How To Add Nitrogen To Soil | Fix Nitrogen Deficiency

One key factor to the success of gardening, whether you’re new to gardening or a horticultural scholar, is understanding the basic elements all plants need. More importantly, how our plants use what is available to them in order to remain healthy and thriving. This understanding begins, literally, at ground level. 

Nitrogen, phosphorus, and potassium are three elements that are critical to every plant’s vitality and productivity. Nitrogen, being at the top of the list, enables plants to produce their own proteins and amino acids.

These metabolic processes pave the way for robust plant structure, root formation, and the ability to receive and process any added nutrients we might offer them. The simple fact is that without nitrogen and all of its benefits, plants will fail.

I’ve put together all my top tips and recommendations on how to add nitrogen to soil depending on your particular gardening needs. You’ll see there are a variety of ways to effectively add nitrogen to soil and to fix any nitrogen deficiency that might exist in your soil.

What Is Nitrogen Deficiency in Soil

Nitrogen deficiency in soil can result from different environmental and agricultural circumstances. Without the means to retain nutrients, elements can easily leach out of sandy soil. Clay-based loams are simply too dense to allow for an easy flow. In regions where the soil is constantly wet, nitrogen is converted into a gas that plants can not absorb. 

In practice, prolonged planting of one crop in the same area often leads to nutrient depletion. Similarly, with permanent plantings, nitrogen-loving trees and shrubs could deplete the soil, over time. That’s why it is so important for the soil that surrounds your trees, shrubs, and crops to be maintained and usually supplemented with the addition of nutrients from time to time.

What Are The Effects Of Nitrogen Deficiency

Without sufficient access to nitrogen, plants simply don’t have enough “energy” to grow properly. Resulting in yellowing leaves, flimsy stems, a sparse root system, stunted growth, and few flowers, fruits, or vegetables, if any. 

nitrogen deficiency 2
Nitrogen Deficient Leaves

Yellowing leaves (known as chlorosis) being the most consequential on this list as this is where photosynthesis occurs. This is the process by which plants convert solar energy into carbohydrates.

Why Do Plants Need Nitrogen?

Nitrogen is a fundamental component of growth and reproduction. Helping every part of a healthy plant develop in perfect form and function. The presence of this vital element stimulates cell division and reproduction through the activation of proteins and amino acids. These building blocks of all life allow the plant to generate new leaves, flowers, and on our crops, fruits, and vegetables. 

Providing this essential nutrient for our plants allows them to provide us with nourishment, the opportunity for healthy exercise, and the simple joy of engaging with nature. Such is the syncopated rhythm of gardening.

What Is the Main Source of Nitrogen in Soil?

Nitrogen can naturally appear in soil in one of two ways. First, from above, rain, snow, hail, fog, all merge with nitrogen gas atoms in the atmosphere and deposit them in our soil. Since much of this water is captured for our consumption, water out of the tap has quite a bit, too.  

And from below, with a little help from the microorganisms that live in our soil. The health and fertility of soil greatly depend on them. As they consume and expel nitrogen molecules, they are transformed into nitrates. This is the easiest and most beneficial form of nitrogen for plants to utilize. 

How to Test Nitrogen in Soil 

If your plants are consistently struggling, that’s a pretty good sign of a nitrogen deficiency.  I’ll explain how to fix a nitrogen deficiency in a moment. But first, you need to know what it is you’re fixing. That comes from doing an effective soil test. 

I find that the best results are obtained by conducting a soil test in fall or early spring. This is because there is little or no risk that your soil will be saturated with snow or rain, or parched from the summer heat. As these factors will distort your results.

Your goal is to achieve 40ppm (parts per million) of nitrogen in your soil and using a good test analysis is going to enable you to determine where your soil is in relation to this measurement. 

Nitrogen Soil Test Kits 

Given the number of home soil test kits on the market, some are bound to be more accurate than others. Be sure to use one specific to nitrogen as accuracy may be substandard when testing for secondary elements. If you know that your soil is highly acidic, you’ll want to get one specifically designed to work with that. 

Soil tests can be immensely beneficial. Giving you a clear view of exactly what your soil is made of, what kind of plants will thrive in it and how to fix a nitrogen deficiency, if necessary. 

