Garden soil is layers and layers of vitamins and nutrients that all work together to nourish and grow your garden. Nitrogen for plants is one of the most essential nutrients to worry about as a deficiency will show in your plant’s growth patterns and coloring very quickly. If you think you have a nitrogen deficiency in the soil, you need to know how to safely add nitrogen for plants using the correct methods.
Since nitrogen is one of the most essential nutrients for healthy plant growth, it makes sense that fertilizers have the NPK rating system, and this stands for nitrogen, phosphorus, and potassium. These are three three biggest factors that help determine how well your plants do.
So, you’re lacking nitrogen for plants, it’ll let you know very quickly. From plant death to stunted growth, they can survive or grow without it. We’re going to look at how to add nitrogen to the garden safely, figure out why it’s so critical, and tell you how to test for too much or too little below.
Nitrogen is a critical component to keeping your plants happy, and different plants require various amounts, so you have to do a little research before you create your garden.
Why Nitrogen is Necessary for Plants
Plants need a host of vitamins and nutrients to thrive, and nitrogen is one of them. Plants use and make nitrogen on their own. When your plants start to lack nitrogen, they lose the ability to make amino acids, proteins, and their DNA. A nitrogen deficiency will eventually lead to stunted growth and death because it stops the plants from being able to make their own cells.
Nitrogen is all around us, and it makes up roughly 78% of the air you breathe each day. However, this isn’t in a usable form for your full sun vegetables. Instead, your plants require nitrogen in the soil because this is easy for them to convert into a usable form without a huge amount of effort.
How Much Nitrogen for Plants You Need
The amount of nitrogen for plants you have to have in your garden depends on the types of plants you want to grow. Generally speaking, any plants that you harvest above the soil for their greens thrive with healthy nitrogen levels. Think leafy greens like chard, kale, lettuce, and spinach. The areas in your garden where you want to grow these vegetables should be very rich in nitrogen.
On the other end of the spectrum, any vegetables you harvest for their fruits or roots like tomatoes, potatoes, carrots, and eggplants will struggle if you have too much nitrogen in the soil. Most gardens do well when the nitrogen levels are around 40 million parts per minute (PPM).
Nitrogen Deficiency Signs
Since nitrogen is necessary for plant survival, the plant will give you visual signs that there is a deficiency. You need this nutrient for your plant’s development and growth, so most people will notice deficient nitrogen signs when the plants are young. If you catch this issue early, it’s relatively easy to correct and have the plants bounce back quickly. A few signs that you don’t have enough nitrogen for plants include:
- Leaves are smaller than average
- Lower leaves start to turn yellow before falling off the stem
- Slow or stunted growth
- Smaller and lower quality fruit
- Smaller than average flowers that die faster than they normally would
- Upper leaves look their usual green color, but the yellowing will slowly creep up the plant over time
There are very obvious nitrogen deficiency signs that you’ll see on your young plants, so this gives you plenty of time to correct it without any long-term effects.
Symptoms of Too Much Nitrogen
If nitrogen for plants is such a good thing, you may think that you can just go ahead and throw a bunch of it into the soil before you plant. However, this isn’t a good idea. It is possible for your plants to get too much nitrogen. At the end, you will get lush, big, green, beautiful plants, but they won’t produce any fruit. A few signs that you have too much nitrogen for your plants include:
- Your plants look leafy, full, and green, but you aren’t seeing many flowers or fruit sets
- The leafy greens are bitter and it’s not due to temperature
- There are lots of disease pressures on your beans, peas, or any other crop that fixes nitrogen
Testing for Nitrogen Deficiencies or Overload
The best way to figure out if you have a nitrogen deficiency or not is to test the soil, but there isn’t an accurate homemade test available. You’ll have to buy a soil testing kit or send the sample away for professional testing. You can also ask your local extension office if they have soil testing services, and pay the small fee.
If you want to test the soil at home, you can use the kit that you can get offline or at most local garden centers or hardware stores. The home tests aren’t quite as accurate as professional testing, but it can give you a close-to-accurate result to help tell if you have a nitrogen deficiency.
Testing the soil is the first thing you want to do if you suspect this is your problem. Adding more nitrogen to the soil when it already has enough will do more harm than good in the long run in your garden as it can kill or burn the plants.
When to Add Nitrogen to the Garden
Every gardener should have their own nitrogen schedule, but when the best time to apply it will depend heavily on how you choose to add it. A generally timeline you can follow to add nitrogen for plants is as follows:
- Fall – Add organic matter that will break down over the winter months to enrich the soil like wood, manure, straw, leaf mulch, or shavings.
- Spring – Incorporate well-rotted compost and a full-season, long-lasting nitrogen like feather meal that is slow-release with a higher nitrogen level.
- Throughout the Spring and Summer – Add liquid fish emulsion and foliar fertilizer with seaweed once a week.
