Apps Ease the Task of Fertigation for Growers

Jim Rogers Research, Technology

By Denise Attaway

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

Rob Last (left), Clemson Extension horticulture agent, and Rogan Gibson, Clemson Extension agronomics agent, study data collected using the Clemson Center Pivot Fertigation Calculator. (Photo by Denise Attaway)

The Clemson Center Pivot Fertigation Calculator and Clemson Drip Fertigation Calculator are free apps created by the Clemson Cooperative Extension Service precision agriculture team to help growers achieve the greatest returns on their investments while protecting the environment.

Kendall Kirk, director of Clemson’s new Center for Agricultural Technology, said these tools are the first of many Clemson-developed digital solutions for the farming community, thanks to funding from the South Carolina General Assembly.


The Clemson Center Pivot Fertigation Calculator is designed to help agricultural producers make more precise fertilizer applications, which will save money and increase crop productivity. This app was developed by Kirk, also a Clemson precision agriculture engineer, with advice from many members of the South Carolina farming community.

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

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

Ben Fogle, a core technician for the Clemson Precision Agriculture program who works with Kirk, said the calculator is convenient in that it can be used anywhere internet is available.

“If a producer is in the field, they can pull out their cell phone and use the fertigation calculation app on their phone,” Fogle said. “This app also can be used on a tablet, on a computer or anywhere that has internet capabilities.”

Convenience is what developers had in mind when they created the calculator. Visit to access it.

“We developed this calculator for center pivot fertigation after a grower called and wanted instructions on how to set up his fertigation system,” Kirk said. “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.”

Jacob Oswald of Allendale, South Carolina, is one of several people who helped develop the calculator. Oswald works with growers across the state to determine how to maximize their yields while still 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 said. “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 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.”

Growers irrigating with center pivot systems should maintain water application uniformity. Uniformity is influenced by nozzle type and size, distribution of water flow, pumping pressure and wind. Irrigation application uniformity is a system’s ability to apply the same irrigation depth as it travels a field. Poor uniformity of water application results in under- or over-irrigation of sections of crop fields. It also can lead to nonuniform distribution of fertilizer and chemicals where fertigation and chemigation are used.


The Clemson Drip Fertigation Calculator is designed to help vegetable growers. This app, developed by Kirk and Clemson Extension horticulture agents Justin Ballew, Rob Last and Zack Snipes, helps farmers make more precise fertilizer applications.

“By adding liquid fertilizer to irrigation systems, plants are given a little bit of fertilizer each time farmers water their crops,” Snipes said. “This reduces runoff and leaching as compared to granular applications.”

To use the tool, growers select the fertilizer formulation to be used, pounds of nitrogen needed per acre per day and the amount of acreage to be fertigated. The calculator determines how many gallons of fertilizer are required to supply the needed nutrients through the drip system. The app has a drop-down menu for users to input the age of a crop to help determine crop nutrient demands at that stage of development. Those recommendations are cross-referenced from the Southeastern U.S. Vegetable Crop Handbook and the North Carolina Strawberry Association’s Strawberry Plasticulture Guide.

“Development stage of crops always has an impact,” Last said. “For example, the amount of fertilizer to be applied to a younger vegetative crop will generally be lower than a more mature crop. Nutritional status of a crop can also play a role. In strawberries, for instance, if the petiole nitrogen content is low then additional nitrogen should be applied. This reduces the risk of nutrients becoming limited and limiting yield potential. The same calculations generated by the app can be done manually and give the same results.”

Jim Basara, a farm coordinator on Spring Island, South Carolina, said the Drip Fertigation Calculator (found at helps make his job easier.

“We are a 6-acre community farm and grow a whole range of vegetables here,” Basara said. “Rather than calculating by hand or building a spreadsheet, everything I need is in an easy-to-use package. I can very quickly and easily go through the requirements for each crop, or group of crops that I want to feed the same way. The calculator makes quick work of figuring out what we need to do.”

Denise Attaway is a writer/editor for the College of Agriculture, Forestry and Life Sciences at Clemson University.


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