The Importance of Nitrogen in Agriculture

Written by Rachel Sim, with expertise provided by Rich Haynes, Technical Agronomist. 

Nitrogen isn’t just a critical nutrient for plants, but for all life. For example, the energy storage molecule ATP has a nitrogen base and it’s also a major building block of both DNA and RNA. Nitrogen is necessary for the formation of amino acids, aiding plants with growth and development and combining to create critical proteins. In plants specifically, nitrogen is a key component of chlorophyll, supporting photosynthesis. 

“Without adequate nitrogen, plants can’t convert sunlight and maintain their own energy,” says Rich Haynes, Technical Agronomist for Sound.

Because nitrogen is so central to all life, organic fertilizers like crop residues or manures contain plenty of natural nitrogen. In addition to soil stabilization, residue from cover crops may provide different nutritional profiles, depending on what crop is used. For example, legumes like cereal rye are nitrogen fixers: they have a symbiotic relationship with bacteria that transform atmospheric nitrogen into a form that plants can use. As a result of this relationship, legume cover crops provide more nitrogen as the residue breaks down.

​“As it grows, rye will use some nitrogen in the soil, but it will also reduce nitrogen loss over the fall and into the spring and bring in atmospheric nitrogen,” says Rich. ​“That plant matter has nutrients in it that will all return to the system, so it ends up being a net benefit.”

However, it takes time for the cash crop to be able to access the nitrogen in organic fertilizers. Unlike synthetic fertilizers, which generally provide nitrogen in an immediately available form, in organic fertilizers, it must be converted through mineralization into a form the plant can use.

​“The nitrogen in organic fertilizer releases more slowly though because it has to be converted to ammonium before plants can take it up,” says Rich.

Microbial Activity and Nitrogen Transformation

The speed at which organic matter breaks down in the soil can vary. Rich says that’s when growers might start thinking about residue digesters to help speed up the mineralization process, but the healthier and more microbially active the soil, the faster plant material breaks down.

Soil microbes are essential for converting organic nitrogen into ammonium (NH₄⁺) and nitrate (NO₃⁻), which are the forms of nitrogen plants can easily use. This process, called mineralization, occurs when microbes break down organic matter in the soil. After mineralization, ammonium is further converted into nitrate through nitrification, making both forms of nitrogen available to crops.

SOURCE® is Sound’s microbiome activator, which stimulates soil microbes, including those that mineralize nitrogen in the soil and those that fix atmospheric nitrogen. These microbes don’t just improve plant access to nitrogen, they also provide access to other critical macro- and micronutrients.

To further expand plants’ access to nutrients like nitrogen, growers can also use BLUEPRINT^TM, Sound’s arbuscular mycorrhizal fungi (AMF) inoculant. AMF works with plants to extend the root zone and helps improve access to macronutrients, micronutrients and water. SOURCE and BLUEPRINT can be used alone, but when paired together, they work synergistically to activate soil microbes and increase the crop’s ability to access nutrition.

A robust soil microbiome is one part of overall soil health and organic matter is another. Microbes break down organic matter, unlocking the nitrogen and returning it to the soil where can be taken up by the crop when it’s needed.

“The more organic matter in the soil, the healthier the soil tilth, which includes microbial health,” says Rich.

Synthetic Fertilizer

There are a variety of synthetic fertilizers available to growers, each with different strengths and potential weaknesses. Which kind a grower chooses will vary depending on their soil health and their unique operational needs, including field conditions and climate.

Ammonium anhydrous is applied as a gas and knifed into the soil. It’s one of the least expensive forms of nitrogen fertilizer, but it can also have some significant downsides, including being very prone to loss. Because of that, application timing is crucial.

“If the fields are too wet or too dry, anhydrous can be lost directly into the atmosphere,” he says. ​“Growers that use it will typically apply in the fall with a stabilizer to minimize loss, but even then, it’s still the form of nitrogen most prone to loss.”

Another issue is that anhydrous isn’t great for soil, killing off the beneficial microbes that offer many benefits to plants, including free access to in-season nutrition.

“Ammonia gas is a soil sterilant,” Rich explains. ​“When it’s applied, it actually sterilizes the microbial populations in the soil and can have a pretty big negative impact on soil health.”

More common and stable forms of synthetic fertilizer include urea and urea ammonium nitrate (UAN). Urea is a granular form of nitrogen usually applied in either the fall or spring. To reduce loss through volatilization, it needs to be properly incorporated into the soil. UAN is even less prone to loss than urea, and because it’s a liquid, it can be applied in a variety of ways, including the surface of the soil or injected into it; the latter reduces the potential for volatilization further.

“One of the nice things about liquid fertilizer is that it lends itself well to more prescribed management; it can be put in the field closer to when it’s actually needed by the crop,” says Rich.

Ammonium sulfate is another form of nitrogen fertilizer that growers in the midwest have increasingly been switching to or adding to their nutrition plan, in part because of the sulfur. Nearly every field in the midwest struggles to get enough sulfur, says Rich.

“Sulfur is a nutrient that is closely tied with nitrogen,” he explains. ​“Putting them on the field together, especially when doing prescriptive management, the sulfur actually helps boost nitrogen use efficiency.”

