As a soil scientist, I enjoy weighing the pros and cons of different types of fertilizers. Comparing granular vs liquid fertilizer forms has surprising results. The answer is to hand down liquid fertilizer but why? The two fertilizer forms interact with the soil and plant in entirely different ways. This means yields, blooms and your garden as a whole will perform differently depending on the type you choose.
Applying science in the garden makes your garden journey a little bit easier by cutting through all the noise. In today’s Gardening in Canada blog post, we are going to be talking about granular versus liquid fertilizer. I personally enjoy liquid fertilizer, especially in the beginning phases of the plant’s journey. I also prefer liquid fertilizers if I have a plant in desperate need of immediate nutrient delivery.
Granular vs Liquid = Apples To Oranges
However, I have used granular forms of fertilizer and enjoyed the result. The convenience factor and the storage ability factor are undeniably beneficial. One thing I want to drive home is that comparing liquid to granular is difficult there are two totally different delivery systems of nutrients. however oddly enough granular organic and inorganic act similarly in the garden.
When I say similar, I mean the way that it is degraded to be made bioavailable for the plant is very similar in process. This can be through mechanical weathering such as sun, water, and wind. Or through a microbial activity that biodegrades polymer coatings or the organic material containing the nutrients.
Positioning Granular Vs Liquid Fertilizer In The Soil System
When we apply granular fertilizer, it is typically mixed throughout the soil system. This form of application means we have it in situ where it no longer is able to move. This is not a big deal for a majority of nutrients that are water-soluble. However, for the nutrients that are not water-soluble, this can be a problem. With granular fertilizers that contain insoluble nutrients such as phosphorus, we have to rely on the roots of the plant to get to that granular position. This must be done in order to uptake the nutrients. Unfortunately, plant roots do not have Spidey sense and are not able to take an educated guess as to where the nutrient granule is located. Plants can be lazy, and they will end up releasing something called an exudate which is a fancy word for sugar.
Can I Use Both Liquid & Granular Fertilizer?
Yes, as long as the granular fertilizer you are using has been underapplied. This is perfect for someone who is forgetful about using the liquid fertilizer every feeding. The goal should always be to fertilize every single time you water.
I will often underapply granular fertilizer in my houseplants and supplement with liquid fertilizer as needed. Something to keep in mind is organic fertilizers are difficult to burn your plants with. So if the concern is that using both liquid and granular fertilizer can be curbed by using a blend. If you use synthetic granular fertilizer and sub it organic liquid fertilizer you will not see any burning effects.
Benefits Of Liquid Fertilizer
The major benefit of liquid fertilizer is the immediate delivery of nutrients. This is because the nutrients are suspended in water within the soil pores. Liquid fertilizer is a pre-dissolved nutrient whereas granular needs to be solubilized with the presence of water.
If you are looking for ways to reduce waste with liquid fertilizer then you will want to pre-water. This simply involves watering your plants with water only prior to fertilizing. This will help will the pore spaces being filled prior to the fertilizer additions. Now you will fertilize with full concentration fertilizer water and maximize results while limiting losses.
Do not worry about overwatering. If you have your potting soil designed for drainage over watering will be a thing of the past.
Benefits Of Granular Fertilizer
Convince and continuous supply of nutrients is the benefits if granular fertilizer. This form of fertilizer is for anyone that is forgetful about fertilizing. Granular fertilizer works in conjunction with your soil to provide nutrients to your plant.
Granular fertilizer can be mixed throughout a potting soil, top dressed or placed into the transplant hole. If you choose to top-dress you may have some losses due to volatilization, aka gassing off. Always aim to incorporate granular fertilizer when possible.
Disadvantages Of Liquid Fertilizer
The disadvantage of liquid fertilizer can be losses if you do no ”pre-water“. Liquid fertilizer can run out of the bottom of your pots which is technically a loss of fertilizer. The other disadvantage is you need to actively remember to fertilize every time you water your plants.
Disadvantages Of Granular Fertilizer
The disadvantage of granular fertilizer is the fact that you need water in the soil solution. Granular fertilizer needs to be solubilized in water before it can be uptaken by the plants.
When using granular fertilizers you want to ensure your soil moisture is adequate. Allowing your plants to go below 20% moisture can result in a number of different issues. This will not only decrease nutrient availability as well as slowing doing microbe activity. Ideal soil moisture will be between 80%-30% for nearly all plants.
Liquid Vs Granular Fertilizer For Tomatoes
Tomatoes are heavy feeders and therefore granular fertilizer is preferred over liquid. Granular fertilizer will supply a continuous level of nutrients, which will maximize results. Liquid fertilizer will only be available to the plant at the time of watering till freshwater flushes out the soil.
Granular fertilizer for tomatoes can be placed in the transplant hole or mixed into the soilless medium. Always follow the granular application rules and place it within the rhizosphere. The rhizosphere is the area of soil that interacts with our plant roots. For tomatoes specifically use fruit and flower formulas because this will have higher levels of phosphorus and potassium along with micronutrients.
Liquid Vs. Granular Fertilizer For Lawns
Liquid fertilizer is the best for lawns when compared to granular. This is because granular fertilizer can have losses through gassing off. Liquid fertilizer being used on lawns allow for deeper penetration of the nutrients into the rhizosphere of the grass. Granular fertilizer needs to be watered in and relies on gravity and solubility.
