If you are growing peppers this year, you might be wondering if they need a lot of nitrogen. After all, nitrogen helps plants to make chlorophyll and produce green growth.
So, do peppers need a lot of nitrogen? Peppers need a lot of nitrogen early in the season, so they can produce lots of green growth (stems and leaves). This green growth will create energy for fruit production later in the season. However, apply only a small amount of nitrogen fertilizer after pepper plants start to set fruit. Too much nitrogen late in the season will delay flowers and fruit, resulting in a poor harvest.
Of course, it is possible for pepper plants to suffer from either a lack of nitrogen or an excessive amount of nitrogen.
In this article, we’ll talk about what happens when pepper plants get too little or too much nitrogen. We’ll also look at how to supply nitrogen and avoid these extremes.
Do Peppers Need a Lot of Nitrogen?
Peppers need nitrogen for proper growth, as do most plants. Nitrogen is a vital component in chlorophyll, which is what makes plants green and helps them to produce energy by photosynthesis.
Pepper plants need more nitrogen early in the season. This is when the plant is producing green growth (stems and leaves) that support energy and fruit production later on.
When a pepper plant gets plenty of nitrogen, it grows strong, thick stems to support the weight of fruit. It also grows healthy leaves, which help to absorb sunlight for energy production.
The plant will use this energy to produce fruit later in the season, unless you over fertilize with nitrogen (too much nitrogen at the wrong time).
So, how can you tell when your pepper plants are getting too little or too much nitrogen? Let’s start with signs of nitrogen deficiency. We’ll talk about excessive nitrogen later.
What are the Signs of Nitrogen Deficiency in Pepper Plants?
One of the most common signs of nitrogen deficiency in pepper plants is chlorosis (yellow leaves). Chlorosis is often an early warning sign, followed by stunted growth of the plant due to a lack of energy.
“Nitrogen deficiency usually presents as lower leaves turning yellow, and then that progresses upward.”https://ask.extension.org/questions/553681
The bottom leaves of the plant turn yellow first because nitrogen is a mobile nutrient. This means that the plant can move nitrogen throughout its tissues (or from one leaf to another).
So, a pepper plant lacking nitrogen will pull this vital nutrient from its lower leaves and move it to the upper leaves. This is because these upper leaves get more sunlight and can make more energy for the plant.
In less extreme cases of nitrogen deficiency, the stem and leaves of a pepper plant may turn light green instead of yellow. However, the underlying reason is the same: a lack of nitrogen.
What are the Causes of Nitrogen Deficiency in Pepper Plants?
There are a few possible reasons for nitrogen deficiency in pepper plants:
- pH imbalance (soil is too acidic or too basic)
- Lack of nitrogen in soil (this can happen due to a lack of crop rotation or soil amendments)
- Excess carbon in soil (too much carbon makes it harder for plants to absorb nitrogen)
It is a good idea to do a soil test before adding anything to your soil. A soil test tells you the soil pH and nitrogen levels (and also the levels of other important plant nutrients).
Let’s take a closer look at the causes of nitrogen deficiency in pepper plants and how to solve the problem.
The ideal soil pH for pepper plants is around 6.5, but anything in the range of 6.0 to 7.0 should be comfortable for them.
If the pH in your garden soil is too high or too low, it will lead to a deficiency of nitrogen or other nutrients in your plants. This can happen even when there is enough nitrogen in the soil.
As the chart shows, nitrogen availability drops off rapidly when soil pH goes below 6.0.
There are several amendments that raise soil pH, such as:
- Lime – calcium carbonate, also called lime, will raise soil pH. Lime will also add calcium to your soil. Be careful about adding too much lime, or your plants will end up with a magnesium deficiency.
- Dolomitic lime – calcium and magnesium carbonate, also called dolomitic lime, will raise soil pH. Dolomitic lime will also add both calcium and magnesium to soil.
You will also see nutrient deficiencies when soil pH is too high. In that case, elemental sulfur or sulfates (iron or aluminum) will lower soil pH.
Lack of Nitrogen in Soil
What if your soil test shows you that the pH is already at or around 6.5? In that case, the soil itself may be lacking nitrogen.
A soil test will reveal a lack of nitrogen in your garden. Another sign is that other plants (in addition to your pepper plants) also have yellow leaves.
