College of Agriculture, Forestry and Life Sciences; Public Service and Agriculture

Clemson researchers develop new technology to make fertigating row crops more appealing


Clemson researchers have developed a new app farmers can use to optimize liquid fertilizers used to feed crops through irrigation systems.
Clemson researchers develop app to help row crop producers save money and increase crop productivity
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BLACKVILLE, S.C. – 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 (app) from Clemson University.

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 Kendall Kirk, a Clemson precision agriculture engineer, with “good 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.

Clemson researchers have developed a new calculator row crop farmers can use to fertigate crops through a center pivot irrigation system.
Clemson researchers have developed a new app row crop farmers can use to fertigate crops through a center pivot irrigation system.

After all of the information has been input, the calculator determines liquid fertilizer flow rate required to supply the needed nutrients through a center pivot system, as well as rate per acre of each fertilizer component and recommended injection pump setting. The calculator also 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 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. As long as internet is available, this app can be used.”

Convenience is what developers had in mind when they created the calculator, which can be found at

“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 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, who graduated from Clemson with a degree in agricultural mechanization and business in 2015, is one of several people who work in South Carolina agriculture 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 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 5 minutes to get an accurate pump setting for injection. I was even able to use this from the browser on my cell phone.”

Irrigating and fertilizing

Corn, cotton, peanuts and soybeans are the state’s major row crops. Efficient irrigation systems and water management practices can help maintain farm profitability. Applying fertilizer to these crops through irrigation systems will benefit row crop producers, said Michael Plumblee, Clemson Extension corn and soybean specialist.

“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 throughout the growing season,” Plumblee said. “Often adding additional fertilizer to crops such as corn are limited due to equipment limitations, 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.

“This is where Dr. Kirk’s app comes into play,” Plumblee. “By filling in information about each system’s parameters, the program provides an output on where to put injection pump settings to ensure that the injected rates are correct and help schedule system run time. In summary, this program helps take out some of the guess work for calibrating and applying fertilizer through irrigation to crops in an appropriate manner.”

South Carolina is comprised of four regions – Upper Coastal Plains, Lower Coastal Plains, Piedmont and Blue Ridge Mountains. Bhupinder Farmaha, Clemson soil fertility specialist, said each region contains many different soil types. Fertile soils provide essential nutrients required for plant growth.

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 shortage of these nutrients can affect plant growth. In addition, too much of these nutrients also can be just as bad.

A soil’s natural fertility largely depends on the parent materials from which the soil has developed and the original vegetation. Overtime on agricultural land, significant quantities of nutrients are lost either through: plant harvests, soil erosion, runoff, leaching and burning of crop residues.

Farmaha said it is important to have regularly soil tested to make sure enough nutrients are supplied to sustain a crop through external inputs such as fertilizer, residue from previous crops, or animal manure can be applied. 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,” Farmaha said. “This is when producers could use the Center Pivot Fertigation Calculator.”

Nitrogen is the most common nutrient supplied through irrigation.

Information from the United States Geological Survey (USGS) shows irrigation is probably the most important use of water worldwide. Farmers could not provide food for the planet’s population without irrigating crops. About 10% of South Carolina crop, pasture, and grazing land is irrigated, Kirk said. A report from the USGS shows South Carolina withdrew between 0 and 200 million gallons of water per day in 2015.

“Our farmers in South Carolina, as well as in the entire United States, are among the greatest stewards of our water resources,” Kirk said. “When someone sees an irrigation system running, it’s because it’s more profitable for the producer to irrigate than not irrigate. And, they don’t irrigate more than they need to irrigate because doing so would result in less profit for them. Better profit for the farmers results in less cost of food for consumers. Oftentimes, what farmers do to impact their profitability also has a positive impact on the environment.”

Other calculators and web apps developed by the Clemson Precision Agriculture Team include a Drip Fertigation Calculator, an Equilibrium Moisture Content (EMC) 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


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