Fertigation Facts

Introduction

Fertigation is the application of fertilizer through an irrigation system (Fig 1). It can be implemented in surface, sprinkler, and drip systems. In the 2013 agriculture census, nearly 135,000 acres of irrigated cropland in Utah utilized fertigation (USDA-NASS, 2014). Utah growers most commonly fertigate corn (33-41% of the total irrigated corn acres) and orchards (37% of total irrigated acres), but it is also used to a lesser degree on small grains, alfalfa, and other hay (9-23% of the total irrigated of these crops).

In most cases, fertilizer used for fertigation is available in liquid solutions or in a soluble form. Liquid fertilizer such as Urea Ammonium Nitrate (UAN), Ammonium Thiosulfate (ATS), Ammonium Polyphosphate (APP), and Anhydrous Ammonia (NH3) are most commonly used due to their convenience, and are currently the primary forms sold by fertilizer companies for fertigation in Utah. In addition to the liquid fertilizers, soluble fertilizers are an additional option for supplementing crops during the growing season. A variety of soluble products are available at local agronomic retailers.

The purpose of this fact sheet is to provide general information on forms of fertigation for primary plant nutrient, fertigation timing, and fertigation economics.

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Nitrogen Fertigation

The most common nutrient applied by fertigation in Utah is nitrogen (N). Nitrogen fertilizers have a high solubility, making them easy and effective to apply with an irrigation system. Because of its high solubility, N is also extremely susceptible to leaching.

Various forms of N can be used for fertigation. One of the most commonly used in Utah is UAN (32-0-0). The nitrogen in UAN exists in three forms - 50% urea, 25% ammonium, and 25% nitrate (Fernandez, 2016). Anhydrous Ammonia (NH3, 82% N) is commonly used in surface irrigation systems because it can be bubbled into the irrigation water. Anhydrous Ammonia is cheaper than soluble liquid nitrogen per unit of N and is a common choice for surface irrigators. However, anhydrous ammonia typically increases the water's pH around the application site, and N losses from volatilization can be as high as 30-50% of the N applied, leading to poor application uniformity (Pettygrove et al., 2009).

Great caution must be taken when using NH3 because of its high reactivity with water on the skin and organs.

Figure 1. Center pivot fertigation. Photo Credit: Kyle Egbert.

Due to the different forms of N fertilizers, it's crucial to choose the correct one for your application. Note that not all forms of nitrogen will be immediately available to the plant. Nitrate and ammonium are the predominant forms used by plants and are usually rapidly available after application. Urea, however, must be converted into ammonium and nitrate by soil bacteria before uptake can occur, a process that can take several days depending on soil conditions and temperature. These factors should be taken into account when deciding fertigation timing.

When choosing a N fertilizer, look for forms that are highly soluble, less corrosive, and will meet the nutrient needs of your crop at the correct time.

Figure 2. Anhydrous ammonia being bubbled into surface irrigation water. Photo credit: California Department of Food and Agriculture.

Phosphorus Fertigation

The most common form of phosphorus (P) fertigated in Utah is APP (11-37-0). Most irrigation water in Utah is hard, containing high amounts of calcium (Ca) and magnesium (Mg). When liquids containing APP are injected into high pH water, Ca-P precipitates may form, causing potential blockage in irrigation lines and emitters, reducing the lifespan of nozzles, and increasing maintenance costs. Applying phosphoric acid instead of APP can usually resolve the issue of precipitates forming in the irrigation system, but may cause increased wear and tear on systems.

Given the hard water challenges in Utah and the fact that phosphorus is not easily leached from the soil, broadcasting and incorporating solid forms of phosphate fertilizers before the growing season is more common.

Potassium Fertigation

When soil tests indicate a need for potassium (K), fertigation is an option. Liquid potassium fertilizer is rare, but most K fertilizers are soluble in water and can be used for fertigation when applicable. The two most common types are potassium chloride (KCl) and the more expensive potassium nitrate (KNO3) (Boman and Obreza, 2015). Potassium can precipitate when combined with other fertilizers, so test small mixtures before fertigation. Nonetheless, K fertigation is often economical only in certain instances such as intensely hayed cropping systems, sandy soils, high-value crops, and depleted soils.

Water Chemistry and Fertigation Compatibility

Water chemistry can adversely affect liquid fertilizers delivered through an irrigation system. For example, aqueous ammonia used as an N source can significantly increase the pH of water, potentially causing dissolved salts to precipitate and clog nozzles and drip emitters. High bicarbonate in water can cause rapid precipitation of calcium and magnesium in fertilizers like calcium nitrate or CAN 17. Phosphate fertilizers are particularly sensitive to precipitation in high pH water with high calcium and magnesium content.

