Since the beginning of time, every gardener has been looking for effective fertilizers for their crops. The most popular forms of fertilizers are pellets (also called granular) and liquid. Which of the forms of fertilizer is more effective? Can we change a fertilizer from one form to another? Today, let us discuss fertilizers.
Note that this article focuses on inorganic fertilizers, not organic fertilizers like manure, compost, etc. Now let us learn what granular and liquid fertilizers are.
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What Are Granular and Liquid Fertilizers?
Granular fertilizers are dry fertilizers made in pellet forms. Potassium nitrate, ammonium sulfate, urea ammonium nitrate, etc. are used to make granular fertilizers.
Liquid fertilizers are in liquid form and are made with water-soluble nutrients like potassium chloride, anhydrous ammonia, etc.
Below are the difference, pros, and cons of both forms of fertilizers.
Pros and Cons of Granular Fertilizers
Here are some advantages of granular fertilizers:
- Granular fertilizers are easy to store
- They are suitable for heavy-feeding plants
- They are cheap when bought in bulk amounts
- Leaching (i.e. drainage from the soil) is reduced or avoided
- They have a slow-release variety which feeds plants for a longer period
The following are cons of granular fertilizers
- They cannot be used in foliar feeding
- Immobile nutrients are not available to plants
- Granular salts can burn plant leaves if not applied correctly
- They can only be used in conventional farming (planting on soil)
Pros and Cons of Liquid Fertilizers
Pros of using liquid fertilizers include:
- Nutrients are readily available
- They can be used in hydroponics
- They help young plants to grow quickly
- Liquid fertilizers can be used in foliar feeding
- They can be used to quickly correct plant deficiencies
- They are easily diluted to regulate how much nutrient is given to plants.
Here are some cons of using liquid fertilizers:
- Storage is difficult
- They leach off the soil easily
- Liquid fertilizers can burn leaves when used without caution
Differences between Liquid Fertilizer and Granular Fertilizer
Asides their forms, what are distinctive features between granular and liquid fertilizers? Here are a few:
Granular fertilizers are cost-effective. According to New Mexico State University, anhydrous ammonia which is mostly used to make liquid fertilizers cost an average of $697/ton.
The cost of granular fertilizer ingredients ranges from $456-$675/ton.
Method of Dispersal
Granular fertilizers are applied on the surface of the soil (in the root zone) or dug 4 inches deep below seeds. Granular fertilizers (except the slow-release type) are applied every six to eight weeks.
Slow-release granules feed your plants for months, so intervals between applying them are long.
Liquid fertilizers can be applied to the soil (around the root zone), sprayed on the leaves (i.e. foliar feeding), or mixed with irrigation water (a process known as fertigation) to water and feed your plants simultaneously.
Liquid fertilizers have nutrients that are readily available to plants. Granular fertilizers, on the other hand, have variations that release nutrients slowly, and variations that give readily-available nutrients to your crops.
Mobility of Nutrients
The nutrients (i.e. elements) in fertilizers are Nitrogen, Phosphorus, and Potassium (or NPK). Nitrogen and potassium are mobile in the soil, so they can easily reach, and be absorbed by plant roots.
The element Phosphorus is immobile in the soil, so pellets with phosphorus that are far away from roots cannot be absorbed by roots.
In liquid fertilizers, there is uniformity of the nutrients in every drop, so plants get both mobile and immobile nutrients when fed with liquid fertilizers.
Effects on Plant Health
Regardless of the type of fertilizer used, when fertilizers are used without caution, they can burn plants. The burning of plant leaves is a result of too many salts in the soil.
When salts are too concentrated in the soil, the root of plants sends out water from the leaves to balance the salt contents in and out of the roots. Absorption/dispersal of water and nutrients in roots is an osmotic process.
Here are the different methods of applying fertilizers when considering the effects of fertilizers on the health of plants:
- Water plants regularly when the soil is fertilized.
- Liquid fertilizers should be diluted with water in a ratio of 1:4.
- Slow-release granular fertilizers can be applied on the plant root region.
- Liquid fertilizers applied daily should be diluted with water in a ratio of 1:10 or more.