What is the Ideal Nitrogen Level in Soil 

A good rule of thumb is up to, but not over, 40ppm (parts per million) of nitrogen in your soil. Anything above 40ppm will restrict the nitrogen regulating activity of all those helpful soil microorganisms and plant damage could follow.  

But, certain environmental factors like temperature, rainfall, and soil composition will differ from region to region. So, the optimum level for your garden may be different. It might just be a matter of adding a little extra well-aged compost or holding back a bit. 

Signs of Too Much Nitrogen In Soil 

I’ve touched on how plants respond to a deficiency but what are the signs of there being too much? Oftentimes, the build-up to what’s called “nitrogen toxicity” is a gradual process.

Plants do need higher levels of nitrogen in the early stages of development. As they move into the flowering stage though, they don’t require as much. Maintaining high levels will result in an explosion of foliage but too much to form blooms and fruit. Prolonged high levels can literally burn the roots that can expand out to the rest of the plant. Exhibiting symptoms similar to a deficiency. A soil analysis will help you get it just right. 

How to Increase Nitrogen In Soil Fast 

So, we know how to recognize a potential nitrogen deficiency and how to test for it. Now, how to add nitrogen to soil so that all those plants you worked so hard to sow don’t die. 

Applying a store-bought fertilizer that’s heavy in nitrogen will definitely help. But, only for the short term. And only your plants will benefit, as they absorb it all. The soil itself will remain deficient, creating more work for you, season after season. The goal is to properly develop your soil so that no matter what you plant in that spot, all the nutrients necessary for success are already there.  

How To Add Nitrogen To Soil Using Fertilizers 

In the late 19th century, breakthrough technology emerged that allowed manufacturers to synthetically create ammonium nitrates. Farmers, who were previously relying on purely natural fertilizing compounds, were now interested in learning how to use this new plant feeding technology. Who wouldn’t want a much faster and more bountiful harvest to take to market?

Over time though, it became apparent that while this new, synthetic option was certainly faster, and clearly benefited plants, it did nothing for the health and fertility of the soil. Eliminating whole populations of soil microbes that were previously so instrumental in conveying nutrients to crops in a completely organic way.  Thus, the debate over organic vs inorganic fertilizers began. 

Organic Vs Inorganic Fertilizers 

That debate continues to this day. And while trends continue to lean toward a more organic approach to gardening, choosing an organic or synthetic fertilizer is still a simple matter of preference, yield expectation, and what your focus is. A basic understanding of how each type works, along with the pros and cons, can help you decide which way to go. 

Inorganic Fertilizer 

Inorganic fertilizers are abundant in today’s market. Each one is specifically formulated to target the specific needs of both plant and gardener. The nitrogen content in these synthetic feeds comes in the form of ammonium nitrate, potassium nitrate, calcium nitrate, and artificial urea. 

While inorganics are mass-produced, they are, by design, fast-acting and can result in a higher yield and abundant blooms. But, they can also potentially contaminate nearby water sources. And as previously mentioned, they don’t necessarily support the fertility of your soil, either. 

Organic Nitrogen Fertilizer 

Organic nitrogen fertilizers are plant or animal-based and typically contain lower levels of nitrogen. This actually prevents plant damage by not overwhelming them. The second benefit is that organics can nourish your crops and flowers for longer periods of time, while also improving your soil. 

Plant-based options typically come already thinned with water and will need to be applied more frequently. Yet, are usually not attractive to animals. Animal-based organics are a bit more concentrated and come with an “earthy” fragrance that may catch your dog’s attention. 

Natural Sources Of Nitrogen For Plants 

Before the advent of synthetic nitrogen sources, farmers and home gardeners relied on and benefitted from, natural materials for plant fertilization. Despite many new options, the use of those time-tested, organic substances continues today. Let’s take a look at a few of them.

Organic compounds like Bat Guano and horn/hoof meal are quick-release choices that provide high levels of nitrogen to plants while advantageously amending soil. They promote the rapid growth of vibrant foliage and are especially good for lawns. Crab waste is used to develop strong disease and pest resistance. And lastly, feather meal, fish meal, shrimp waste, and yes…even human hair, are all used as slow-release, high-nitrogen feeds in organic farming practices all around the world. 