A simple jar test can be performed before fertigation injection to test for irrigation water incompatibility with liquid fertilizers. Fill a glass jar with irrigation water and mix in liquid fertilizer at the desired concentration, shake and aerate the solution, and then let it stand. If any cloudiness forms or solid precipitates appear, there is significant likelihood of nozzle or emitter plugging.

Figure 3- Nutrient uptake of corn from Heard, 2006. pip Figure 4 - Small grain nutrient uptake from Malhi, Johnston, Schoenau, Wang, and Vera, 2006.

Timing of Fertilizer Application and Nutrient Uptake

One of the most important benefits of fertigation is the increased control over application timing, which allows for in-season nutrient applications that can be split and applied to better match rapid nutrient uptake periods. In addition to timing, fertigation can be a vital management practice in soils prone to leaching or other nutrient loss pathways. Therefore, when planning fertigation amount and timing, it is crucial to account for the crop's total nutrient needs, timing of the need, estimated nutrition provided by the soil, and leaching potential.

Crops use different amounts of nutrients at different growth stages. For example, less than half the total N and P uptake occurs before the reproductive corn stages, while nearly 80% of K uptake happens before reproductive stages. For smaller grains, nutrient uptake is more consistent, occurring mainly during tillering and stem elongation. Information of this sort aids in determining optimal fertigation timing. Soil and tissue testing can specify crop nutrient requirements, helping to match fertigation with major crop uptake periods, thereby maximizing nutrient efficiency and increasing yields and quality.

In scenarios with high nitrogen loss, more frequent, lower-rate applications of leachable nutrients can enhance nutrient use efficiency and save fertilizer costs. For example, applying 20-30 lb N/acre per irrigation for corn from the first irrigation until nitrogen uptake ceases is recommended in states like Nebraska (Ferguson, 2009).

Economics of Fertigation vs. Broadcast Applications

Few economic comparisons of fertigation vs. broadcast application of fertilizers have been conducted because of the difficulty in comparing total fertigation prices among agronomic companies. In addition to fluctuating product prices, each company charges differently for various components and services. Agronomic companies often attempt to outbid one another and develop different pricing structures. A simple method to evaluate the two methods is a partial budget approach. This approach evaluates changes due to the use of either fertigation or broadcasting. The following table provides a framework for such an evaluation:

Table 1

Partial Budget Framework for Fertigation Application.

Key Variable Changes	Fertigation Application	Impact
Yield Change	Does fertigation provide a change in yield to offset increased price?	+ or -
Cost Change	Evaluate the cost per acre for each method, including fertilizer, application, equipment, and maintenance costs.	+ or -
Overall Change	Add up the changes to provide an overall analysis.	+ or -

Additional Information

Note that fertigation applications are only as uniform as the irrigation applications. Windy conditions can significantly decrease the uniformity of fertigation applications from overhead sprinklers, so it is not recommended to use pivots for fertigation during windy conditions.

Fertigation in furrow/flood irrigation systems is generally riskier and less efficient than in pressurized systems due to the risk of fertilizer loss in runoff water and low application uniformity. Fertilizer loss in runoff water also poses an environmental pollution risk.

Effective fertigation requires careful monitoring of timing, crop growth stages, irrigation system operation, rates, and equipment maintenance. Keep in mind that fertigation setup procedures are more involved than traditional broadcasting, potentially requiring more monitoring and maintenance.

However, once fertigation systems are set up, subsequent applications should require much less effort.

For more information on setup and equipment involved in fertigation, see the companion USU Extension publication titled "Chemigation Guide".

Summary

The use of fertigation for field and horticultural crops is increasing in Utah. Fertigation can be an effective method for improving nutrient stewardship and boosting crop yield and quality. Keys to successful fertigation include irrigation system maintenance and uniformity, proper fertigation setup and management, and timing nutrient applications to match crop needs.

References

Boman, B., and T. Obreza. 2015. Fertigation nutrient sources and application considerations for citrus. University of Florida Extension. Circular 1410. Available at https://edis.ifas.ufl.edu/pdffiles/CH/CH18500.pdf.

California Department of Food and Agriculture. Nitrogen fertilizers and management. Available at https://www.cdfa.ca.gov/is/ffldrs/frep/pdfs/Section3NMP.pdf (verified 31 July 2019).

