Fertilizers are necessary for amending soils of all kinds to supply plants with the nutrients they need to grow and thrive. They can be applied to the leaves of your plants or to the soil. There are many ways in which fertilizer can be incorporated into the soil, but the steps to mixing fertilizer with soil are more or less the same.
Here are a few steps that explain how to mix fertilizer with soil so you can feed your plants well:
- Conduct a soil analysis to understand your soil components.
- Determine what nutrients your plants need and when.
- Assess your goals for fertilizer usage.
- Figure out a schedule for fertilizer application.
- Improve your soil’s texture and overall condition.
- Correct the soil’s pH if necessary.
- Irrigate your soil thoroughly.
- Dilute your fertilizers and use less than recommended.
- Work your fertilizer into the soil.
In this article, I will explain each of these steps in more detail so you will know exactly how you can go about mixing your fertilizer with soil. I will also explain why these steps are important, so read on!
1. Conduct a Soil Analysis to Understand Your Soil Components
Soil analysis or testing is an important step in fertilizing your soil when planting crops or directly rooting your houseplants in the garden soil. Plants need three macronutrients and several micronutrients to grow and thrive. As they grow, these nutrients get depleted in the soil and need to be replaced with fertilizer and manure to ensure consistent yields.
A soil analysis will determine what nutrients are present in the soil and their amounts. It will also detail the texture of your soil. This clarifies whether your soil is primarily made up of sand, silt, or clay, so you can amend the soil to suit your plants’ requirements.
As a general rule of thumb, a balanced mixture of sand, silt, and clay results in loam, which has good drainage and sufficient water and nutrient retention capacities.
A soil analysis will also tell you the pH of your soil. Many slow-release fertilizers depend on soil pH and temperature to release their nutrients. So knowing what’s your soil pH allows you to assess what fertilizers you require and whether you need to amend your soil pH to meet the needs of your plants.
A soil analysis should be conducted every two years. You’ll have to collect several soil samples from your garden to send to the lab. When collecting the samples, make sure you pull up at least 6-7 inches (15-18 cm) of a core to ensure that you’ve got a good amount of topsoil for analysis.
2. Determine What Nutrients Your Plants Need and When
In addition to conducting a soil analysis, you need to determine what nutrients your plants need to survive.
Follow the below guidelines:
When Using Potting Soil
If you’re rooting your plants in potting soil, you will need to add fertilizer exclusively based on your plants’ requirements. Most potting soil doesn’t contain any fertilizer, let alone the nutrients available through organic matter and minerals such as in garden soil.
Consider the Type of Plant and Season
Different plants have different nutrient requirements, and these requirements vary based on the season.
Most plants need their fertilizer to supply a combination of the three macronutrients known as NPK:
Trees and lawns usually need nitrogen-heavy fertilizers, while ornamental plants and fruiting trees need heavy phosphorus fertilizers early in the growing season to help them root well. In the second half of the growing season, the ornamental plants and fruiting trees need potassium heavy fertilizers to help with water intake and ensure high yields.
Newly Potted Plants
Newly repotted plants may have slow-release fertilizers mixed in with the fresh potting soil to support the plants and aid their growth after recovering from transplant shock. But they are not fed for a while after repotting to ensure that the new, tender roots don’t end up scorched.
When Planting Seedlings
If you’re planting seedlings, you might add some starting solution to the plants, which is a very diluted liquid fertilizer. This fertilizer is typically heavier on phosphorus and nitrogen and helps the young plants develop quickly by supplying the nutrients in a way that is easy for them to uptake.
Knowing what nutrients your plants need and when they will need them will help you determine what kind of fertilizers you need to use and set up a schedule to apply them.
3. Assess Your Goals for Fertilizer Usage
When you assess your fertilizer usage goals, you’re considering why you’re applying fertilizer in the first place. Depending on your needs, you’ll be able to pick the right type and application of fertilizer.
Organic or natural fertilizers like manure and compost do more than supply nutrients to your indoor and outdoor plants.
These fertilizers improve the nutrient and water retention capacities of your soil. The organic matter present in natural fertilizers also attracts microbes and other organisms that aerate the soil and process the particles, improving overall soil quality.
