Fertilizer works by feeding plants and soil, giving them essential nutrients to grow and thrive. Unfortunately, fertilizer doesn’t last forever, so you must reapply it now and then. But how long does fertilizer stay in the soil?
Fertilizer stays in the soil for around 2 weeks if it’s liquid. It should remain in the soil for up to 6 months if it’s granular. Organic fertilizer stays in the soil for around 6 months, but it can last longer than this. The exact amount of time depends on the specific plants and fertilizer.
This article will discuss how often you should apply fertilizer to the soil. It will also shed more light on how long each fertilizer type stays in the soil, the best time to apply fertilizer, and the longest-lasting fertilizer. Let’s get started!
How Often Should You Apply Fertilizer to the Soil?
You should apply fertilizer to the soil every one or two weeks if it’s liquid. You should use granular fertilizer twice a year in most cases. However, this largely depends on the plants and the specific fertilizer. You should apply organic fertilizer once or twice a year.
An important thing to note is that you should always read the instructions on your fertilizer packaging. While some granular fertilizers need to be applied twice a year, your granular product might need to be used once a month.
How often you should apply fertilizer to the soil will also depend on the plants. Some plants are heavy feeders and need frequent fertilizer applications during the growing season, while others won’t need a lot.
According to Oregon State University, the following vegetables are heavy feeders:
- Beets
- Kale
- Collard
- Tomato
- Spinach
Now, let’s take a closer look at each fertilizer and how often you should use them.
Liquid Fertilizer
In most cases, liquid fertilizer stays in the soil for 1-3 weeks, so you’ll need to reapply it frequently during the growing season. But it’s essential to be aware that different products might have various recommendations, so always check the instructions before using liquid fertilizer.
According to Michigan State University, liquid fertilizer works faster than granular fertilizer because plants can immediately absorb nutrients. With liquid fertilizer, you can apply it directly to the foliage and base of the plant.
Since liquid fertilizer feeds the plants right away, it doesn’t last as long as granular and organic fertilizers—that’s why you need to apply it more frequently.
Granular Fertilizer
Generally, granular fertilizer will stay in the soil for a whole season. So, you only need to apply it once in spring and once in fall. One advantage of granular fertilizer is that it’s a slow-release product, so it feeds plants for a more extended period.
Unlike liquid fertilizer (that you can apply directly to the foliage of a plant), you must apply granular fertilizer to the base of the plant around the soil. If using granular fertilizer for your lawn, you can use a spreader to ensure it’s evenly distributed.
It’s best to apply granular fertilizer in early spring when you’re sowing the seeds and again in fall when the growing season is ending. However, it’s important to read the instructions on the packaging to determine the correct application procedures.
Organic Fertilizer
Organic fertilizer can last around 6 months to a year in the soil, so you should apply it once or twice annually. It is generally one that you make at home. It’s also known as compost, and you can make it with things like:
- Leftover food scraps
- Fish
- Grass clippings
- Shredded newspaper
Compost contains all the nutrients other fertilizers have, although it’s generally not as concentrated. When you mix it into the soil, it will decompose over a few months. Applying organic fertilizer before sowing your seeds in spring and fall (although it’s not always necessary to use in fall) is highly recommended.
Depending on the soil condition, you may want to use compost in addition to fertilizer. I’ve written an extensive guide about their difference and what to consider applying both. Don’t miss it: Do You Need Compost if You Already Used Fertilizer
How Long Does Liquid Fertilizer Stay in the Soil?
Liquid fertilizer stays in the soil for 1-3 weeks (in most cases). It doesn’t last very long because it gets absorbed instantly by the surrounding plants. Although liquid fertilizer only lasts a few weeks in the soil, you should only use it during the growing season.
For example, if you have perennial plants that go dormant during winter, you won’t need to apply liquid fertilizer in winter. If you do, you might over fertilize the plant because it won’t need all the nutrients you’re giving it.
But some plants, like evergreen houseplants, may need liquid fertilizer all year.
For example, dragon trees are indoor evergreens that benefit from year-round liquid fertilizers. Since the fertilizer only lasts a few weeks, you should feed a dragon tree with a liquid fertilizer every 1-3 weeks during every season.
How Long Does Granular Fertilizer Stay in the Soil?