Ferguson, R. 2009. Using fertigation for efficient nitrogen application. University of Nebraska. Available at https://cropwatch.unl.edu/using-fertigation-efficient-nitrogen-application (verified 22 March 2019).

Fernandez, F.G. 2016. The three biggies: Urea, anhydrous ammonia, and UAN. University of Minnesota Extension. Available at https://blog-crop-news.extension.umn.edu/2016/05/the-three-biggies-urea-anhydrous.html (verified 22 March 2019).

Heard, J. 2006. Nutrient accumulation and partitioning by grain corn in Manitoba. In: Great Plains Soil Fertility Conference Proceedings. A. Schlegel (ed). Vol. 11. March 7-8, 2006. Denver, Colorado. p. 180-185.

Kenkel, P., & Fitzwater, B. 2015. Causes of fertilizer price volatility. Available at: https://articles.extension.org/pages/72692/causes-of-fertilizer-price-volatility (verified 31 July 2019).

Malhi, S.S., A.M. Johnston, J.J. Schoenau, Z.H. Wang, and C.L. Vera. 2006. Seasonal biomass accumulation and nutrient uptake of wheat, barley, and oat on a Black Chernozem soil in Saskatchewan. Canadian Journal of Plant Science. 86: 1005-1014. DOI: 10.4141/P05-116.

Pettygrove, S., L. Schwankl, C. Frate, and K. Brittan. 2009. Improving water-run nitrogen fertilizer practices in furrow- and border check-irrigated field crops. Final Report to California Dep. Food Ag. Available at: https://www.cdfa.ca.gov/is/ffldrs/frep/pdfs/completedprojects/04-0747.pdf.

USDA-NASS. 2014. Census of Agriculture. USDA-NASS. Available at: https://www.nass.usda.gov/Publications/AgCensus/2012/ (verified 29 March 2019).

Revised December 2019 and published to the Web May 2022. Utah State University Extension. Peer-reviewed fact sheet.

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Authors

Kyle Egbert, Matt Yost, Bryce Sorensen, Grant Cardon, Niel Allen, and Ryan Larsen. Utah State University Specialists.

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Whether it's a large-scale commercial farm or a small backyard garden, gardening requires great effort. From preparing the soil and planting seeds or transplants to installing efficient irrigation systems like drip irrigation, every step is crucial to ensure healthy and productive plants. Fertilizing is a key component of this process. Fertilizing through a drip irrigation system is known as fertigation. It uses drip irrigation technologies to supply water and nutrients directly to plant roots. Once you know what fertilizer to use and how to insert it into the injector, fertigation is simple.

Read on to learn about how to choose the best fertilizer for your drip irrigation system and look at popular injection methods, including Ez-Flo injectors, Mazzei systems, and Dema MixRite.

So, let's get started!

Things You Need to Know Before Fertilizing through Your Drip Irrigation System

Fertigation, which involves applying fertilizer via an irrigation system, can be a little time-saver. However, if not done right, it might cause damage to your drip irrigation system.

Here's why: Fertilizers usually contain salts that can clog nozzles and cause pipe buildup, potentially causing your system to fail. Furthermore, they can change the pH of the water, making it more acidic and potentially harmful.

To avoid such problems, use a reliable fertilizer and check the pH of the water before applying it. Also, flush the system regularly to remove any salt or sediment buildup. Taking some measures can keep your drip irrigation system in good shape while reaping the benefits of fertigation.

Pros and Cons of Fertilizing through Drip Irrigation System

Pros

• Precise Nutrient Control: Fertigation controls nutrient dosage according to plant and soil needs. It's adaptable to both traditional and hydroponic setups, outperforming traditional methods.
• Reduced Leaching: By providing the right amount of nutrients and water, fertigation minimizes the risk of leaching.
• Efficient Resource Use: This system reduces waste and enables better resource management by controlling nutrients and fertilizer amounts. Fertigation eliminates fertilizer waste through traditional watering and manual mixing.

Cons

• Increased Maintenance: Fertigation systems require more maintenance, including daily checks for leaks and consistent fertilizer feeding. Regular cleaning is crucial to avoid contaminants that can disrupt nutrient delivery.
• Higher Installation Costs: Installing a fertigation system involves additional costs for specialized hardware like control units and sensors, making it more expensive, especially for larger operations.

Can You Fertilize through Your Drip Irrigation System at Home?

Fertigation, the process of combining fertilizer and irrigation, is more commonly used in large-scale agriculture than home gardens. Here's why:

• Fertigation is most effective when used with accurate drip irrigation systems. Setting up such a system at home might be difficult and expensive