A nitrogen deficiency can happen if you plant the same crop in the same place for many years. It can also happen if you plant different nitrogen-hungry crops in the same spot each year without replacing nitrogen in the soil.
Given enough time, the plants will take the nitrogen out of the soil faster than nature can replace it. To prevent this from happening, practice crop rotation or use soil amendments in your garden to replace nitrogen (more on these methods later).
Excess Carbon in Soil
If your soil has the right pH (around 6.5 for peppers) and enough nitrogen, then it is possible that there is too much carbon in the soil.
According to Wikipedia, adding too much carbon to soil will tie up nitrogen. Too much carbon makes nitrogen unavailable to plants, even when there is enough nitrogen in the soil.
Adding sawdust to your garden is one reason that you might have too much carbon in your soil. Sawdust contains lots of carbon, so putting too much of it in one spot can cause a nitrogen deficiency in your pepper plants.
Instead, try adding sawdust to your compost pile along with food scraps, leaves, and grass clippings. Then, give the sawdust time to decompose and break down with the other materials.
Eventually, the compost will ready, and it will provide balanced nutrition for your garden. You can learn more about how to compost sawdust in my article here. (You can also use sawdust as bedding for animals).
If you suspect that there is already excessive carbon in your soil, try mixing in some new low-carbon material. This could be soil from another part of your yard, or it could be compost that does not contain so much carbon (made from more green than brown materials).
What is a Good Source of Nitrogen for Pepper Plants?
There are lots of things you can use to add nitrogen to your garden to make pepper plants grow, including:
- Cover crops (green manure)
Good compost has a balanced mix of nutrients, including nitrogen. As an added benefit, compost also contains organic material (also known as humus).
Humus promotes the growth of organisms such as bacteria and earthworms in your garden. Organic matter also helps sandy soil to retain water and improves drainage of clay soil.
The best thing about compost is that you can make your own for free, using only kitchen scraps and yard waste. You can learn more about how to make your own compost in my article here.
Manure means animal bedding and waste. Manure has a good amount of nitrogen, but the amount will vary depending on the animal it came from.
Common sources of manure for gardens are from chickens, horses, and cows. Remember: you need to allow manure enough time to age before adding it to your soil.
Aging manure neutralizes pathogens that may be present. It also reduces the risk that you will burn your plants with “hot” manure.
Cover Crops (Green Manure)
As mentioned before, a lack of crop rotation will eventually cause a nitrogen deficiency in your garden. To prevent this, you should plant different crops in the same area every year.
Green manure (cover crops) is used to replace nutrients in soil between plantings.
For instance, legumes are plants that move nitrogen into soil from the air. This happens thanks to bacteria that live on the roots of legume crops.
These bacteria fix nitrogen in the soil by converting nitrogen in the air into nitrogen compounds, such as ammonia and ammonium.
Two common green manure cover crops are alfalfa (lucerne) and clover. You can learn more about green manure in my article here.
Maybe you plant crops that use up lots of nitrogen. In that case, your soil may still need a boost, even after using compost, manure, and crop rotation.
In that case, fertilizers are an option for you. Some fertilizers are potent and have very high nitrogen content, but this high concentration comes at a price.
It is all too easy to burn plants with excessive nitrogen if you over fertilize them. One way to burn plants is to forget to water after fertilizing.
You can also burn plants if you add too much fertilizer at once. Always follow the instructions on the package, and water in your fertilizer after you add it to the soil.
As alternatives to synthetic fertilizers, some of the best organic fertilizers for pepper plants that provide lots of nitrogen are:
- Feather meal
- Blood meal
- Fish emulsion
Remember: some fertilizer that is used in large-scale farming may not be good for the home garden. For example, according to the Colorado State University Extension:
“Urea or ammonium nitrate fertilizers are not recommended sources of N.”https://extension.colostate.edu/topic-areas/yard-garden/vegetable-gardening-nitrogen-recommendations-7-247/
The high concentration of nitrogen or salt means that these fertilizers are too strong for home gardens.
Which Fertilizer is Best for Peppers?
The best fertilizer for peppers is one that provides a balanced dose of the big 3 NPK nutrients: nitrogen (N), phosphorus (P), and potassium (K).
