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The Nitrogen Cycle and Fertigation: Fueling Crop Success


The nitrogen cycle is complex, but growers who understand it can use that knowledge to inform their nitrogen application decisions.

When it comes to crop production, Nitrogen (N) takes center stage. It promotes vigorous growth and helps foster top-notch yields.


But there’s a delicate balance between nitrogen application and the intricate nitrogen cycle at play. Both factors play a critical role in the success of our agricultural systems.


Managing nitrogen — and understanding its natural cycle — can be a challenge. But if you can nail nitrogen management, the benefits go beyond just boosting crop productivity. It has far-reaching implications for the environment, too.


Understanding the Nitrogen Cycle: Processes, Microorganisms, and Nutrient Management


The nitrogen cycle, a foundational process in agriculture, encompasses five interconnected steps:


1. Fixation: In this process, atmospheric nitrogen is converted into forms that are readily available for plant uptake.


2. Mineralization: Decaying plant and animal matter release organic nitrogen, ready for plant absorption.


3. Nitrification: Ammonium transforms into nitrate, an essential form of nitrogen that supports plant growth.


4. Immobilization: As microorganisms consume nitrogen, the nutrient gets temporarily tied up, which influences plant availability.


5. Denitrification: This process completes the whole nitrogen cycle by converting nitrates back into atmospheric nitrogen. Volatilization is a similar process but is limited to nitrogen fertilizer converting into a gaseous form instead of being incorporated into the soil.


Once denitrification is complete, the nitrogen cycle repeats.


Unfortunately, conventional farming practices can disrupt the nitrogen cycle’s delicate balance. In an ideal world, the amount of nitrogen fertilizer applied at any given time would be the exact difference between: 1) the crop’s nitrogen need and 2) how much non-fertilizer sources are supplying.


Thankfully, applying nitrogen-based fertilizers replenishes the nutrient levels that plants need to develop. And with data-driven technologies such as N-Time™, which seek to quantify crop nitrogen needs, farmers and their trusted agronomic advisors can make smarter nitrogen management decisions.


Unlocking Nitrogen Sources


When you’re deciding on the best approach to add nitrogen to your crop, there are multiple sources of nitrogen to choose from. Let’s explore a few:


Anhydrous Ammonia: This commonly used source is a highly concentrated form of nitrogen applied directly to the soil. Due to its high reactivity, it requires careful handling, specialized equipment (like anhydrous tanks), and injection into the soil at or below 50 degrees Fahrenheit to ensure accurate placement and minimize volatilization and loss.


Urea: In its solid granular form, urea can be surface-applied or incorporated into the soil. Soil enzymes must convert urea into ammonium before it’s available for plant uptake. Urea can be sidedressed (applied to the soil near the growing plants). This ensures the nutrients get directly to the root zone. The cost of a urea sidedress application includes labor, equipment, and fuel expenses. It’s also important to note that a urea application requires rain or irrigation in order to be dissolved and incorporated into the soil. Slow-release urea can help to control when nitrogen from this source becomes available to plants during the growing season


Urea Ammonium Nitrate (UAN): Urea may be dissolved and combined with ammonium nitrate in liquid form to produce Urea Ammonium Nitrate (UAN). When it’s in this liquid form, a fertigation system can inject the solution into irrigation water to deliver it to the plant. This blend of fertilizer serves complex crop nutrition needs because different components of the blend make nitrogen available at different rates. This complex solution sustains crop nutrition immediately and for a period of time after it is applied.


Organic Sources: Organic sources like manure and cover crops are valuable alternatives to synthetic fertilizers. They contribute organic matter to the soil and release nitrogen slowly over time as they decompose. These sources provide a more balanced nutrient supply and can improve soil health. However, their nutrient content may vary, so consider nutrient ratios and availability before using. Incorporating organic sources can enhance soil fertility, improve water-holding capacity, and promote beneficial microbial activity.


Biologicals: Biologicals, such as microbial inoculants and biofertilizers, harness the power of beneficial microorganisms. These can enhance nutrient availability and improve plant growth. Biologicals contain specific strains of bacteria or fungi that can establish symbiotic relationships with plants. The nitrogen-fixing bacteria convert atmospheric nitrogen into a form plants can use, which reduces the need for additional fertilizers. Our team at Sentinel conducted a case study that showed biologicals’ ability to improve nitrogen use efficiency (NUE), and how N-Time™ can be used to monitor their effectiveness during the growing season.


Precision Placement


Numerous nitrogen fertilizer application practices exist. Here are a few:


Apply all the nitrogen up front in fall or spring. This can result in the applied nitrogen lingering in the soil for extended durations when crop nitrogen uptake is minimal and the risk of heavy rainfall is high. This could lead to runoff and leaching. In addition, applying all the nitrogen at once can result in substantial profitability losses, with only 21% of anhydrous reaching the corn crop when applied up front in the fall. However, despite the risks of runoff, leaching, and profitability loss, applying nitrogen all at once means minimal labor is required.


Use a split application. This involves a partial up-front application followed by a sidedress application as the crop matures. While this method represents an advancement in nitrogen management, there is still a certain level of leaching risk.


Apply nitrogen via fertigation. This process offers multiple benefits around nutrient management and environmental sustainability. Through fertigation, farmers can spread nitrogen applications across the growing season when the crop needs high amounts of nitrogen the most (for corn, this begins at V8 and continues through the reproductive stages). This minimizes excess crop-available nitrogen from fertilizer in the soil and reduces nitrogen loss to the environment.


Fertigation combines nitrogen fertilizers with irrigation water — and with its precise placement of nutrients at the right time and in the right quantities, fertigation can enhance nutrient efficiency, minimize losses, and lower the risk of nutrient runoff.


In addition, fertigation utilizes existing irrigation systems. This eliminates the need for separate application equipment and provides a convenient, efficient option for nitrogen management in agriculture.


Nitrogen Management with Fertigation:

Even with advanced techniques such as fertigation, managing nitrogen can pose challenges. Similar to other methods of nitrogen application, fertigation involves challenging decision-making about the necessity of each application pass, the appropriate growth stages for application, the actual nutrient requirements of the crop, and the overall profitability and ROI of the process.


Data-driven analytics and recommendation tools like N-Time™ can help with those decisions, optimize the process, and guide you towards better nutrient efficiency.


With better NUE, farmers can minimize nitrogen losses through runoff and volatilization — and reduce environmental impact. Fertigation allows for real-time adjustments based on crop needs, especially when you use technologies like N-Time™, which provides insights into the crop's nitrogen requirements.


The bottom line:


Given the complexity of the nitrogen cycle, nitrogen management often raises numerous questions. How much do I apply? When? Am I applying too much nitrogen?


The good news is, these can be addressed with accurate information. Data-driven technologies can quantify crop nitrogen needs to help farmers and their trusted agronomic advisors make better, more informed nitrogen management decisions.


By implementing precise fertigation techniques and leveraging tools like N-Time™, farmers can apply proper nitrogen amounts tailored to their specific crop needs. This helps them optimize nitrogen use, improve their yields and profitability, minimize environmental impacts, and forge a path towards more sustainable agriculture.


To further explore nitrogen management through N-Time™ and Sentinel Fertigation, reach out to our knowledgeable team or visit our website for more information.


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