Can You Mix Two Fertilizers for Your Plants?

Fertilizers are an important soil amendment that works with pesticides to improve the health of your plants and help them grow. There are many different fertilizers, each with different ratios of the macro and micronutrients that plants need. There are single-nutrient fertilizers as well.

You can mix two fertilizers for your plants, especially if they are single-nutrient fertilizers. Mixing your fertilizers ensures that you can supplement all your plants’ needs at once. However, you have to be careful and ensure that the fertilizers you’re using are compatible.

In this article, I’ll explore the various upsides and downsides of mixing your fertilizers. I’ll also tell you everything you need to know about fertilizer compatibility and what you need to consider before mixing fertilizers, so read on!

Upsides and Downsides of Mixing Fertilizers for Your Plants

There are several upsides and downsides to mixing fertilizers. Mixing fertilizers can be quite beneficial to your plants and save you time and money.

Advantages of Fertilizer Mixing

Here are the upsides of mixing two fertilizers for your plants:

Lower Cost & Higher Convenience

Applying a mixed fertilizer is more cost-effective than applying different fertilizers to your soil at different times. It’s also naturally easier to apply one fertilizer that meets all your plant’s nutrient needs instead of applying multiple fertilizers one at a time.

Accounts for Micronutrients

Most premixed fertilizers don’t account for micronutrients like calcium and magnesium, or they might have them in quantities that don’t meet your needs.

Mixing your fertilizers ensures that you can get your plants the micronutrients they need.

Can Be Tailored to Your Plants and Soil

Mixing your fertilizers ensures that you can tailor the nutrient ratios to the needs of your plants. If you’ve had a soil analysis done recently, you can tailor your mix, so it only supplies the nutrients missing from your garden soil.

Reduces Wastage

Applying fertilizers that your plants don’t need leads to wastage as the plant will not uptake the nutrient. The nutrient then accumulates in the soil or leaches into water bodies.

However, when you mix your fertilizer, you ensure that you’re only using the nutrients your plants need.

Prevents Fertilizer Burn

Accumulation of unused fertilizer in the soil leads to a concentration of mineral salts that can cause fertilizer burn in your plants. Mixing your fertilizers lets you use what you need, preventing the possibility of fertilizer burn.

The advantages above are why many people choose to mix their fertilizers.

Disadvantages of Fertilizer Mixing

However, there are some downsides to mixing fertilizers for your plants, including:

Requires More Time and Effort

Mixing fertilizers needs you to check your soil analysis and the needs of your plants, then find fertilizers that can be mixed.

Not putting in the effort won’t give you any benefits of mixing your fertilizer, so you need to be sure that you have the resources to do this.

Making More Than You Need

When mixing a balanced fertilizer, you’re likely to end up with excess. You’re likely to have a lot of the final mixed fertilizer or extras of the single nutrient fertilizers you’re using to mix your fertilizers.

Calculating Ratios Is Difficult

If you’re mixing two fertilizers with set ratios of the three macronutrients already, then identifying the new ratio is tricky. You have to account for the percentage of fillers or spreader materials, then determine the new percentage of each of the macronutrients.

Some Can’t Be Mixed

Ideally, the fertilizers you are mixing should be made of the same materials. So, granular fertilizers can be mixed with other granular fertilizers but not with liquid fertilizers. Also, some fertilizers cannot be mixed because of nutrient loss or other issues.

Despite these downsides, mixing fertilizers is worth the effort for your plants.

Everything You Need to Know About Fertilizer Compatibility

As I mentioned earlier, some fertilizers just can’t be mixed. Fertilizers that are incompatible do not mix well together, as mixing them can lead to a number of issues. Caking, nutrient loss, and damage to equipment, are all problems that may be caused by mixing incompatible fertilizers.

