This article presents frequently asked questions and answers about garden fertilizers.
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In This Article
1. Why Do Plants Need Fertilizer?
Organic fertilizer is the most important thing you can add to your garden. It is the one thing that will ensure consistent growth year after year.
Fertilizers are one of the best ways to correct deficiencies or provide extra nutrients early, mid, or at the end of the growing season.
Depending on your needs and the type of plant you are growing, they can be purchased as liquids, powders, granules, or pellets. A fertilizer is a substance used to enhance the growth of plants.
2. How Do I Know If I Need Fertilizer?
You can tell if you need to fertilize your plants by looking at the signs of the lack of nutrients. If your plants are growing slowly, looking sickly, or not producing as much as they used to, then you need to fertilize them.
If your soil is rich in nutrients, you will have a healthy and thriving garden. You will see a healthy green color, vigorous growth, and beautiful flowers.
3. What Are The Types Of Fertilizers?
The following is a list of different types of fertilizers.
Mineral Fertilizers
Mineral Fertilizers are naturally occurring raw materials that are transformed into a form suitable for plants using industrial processing. These natural minerals contain a high amount of nutrients. You can find several types of mineral fertilizers at your local garden center.
Organic Fertilizers
Organic fertilizers are made from organic matter such as:
- Animal Manure is made from animal discharge like goat manure or cattle manure. Goat droppings are rich in nitrogen and potash, while cow manure is a great organic carbon and nitrogen source.
- Compost is organic matter (plants or animal manure) that goes through the decomposition process by composting.
- Chicken Litter is made out of chicken manure and sawdust. It contains a high level of potash and nitrogen.
- Vermicompost results from the organic material (such as food waste or animal manure) decomposed by various worms species. The vermicompost is also known as ‘worm manure’ and ‘earthworm manure.’
- Bone Meal is animal bones from a slaughterhouse ground into a fine powder or granules. Bone meal fertilizer is a perfect source of amino acids and phosphorus.
- Rock Phosphate is a source of phosphorus and calcium. It is mined from deposits of phosphate-rich rocks and has a composition similar to bone meal. Rock phosphate breaks down slower than the bone meal, so it can be used as a long-term phosphorus supply.
- Lime is commonly used as fertilizer for lawns and gardens to correct soil acidity. The correction allows microorganisms to thrive and break down organic matter in the soil. Consequently, releasing necessary elements for plants to grow healthy. Lime is a natural compound. It is a white crystalline solid mineral formed by the weathering of limestone. [1]
Synthetic Fertilizers
Synthetic fertilizers are prepared from inorganic compounds. They can be in granular or liquid forms. These are usually more concentrated than organic fertilizers and contain nitrogen (N), phosphorus (P), and potassium (K) as the primary nutrients for plants.
They include calcium (Ca), magnesium (Mg), and sulfur (S) as secondary nutrients. In addition, synthetic fertilizers can also include other nutrients such as boron (B), copper (Cu), chloride (Cl), iron (Fe), molybdenum (Mo), manganese (Mn), and zinc (Zn). [2]
4. Why Choose Organic Fertilizer Over Synthetic?
The main advantage of using organic fertilization is that it builds your soil over time. These fertilizers are made from natural sources, such as compost, manure, and other byproducts of animals or plants. They help plants grow, strengthening soil texture and overall health.
Chemical fertilizers can deplete soil microorganisms and leach into waterways. [3]
So, organic fertilizers are much more sustainable than chemical fertilizers. It is much more beneficial for the environment and the soil itself. The beneficial microbes that live in healthy, productive soil help plants grow, increase their immunity and help the soil stay fertile.
5. What Are The Three Fertilizer Numbers?
Nitrogen (N), phosphorus (P), and potassium (K) are the three numbers that are separated by hyphens on the fertilizer packages. They represent the percentage of each nutrient in the fertilizer. For example, 10-20-10 fertilizer has 10% nitrogen (N), 20% phosphorus (P), and 10% potassium (K).
The rest of the fertilizer is composed of stabilizers or fillers such as sand or other material types that have no nutritional value for plants.
6. What Is NPK?
NPK is an abbreviation for nitrogen (N), phosphorus (P), and potassium (K). These are the three primary nutrients used by plants.