Your planting zone, the time of year, and what you want to grow will all factor in to when you add nitrogen to your garden for the best results.
How to Safely Add Nitrogen for Plants to the Soil
When you’re positive that you have a nitrogen deficiency, you’ll have to amend your soil and add more nitrogen for plants. Using an organic method will take time, but it’ll distribute more evenly over time. You can also use non-organic methods, but this increases the chances of accidentally burning your crops if you add too much. A few popular ways to increase your nitrogen for plants include:
1. Bone and Blood Meals
If you go to your local nursery or garden center, they’ll have a blood meal or bone meal available. These types of fertilizers are nice ways to add phosphorus and nitrogen to the garden. You can buy both options, and you can also make your own. You can save bones from cooking and make a bone meal or broth to feed your plants. Both options have higher nitrogen contents and need to have the appropriate application to avoid burning the plants.
Incorporating a blood meal is one of the fastest ways to add nitrogen to the soil. It’s very rich with this nutrient, and you can sprinkle it around the plant on the soil’s surface and water deeply to give your plants a very fast boost. The biggest problem with this option is the smell. It attracts animals to the garden, especially bears. If you’re worrying about it, try an alfalfa meal instead.
2. Coffee Grounds
If you’re a coffee lover or you have someone who works in a coffee shop and can save you the grounds for free, this is a nice way to boost your nitrogen for plants. Coffee grounds are a great source of nitrogen. You can add them into your compost pile or mix them right into the soil. It takes time for the coffee grounds to break down and release the nitrogen into the soil, but they also work to aerate your soil and improve the drainage.
3. Composted Manure
Animal waste has a high nitrogen content, and it’s so high that you’ll rarely add straight manure to the soil because it can burn the plants. The manure type you use also varies when it comes to hotness, so you’ll need to add it to your compost bin or pile to let it rot for at least six months. You can put it right with your garden and food waste without a problem.
Chicken manure is the hottest manure, so you need to compost it before using it. Goat, rabbit, and cow manure isn’t as hot, and you can add them to your soil without worrying so much about burning anything. However, it’s typically safer to compost them before you add them. It takes time for the manure to break down and work into the soil, so this isn’t the solution you’re after for an immediate fix. However, it lasts the longest in your soil.
4. Fish Emulsion
Fish emulsion is another way to add nitrogen for plants, and it has a 5:1:1 NPK ratio. This means that it does give your plants nitrogen, but the dose isn’t high enough to cause burns. One benefit of using fish emulsion is that it has other micronutrients that benefit the plants, including:
A lot of garden centers have fish emulsion as a concentrated form that you’ll mix with water before applying it. The average ration for it is a gallon of water to two or three tablespoons of the emulsion. Once you mix it, you spray or pour it onto your plant leaves and the soil.
If you have an aquarium, you don’t want to just dump out the water. It’s a lite, free type of fish emulsion. Fish droppings and fish waste in the water have a lot of nitrogen. You can water your plants with the fish water, and this gives them immediate nutrients to use.
5. Grass Clippings
During the spring and summer, if you spend a lot of time cutting the grass, you can use those clippings in the garden as long as they don’t have any chemicals or pesticides on them. Apply your grass clippings in your garden as a form of organic mulch. As they start to break down and decompose, they leech nitrogen.
Grass clippings are a natural source of nitrogen that doubles as a nice layer of mulch in your garden.
6. Green Manure Crop
You can plant some crops in your garden bed that formerly had nitrogen-hungry plants to help fix a deficiency. The main difference between planting legumes or beans and growing a green manure cover crop is that you don’t grow this to harvest it like you do beans or legumes. You plant this at the start of the off-season and remove them when it’s time to add your normal vegetable crops. The downside of this option is that it can be time-consuming.
7. Nitrogen-Fixing Plants
There are plants that are considered to be nitrogen-fixing, and all this means is that they’ll add nitrogen to the soil as they start to grow and thrive. The two main plants are legumes and beans. So, instead of absorbing nitrogen from the soil as they grow, they add it back in. This makes them a good option to plant wherever you had nitrogen-hungry plants the previous years. This is why crop rotation is such a huge deal and you want to plan it out years in advance.
Also, it’s important to note that you want to avoid or cut back on fertilizing the garden beds or spaces where you grew any bean crops the year before. This is a good way to end up with too much nitrogen for plants that stunt the growth.
8. Nitrogen-Heavy Plant Fertilizer
You will find nitrogen in chemical fertilizers and organic ones. When you pick out a fertilizer for your plant, look for one that has a higher first number in the NPK ratio. You’ll find this ratio on the package of fertilizer, and it’s usually written out as 10-10-10 or 20-20-20.
The first number represents the amount of nitrogen, so using one with a higher first number will give your soil a boost. However, one big drawback is that chemical fertilizers tend to be short-lived, and they can easily burn the plants but inject too much nitrogen at one time. The organic options have lower numbers but they take longer to absorb into the soil.
