Plants need fertilizer to help them grow strong roots and leaves and have large, healthy yields. However, this nutrition needs to be supplied to plants so it’s easy for them to absorb and use for their growth.
It is better to fertilize plants in the morning, though you will not harm your plants by fertilizing them in the evening. It is more important to avoid fertilizing your plants in the sun’s heat, which peaks in the late morning or afternoon. Applying fertilizer at this time leads to fertilizer burn.
In this article, I’ll explain the factors that affect nutrient uptake in plants to explain why it’s better to fertilize plants in the morning. I’ll also explain why you can fertilize at night even if the morning is a better time, so read on!
Factors Affecting Nutrient Uptake in Plants
Nutrient uptake refers to the way plants absorb, move, and utilize nutrients supplied to the soil via fertilizer. Nutrient uptake depends on several factors, but for this article, I’ll focus on external factors that affect nutrient uptake.
Some external factors that determine nutrient uptake in plants include environmental factors like light, temperature, and humidity. Other external factors include the type and method of fertilizer application. As much as possible, ensure that optimal conditions are present for your plant to absorb and process nutrients properly.
Availability of Light
The availability of light is important for plant growth as plants use the process of photosynthesis to convert nutrients to energy. The intensity of light available is particularly important for plant nutrient uptake. Plants use nutrients most efficiently when the light is more intense, as it’s during the daylight hours.
Applying fertilizers in the morning (particularly fast-release fertilizers like liquid fertilizers) allows the plant to efficiently utilize the newly absorbed nutrients. Therefore, fertilizing in the morning is a great way of minimizing nutrient loss and fertilizer wastage.
If you’re applying liquid fertilizer to your plants’ leaves as part of your foliar fertilization plan, applying the fertilizer in the morning will ensure that the fertilizer has all day to dry. As soon as it’s dry and absorbed by the leaves, they can work on using the nutrients to make sugar.
One of the most important nutrients for plants is nitrogen, a macronutrient necessary for plant growth. The regulation of nitrogen uptake in plants is determined by the quantity and quality of light available to the plants. Uptake is increased when plants have more light.
Insufficient light makes it difficult for plants to utilize the fertilizer they’ve absorbed. This means the excess fertilizer is left behind in the soil instead of being absorbed, which is a waste.
A build-up of fertilizer salts in your soil can lead to fertilizer burn in your plants. Fertilizer burn is caused when excess mineral salts in the fertilizer draw water out of your plants, causing desiccation, wilting, and scorching. This affects the overall health of your plants and delays yields while your plants recover.
Temperatures at the Time of Applying Fertilizer
Temperature plays an important role in plant growth and, therefore, in the nutrient uptake of plants. When the weather gets too cold, like in late fall and winter, plants go into dormancy. During this time, plants don’t grow. Instead, they use stored nutrients to stay alive.
Plants, especially outdoor plants, aren’t fertilized during dormancy as the nutrient will simply sit on the surface of the cold hard ground. Even if it does disperse into the ground, the plants won’t use the fertilizer, leading to leaching into water bodies or fertilizer burn.
When temperatures are cooler, plants grow slower and therefore utilize fewer nutrients. Their fertilizer requirements are lower under cooler temperatures. So when you apply fertilizer at night when temperatures are lower, plants won’t absorb all of it, causing waste.
In the morning, when temperatures are slightly warmer than at night, the plant can absorb nutrients better. Water viscosity is also better in warm weather, which means the roots can easily absorb water and nutrients from the fertilizers.
However, temperatures cannot be extremely high either. In very hot weather, most plants struggle to stay hydrated, so they need water a lot more than they need nutrition. (Of course, there are those like cacti that have evolved to withstand extremely hot temperatures, but they’re the exception to the rule.)
Fertilizer uptake requires a lot of water. If you apply fertilizers when surrounding temperatures are high, the mineral salts present in the fertilizers will draw water from the plant tissues, causing leaf and root scorch and even plant death.