They are the macronutrients that are essential for plant growth and development. In short, NPK are the most critical factors in producing quality crops. We need these three elements in the correct ratio to grow our plants.
7. What Do Nitrogen (N), Phosphorus (P), Potassium (K) Do For Plants?
Nitrogen – improves foliage growth and pollen production.
Nitrogen is an essential component of green plant matter. Plants need nitrogen for growth to produce more leaves, stems, roots, flowers, fruits, and pods. Plants look scraggly and pale green when the soil becomes depleted of nitrogen. So, when plants lack nitrogen, they cannot develop or reproduce.
Phosphorus – is vital for root development.
Phosphorus is also necessary for fertility, flowering, fruit set, and seed formation. Plants need it to make their seeds, produce flowers, fruits, and healthy root development. Phosphorus is essential for plant photosynthesis.
Potassium – improves plant stress tolerance and promotes flowering and fruiting.
Potassium plays a crucial role in cell division and improves growth and fruit production. It helps regulate the amount of water and nutrients in plant tissues and helps plants produce flowers. [4]
8. What Fertilizers Do For Plants?
Fertilizers are used to improve the health and growth of plants by enriching the soil. They can be applied to the soil, through watering, or to the leaves, stems, roots, and flowers.
9. Are Higher NPK Amounts Better?
Higher NPK amounts do not always mean more effective fertilizer. Higher amounts can cause problems for the plants. These problems include:
- Risk of “burning” your plant roots, causing them to become weak and possibly die.
- Risk of fertilizer runoff into waterways, which can cause water pollution.
- Risk of nutrient build-up in your plants. When this happens, the plants may look healthy, but they are not actually producing as much fruit or as many seeds as they could be.
- Excess nutrients could cause the risk of pests attacking your plants.
Organic fertilizers are typically much lower in NPK than synthetic fertilizers. They supply nutrients to plants slowly. The release of nutrients is more efficient and maintains the fertility of soils for longer.
10. Can Fertilizer Hurt Plants?
An excessive amount of fertilizer can cause plants to grow too fast. This means that plant roots don’t get enough time to develop to support growth, and plants can die.
Also, too much fertilizer can burn the plant roots. Always use as described on the label.
11. Can Fertilizer Kill Plants?
Fertilizers are an excellent way to keep plants healthy and growing, but they can cause problems if applied in excess. It is crucial to understand how they work and when to use them.
The best fertilizer for your garden is a mix of organic and mineral fertilizers. Too much fertilization will leave your plants vulnerable to garden pests and disease infestation. So, yes, fertilizer can kill your plants.
12. Can I Make My Own Liquid Fertilizer?
Make a liquid organic fertilizer using all-natural ingredients that you can use to fertilize your garden, and here are a few ways to do this:
- Blending food waste. Place kitchen food waste (the same waste as you would use for compost) into a blender. Run the blender until the mixture turns into smoothy. Dilute it with water before pouring the mix into your garden.
- Marinating food waste. Place kitchen waste into the bucket with water. Cover it and leave it to marinate for 3 to 5 days. This process will release nutrients into the water. Then, all you have to do is dilute the marinate with water and pour it beside your plants. The marinate will be smelly, so do it outdoors.
- Marinating grass clippings or weeds. Place the weeds you pull from your garden or clippings from your lawn into a bucket of water. Cover it and leave it to marinate for 3 to 5 days. Then, dilute it with water and pour it around your plants. The marinate will be smelly, so do it outdoors.
13. How Do I Know If My Plants Need Fertilizer?
If your plants show signs of malnutrition, you’ll need to add more nutrients to the soil. Signs include:
- Pale green or yellow foliage when nitrogen levels are low,
- Chlorosis (dark green veins on pale green leaves) when potassium is low,
- Dull, dark green foliage with purple leaves at the base of the plant or reduced flowering when phosphorus is low.
- Blossom-end rot is a calcium deficiency symptom. Overwatering or underwatering can also cause this problem, so knowing how to treat it is essential.
Not all signs of nutrient deficiencies are clear. So, it is not always easy to identify what exact nutrients your plants need, even if you are a pro gardener. You can always use general organic fertilizers if you are unsure.
