling method is the UGA EASY Pan. It is based on the water balance theory of water application. That is, you balance the amount of water loss through evaporation and transpiration with rainfall received and water applied via irrigation. The EASY Pan method requires a properly calibrated “pan” that acts like an evaporation pan. Your local county extension agent can help make arrangement for getting an EASY Pan set up in your fields.
Another irrigation scheduling method is the simple “check book” method. In this method you monitor rainfall events and totals and make sure each field receives two inches of water per week via rainfall or supplemental irrigation starting at early bloom and ending about 3-4 weeks prior to harvest. Irrigation applications in the last several weeks prior to harvest are made to alleviate heat and drought stress, much like we experienced in September of 2005. If irrigation is available we should never let drought stress occur in the last few weeks or yield potential and quality will decline.
We are conducting research trials on another irrigation strategy that we hope to implement in 2007. We need one more year of research comparing the experimental strategy to Irrigator Pro and EASY Pan before we feel confident in releasing it to the public.