When it comes to liquid fertilizers applied on leaves, the surrounding temperature can affect the rate of drying and affect the way the nutrients are absorbed.
A temperature that’s too high will result in the fertilizer drying too quickly, so most of the nutrients will be lost through evaporation. If it’s too cold, the fertilizer won’t absorb at all, leading to leaf scorch due to salt accumulation on the leaves.
Humidity Levels of the Region
Like temperature, the humidity of a region affects the nutrients absorbed by plants. Regular levels of humidity are preferable for optimum nutrient absorption, especially for foliar applications. The fertilizer applied to the leaves will evaporate in extremely dry weather before the nutrients are absorbed. This is why fertilizers shouldn’t be applied at midday or the afternoon.
However, the humidity cannot be too high either. High levels of humidity and soil moisture are associated with ammonia volatilization. Foliar applications may also remain on the surface of the leaves without being absorbed, which keeps the leaf wet and vulnerable to attacks by pests and fungi.
At night, when temperatures are lower, and the relative humidity is higher, fertilizers will not be absorbed as well as in the morning. This is why fertilizing in the morning is better than fertilizing in the evening.
Type and Method of Fertilizer Application
The type of fertilizer you’re using can determine the best time to apply it. Fast-release fertilizers make nutrients immediately available for plant use, so it’s important to time the application to ensure that plants can use the nutrient efficiently.
Solid fast-release fertilizers like fertilizer granules can be applied in the morning or evening, as these take time to dissolve.
Liquid fertilizers (especially ones used as starter solutions) work quickly, so they must be applied in the morning to ensure nutrient uptake and prevent any leaching or nutrient loss.
On the other hand, slow-release fertilizers like compost are a great way to naturally fertilize indoor plants, and they can be applied at any time of the day.
Plant food spikes are another type of slow-release fertilizer that can be used for your plants throughout the year and are usually more convenient. But slow-release fertilizers are better at conditioning the soil than immediately helping your plants grow.
Fertilizing Plants at Night
If you can consistently feed your plants in the morning, early mornings are the ideal time to fertilize your plant. However, if your only option is to fertilize your plant in the evenings, that isn’t the end of the world.
Plants use the night to recover from moisture loss in the morning and grow roots as the temperature cools. The roots grow outwards searching for nutrition, so the evening is a good time as any to apply fertilizer to your plants.
Evenings are also a great time to apply water-soluble granulated fertilizer. You can apply diluted liquid fertilizer to your plants in the evening. However, be careful not to apply too much to prevent wastage, leaching, and salt accumulation.
As I’ve mentioned earlier, slow-release fertilizers can be applied at any time, as these fertilizers release nutrients through microbial activity. Only a small percentage of nutrients is made available to the plants at a time, which can be absorbed easily.
Do Plants Uptake Nutrients at Night?
Applying fertilizer at night doesn’t have any negative effects on your plants, though nutrient uptake is easier when the plant is actively consuming nutrients (and they usually do so during the day). However, this doesn’t mean that plants don’t uptake nutrients at night.
Plants uptake nutrients at night. In fact, plants uptake nutrients, particularly nitrogen and phosphorus, throughout the day. About 45% to 46% of the nitrogen and phosphorus absorbed by plants is absorbed at night, even if they do not immediately utilize it.
So even if you can only fertilize your plants in the evening, you don’t need to worry about nutrient uptake. Plants will uptake nutrients at night as well as during the day.
Final Thoughts
Plants can be fertilized in the morning or the evening, though the morning is better as the light, temperature, and humidity ensures complete nutrient uptake. Plants are actively consuming nutrients in the morning, which makes it easier for them to absorb and use the nutrients supplied by the fertilizers.
It’s more important to avoid fertilizing plants when the sun is at its hottest — at midday and the afternoon — to prevent nutrient loss and leaf scorch caused by the fertilizer salts.