14. How Do You Fertilize Garden Plants?
Annual and perennial plants have a specific way to be fertilized. These are described below.
How Do You Fertilize Annual Plants (Most Vegetables And Some Fruit Varieties)?
Before starting the growing season, fertilize your plants with granular organic fertilizer and work it into the soil.
After your seedlings grow a second set of true leaves, fertilize your plants with half of the usual amount of liquid fertilizer every 14 days (2 weeks). Then as the plants grow, apply the full amount of the fertilizer (follow the instructions on the label).
Pro Tip: As you know, not all fertilizers are the same. So, if you are applying fertilizer that you have never used before or switching to a different brand, always test it on a few plants before applying it to the whole garden.
For example, if you switch fertilizers for your tomato, cucumber, and strawberry plants, select a couple of each plant and test the new fertilizer on them first. Suppose you see no damage by the time the next fertilizer application is due (usually after 14 days). In that case, you can use the new fertilizer for your tomatoes, cucumbers, and strawberries.
How Do You Fertilize Perennial Plants (Most Fruits, Flowers, And Some Vegetables)
When planting perennials, add slow-release granular organic fertilizer and work it into the soil around the plant. Then add some more when your plants are established (usually two years after planting).
Read the label on the package to determine how much fertilizer to add to your soil. Slow-release organic granular fertilizers allow your plant to slowly and continuously uptake nutrients over a longer period.
This is great for ensuring your plants get the nutrients they need during their growing stage. Slow-release fertilizers can be found in compressed pellets, granules, or wafers in your local garden store, or you can get them online.
For ornamental trees and shrubs, apply fertilizer when plants are in their early growth stages at the beginning of their growing season.
15. How Long Does Fertilizer Last In Soil?
It depends on the type of fertilizer. There are two types, fast-release and slow-release fertilizers.
Fast-Release Fertilizers
Liquid or powder fertilizers can last in the soil for 7 days to a few months. It can depend on a couple of things:
- Weather. Rain can wash out fertilizers from your soil, especially if you have raised beds.
- Type of fertilizer. Liquid fertilizers tend to be used up quicker by plants than powder fertilizers.
- Type of plant. Some plants need more fertilizer than others. So, it depends on the kind of plant you have in your garden.
- Number of plants. If you have plants that are too close to each other, they will soak up fertilizer faster.
- Weeds. They love fertilizer too! The more weeds you have, the more nutrients they will soak up, and the less fertilizer is available for your plants.
Slow Release Fertilizers
Slow-release fertilizers are available in a wide variety of products. They can be granular, pellets, or tablets. The main advantage of slow-release fertilizers is that they release nutrients into the soil over a longer period. This allows your plants to absorb nutrients throughout the growing season. So, your plants will get enough nutrients over time.
Slow-release fertilizer can last in the soil anywhere from 2 to 9 months. You don’t have to apply it to your soil as many times as you would apply fast-release fertilizer.
Always follow the instructions on the package. This is the most important thing. Some slow-release fertilizers need to be applied at the beginning of the growing season. Some can be applied throughout the growing season.
16. How Long Does It Take For Granular Fertilizer To Work?
Granular fertilizers are slow-release fertilizers, and they begin to improve plants several weeks after it is applied. This is a great way to ensure your plants get the nutrients they need throughout the growing season and reduce the need to use fertilizers more frequently.
Slow-release fertilizers take longer to work, but they also last longer than instant-release fertilizers, which are effective but don’t last long. Plants take in nutrients from instant-release fertilizers within 15 to 24 hours.
Always read the fertilizer label you are using to determine how often it should be applied.
17. How Much Liquid Fertilizer Does a Plant Need?
Liquid fertilizer should be mixed in water as directed on the package (usually every 14 days). Once the liquid fertilizer is mixed and diluted with water, it should be given to plants at the same time as your usual watering.
Liquid fertilizers are instant-release fertilizers that work quickly and are easy to use. They are designed to release nutrients into the soil as soon as they come into contact with water. Plants then absorb these nutrients.
18. How Often Should I Apply Slow-release Fertilizer?
Apply slow-release fertilizers to your garden every six to eight weeks unless the instructions given on their packaging indicate otherwise.