Compost can be easily mixed in with potting soil in a ratio of 1:3 of compost to the soil when you first pot your plants. You can also mix it with your garden soil to prepare the soil for planting in spring.
If your goals are to ensure that your plants grow big and tall, you will need to consider their growing season. Plants need a lot of the macronutrients in their growing season, and you will probably need to apply additional fertilizer at this time to ensure they are able to grow well.
You’ll probably need multiple fertilizer applications with varying ratios for agricultural and yielding plants to ensure healthy flowers and a high yield. Vegetables, ornamental plants, and fruiting trees will need regular fertilizer applications in the flowering and fruiting seasons to ensure their productivity.
4. Figure Out a Schedule for Fertilizer Application
Once you know what nutrients your soil is deficient in, what nutrients your plants need, and when they need them, you can now set up a schedule to apply your fertilizer.
A schedule ensures that your plants receive nutrients when they need them. It will also help prevent cases of fertilizer burn caused by over-enthusiastic fertilization.
With plants rooted in garden soil or fields, the fertilizer schedule begins in fall, which is when you would apply natural and other slow-release fertilizers to the soil. These fertilizers release nutrients through microbial activity in quantities easily uptaken by plants, even in dormancy.
Applying slow-release fertilizers during fall improves overall soil quality and reduces the amount of fertilizer that your plants will require in the growing season.
The next fertilizer application usually occurs in early spring, just as the growing season begins for most plants. Fertilizer needs to be worked into the soil before plants are rooted to ensure that the plants receive enough nutrients to support their initial growth.
If you are dealing with seedlings, you may also want to supply a diluted liquid fertilizer as a starting solution to help them root. Newly planted crops and plants need a few weeks of root growth before they are ready to uptake any additional fertilizer.
After the first application, your schedule will depend on the plants’ requirements and the environmental conditions. Hold off applying fertilizer when the temperatures start soaring because heat-stressed plants will not have enough water to uptake nutrients from the soil.
Otherwise, you might even end up causing fertilizer burn in your plants.
This can also happen with plants that need a lot of feeding like tomato plants, and fixing fertilizer burn in tomato plants takes a long time.
When applying fertilizer, it is important to consider the timing. Avoid fertilizing your plants in the heat of the sun. Instead, stick to cool mornings that allow plants to utilize the nutrients as they absorb them.
5. Improve Your Soil’s Texture and Overall Condition
Your soil’s texture and condition determine how easy it will be for you to mix the fertilizer in and how much of the fertilizer will be retained by the soil. As I’ve mentioned earlier, soils with good sand, silt, and clay balance will ensure good drainage, sufficient water, and nutrient retention.
Soil that is rich in organic matter tends to retain water better, which is why incorporating dried leaves, sawdust, and other organic matter into your soil is helpful. The organic matter also breaks up the soil particles, which ensures good drainage.
Fertilizers like compost and manure can be added along with organic matter to not only improve water retention and aeration but also add nutrients to the soil. Incorporating this organic matter in fall is a great way to prepare your soil for spring planting.
The increased aeration will mean that your soil is looser and easier to work with, rather than compacted like clayey soil or too loose and unstable like sandy soil. Sandy soils are not ideal for gardening and planting because any fertilizer will be leached away quickly, with the fertilizer draining away with the water.
Correcting the texture and conditioning of the soil ensures that the application of fertilizer will actually be effective and economical.
6. Correct the Soil’s pH if Necessary
The acidity or alkalinity of soil is what is indicated through the pH value of the soil. Plants like lavender and honeysuckle prefer alkaline soils, while a lot of tropical plants tend to prefer mildly acidic soils.
The pH value of soil affects its fertility. Maximum nutrients are made available to soils with a pH range between 6-7.5, and some nutrients like phosphorus are more affected by the pH value than others.
In soils where pH values are above 7.5, phosphorus, commonly known as phosphate, combines with calcium and becomes a less soluble compound. A lower solubility increases the difficulty of nutrient uptake and utilization by plants.
So, even if you add phosphorus and calcium heavy fertilizers like bone meal to your soil, if the pH value is above 7, the phosphorus will be unusable for your plants.
