Doing The Math On Fertigation

New calculator helps producers figure liquid fertilizer flow rate, injection pump settings and a schedule for center-pivot fertigation.

center-pivot irrigation in peanut
Clemson researchers have developed a new app farmers can use to optimize liquid fertilizers used to feed crops through irrigation systems.

The days of manually calculating numbers on spreadsheets to determine how much liquid fertilizer should be used to fertigate row crops may soon be gone, thanks to a new web-based calculator from Clemson University.

The Clemson center-pivot fertigation calculator is designed to help producers make more precise fertilizer applications, saving money and increasing crop productivity. The app was developed by Clemson precision agriculture engineer Kendall Kirk, with help from South Carolina farmers.

“This resource was created to help producers calculate the flow rate of liquid fertilizer and injection pump settings needed to fertigate through a center-pivot irrigation system,” Kirk says. “It is designed to make the math a little easier.”

Making The Math ‘A Little Easier’

Information required includes fertilizer formulation, pivot size, pivot travel time, fertilizer rate and injection pump manufacturer/model. After the information has been inputted, the calculator determines liquid fertilizer flow rate required to supply the needed nutrients, as well as rate per acre of each fertilizer component and the recommended injection pump setting. The calculator also creates a fertigation schedule. Results and direct links to the inputs can be sent to the producer’s email address.

Ben Fogle, Clemson precision agriculture technician, says the calculator is convenient in that it can be used anywhere internet is available.

“A producer in the field can use the fertigation calculation app on their phone,” Fogle says. “It can also be used on a tablet or computer.”

Kirk says, “We developed the center-pivot fertigation calculator after a grower called and wanted instructions on how to set up his fertigation system. We realized a lot of calculations are involved when growers fertigate, and we could make people’s lives a lot easier if we could give them a system that could calculate some of these things for them.”

Multiple Sources Rolled Into One

Another collaborator on the project was Jacob Oswald of Allendale, South Carolina, who earned a degree in agricultural mechanization and business from Clemson. Oswald works with growers across the state to determine ways to maximize yield while maintaining an efficient economic investment in their farming operations.

“I find this calculator particularly useful because calculating the correct application rate for nutrients injected through irrigation systems can be a difficult process,” Oswald says. “A lot of times, the information required comes from multiple sources, such as the pivot application chart, the specific injection pump manual, as well as nutrient labels.

“This calculator has taken all of these variables and research and combined them into one user-friendly platform. I ran the calculator for one of our irrigation systems, and it took less than five minutes to get an accurate pump setting for injection. I was even able to use this from the browser on my cell phone.”

Setting Injection Rate

Clemson Extension corn and soybean specialist Michael Plumblee says, “Being able to apply fertilizer in small amounts throughout the growing season is beneficial in meeting the crop nutrient requirements as they increase or progress through the growing season. Often, applying additional fertilizer to crops such as corn is limited by equipment, labor and time.

“The most difficult part of fertigation is often coupled with determining how much fertilizer to put into the irrigation water so that appropriate rates are applied. By filling in information about each system’s parameters, the program provides injection pump settings to ensure that the rates are correct, and it helps schedule system run time.

“This program takes out some of the guess work for calibrating and applying fertilizer through irrigation to crops in an appropriate manner,” Plumblee says.

Start With Soil Testing

Essential nutrients required by plants include macronutrients — nitrogen, phosphorus, potassium, sulfur, calcium and magnesium, as well as micronutrients — copper, zinc, iron, manganese, boron and molybdenum. A soil’s natural fertility largely depends on the parent materials from which the soil was developed and the original vegetation. Over time on agricultural land, significant quantities of nutrients are lost through plant harvest, soil erosion, runoff, leaching and burning of crop residues.

Bhupinder Farmaha, Clemson soil fertility specialist, says it is important to have regular soil tests to make sure enough nutrients are supplied by the soil or through external inputs.

“When nutrient removal exceeds nutrient inputs, the soil’s nutrient reserves are depleted and may cause yield loss. On irrigated land, farmers can supply different nutrients during the growing season and tailor it more with crop demand. This is when producers could use the center-pivot fertigation calculator.”

Other calculators and web apps developed by the Clemson precision agriculture team include a drip fertigation calculator, an equilibrium moisture content calculator, an injection pump settings calculator, a lime rate calculator, a peanut digger conveyor speed calculator, a peanut yield estimator, a soil acidification calculator and a Watermark soil moisture calculator. For information on these and other precision agriculture topics, go to PG

Article provided by Clemson University College of Agriculture, Forestry and Life Sciences.

New Peanut Loan Rate Calculator

Clemson University precision agriculture and agribusiness program researchers, along with the U.S. Department of Agriculture’s National Peanut Lab, worked together on a peanut loan rate calculator.

Clemson precision agriculture engineer Kendall Kirk says, “If you’ve ever tried to calculate peanut discounts, premiums and values as a function of outputs on your inspection sheets, you know that the calculations can be overwhelming.

“We’ve put together a web app that allows you to do these calculations from your phone or computer for performing your own, unofficial ‘what-if’ scenarios and for converting loan rate to a dollars-per-acre basis. You can even explore historical loan rates for the same inputs.”

The calculator and other web-based tools from Clemson can be found at

Previous article
Next article

Related Articles

Connect With Peanut Grower

Quick Links

E-News Sign-Up