Let Water Carry The Load

More Yield With Less Nitrogen Through Fertigation


Besides being a necessary element, water can also be an efficient method for transporting pesticides and nutrients to the crop. 

“Fertigation is applying fertilizer to the plant through a center pivot irrigation system via the soil so the plant can take it up and use it,” said former superintendent of the University of Georgia’s C.M. Stripling Irrigation Research Park Calvin Perry, who was a speaker at a recent precision ag workshop hosted by Auburn University and the Alabama Extension Service.

“Water is the carrier to move that product to the field and get it to the soil so the plants can utilize the nutrients. Fertigation is not just applying fertilizer by overhead sprinkler or foliar feeding. With fertigation, we are trying to get down to the roots,” he said. 

UGA Extension irrigation specialist Wes Porter said, “If you are considering fertigation using the pivot, keep in mind that the goal is to get the fertilizer into the top few inches of the soil. Ensure that you are applying the water at a rate to accomplish this. 

Applying nitrogen through the center-pivot irrigation system is not foliar feeding because the rate used puts the soluble nitrogen in the top few inches of soil for plant roots to take up.

Porter said too little water will only reach into the canopy. Too much water could cause runoff or leaching of the nutrients.

Knowing your irrigation system is applying the required rate is a must before adding product to the water, Perry said.

“Don’t get into chemigation or fertigation before you make sure your center pivot is applying water in a uniform, proper manner. You need to make sure your baseline is correct before adding to your technology. Make sure your system is in tip-top shape before you get into something like injecting fertilizer,” he said.

Advantages Of Fertigation

Advantages Of Fertigation: Timeliness. Reduced application costs. Improved management. Less environmental contamination. Reduced damage to the crop. Reduced soil compaction. DIsAdvantages Of Fertigation: Extra equipment needed. New management required. Application time for pivot to move across the field. Reaction with equipment if not properly flushed. Environmental contamination possible without safeguards.

Applying nutrients through the pivot offers several advantages. Not having to run a tractor and rig across the field reduces damage to the crop and lessens soil compaction.

Timely application of the product is a big advantage, Perry said. “You don’t have to worry, ‘is the field too wet to get an applicator out there?’ With a center pivot, you have the ability to get the product out any time you need to. 

“If we get behind and need a rescue treatment of fertility, we have that capability with the center pivot to move it across the field, allowing us to correct nutrient deficiencies at any stage,” he said.

Fertigation offers an opportunity for improved management of the crop, according to Perry. 

“We can optimize when we put out those needed nutrients. We can split applications of nutrients to the crop, which has shown proven benefits to cotton and corn. We’ve also seen data that shows we can reduce the total nitrogen applied by splitting applications,” he said. 

Overall, Perry said it is possible to spoon-feed the crop, even though nutrients are being applied with a volume of water needed to reach the soil. 

“If we properly design and accurately calibrate the system, we can put that fertility on in a timely manner, reducing environmental degradation from either runoff or deep percolation.” 

Research conducted at the irrigation park and other universities shows an increase in yield and more efficient use of the nutrients are possible with fertigation. 

Yield Increase, Efficient N Uptake

In their article “The Advantages and Disadvantages of Fertigation,” authors Mary Dixon, formerly a graduate student at the University of Florida and Guodong Liu, a UF associate professor, said that applying nutrients with water has been shown to result in greater crop growth and yield when compared to traditional soil application methods of fertilizer. 

“Yields were observed to be greater when nitrogen was supplied through fertigation as opposed to granular fertilization,” they said. Among other crops, the yield increase for cotton was 11.7% when fertilizing with fertigation, and the yield increase was largely attributed to meeting crop nutrient requirements in a timely fashion.

The authors said fertilizing and irrigating crops through fertigation increases water- and nitrogen-use efficiency. 

“Because nutrients are supplied through irrigation water, they are already in soluble forms available for plant uptake. Soil nutrient concentration is managed within a small range in the root zone, and the nutrients applied to this zone are taken up with great efficiency.” 

Their meta-analysis found that without reducing crop yield, nitrogen use decreased 23% on cotton when applied through fertigation.

Equipment, Safety Check Valves

The primary disadvantage to fertigation on row crops is that special equipment is needed. 

Companies, such as Agri-inject, offer injection pumps with the necessary safety equipment, plus apps that help take the guesswork out of selection and rate calibration.

“You’ve got to have the equipment at your center-pivot pump to be able to inject that product into the water stream,” Perry said. “You need injection equipment and the safety devices on your irrigation system to be able to safely, properly and accurately inject the product.” 

Safety equipment is required to prevent backflow of the product that would contaminate the water source.

“Your injection system and pump should be interlocked so that if your pump stops, the injection system stops as well. That’s a requirement in Georgia. Also required is a backflow prevention device at the water supply.” 

Perry said several companies offer various products for fertigation, from an all-in-one piece of hardware to injection pumps and apps, such as from Agri-inject and SurePoint Ag, help take the guesswork out of calibration and control. These systems are also good for record keeping and reporting. 

Overall, Perry said fertigation takes more management skills. 

“There’s more hardware that you have to properly calibrate to inject product into the water to achieve the amount you want to put out. You also must plan for the time it takes for the center pivot to traverse the field.” 

As states move toward reducing fertilizer losses to protect groundwater, more efficient methods of nitrogen uptake will be required. Reducing the amount of nitrogen needed to maintain or even increase yields, while also saving time, labor, fuel and equipment costs, are good reasons to give fertigation a look.

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