Thankfully, amending your soil is easily done by adding natural fertilizers like compost. A few inches of compost worked into the soil in the fall will change the pH value of alkaline soil and make it more acidic for early spring.
Maintaining the pH value of soil is also beneficial to the release of nutrients of slow-release fertilizers like plant food spikes, as a higher pH breaks through the coating on these fertilizers.
7. Irrigate Your Soil Thoroughly
Most inorganic fast-release fertilizers are water-soluble, so nutrients from these fertilizers are inaccessible to plants in dry soils. Even nutrients from organic and slow-release fertilizers cannot be taken up by plants when the soil is dry because plants use water as a carrier to disperse nutrients.
Irrigating your soil thoroughly before you mix fertilizer into your soil is a necessary step for multiple reasons:
- The water fixes the fertilizer to the soil particles.
- Water disperses the fertilizer deeper into the soil.
- Soluble fertilizers dissolve into water, making nutrients accessible to plants immediately.
Well-irrigated soil is able to hold onto the fertilizers better. The water takes it to the deeper layers of the soil, bringing the fertilizers in contact with the finer root hair, thereby ensuring quick uptake.
Plants also need water to uptake nutrients, even if the fertilizer itself is not water-soluble. In dry soils, the nutrient’s mineral salts accumulate outside the roots and start drawing water out of the plant tissue, causing fertilizer burn.
Fertilizer burn can manifest as wilting, yellowing, browning, and death of leaves and roots of your plant. Avoid fertilizer burn and other fertilizer-related issues by watering your soil thoroughly before adding any fertilizer.
8. Dilute Your Fertilizers and Use Less Than Recommended
Over-fertilization is a common problem that can have a number of detrimental effects on your plants, including stunted growth, excessive foliage growth, low yields, and leaf scorch. More often than not, overfertilization occurs with inorganic fast-release fertilizers.
That is not to say that you can’t over-fertilize with slow-release fertilizers. Adding too much compost or manure can result in nitrogen saturation in the soil, resulting in plants that grow too quickly. This makes them susceptible to diseases and pests because the speed of growth makes the plants fragile.
It is important to remember that you can always add more fertilizer when necessary. However, plants take a long time to recover from fertilizer burn, and the process of rescuing them isn’t easy.
9. Work Your Fertilizer Into the Soil
Surface applications of fertilizer can be useful for immediate nutrient supply or additional application through the growing season. However, you shouldn’t apply a lot of fertilizer during surface applications as there is always the risk of run-off and leaching.
Mixing fertilizer into the soil is one of the best ways to incorporate larger amounts of fertilizer within the soil and prepare it for planting. Depending on the type of fertilizer, there are different ways of mixing it with your soil.
Mixing Solid Fertilizers With Soil
Here are some of the ways to mix solid fertilizer with soil:
Basal broadcasting refers to the method by which you incorporate fertilizer uniformly through your field or garden. The fertilizer is mixed into the top 4 inches (10.16cm) of soil.
Placement is a fertilization method by which solid fertilizers are placed deep in the ground using plows or fertilizer drills.
Banding is a method of fertilization in which the fertilizer is worked in a band alongside rows of vegetables, or flowering and fruiting trees.
Mixing Liquid Fertilizers Into Soil
Here are some ways in which you can mix your liquid fertilizer into the soil:
Fertigation refers to the method by which fertilizers are mixed into the soil through irrigation water. The method involves dissolving fertilizers into the water used to water your garden or fields.
Nutrients are therefore easily accessible and taken up by plants. This method is commonly used for nitrogen-heavy fertilizers.
As the name suggests, liquid fertilizers can be injected directly into the soil. While this injection may be surface level, more often than not, the fertilizer needs to be injected into furrows. These furrows must be covered immediately to prevent the loss of nutrients through ammonia volatilization.
As you can see, mixing fertilizer with soil is a simple process. Get your soil tested and check on your plants to see what nutrients they need so you don’t end up overfertilizing your plants.
After that, you can prepare your soil by ensuring it has the right texture, pH value, and moisture levels to retain the fertilizer and make the nutrients available to your plants easily.
Finally, work the fertilizer into the soil using an appropriate method depending on whether you’re using a solid or liquid fertilizer just before planting season.