Granular fertilizer is also notorious for burning your lawn due to the high localized concentration of salts. For lawn applications, the granular fertilizer has less interaction with the soil interface. This lack of interaction can result in the burning of the surrounding foliage.
How To Use Liquid Fertilizer?
There is a right and wrong ways to use liquid fertilizers for houseplants and the garden. The correct application will allow for reduced waste and prevent the burning of the plant roots.
- When it comes to using liquid fertilizer I encourage a pre-water application. This simply means doing a thorough watering with just plain water.
- After everything is fully saturated you can apply your liquid fertilizer. This will prevent again burning and reduce waste from run off.
How To Use Granular Fertilizer?
Using granular fertilizer simply involves even distribution to reduce the burning of roots. There are three ways to use granular fertilizer, each one has their own benefits and disadvantages.
- Mixed in with potting soil
- Root placed during transplanting
- Topdressing also known as broadcasting
If you are using granular fertilizer in potting soil then simply mix it in prior to potting up your plants. For those of you wanting to use granular fertilizers when transplanting you want to avoid too much fertilizer near the roots. Roots take up nutrients through osmosis and diffusion, meaning based on salts. An excess of salt needs the roots can cause burning and harm the nutrient uptake of the plants.
Steps for using granular fertilizers when transplanting:
- Dig a transplant hole 3x larger than the root ball.
- Mix the granular fertilizer with the removed soil
- Place the seedling into the hole and fill in the area around it with the soil fertilizer mix.
- Water the area thoroughly
Exudates & Fertilizers
This sugar is the equivalent of a microbe big gulp and therefore it attracts microbes that then will decompose surrounding organic material. This decomposition process turns the soil’s carbon-based structures into a format that is usable for the plant. This means the roots no longer have to travel to the area that contains phosphorus they can just produce it within that region.
This means when answering of which is better, granular vs liquid fertilizer, we can say liquid is more available. The plant has little to no work to do with liquid fertilizers. With granular fertilizers, we need the plant to do some work.
Liquid Fertilizer Soil Dispersion
With a liquid fertilizer, soil dispersion is a little bit different. This is because it is mixed into the soil water solution. Therefore, we have the benefit of saturating the entire soil system with equal parts of nutrients. Meaning the plants do not have to travel to get those water-insoluble nutrients. It has been delivered directly to the root system as a whole. This arguably could be less stressful for the plant especially if it’s going through a rough time.
Best Time To Apply Liquid Fertilizer Over Granular
Liquid fertilizers are far superior in specific situations. One case where it would be more beneficial for nutrient delivery would be after:
- After a major storm that has caused any sort of stress
- During a pest invasion whether that be fungal, bacterial or insects
The best way to think of liquid fertilizer is as a protein shake. Granular is the T-bone steak.
Hot Zones In The Soil Is The Granular Fertilizer Issue
Hot zones are common with granular fertilizer. Due to the manufacturing process salts are common in fertilizer both organic and inorganic. However, with a granular system, it tends to be a bit more relevant. This is due to the localized area that which granular is applied. As water penetrates the system and the granular fertilizer is broken down. Salt will be released into that general area of the grain. If you have a salt-sensitive plant ultimately what happens is the roots will avoid that hot zone.
This evasion of the hot zone is a way for the plant to protect itself from the salt burn. that means the nutrients that are not mobile are therefore hard for the plant to obtain without the use of exudates. with a liquid formula, we are not out of the hot zone necessarily, but it is dispersed throughout the entire system. what this means is that if we over-fertilize, we tend to get signs of fertilizer burn.
How To Recover From Over Fertilizing
Salts are water-soluble meaning we can use the laws of physics and simply drown out the system for lack of a better term. This could only happen with the overapplication of liquid fertilizer. With the overapplication of granular fertilizer, we would actually have to remove the plant and all the soil that comes with it. This means starting from scratch. Liquid allows us to back out of our mistakes by simply washing out or flooding out the access levels of salt.
When looking at granular vs liquid fertilizer we can say liquid is less likely to overapply.
Consistency in the number of nutrients in each granule is hard to determine. However, with liquid fertilizer, it is almost a guarantee that it is equally dispersed throughout the entire product. It is important to remember that we need to shake a liquid fertilizer in order to ensure equal dispersion in the liquid. If we fail to shake the product, we may end up with more of 1 nutrient than the other as things tend to settle out in the package.
This is especially true with organic fertilizers that do not use agents to help with mixing. The other issue with liquid is that it cannot freeze, and storage is important. If we allow a liquid fertilizer to freeze it is more or less garbage. I personally would not use this on my plants mostly because I would be concerned about the potential denaturing of the nutrients.
Granular Fertilizer Benefits
With granular however storage is much easier. As long as you keep a granular fertilizer moisture-free you can let it get as hot as you like or allow it to freeze. Granular is not only cheaper to purchase it lasts longer if you do not use it all within one season. With organic granular, it is important that you do allow the product to breathe sometimes. Because organic products are alive and do require some microbial activity to stop it from going completely anaerobic. You will know an organic granular product has gone bad if it smells rancid.
The last factor that may go into determining whether or not you want to use granular versus liquid is the convenience factor. How often are you willing to fertilize once a week or once a season? if the answer is once a season then granular is your choice. But if you’re a helicopter plant parent then something like a liquid may be more beneficial.
I hope you guys enjoyed this post if you did let me know in the comments down below and be sure to share. what is your preferred method for fertilizing liquid or granular?