9. Plant-Based Compost
You can use the following materials around the house to make a nitrogen-rich amendment to the soil. For the most part, you’ll let them sit in the compost pile to give the soil a buffering effect instead of mixing them right into the garden soil. The plant-based compost list includes:
- Coffee grounds
- Earthworm castings
- Food waste
- Fruit vinegars
- Grass clippings
- Manure from herbivores
- Yard waste
You can spread your homemade compost as an inch-thick top dressing on your lawn to increase the nitrogen for plants ratio. You can also spread it out as mulch over garden beds or landscaped areas to give them a nutrient boost and a neat finished look.
The mix of nitrogen-rich materials you use will depend on the surroundings. You can get a lot of freely-available seaweed, but you may not have access to herbivore manure. Wherever is available in your particular planting zone, you want to sustainably collect it.
Compost is a great way to boost a whole host of nutrients in your garden, and there are many ways you could go about this, depending on what you have available in your location.
Incorporating Nitrogen Indirectly into the Soil
Many people treat their garden soil as a static element that they have to amend and build by adding things. However, a much better way to grow your fruits and vegetables is to work with nature by promoting soil life, and life will do most of the hard work for you. Garden soil is alive and dynamic instead of static.
How it Works:
As your organic materials start to break down, it feeds the soil. The soil life makes the nutrients that were in the organic material available to feed the plants, and this includes nitrogen. Your plants will feed the soil life in return but releasing exudates. So, there is a constant back and forth arrangement between the soil life and the plants where they share nutrients and recycle it over and over.
Using this exchange, the soil nutrients that your plants could’t access naturally are now available. Fungi can connect directly to the roots of your plants to expand into the plant’s root zones. Fungi, and bacteria in the soil, will increase the amount of nutrients available to the plants. All you have to do is support the soil life.
Myths About Nitrogen
There are dozens of natural fertilizer ideas floating around the internet, but do they all act like useful nitrogen for plant sources? The most popular suggestions that won’t work well for you include:
Eggshells are a very common kitchen scrap that people routinely throw into the garden. We prefer to put them into the compost pile, but is there any use in putting them right into your garden soil to help fix a nitrogen deficit? Eggshells do have trace amounts of nitrogen, but it’s such a small amount that it won’t make a difference if you have a severe nitrogen deficiency. Crushed eggshells can work to keep the snails and slugs from getting too close to your greens though.
Many people claim that urine is a great nitrogen source. However, this is very unhygienic, especially if you start collecting it to use later. It’s a lot of effort for very little payoff. Concentrated urine can easily kill your plants, so we advise against using it. Also, not all urine is free of viruses or bacteria, and you don’t necessarily want to transmit this into your soil or to your plants.
Waste – Human or Dog
You may have heard about adding waste products to the soil. First, any animal waste you want to use should go straight into the compost pile before you add it to your garden, and you don’t want to stick your dog’s feces into the compost bin. You’re very likely to contaminate your food supply and spread parasites or diseases.
The bottom line with these three things is that they will slightly alter the soil, but none of them are strong enough to add nitrogen to the soil without causing some type of damage. Limit yourself to the options we outlined earlier for the best results.
Frequently Asked Questions
It’s common for people to have questions about nitrogen for plants because you don’t want to accidentally burn your crops by adding too much or stunt the growth by adding too little. The following questions should address many queries you have.
1. What is a solid source of nitrogen for plants?
The richest organic source of nitrogen for plants are manure, seed meals like cottonseed or soybean meal, or ground-up animal parts like leather dust, feather dust, bone meal, or blood meal.
2. How do you correct a nitrogen deficiency?
You work to correct a nitrogen deficiency by applying an inorganic or organic fertilizer, but ammonium or nitrate-based fertilizers work the fastest to improve the soil. Any general-purpose formula will also give you enough nitrogen to fix a deficiency.
3. Do eggshells have a decent amount of nitrogen?
Eggshells have calcium, and this plays a vital role in helping thicken and strengthen the plant cell wall. On average, broken down eggshells contain 0.4% nitrogen, 39.15% calcium, and 0.38% magnesium.
4. On average, how long will it take to fix a nitrogen deficiency?
Plants that are deficient in nitrogen will absorb it immediately once you make it available. The plant’s coloration will improve and turn a healthy green, but severely affected leaves won’t recover. It will take roughly a week for your plants to recover.
5. What adds nitrogen to the soil?
Nitrogen gets naturally added to the soil from the N fixation by legumes, soil bacteria, and atmospheric deposits during rainfalls. Manure, fertilizers, and other organic materials will also boost your nitrogen for plants.
We’ve outlined several ways you can increase your nitrogen for plants with both organic and non-organic options on the table. You can experiment and see which ones work best for your space and the specific plants you want to grow. If you get adequate nitrogen, your plants will thrive.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.