Does Soil Need Sunlight

Confused about whether the soil requires sunlight in order to be fertile, or it is not entirely that?

Does Soil Need Sunlight” is YES, but not directly. Let’s put it this way, there is a lot of sunlight in the deserts, but does it matter? Ca Lack of basic nutrients that the soil requires in order to be fertile.

The sunlight directly affects the living organisms in the soil like Cyanobacteria, Algae, etc, these organisms require sunlight to produce carbohydrates, which benefit the soil.

But that’s not it! All of this may sound so easy and simple at first, but that is not the case, there are several factors as to how the soil is affected by the sunlight.

Following are the factors which provide detailed insight on the topic.

How Does Sunlight Affect Soil:

As mentioned above, Sunlight doesn’t directly affect the soil, it actually affects the microorganisms above or below the surface. Cyanobacteria and Algae are some of these microorganisms.

These organisms synthesis essential nutrients for the soil, such as Carbohydrates. Sunlight plays an important role in making the soil fertile for plant growth.

Sunlight helps plants in photosynthesis, as you all know. Plants produce their food with sunlight, and the more photosynthesis, the more the benefit for the soil.

Then, come the solar radiations, the scorching heat which travels all the way from the sun to the earth, and is absorbed by the soil, which results in the increase in soil temperature.

An increase in soil temperature can either be good or bad. It can either instantly kill the microorganisms inside, or it can increase the number of nutrients in the soil.

Simply put, warm soil proves to be more fertile, compared to cool(low temperature) soil.

Do Microorganisms in Soil Need Sunlight?

Now that’s a YES, they do. But how? Although organisms like Bacteria need relatively less sunlight to grow, and to synthesize the nutrients needed by soil.

A study found out that bacteria can actually tell light and dark apart. The sunlight can make bacteria even more dangerous.

Still, Algae and Cyanobacteria require sunlight, almost the same as plants, they are photosynthetic. Cyanobacteria are said to be one of the oldest forms of life and one of the reasons for oxygen on earth.

Sunlight is the most abundant energy resource on earth, renewable as well. Of course, microorganisms require sunlight to grow, in the soil as well.

The growth of Algae is dependent on sunlight. Ponds or water bodies that are more exposed to sunlight tend to have more algae growth, compared to less sun exposure.

These microorganisms like Algae possess chlorophyll, for converting the sunlight into chemical energy, which directly affects algae growth.

Striping Algae off the sunlight can result in their death. Concluding this point is the microorganisms DO need sunlight for growth purposes.

Does Sunlight Cause Weeds to Grow on Soil?

Weed seedlings can grow exceptionally well when exposed to sunlight. Weed AKA Marijuana, is a member of the Cannabaceae family. These family plants are either male or female.

Weed plants require organic matter-rich soil to grow. Actually, they require approximately 10 to 13 hours of direct sunlight.

In other words, these plants are happiest when exposed to sunlight. Marijuana plants don’t just require constant sunlight, but also keep control of different wavelengths of light.

Like other plants, Marijuana plants also have chlorophyll for converting light into food energy. Simply put, If you really want your Marijuana or Cannabis plant to exponentially, you need to put it in sunlight all day till sunset.

YES, the sunlight does cause weeds to grow on soil.

Will Covering Soil with Fabric or Mulch Affect It?

Covering the soil with mulch may prove to be good for the soil, but covering it with fabric or landscape fabric might be the last thing you wanna do.

Landscape fabric has more cons than pros when it comes to covering the soil with it. Covering the soil with fabric prevents rapid weed growth on soil. It also decreases the weed control need and keeps the soil moist.

But, as time passes the decomposed soil particles block the cloth holes, making it difficult for the required amount of water to reach the roots and it results in the plant’s death.

It also prevents the earthworms to oxygenize the soil, which leads to unhealthy soil. Marijuana can still develop in mulch above the fabric.

Now, if we look at Mulch, that’s a relatively different story. Mulch also helps keep the soil moist, which helps healthy contents to reach plant roots meaning, healthy plants as well.

Mulch also keeps the soil from losing water by keeping the soil moisture. Mulch put out rapid weed growth as well, and most importantly it protects the soil from harsh temperatures, especially from cold.

Mulch also consumes soil decay, which makes the soil even healthier


Does the landscape fabric allow water drainage? Yes, it does. But it is both good and bad news for you. How? Landscape fabric allows water through it as well as air.

You might find it beneficial to use landscape fabric at first, but wait till you see soil decay blocking it either for air or water.

Mulch, on the other hand, helps improve the drainage of soil with the passage of time. It improves the structure of soil by breaking down slowly to help drain the water and to keep the moisture.

Weed Growth:

Landscape fabric is good but not ideal for decreasing weed growth. First, the fabric needs to be accessible to water and air. But still, as time passes the soil decay will start to build up on fabric, allowing weed to grow on the fabric

Thick mulch applied on weed areas prevents the weed from growing a second time. It first requires hand weeding to pull out weed from their heads by hands before it has the time to go back to seed and emerge a second time.


As you all know Mulch keeps the soil relatively warm by capturing the sun’s heat and then directly sending the heat to the soil below. It may be good for the soil in winters, but not in summers.

As already warm soil gets warmer by mulch, it may prove to be unhealthy for the soil, overheating is never good for anything, no?

Temperature doesn’t have much negative or positive effect on landscape fabric, for that matter.

Water Retention:

Mulch is ideal for water retention in soil. As a matter of fact, it is the basic feature of mulch. Simply put, If you cover the soil with mulch, it prevents direct sunlight, which results in relatively less water loss.

As for landscape fabric, it is not actually made to keep water, it is water permeable, allowing water to escape and enter through it without much effort.

Soil Pests:

Mulch has been ideal in several ways mentioned above, but here? Not so much. Mulch can be an ideal home for soil pests to exist and reproduce.

Applying mulch so close to your house may not be the best decision as it allows your little hidden enemies to make their way into your home.

Will Covering Soil Prevent Weeds?

Yeah! It will. Covering the soil with plastic sheets will kill the weeds leaving you with good garden space. You can use landscape fabric here by putting it on bare soil around tree trunks.

It will block the weeds and their growth and will allow the water and basic nutrients to pass through it.

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