- Granular fertilizers should not be applied directly on plant roots. Spread them a few inches away.
Effects on the Environment
When fertilizers are used regularly, some may drain from the soil, finding their way into aquifers (i.e. groundwater), rivers, streams, lakes, etc. causing water to be enriched with nutrients (a process known as eutrophication).
Slow-release fertilizers cause less damage to the environment. Liquid fertilizers are fully water-soluble and leach faster during rainfall or when plants are watered.
To prevent leaching of fertilizers, apply what the plants require, and do not fertilize a nutrient-rich soil.
Correction of Nutrient Deficiencies
Plants show symptoms when they are lacking a specific nutrient. For example, potassium deficiency makes plants lose their green pigmentation (a process known as chlorosis), the tip of plant leaves curls or burns, etc.
When a nutrient deficiency is observed, it should be corrected immediately. Liquid fertilizers are more advantageous in correcting the deficiency of nutrients.
In foliar feeding (i.e. spraying liquid fertilizer on the leaves), the leaf of plants absorbs the nutrients quickly, so you do not have to wait for long before you see healthier plants.
Granular fertilizers (especially slow-release granules) will take a longer time to be absorbed and used by plants.
Granular fertilizers are easy to store because they are solid and dry. Do not store granular fertilizers in a humid room because microorganisms need nutrients and moisture to grow.
Liquid fertilizers should be stored in an air-tight and dark container. If you open the lid of containers containing liquid fertilizers, microorganisms (which can compete with, and harm your plants) will begin to grow in it.
A dark container prevents light from getting in. Without light, photosynthetic activity can not take place.
Other differences between granular and liquid fertilizers are equipment used, shelf life, etc.
List of Plants that Do Better with Granular Fertilizer
During nutrient absorption, plants cannot tell the differences between nutrients from granular fertilizers and nutrients from liquid fertilizers. However, young plants, heavy feeders, trees, etc. have different nutrient absorption rate.
Since the availability of nutrients differs in the forms of fertilizers, different kinds of plants (and different phases in plant growth) may prefer a form of fertilizer over the other.
Here are some kinds of plants that prefer granular fertilizer:
- Light feeders
- Slow-growing plants, etc.
Some plants that seemingly perform better with liquid fertilizers are:
- Heavy feeders, etc.
How to Turn Granular Fertilizer into Liquid
Considering the differences between granular and liquid fertilizers, you can tell that choosing one over the other is based on preference, method of application, and types of plants grown. If you already have one form, can you convert it to another?
Liquid fertilizers cannot be converted to granular fertilizers, but you can convert a fertilizer from granular to liquid form. If you already have granular fertilizers, you do not need to buy liquid fertilizers.
To convert a fertilizer from liquid to granular form;
- Soak the granules in distilled water for 24 hours. Start with a 1:1 ratio and adjust based on your plants needs.
- Mix the solution then filter out the undissolved solids.
- Do not throw the undissolved solids away. Apply them to your garden.
- Store the liquid fertilizer in a container with a closed lid, and a dark room.
Note: You should use pure water because the population of microorganisms in nutrient-rich water grows. When the fertilizer is applied to your plants, the microbes will compete with your plants for the nutrients or harm your plants.
3 Ways to Apply Your Liquid Fertilizers
1. Direct Soil Application
You can apply liquid fertilizers directly to the soil. If you wish to apply daily, mix 1 part liquid fertilizer with 10 part water.
2. Foliar Feeding
This is the quickest method to correct plant nutrient deficiencies. Put some fertilizer (with more of the nutrient that the plant lacks) into a spray bottle then spray the fertilizer on/around the leaves.
This is the process of feeding and watering your plants at the same time using your irrigation system. Pour some fertilizer into your irrigation tank then water your plant daily. You should mix 1 part fertilizer with 25 part water because the plants are water/fed daily.
Every plant requires nutrients, so fertilizers must be provided for plants to grow. Fertilizers come in granular and liquid forms. Granular fertilizers can be converted to liquid fertilizers. Methods of applying liquid fertilizers are soil application, foliar feeding, and fertigation.
Which do you prefer between granular and liquid fertilizers? Share your thoughts in the comment section below.