Granular fertilizer stays in the soil for around 6 months. Most granular fertilizers release nutrients slowly over a long period, which is why they last a long time. If you have a vast array of crops or a large lawn to feed, it’s best to use granular fertilizer.
Since you only need to apply most granular fertilizers twice a year, it’s best to use them with extensive lawns or many crops and plants. If you apply liquid fertilizer to your lawn, you’d need to apply it every few weeks, which would be a pain if you have lots of grass to cover!
And since granular fertilizer often contains high levels of nutrients like nitrogen and potassium, you must be careful not to use it too frequently. Using granular fertilizer more than twice a year could damage your crops by causing fertilizer burn.
While these nutrients are essential for plant health and development, too many of them can cause irreversible damage.
How Long Does Organic Fertilizer Stay in the Soil?
Organic fertilizer stays in the soil for up to a year (in some cases). However, it can also last for six months. The exact time it will last depends on certain factors, including the soil type. For example, dense clay soil retains organic fertilizer better than loamy soil.
Like granular fertilizer, organic fertilizer also releases nutrients slowly over a long period. Many people apply it to the soil once a year (generally during early spring before sowing seeds) to amend the soil and add nutrients.
The nutrients from organic fertilizer can stay in the soil for a year (and even beyond in some instances). However, it would help if you considered factors like rain and soil type.
For example, if it rains often, the organic fertilizer might not last as long as it would in dry weather. This is because rain can wash away the fertilizer. However, this is true for all kinds of fertilizer—not just organic.
Later in the article, I’ll discuss how soil type can affect fertilizer retention.
Best Time of Year To Apply Fertilizer to the Soil
Now that you know more about how long each fertilizer type lasts in the soil, it’s good to know when to apply each one to the ground. There are a few things that will determine when the best time to apply fertilizer is, including:
- The type of plant
- The climate
- The fertilizer you’re using
For example, if you live somewhere hot and sunny all year, you’ll likely need to apply fertilizer every season. But if you live somewhere with cold winters, you’ll only need to apply fertilizer for one or two seasons.
It’s essential to keep these things in mind before applying fertilizer!
You should apply granular fertilizer to the soil during spring when the growing season begins. For edible plants (like vegetables), it’s best to apply granular fertilizer before sowing seeds so that you can work it into the soil. Doing so gives the fertilizer a chance to develop before planting any crops.
But if you’re fertilizing flowers and other plants, it’s best to fertilize them right before they begin to flower. Once you’ve fertilized your vegetables and other plants in early spring (using granular fertilizer), you can leave them be for the rest of the season. All you’ll need to do is water frequently.
Once the growing season has come to a close during late fall, it’s a good idea to apply granular fertilizer again, as doing so will allow your plants, vegetables, and lawn to grow stronger the following spring.
You should also use liquid fertilizer during spring and stop using it near the end of fall (unless you’re feeding evergreens or live in a hot climate).
What Is the Longest-Lasting Fertilizer?
The longest-lasting fertilizer is any slow-releasing type, such as granular or organic fertilizers. If you’re looking for a long-lasting product, you should avoid liquid fertilizer. Most synthetic granular fertilizers last up to 6 months, which makes them an excellent long-lasting solution.
It’s important to understand that no fertilizer lasts in the soil indefinitely. All fertilizers, whether granular or liquid, will fully decompose over time. Other than granular fertilizer, organic compost lasts months and even a year in the soil.
Therefore, organic compost fertilizer is a decent, long-lasting choice. However, organic fertilizer won’t be a good choice if you need a strong fertilizer or a fertilizer that has high concentrations of a particular nutrient as you can’t control the specific amount of nutrients in organic fertilizer.
Since some plants and soil need high levels of some nutrients and low levels of others, synthetic granular fertilizers are often the better choice because they’re more controlled.
For example, you can purchase granular fertilizers that are high in nitrogen and potassium but low in phosphorus. It’s not possible to buy organic fertilizers with these specifics.
So, organic fertilizer would be an excellent choice if you need a general, all-purpose fertilizer that lasts a long time. But if you have specific nutrient requirements and want the fertilizer to be long-lasting, you should go with synthetic granular fertilizer.
How Long Do Fertilizer Spikes Stay in the Soil?