Soil Testing for Precision Nitrogen Management

Growers strive to provide their crop with plant-available forms of nitrogen and other nutrients when it’s needed and in the right amounts while minimizing loss. Knowing what is in your soil and available to plants is critical for developing an efficient and effective nutrition plan. While zone- or grid-based soil testing every 2 to 4 years is common, more data is never a bad thing. 

“If growers can afford it, I recommend at least once every four years soil testing acre grids or smaller, because that’s when you really start to understand what’s available in your soil and what you can do with it,” says Rich. 

To really dial in NUE, growers can also conduct pre-plant and pre-sidedress soil nitrate tests. These soil tests show how much nitrogen in the soil is plant available or will become plant available, allowing for more precision in fertilizer application. A pre-plant test can help growers decide how much nitrogen to put down at the beginning of the season with their planter. Then, a little later, a pre-sidedress nitrate test to make sure there’s enough nitrogen for the crop to finish the season strong.

“A pre-sidedress nitrate test between V4 and V5 will tell you what your nitrate levels are going into the rapid growth stage,” says Rich. ​“If you’re a little low, that’s when you can make a decision to do a sidedress pass to make sure nitrogen gets into the tissue during that critical growth time.”

Timing of Fertilizer Application

For corn, the V4 to V6 growth stage is critical, which is why Rich suggests pre-sidedress nitrate tests to make sure the crop is set up for success. Tissue tests are another way to get a snapshot of nutrient levels during the season and address nitrogen deficiencies early.

​“As the crop starts to come into tassel, a tissue or sap test will show how the plants are doing. If nitrogen levels are low there’s still time to put more nitrogen out and get a benefit at tassel, but much after that, you’re too late,” says Rich. That’s not just because the crop is getting too tall to get equipment over; once corn heads into its reproductive stage, it mostly uses nitrogen it’s already taken up.

Preventing Nitrogen Loss

Like any input, any nitrogen put in the field represents a financial investment, and loss through volatilization or leaching is like flushing money away. Minimizing loss is an important way for growers to safeguard their finances, and focusing on nutrient use efficiency (NUE) can help growers ensure they’re not applying more than the crop can use.

Another soil test called the Haney test can also be incredibly useful for understanding both nitrogen availability and soil microbial levels. One of the things the Haney test measures is the soil’s water-extractable organic nitrogen (WEON) level.

​“Looking at a WEON percentage, we might see that there’s lots of nitrogen, but it’s not available right now,” says Rich. ​“But it also helps measure microbial activity and the potential for mineralization. The better your WEON percentage, the less synthetic nitrogen the crop needs because the soil and the microbes are able to provide.”

SOURCE activates these beneficial soil microbes that help plants access the nitrogen already in the soil and convert inaccessible atmospheric nitrogen into a form plants can use. By increasing microbial activity, SOURCE improves nitrogen availability, helping farmers reduce their reliance on synthetic fertilizers while supporting healthier crops and soil.

“The easiest place to look for NUE opportunities is always the most loss-prone application and that likely means looking at any fall or spring applied nitrogen,” says Rich. ​“With SOURCE, we’ve shown that you can cut that pretty consistently and improve both plant quality and yield. That’s because you’re adding more opportunities for the microbial population to stabilize nutrition instead of relying on that synthetic fertilizer to be there months later when the plant needs it.”

Growers are increasingly looking to their NUE to minimize the loss of costly inputs while ensuring crops are provided with the nutrition they need when they need it. New tools like advanced sensors can also help growers better understand and manage their nitrogen applications. One way is by looking at chlorophyll content. 

“These drones sensors can look at the light that bounces off chlorophyll and extrapolate the ratio of chlorophyll to nitrogen in the plants,” says Rich. ​“That gives us an idea of how nitrogen-saturated that plant is.” 

While sensors on drones, satellites, planes and even mounted-on equipment can provide valuable insights, the technology is still relatively new. How the information these sensors gather can be best used is still a work in progress. 

Calculating Nitrogen Use

One of the best things growers can do to improve both their nitrogen efficiency and farm finances is to take the time to develop a full understanding of the nitrogen on their operation. They may find it’s in more places than they think. 

“A lot of people under calculate the amount of nitrogen they actually apply because they may not take into account things like manure, legume credits or irrigation water,” says Rich. ​“Developing a realistic picture of nitrogen use lets you make more informed decisions about whether what you’re doing is working.” 

Effective nitrogen management is vital for optimizing crop yields, improving soil health, and minimizing nutrient loss. Whether you’re leveraging organic fertilizers, synthetic options, or advanced microbial activators like SOURCE® and BLUEPRINT™, tailoring your approach to your soil and crop needs is key to long-term success.

At Sound, we’re committed to helping growers improve their nutrient use efficiency and achieve sustainable agricultural practices. With innovative products and expert guidance, we make it easier to enhance your soil health and crop performance while reducing reliance on synthetic inputs.

Ready to elevate your nitrogen management strategy? Contact us today to learn how Sound’s solutions can help you achieve better results for your farm. Let’s work together to support healthier crops, stronger soils, and a brighter future for agriculture.