Here are some common incompatible fertilizers and a description of what happens if you mix them:

  • Calcium nitrate and phosphates: A combination of these fertilizers results in the formation of calcium phosphate. Calcium phosphate is insoluble in water, which means that plants can’t uptake it.
  • Urea and ammonium calcium nitrate/KCI/SSP/ or TSP: A combination of these fertilizers results in a mixture that absorbs moisture from the air very easily. This leads to an almost muddy texture that is unusable. Not to mention that the mixture will draw water out from plant tissues immediately and kill the plant with fertilizer burn.
  • Epsom salt with complete fertilizers: Epsom salt or magnesium sulfate will mix with the phosphates in complete fertilizers to make an insoluble compound. Insoluble compounds need to be broken down in some other way to be useful as plant nutrients, or they can’t be used as fertilizer.
  • Calcium nitrate and magnesium sulfate: Calcium nitrate and magnesium sulfate combine to form calcium sulfate. Though it’s a little more soluble than calcium phosphate, it is still unusable as a fertilizer.
  • Ammonium phosphates and lime/slag/rock phosphate: Slaked lime or calcium hydroxide combines with ammonium phosphates to release ammonia gas. The formation of ammonia gas results in most of the nitrogen escaping as gas, so the plants aren’t able to absorb as much nitrogen as they need.

Some fertilizers like potassium chloride can be mixed with most fertilizers but must be mixed just before use. They’re fine once applied but have adverse reactions when stored for too long as they begin to absorb moisture from the air around them, resulting in a cakey mess.

Things to Do Before Mixing Fertilizers for Your Plants

To ensure you’re mixing your fertilizers correctly and in a way that ensures your plants get the maximum benefits, you have to do a few things before you mix your fertilizers:

Get a Soil Analysis Done

Performing a soil analysis every two years is useful as it helps you identify what nutrients are being depleted from your soil. This way, you won’t add unnecessary nutrients that will just end up adding to the salt concentration in your soil or polluting water bodies.

Determine the Ratio Necessary

Once you’ve done a soil analysis, you need to consider what your plants need. If they’re young seedlings, you might need more phosphorus to help with root growth. If they’re mature plants in their growing season, you might need a higher ratio of nitrogen.

Decide Which Medium You’re Using

As we’ve seen earlier, fertilizers of the same type can be mixed together. So granulated fertilizers can be mixed with each other, and liquid fertilizers can be mixed with each other.

The medium will determine the application, so you should decide on one medium and stick to it.

Make Sure They Don’t Have Additives

A lot of fertilizers have pesticides like herbicides mixed in, so they shouldn’t be mixed together. It is difficult to tell how the pesticides will react in the mixture, which is why you should stick to pure fertilizers.

Identify if You Need Fillers or Carriers

Once you’ve determined the ratio of nutrients you require, you need some way of arriving at the right quantity and concentration. This is where fillers (or carriers, if you’re using liquid fertilizers) come in.

Sand, coal, and ash are all examples of fillers you can use.

Add Conditioners and pH Balancers if Necessary

Conditioners are used to prevent any caking of the fertilizers over time. These could be materials like peat, paddy, or tobacco stem. PH balancers like lime are added if your fertilizer mixture ends up being too acidic for your soil to keep your soil and plants healthy.

Ensure You Have a Good Storage Space

Ideally, you should mix your fertilizer just before you need to use it. Nevertheless, if you have to store your fertilizer for a day or two, you still need a clean, cool, and dry place to store it.

Identify a Good Space to Mix Them

When mixing your fertilizers, keep in mind that plant fertilizers should be mixed on a non-reactive surface, like a concrete floor.

Do a Jar Test

There’s no way to identify the compatibility of all the different components used in fertilizers. Doing a jar test helps you work around this gap in information.

You can mix a small amount of your fertilizers in the desired concentration and see if the mixture reacts in any undesirable ways.

Final Thoughts

You can mix two fertilizers for your plants, but you need to ensure that they have the same medium and aren’t incompatible with each other. Incompatible fertilizers become insoluble, lose nutrients, or cake up when mixed together. It’s important to do a jar test before mixing to ensure that your fertilizers are compatible.

Before mixing your fertilizers, you also need to determine the ratio of fertilizers you need, then gather fillers and carriers, conditioners, and pH balancers as necessary. Finally, identify a good place to mix your fertilizer, plus a suitable place to store it.

Alexander Picot

Alexander Picot is the founder of and its lead content writer. He created the website in 2022 as a resource for horticulture lovers and beginners alike, compiling all the gardening tips he discovered over the years. Alex has a passion for caring for plants, turning backyards into feel-good places, and sharing his knowledge with the rest of the world.

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