Unless your soil is deficient in nitrogen, you will want to use a low-nitrogen fertilizer or perhaps a fertilizer with a moderate amount of nitrogen (such as 10-10-10).
Can Peppers Get Too Much Nitrogen?
It is possible for pepper plants to get too much nitrogen. According to the University of Michigan Extension:
“Unlike their relative the tomato, peppers will respond to more nitrogen by producing more fruit – at least to a point. Peppers can be over-fertilized, which can delay flowering and fruiting.”https://www.canr.msu.edu/news/its_time_to_review_your_pepper_fertilization_program
This means that peppers will benefit from a moderate amount of nitrogen early in the season. However, too much nitrogen that comes too late will hurt your harvest.
“Too much nitrogen fertilizer often results in poor yields, although the plant will appear large and healthy.”https://www.uaex.edu/publications/PDF/FSA-6015.pdf
This is tricky, because the plant will look fine until it is too late to do anything about poor fruit set. The last thing you want is to get pepper plants with lots of green growth (stems and leaves), but no flowers or fruit!
To avoid this problem, Michigan State University suggests that you “front load” nitrogen in your garden. That is, apply most of the nitrogen before the peppers flower or set any fruit.
The reason is that vegetative growth will slow down once fruit begins to set. As a result, the plant won’t be able to use all that nitrogen for producing leaves and energy.
So, let the plant use nitrogen and produce green growth early in the season. Michigan State University recommends 3 phases of nitrogen application for pepper plants, as follows:
- Pre-Season – apply 30% of the nitrogen before transplanting the peppers into the garden. Scatter the fertilizer and mix it into the soil where you will plant the peppers.
- Post-Planting – apply 45% of the nitrogen after transplanting peppers. Wait two weeks after planting, and then add about 10% per week for 4 to 5 weeks or until fruit starts to swell.
- Maintenance – apply 25% of the nitrogen in the last part of the season.
This tells us percentages, but how much nitrogen do we actually use? Well, according to the Colorado State University Extension:
“Apply 4 ounces of N per 250 foot of row after the first flush of peppers is set.”https://extension.colostate.edu/topic-areas/yard-garden/vegetable-gardening-nitrogen-recommendations-7-247/
Great, but how do we know what amount of nitrogen to use, and when? Let’s look at an example.
Let’s say that you are growing 5 rows of peppers, and each row is 10 feet long. That would be 5*10 = 50 feet of peppers.
50 is one-fifth of 250, so you would need one-fifth of 4, or 0.8 ounces of nitrogen. If you are using a 10-10-10 fertilizer (which is 10% nitrogen by weight), then you need 0.8/0.1 = 8 ounces of fertilizer.
Then you would apply the following amounts:
- Pre-Season: 30% of 8 ounces, or 2.4 ounces of fertilizer.
- Post-Planting: 45% of 8 ounces, or 3.6 ounces of fertilizer.
- Maintenance: 25% of 8 ounces, or 2 ounces of fertilizer.
You can use the following formula for your specific situation:
Total amount of nitrogen to use (in ounces): N = 1.6xF / P
F = how many feet of peppers (for example, 4 rows that are 6 feet each would be 4*6 = 24 feet)
P = percentage of nitrogen in your fertilizer (the first number: so 12-8-6 is 12% nitrogen, P =12 in that case).
Pre-Season Amount: multiply total by 0.3
Post-Planting Amount: multiply total by 0.45
Maintenance Amount: multiply total by 0.25
Be careful not to over-apply fertilizer! You can always add more, but it is difficult to fix the problem if you add too much.
Blossom end rot causes the bottom of peppers (and tomatoes) to become brown and sunken (due to a calcium deficiency, which can have several causes).
If you already have too much nitrogen in your soil, there is one fix you can try. According to the University of Mississippi Extension:
“Some diseases that are made worse by too much nitrogen may at least be partially reduced by increasing potassium.”http://extension.msstate.edu/publications/information-sheets/the-plant-doctor-plant-disease-and-fertilization
So, if you overdid it with nitrogen fertilizer, try adding potassium (potash) to see if you can save your crop. You can find high-potassium fertilizers in my article here.
Now you know how much nitrogen peppers need. You also know some ways to provide it to your plants.
I hope you found this article helpful. If so, please share it with someone who can use the information.