Using Urea Efficiently

Urea

Because soil-applied fertilizer is intended for root absorption by plants, growers should manage fertilizer nitrogen (N) to keep as much of it as possible in the root zone to maximize crop N uptake and yield, as well as protect the environment. To keep urea fertilizer N in the root zone, incorporate urea into the soil with water or cultivation within a day or two of application, and don’t over-irrigate when incorporating urea using water.

Inject liquid fertilizers containing urea (for example, UAN32) into irrigation systems in the middle third of the irrigation set. This delivers urea N evenly through the root zone, avoiding leaching that can occur when urea is injected too early in the set and limited root zone distribution when injected too late in the set.

Urea is the most commonly used dry nitrogen (N) fertilizer in the U.S. It provides half of the nitrogen in UAN (Urea Ammonium Nitrate) 28 or 32 liquid fertilizers. Dry and liquid fertilizers that contain urea have several advantages — relatively high N content (28% to 46% N), ease of handling, and reasonable price relative to other N sources.

However, nitrogen from applied urea can be lost from the root zone when used improperly, wasting money, reducing plant available N, and risking reduced crop growth and yield. The lost N can also be an environmental contaminant. Growers and pest control advisers should be aware of how to avoid N losses and get the most from urea fertilizer dollars.

Two Ways To Lose

Within days of application, urea N can be lost from the crop root zone in two ways — through ammonia volatilization or urea leaching. The uncharged urea molecule (H2N-CO-NH2) breaks down in or on the soil into two ammonium molecules (NH4+) and a bicarbonate molecule (HCO3) within days of application. Urease, a naturally occurring enzyme in soil and on plant surfaces, drives this reaction. Ammonium produced by urea breakdown (urea hydrolysis) has many potential fates. It can shift form to ammonia (NH3; a gas), a process accelerated by high temperatures (more than 70°F) and high pH. It can be held by the cation exchange capacity of clay or organic matter, absorbed by soil microorganisms or plants, or changed into nitrate (NO3) by certain soil bacteria (nitrification). Where urea transformation occurs has a major impact on whether the N applied actually enters and stays in the root zone.

Ammonia Volatilization: Urea fertilizer — dry or liquid — applied to the soil surface and left there for days to weeks can lose more than 50% of N content into the air through ammonia volatilization. High soil pH, high soil temps (more than 70°F), sandy soils with low cation exchange capacity (CEC), weeds or turf, and moist soils/heavy dew are all factors that increase the ammonia losses from unincorporated urea. Incorporate urea into the soil within a day or two of application to avoid significant N loss.

Urea Leaching: Dissolved urea moves with water. Why? Urea hydrolysis takes several days to complete. Until hydrolysis occurs, the uncharged urea molecule won’t bind to soil particles. This helps with water incorporation, but can result in leaching of urea below the root zone during irrigation if excess water is applied. The most efficient use of urea fertilizer requires good irrigation management. Don’t over-irrigate when incorporating surface applications or injecting urea-containing fertilizers through irrigation systems.

“The Middle Third” Rule

When injecting urea fertilizer in a micro-irrigations system, a good general rule is to add the fertilizer in the middle third of an efficient irrigation set, a set that won’t push water down below the bottom of the root zone.

For example, in a 12-hour irrigation set, add the urea in hours 4 to 8. This reduces the chances of pushing urea below the root zone or at least deeper in the root zone where there are fewer roots.

On the other end of the spectrum, urea-containing fertilizer added late in the set is concentrated near the water source and not evenly distributed in the root zone.

How you use urea can go a long way to helping you get the most out of your fertilizer dollar.