How To Add Nitrogen Instantly 

For plants grown in poor soil or in areas with short growing seasons, there are a few natural (albeit, unconventional) compounds that offer an even faster infusion of nitrogen than the ones mentioned above. These are…

Blood Meal or Alfalfa Meal 

Blood meal is a by-product of raising cattle as a food source. Encouraging the practice of nothing going to waste. Dried in a powder, its rich-nitrogen content gives plants an immediate boost while lowering pH levels when used on acid-loving plants. As a vegan alternative, alfalfa meal provides the same fast results. By simply adding a larger amount, the same level of nitrogen can be introduced. 

Diluted Human Urine 

While this one may seem a little odd to some, when resources are scarce, you go with what you’ve got. In its naturally concentrated form, salt and nitrogen levels are too high to be of benefit. However, when diluted with water, with a ratio of 10:1, this surprising fertilizer can provide plants and soil with a beneficially organic source of nutrients. 

Manure Tea 

Another interestingly sourced, nitrogen-rich option is the simple practice of making a “tea” from farm animal waste. Sadly, this doesn’t include dogs or cats as their waste often contains a number of unhealthy parasites that can affect plants and people. Manure tea or an organic garden waste version called compost tea are flexible methods because the amount of nitrogen applied at any one time can be controlled by how much water it is diluted with. Allowing you to effectively increase the soil’s fertility while promoting a prosperous yield. 

How To Improve Nitrogen Levels Over Time 

So, now we know of some organic ways of applying nitrogen to plants and soil. Let’s look at some options to achieve that well-curated and fertile soil we all aspire to. Remember, the more fertile your soil is, the less fertilizer you’ll have to buy and manually apply. Fertile soil does all that work for you. 

Composted Manure 

Composted material, whether it be farm manure or kitchen scraps, is the best tool in your gardening toolbox. It builds fertile soil structure, increases water retention capabilities (lowering your water bills), and provides slow-release nutrients to growing plants, over time. Allowing you more time to simply enjoy being in your garden, without breaking a sweat. Side benefits of adding compost to your soil include eliminating pathogens and weed seeds. 

Leaf Mulch and Grass Clippings 

If you have a leaf shredder you can mulch with autumn-fallen leaves which provides excellent levels of nitrogen. As a natural soil tonic, this mix has similar benefits to compost like improved soil structure and water retention capacity all while creating a habitat and food source for beneficial microorganisms. 

Leaving grass clippings on your lawn after mowing, rather than raking it all up and tossing it, is the perfect way to cycle all that nitrogen back into your lawn without having to add any extra. Combining leaf mold and grass clippings (at a ratio of 2:1) will provide a well-balanced mix of healthy nutrients for other areas of your garden, as well. 

Nitrogen-Fixing Plants 

Crops themselves can contribute to the long-term development of fertile soil. Legumes, like beans and peas, collaborate with a soil bacteria called rhizobia to capture nitrogen from the air as it penetrates the soil. Nitrogen is then converted to nitrate which is more easily consumed by plants. Other plants with this collaborative ability are clover, soybeans, alfalfa, lupins, and peanuts. 

How To Add Nitrogen To Garden Soil Indirectly 

In addition to adding organic compounds and specific plants to develop a continuous presence of nitrogen in your soil, there are a couple of gardening practices that will greatly contribute to its fertility. While at the same time, creating less work and a more fruitful garden for you. 

Stop Tilling 

In studies, constant soil tilling, year after year, has proven to push nitrogen down away from plant root level toward underground water sources, where plant roots can no longer access it. Thereby, depleting the soil of this much-needed nutrient and contaminating those water sources. Creating the unfortunate need to add fast-acting synthetic fertilizers to crops in order to maintain a high yield. 

No-till soils maintain healthy structure and fertility without disrupting beneficial microbial activity. Alternatives to tilling are introducing an earthworm population that works in tandem with microorganisms. Planting crops like carrot, parsnip, and radish that work to break up the soil as they grow, as well as gentle surface plowing. 

Polyculture 

Polyculture, as it relates to gardening, is more commonly known as “companion planting” which has been practiced for centuries. By growing certain crops together, (like pole beans, corn, and squash), you can maximize the unique benefits of each by having them benefit each other. Polyculture promotes the establishment of a synergetic ecosystem that increases soil fertility, weed, and pest control, and disease resistance. 

How To Add Nitrogen to Soil FAQ