19. How Often Should I Fertilize My Tomato Plants?
Tomato plants should be fertilized throughout the growing season, especially in colder climate zones. They need fertilizer once every 2 weeks. This will encourage them to produce flowers and fruits.
If your tomato plant was damaged by frost, give them a heavier fertilizer to encourage new growth. This tactic does not always work, but it is worth trying. It might just save your plants.
20. How Often Should You Fertilize Flowers?
Different types of fertilizer have different application timings, so always follow the guidelines provided by your fertilizer manufacturer.
Liquid or water-soluble fertilizers are typically applied every two weeks. They are always mixed in with the water your plant normally receives.
Slow-release fertilizers should be applied at the beginning of the season, just as plants are starting to grow.
To grow great fruit, vegetables, and flowers, you must first prepare the soil properly. Organic soil amendments are an excellent way to achieve this.
21. Should I Feed My Plants Every Time I Water?
- Garden plants should be fed with a water-soluble fertilizer once every two weeks unless the fertilizer labeling says differently.
- Outdoor container plants should be watered with a water-soluble fertilizer once every two weeks.
- House Plants should be watered with a water-soluble fertilizer once a week.
22. Should I Water My Plants Before Fertilizing Them?
If the soil is dry, you should water your plants before using liquid fertilizer.
This is to do with a simple law of physics. Water will always find its way to the lowest point in the fastest way possible. If your soil is dry and cracked, it will penetrate any crevices or paths that facilitate its flow downwards.
So, by pouring liquid fertilizer onto dry soil, most of it will run down into the cracks and lead to nutrient burn or nutrient leaching, especially if you are growing in raised garden beds.
The soil will soak in water if you water your plants before fertilizing. Wet soil will allow fertilizers to be evenly distributed.
If you use a slow-release fertilizer, you do not have to water your plants before use.
23. What Are Some Examples Of Natural Fertilizers?
Natural fertilizers are organic fertilizers that are extracted from animals or plants. These can be:
- Aged Poultry Manure,
- Aged Cow Manure,
- Aged Horse Manure,
- Mushroom Manure,
- Blood Meal,
- Bone Meal,
- Kelp Meal,
- Compost,
- Seaweed,
- Worm Castings,
- Peat,
- And many more.
These natural fertilizers can be used alone or included in homemade fertilizer mixes.
24. What Fertilizer Helps Flowers Bloom?
Phosphorus (P) is an essential element in the production of flowers. However, avoid fertilizers with large quantities of phosphorus, which can be toxic to plants. For example, a fertilizer with 30 percent phosphorus could cause blooms to form too quickly. In comparison, a fertilizer with only 5 percent phosphorus could promote lush growth but not flower production.
An adequate amount of phosphorus is already present in most non-agricultural soils. So, there is no need to add an excessive amount of it. But, if you need to add extra to help your flowers bloom, you can buy phosphate rock to add it to your garden. Phosphate rock is the most common source of phosphorus.
25. What Is a Good Fertilizer For Orchids?
Orchids need a balanced fertilizer, such as a 20-20-20 blend. Use the fertilizer as described on the fertilizer label.
Regardless of the fertilizer brand you choose for your orchids, it must contain only a tiny amount to none of the urea.
26. What Time Of Day Should I Fertilize My Plants Or Flowers?
If you use liquid fertilizer, you should fertilize your plants in the morning. This way, plants can absorb nutrients from the soil before the midday heat.
If you use granular fertilizer, the time of day you fertilize your plants is not essential. As it is a slow-release fertilizer, the nutrients will stay in the soil for weeks and months after application.
27. Which Fertilizer Makes Plants Grow Faster?
High-nitrogen (N) fertilizers are great for growing plants. Look for fertilizers with a high first number, which indicates that they have a high content of nitrogen (N).
Nitrogen is the primary building block of proteins, the main source of energy for plant growth and development, and a significant component of chlorophyll. Plants use nitrogen to make amino acids and other molecules used in cell structure, metabolism, and defense against environmental stresses. [5], [6]
What To Do Next
Check out our Growing Guides to learn more about how to grow plants of your choice. Learn and help your plants by reading these guides.
Also, check out other similar articles in our Soil and Fertilizers section.
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