Leave a Reply

One comment on “Using Urea Efficiently

Featured Stories
honeybee
Crop Protection
May 31, 2016
Honey Bees Collect Urban Pesticides Via Non-Crop Plants
Purdue study indicates pollen is consistently contaminated with not only agricultural, but urban pesticides. Read More
A herbicide screening trial in a non-bearing almond orchard treated in early January 2011.  The middle plot is a glyphosate-only program whereas the foreground and background plots had residual herbicides.  The photo was taken four months after the January treatments. (Photo credit UCANR)
Nuts
May 31, 2016
Keep Resistant Weeds At Bay While Not Breaking The Bank
Rather than focusing all of a pre-emergent spray program in the winter to attack winter-emerging weeds, University of California Cooperative Read More
potato late blight leaves
Crop Protection
May 31, 2016
A Preventive Approach Reduces Infection Risk In Potatoes
Conditions favoring disease development and spread have led to the establishment of early warning or forecast programs for late blight and early blight. Read More
An aerial photo shows a checkerboard pattern of the cover crop project at the experiment station’s Woodman Horticultural Research Farm. Credit: Rich Smith, University of New Hampshire
Crop Protection
May 31, 2016
Radish Cover Crop Suppresses Weeds, Boosts Yields
In trials conducted at the University of New Hampshire, the cover crop was consistently among the highest biomass-producing treatments in the fall. Read More
Susan Driscoll of Surterra Therapeutics holding a cannabis plant in her company's cultivation facility
Citrus
May 31, 2016
Cannabis Cultivation Quest Becoming Reality For Florida Nurseries
Planning, preparations finally giving way to production and dispensing of ‘Charlotte’s Web.’ Read More
Contour Farming
Farm Management
May 31, 2016
8 Ways To Make Your Farm More Sustainable
Several practices can help ensure profit and leave the land in better shape for the next generation. Read More
Tom Stenzel, President and CEO, United Fresh Produce Association, talks with members of the French Delegation, detailing United Fresh’s work to increase children’s access to fresh fruits and vegetables at schools across the country.
Fruits
May 30, 2016
‘Fresh Attitude Week’ Promotes Variety In Fruits And Vegetables In School Meals
The largest U.S. urban school districts host weeklong celebration, Fresh Attitude Week, which highlights fresh fruits and vegetables and other nutrition education activities. Read More
The team at Lamont Fruit Farms  takes a progressive approach to staffing. “Give people the opportunity to excel,” Jose Iniguez says. “If our employees want it, we give them the chance.”
Apples & Pears
May 30, 2016
Is Your Orchard Ready For Mechanization?
Automation is on the horizon, and it would be beneficial if you’re planting with that in mind. Read More
high denisty apple orchard washington
Apples & Pears
May 29, 2016
Orchard Systems Matter With Mechanization
“It takes years to turn orchards from a big, wild 3-D tree to a narrow canopy — a lot of Read More
upclose of Israeli apple harvester
Fruits
May 28, 2016
Orchard Automation Is On The Horizon
Industry experts say the advent of fully automated orchard tasks are on the cusp of happening — with a few companies leading the automotive harvest charge. Read More
The Latest
Crop Protection
May 31, 2016
Honey Bees Collect Urban Pesticides Via …
Purdue study indicates pollen is consistently contaminated with not only agricultural, but urban pesticides. Read More
Nuts
May 31, 2016
Keep Resistant Weeds At Bay While Not Br…
Rather than focusing all of a pre-emergent spray program in the winter to attack winter-emerging weeds, University of California Cooperative Read More
Crop Protection
May 31, 2016
A Preventive Approach Reduces Infection …
Conditions favoring disease development and spread have led to the establishment of early warning or forecast programs for late blight and early blight. Read More
Crop Protection
May 31, 2016
Radish Cover Crop Suppresses Weeds, Boos…
In trials conducted at the University of New Hampshire, the cover crop was consistently among the highest biomass-producing treatments in the fall. Read More
Citrus
May 31, 2016
Cannabis Cultivation Quest Becoming Real…
Planning, preparations finally giving way to production and dispensing of ‘Charlotte’s Web.’ Read More
Farm Management
May 31, 2016
8 Ways To Make Your Farm More Sustainabl…
Several practices can help ensure profit and leave the land in better shape for the next generation. Read More
Fruits
May 30, 2016
‘Fresh Attitude Week’ Promot…
The largest U.S. urban school districts host weeklong celebration, Fresh Attitude Week, which highlights fresh fruits and vegetables and other nutrition education activities. Read More
Apples & Pears
May 30, 2016
Is Your Orchard Ready For Mechanization?
Automation is on the horizon, and it would be beneficial if you’re planting with that in mind. Read More
Apples & Pears
May 29, 2016
Orchard Systems Matter With Mechanizatio…
“It takes years to turn orchards from a big, wild 3-D tree to a narrow canopy — a lot of Read More
Fruits
May 28, 2016
Orchard Automation Is On The Horizon
Industry experts say the advent of fully automated orchard tasks are on the cusp of happening — with a few companies leading the automotive harvest charge. Read More
Apples & Pears
May 27, 2016
Washington Apple Commission Elects New L…
The commission board also approved the export budget of $7.7 million for the upcoming 2016-17 crop, based on a crop of 135 million cartons. Read More
Farm Management
May 27, 2016
California Drought Far From Over
To preserve orchards and vineyards, growers are expected to fallow up to 350,000 acres of corn, wheat, cotton and alfalfa. Read More
Apples & Pears
May 27, 2016
How Best To Integrate Man And Machine
If you want to implement labor-saving mechanization, you should start the conversation with the end user – your employees. Read More
Farm Marketing
May 27, 2016
Consumers Don’t Really Know What G…
A study from the University of Florida confirms what many farm marketers suspected: Consumers don't understand genetically modified food and organisms as well as they think they do. Read More
Insect & Disease Update
May 27, 2016
Alabama Agriculture Department To Conduc…
Currently, Alabama is the only citrus-growing state that has not yet detected citrus greening. Read More
Insect Control
May 26, 2016
Temperature, Location Key To Predicting …
This year, leaffooted bugs are expected to be a significant problem in almonds and pistachios, but watching temperature and the Read More
Fruits
May 26, 2016
Consider Fumigating For Nematodes Before…
Stone fruit and almond growers looking to replant orchards might want to invest in soil samples to assess nematode populations Read More
Farm Marketing
May 26, 2016
Who Grows Organically — And Who Doesn…
We surveyed 816 fruit and vegetable growers and found that farm marketers and vegetable growers are much more likely than their peers to embrace the practice. Read More
[gravityform id="62" title="false" description="false"]