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How to Add Nitrogen to Soil for Healthier Crops

Published:

October 23, 2024

Key Takeaways

Optimal nitrogen levels are important for proper crop growth and development since nitrogen is essential for chlorophyll production and other biological functions.
Although it is possible to detect nitrogen deficiency through signs like stunted growth, yellowing leaves, and delayed maturity, testing soil is necessary before adding nitrogen.
The most common methods to add nitrogen to soil include the use of compost and manure, growing nitrogen-fixing plants, and applying synthetic fertilizers in serious cases.
Maintaining optimal nitrogen levels is possible through the right time of applying fertilizers, increasing organic matter in the soil, and implementing crop rotation.

Quick Summary

To enrich soil nitrogen, apply organic matter like compost or manure, use nitrogen-fixing cover crops (e.g., legumes), or apply nitrogen-specific fertilizers for targeted boosts. Each method supports plant growth but has a different speed of action and effects on soil health.

Plants need many natural elements and chemicals in the soil to grow, but few are more important than nitrogen. Nitrogen is necessary for plants to produce chlorophyll, the substance that allows them to pull energy from sunlight. In addition, it is also one of the building blocks of the amino acids plants need for their biological functions to continue.

Unfortunately, maintaining nitrogen-rich soil can be difficult. First of all, it becomes depleted faster than other soil nutrients. Second, many plants, especially some of the most popular cash crops like corn and lettuce, can burn through the nitrogen in their soil quickly.

So, in most cases, it's necessary to replace the nitrogen in the soil for crops to continue growing well. There are several methods of doing this, including organic ways that will promote long-term soil health. So, let's talk about how to boost nitrogen in the soil, along with the pros and cons of various methods.

Monitoring Nitrogen in Soil: Signs of Low and High Levels

Of course, there’s one question that should be answered first: how do you know that your soil is low on nitrogen? Most of the time, your plants will tell you. Exact signs vary between species, but some of the most common symptoms of nitrogen deficiency include:

Delayed maturity
Stunted growth
Reduced yields
Smaller leaves
Rapidly-yellowing leaves
Early leaf drop
Red or purple shades of discoloration

While many of these symptoms can also be caused by crop diseases, seen together they are most commonly a sign that you need to increase nitrogen in the soil.

However, the first step is to get your soil properly tested. For home gardens and smaller operations, there are basic soil testing kits that can be purchased at most "home and garden" style stores. For larger operations, professionals can come in and quickly test for nitrogen content, with better accuracy than DIY kits.

You should always have your soil tested before any attempt to add nitrogen. Having too much nitrogen in the soil can also damage plants and ruin crops. For the record, signs of too much nitrogen include:

Unusually rapid growth
Extremely green and/or shiny leaves
Weakened shoots and stems
Claw-like bends on leaf tips
Premature leaf yellowing and death

In effect, too much nitrogen causes your plants to "run hot" and burn themselves out by growing too quickly and lushly. So, testing the soil before using any nitrogen additives for plants is a must.

Ways to Put Nitrogen in Soil

Now, let's talk about ways to give plants nitrogen, along with the pros or cons a farmer should know about.

Composting. Natural waste like compost is an excellent source of nitrogen, and it’s one of humanity's oldest tools for maintaining soil nutrients. Compost is a great "slow but steady" organic option for raising nitrogen levels, but it won't do much for plants already suffering from nitrogen depletion. A more direct option when you need small batches of high-nutrient fertilizer is creating compost tea, by allowing compost to seep in water, before watering plants with the result. This will work much more quickly than solid compost, but may not be cost-effective for larger operations.
Manure. Manure is another perennial go-to option for fertilizing farms, and it contains plenty of nitrogen. Plus, if you run a mixed farm with livestock as well, you've got a never-ending supply of manure to work with. However, as with compost, this is better for maintaining nitrogen levels over time. Also, some may choose to add manure to their compost, rather than putting manure directly on the soil. This often produces a richer fertilizer blend, which allows it to provide nitrogen to plants better.
Animal Products. Aside from manure, many other animal byproducts have been processed into natural fertilizers that can improve nitrogen levels in the soil. Fish emulsion, made from fish oil and other fish processing waste, is one of your best natural fertilizers. Blood meal, a byproduct of slaughterhouses, is another good option along these lines. They work more quickly than traditional manure and compost. The only real downside is that they smell terrible, even by the standards of fertilizer.
Biosolids. "Biosolids" means reclaimed waste from municipal water treatment plants. That is to say, it's basically human manure. Many water plants will sell off their biosolids as fertilizer, and this was a common option in the 20th century. However, there is increased debate over the practice. Water treatment waste increasingly holds potentially dangerous chemicals such as PFASes and pharmaceutical drugs. Some areas have even banned the use of biosolid fertilizer outright. Do research into your local laws and local water treatment before considering this option.
Nitrogen-Fixing Plants. One of the best options for maintaining natural nitrogen for plants is to utilize crops that contribute nitrogen. Unlike other plants, legumes such as peanuts or soybeans are able to take in nitrogen directly from the atmosphere with the help of nitrogen-fixing bacteria in their root nodules. After harvesting, when these plants die, they put some of that nitrogen back into the soil. Rotating between nitrogen-hungry crops and legumes is an excellent organic way to maintain nitrogen levels, without having to manually put nitrogen in soil. Assuming it's economically practical for your farm, this is a solid choice — and ensures diversity in your crops as well.
Synthetic Fertilizers. When your crops are already showing signs of nitrogen depletion and need fast intervention, lab-made synthetic nitrogen fertilizer can be a workable option. It contains far more nitrogen than most other sources, allowing you to 'shock' the soil with a big nutrient boost. However, there are serious concerns about the long-term impact of synthetic fertilizers. They tend to harm microbial life in the soil, reducing its overall health. Synthetic fertilizers may also run off, making their way into water supplies and harming the environment. Chemical fertilizers should be used sparingly, and only when organic options are inadequate.

Maintaining Nitrogen Levels in Soil

It’s better to maintain nitrogen levels in the long term so that you don’t find yourself at the point of having to take emergency measures to raise nitrogen in the soil. These are some interventions that can help achieve such stable levels.

Proper Timing. If you're adding nitrogen-rich fertilizer, it's best to add it in fall or spring, during the plants' growth phases. Avoid adding it in the middle of summer, as the heat may reduce the fertilizer's effectiveness. As an exception, compost and manure can be added pretty much any time — they'll release nitrogen slowly for months.
Don't Fertilize After Rainfall. A combination of nitrogen fertilizer and fully wet soil can cause the nitrogen to be converted into nitrogen gases by microbes in the soil. This makes it useless to plants and can also contribute to the release of nitrous oxide, a greenhouse gas.
Increase Organic Matter in the Soil. Nitrogen tends to bond to carbon, so any organic matter in the soil will help you hang onto more nitrogen. For example, allowing grass to grow higher and develop longer roots, or encouraging greater soil biodiversity.

When you have questions, we'll help you find the answers you need to take control of your fields and the harvest you care about. Contact Cropler to discover more about our products and the ways we help you proactively protect your operations from the effects of crop diseases. Learn More

Proper Fertilization Keeps Your Crops Healthy

In short: few chemicals are more important to your crops than nitrogen. You should be monitoring your crops and soil chemistry closely, and look towards long-term solutions — such as crop rotation — to keep the soil full of nitrogen.

Cropler can help! Our revolutionary crop monitoring system for farmers combines rugged weatherproofed agri-cameras with an always-accessible online dashboard. You can monitor your crops' health 24/7 while collecting vital data to maintain their health in the future. Contact us to learn more about Cropler!