Fertilizer spikes stay in the soil for up to two months for small plants. However, they can last for around six months if they’re made for larger plants, like trees and shrubs. If using fertilizer spikes, you should always read the instructions because the requirements may vary.
Some of the most popular fertilizer spikes are Miracle-Gro products. They sell spikes for different plants—the spikes they sell for smaller plants usually need to be applied once every two months during the growing season.
For things like trees, you can apply the spikes as frequently as granular fertilizer—twice annually (once in spring, once in fall).
Is It OK To Use Fertilizer Once a Year?
It is OK to use fertilizer once a year if it releases nutrients slowly. However, applying a fast-releasing fertilizer (such as liquid fertilizer) won’t be helpful once a year. You should use that every few weeks. Most lawns and plants will benefit from an annual granular fertilizer application.
However, it’s better to apply slow-releasing fertilizer twice a year for added strength. If you only plan on fertilizing your plants, vegetables, or lawn once a year, you should do it in spring rather than fall to ensure your plants have the strength they need to grow during the summer.
When using fertilizer once a year (during spring), ensure you don’t use it too early—otherwise, it can affect your plants’ growing cycle. Late spring is sometimes best for lawn fertilizer.
How Long Does Grass Fertilizer Stay in the Soil?
Grass fertilizer stays in the soil for up to six months but doesn’t always last this long. You’ll need to apply lawn fertilizers once every two or three months during the growing season for the best results. But in most cases, it’s OK to fertilize grass once or twice a year.
But as I’ve mentioned previously in this article, it’s always essential to read the fertilizer packaging instructions before using it. Some grass fertilizers will tell you to reapply the product twice a year, while others recommend applying it four or five times a year.
It’s better to under-fertilize than to over-fertilize. So if you’re unsure how long your grass fertilizer will stay in the soil, you should use it once or twice a year to be safe. Using too much grass fertilizer could burn the grass and even lead to irreversible damage.
Can Fertilizers Stay in the Soil for More Than a Year?
Fertilizers usually can’t stay in the soil for more than a year. Unfortunately, most fertilizers will fully dissolve into the ground and plants within six months of applying. The only fertilizer that might sometimes stay in the soil for more than a year is organic fertilizer, like compost.
However, it’s unlikely for it to last that long. Therefore, it’s best to apply fertilizer at least once a year. Ideally, it would be best if you used it twice annually.
When you apply fertilizer to the soil, the surrounding plants absorb it. On top of that, it begins to break down naturally. Technically, it’s a good thing that fertilizer usually doesn’t last for more than a year because it means the plants are absorbing it and using the nutrients.
Fertilizer is more likely to last longer in the soil if the soil is hard and clay-like. I’ll discuss this further in the next section.
What Soil Type Is Best for Fertilizer Retention?
Hard, clay soil is the best soil type for fertilizer retention. When soil is light and loamy, fertilizer can escape through the gaps more quickly, meaning it won’t last as long. But it’s more challenging for fertilizer to flee in hard soil because there aren’t as many air gaps.
According to Oregon State University, clay soils can easily hold onto things like fertilizer and pesticides. Additionally, they can retain water for extended periods, which can be a good and bad thing.
Even though fertilizer retention is a positive aspect of clay soil, there are many downsides. Many plants and vegetables can’t grow and thrive in this soil because it’s too dense. Therefore, the roots can’t grow and spread as easily as they can in light, sandy soil.
Additionally, clay soil can get waterlogged more easily. If you don’t realize your soil is hard and clay-like, you may overwater and over-fertilize unknowingly (because it will retain these things more than other soils).
So if you know that your soil is hard and clay-like, you should assume that the fertilizer will last longer than in other soil. In this case, you may only need to apply granular fertilizer once a year. But to be sure, it’s best to conduct a soil test now and then.
Even though clay soil retains fertilizer better than sandy soil, it’s generally better to have sandy soil because most plants thrive in it—you’ll just need to fertilize more frequently!
Conclusion
Fertilizer stays in the soil for up to six months in the case of granular fertilizer. If it’s liquid, it will only last a few weeks because it gets absorbed by plants quickly. Organic fertilizer can last anywhere from six months to a year (and even beyond sometimes).
Although these are general guides, the specific amount of time fertilizer stays in the soil depends on several factors, including:
- The soil type
- The fertilizer brand and instructions
- The plants
- Weather conditions
