Monday, June 14, 2021

Irrigation Scheduling Options

Find a method that fits your needs and management style

  • By Amanda Huber

Peanut growers have several options for scheduling irrigation. Any one of these methods is better than waiting for visible stress, says University of Georgia Extension irrigation specialist Wesley Porter.

Irrigation recommendations from Irrigator Pro are based on long-term, multi-crop irrigation management research performed by the USDA Agriculture Research Service’s National Peanut Research Laboratory in Dawson, Georgia.

“Based on the irrigation survey we conducted, we know that a lot of peanuts are still being irrigated based on visible stress and fewer are using more advanced scheduling methods,” he says.

Make The Most Of Your Dollar

Porter reminds growers that although they don’t pay for water, they do pay to move that water with energy costs.

“This year’s budget costs for pumping irrigation has the average irrigation cost at $8.50 per acre-inch of water applied. For 500 acres of irrigated land, if you put out 10 acre-inches of water, that’s $42,500.

There are many irrigation scheduling tools available to producers from the checkbook method to computer models and soil moisture sensors. Depending on your operation and irrigation capabilities, one of these methods may be a good fit.

The checkbook method is available for corn, cotton, peanuts and soybeans and is published in each respective production guide. It is free and requires minimal user input.

“This method is not advanced and is one step above irrigating a set amount of irrigation a certain number of times per week,” says Porter. “It also tends to be conservative, meaning that it can lead to over irrigating in wet years and under irrigating when it’s dry.”

The checkbook methods are all developed based on a historical average crop water use and evapotranspiration.

Computer Models

The next step up in irrigation methods, according to Porter, is one of the computer models.

Water requirement for peanuts.

Producers have several options including smart irrigation apps, PeanutFARM and Irrigator Pro.

These methods are usually free and also require minimal user input. The real-time daily data used in computer models often comes from a local network of weather stations.

“These models use the checkbook as the backbone but rely on daily real-time data to make decisions. One benefit is they take soil type into consideration.

“A localized computer model can be a very good option for a producer new to scheduling irrigation. It can help them keep a track of how much irrigation they need and when to apply it based on current climatic conditions.”

Soil Moisture Sensors

The most accurate way of scheduling irrigation currently is with the use of soil moisture sensors. There are many types of sensors, and costs can range from $500 up to $2,500 per site.

Irrigation scheduling with the use of soil moisture sensors provides current data to be used to make hourly to daily irrigation decisions. User input is required for these methods and use of the data can be a challenge, but it is an accurate method when used correctly.

“It’s not readily adopted because of the investment and, like any electronic device, you are going to have problems because the sensors are placed into a harsh environment.

“Also, the data can sometimes be difficult to interpret or make accurate decisions from. Once you get this data, how will you use it? If you’re at this last stage and saying, ‘I’ve got this data but I’m not real sure how to use it,’ I would encourage you to use a hybrid systems.”

A Hybrid System

Irrigator Pro is considered a hybrid system that can be used multiple ways.

“It can be used for soil-water balance such as the computer models, and it has an option where soil temperature and/or soil metric potential data can be manually entered or automatically populated into the model using soil sensors,” says Porter.

Irrigator Pro, which is available for peanuts, corn and cotton, calculates the available water in the soil and the daily water needs of the crop based on its growth stage. If the water needs of the crop exceed the available water in the soil, irrigation is recommended.

Irrigation recommendations are based on long-term, multi-crop irrigation management research performed by the Agriculture Research Service’s National Peanut Research Laboratory in Dawson, Georgia.

Rainfall and irrigation data can be manually entered into Irrigator Pro, or the data can come from another source, such as soil water potential sensor values from a UGA Probe and Bridge device or from the Trellis wireless soil moisture system.

Work on Irrigator Pro continues and in 2022, Porter says, it will include volumetric measures of water content using capacitance sensors.

Know The Critical Time

Water requirement for peanuts in line graph.

Once the peanut crop is in the ground, it’s time to start considering how to manage it and specifically how to manage irrigation.

Porter says to keep in mind that the water requirement for peanuts is irrigation plus rainfall, and the weekly water requirement recommendation was developed based on the historical average of evapotranspiration.

“Your actual water and irrigation requirement may vary slightly based on weather conditions and rainfall during the growing season.”
Peak water use for peanuts is at 70 to 100 days after planting.

Why Is Uniformity Important?

Just as crop uniformity is important to reach maturity equally, so is the uniformity of water application.

University of Georgia Extension water educator David Hall says systems not properly checked and maintained can lead to significant losses in potential income.

“A farm’s return on investment is directly affected by the way water is applied to crops. The wrong end-gun settings can result in overwatering or underwatering large portions of field acres. Clogged or partially clogged nozzles lead to obvious water shortages that can be visually observed or measured using yield monitors.”

By request, UGA Extension’s mobile irrigation lab can perform a pivot test. Contact your local Extension office for assistance with this process.

Possible causes of poor uniformity

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