What Is Biochar Fertilizer? How It Works in Tropical Soils

3 hours ago

5 min read

TL;DR: Biochar fertilizer is a soil improver made from biochar, a porous charcoal produced by heating plant material with little or no oxygen, combined with beneficial soil microbes. The biochar holds water and nutrients in its tiny pores, and the microbes make nitrogen and phosphorus easier for roots to take up. It builds soil health over time rather than giving a single quick feed.

Black, carbon-rich charcoal pieces spilling from a burlap sack

What is biochar?

Biochar is a fine-grained, highly porous charcoal made by heating plant material such as wood, crop residues or nut shells with little or no oxygen. The International Biochar Initiative describes it as a material that helps soils hold nutrients and water. Unlike cooking charcoal, it's made to be added to soil, not burned.

One gram of biochar has a very large internal surface, full of tiny pores. Those pores are what make it useful: they hold water, hold on to nutrients that would otherwise wash away, and give soil bacteria a protected place to live.

What makes biochar a fertilizer?

On its own, biochar contains few plant nutrients. It becomes a fertilizer when it's combined with nutrients or with microbes that make nutrients available to plants. That second type is called a biofertilizer or microbial fertilizer.

A biochar fertilizer works in two stages. First, the biochar acts as a carrier: beneficial bacteria are grown into its pores, where they form a protective film (a biofilm) that shields them from heat and drying out while the product is stored and spread. Second, once the fertilizer is in moist soil, the bacteria move out of the biochar and settle on the plant's roots. There they fix nitrogen from the air, release phosphorus that's locked up in the soil, and produce natural plant growth hormones such as indole-3-acetic acid (IAA) and gibberellic acid, which help roots grow and help plants cope with stress. Meanwhile, the biochar stays in the soil and keeps holding water and nutrients for seasons afterwards. The result is a fertilizer that feeds the soil's own biology rather than only the crop, so the benefit builds over time instead of washing out after one season.

How biochar fertilizer helps your soil

What it does	Why it matters on a Nigerian farm
Holds water in its pores	Crops cope better with dry spells between rains
Holds nutrients in the root zone	Less nitrogen and potassium washed away by heavy rain
Hosts beneficial bacteria	More nitrogen fixed and more phosphorus released for the crop
Adds stable carbon to the soil	Better soil structure, aeration and organic matter over time
Bacteria colonise the roots	Helps crowd out harmful soil organisms

Biochar helps most on poor, sandy or worn-out soils, the kind found across much of Northern Nigeria. A study on a tropical sandy soil in Brazil found that biochar lowered soil density and raised the amount of water available to plants. Results vary with the type of biochar and the soil, so it isn't a cure-all, but sandy, low-fertility soils gain the most.

Biochar fertilizer vs compost vs chemical fertilizer

Feature	Biochar fertilizer	Compost / manure	Chemical (NPK, urea)
How fast it works	Builds over weeks and seasons	Weeks to months	Days
Feeds	The soil's biology, and through it the plant	Soil and plant	The plant directly
How long it lasts	Biochar stays in soil for years	One to two seasons	Weeks; much washes out
Water holding	Large improvement	Moderate	None
Amount per hectare	About 100 kg (Vertelizer)	Several tonnes	Typically 100s of kg
Effect on soil over time	Improves structure and life	Improves	Can acidify soil if overused

For a fuller comparison, see Organic vs Chemical Fertilizer: Which Is Better for Your Farm?

How to apply biochar fertilizer

Vertelizer is Vertex Agro's biochar fertilizer, made from biochar and indigenous bacteria developed for tropical farmland. It comes in 5 kg and 25 kg bags.

Feature	Vertelizer (granules)	Vertelizer Plus (liquid)
What it is	Biochar plus specially developed bacteria	Liquid form with extra microbes, for quicker action
Rate per hectare	100 kg	2–4 litres
Small plot	About 10–20 kg	250–300 ml per 16-litre knapsack, sprayed
First application	Before planting or after germination	After germination
Repeat	Once a month for two months	Once a month for two months
Packs	5 kg, 25 kg	1 litre

Vertelizer Plus is registered with NAFDAC (A10-100989).

Crops: cereals (maize, sorghum, millet, rice), tubers (yam, cassava, potato), plantation crops (cocoa, rubber, bananas), vegetables and lawns.

Tips:

Apply to moist soil, or water after applying. The bacteria need moisture to leave the biochar and reach the roots.
Place it close to the root zone, not scattered across bare ground between rows.
Don't mix it into the same tank or bag as fungicides or strong chemicals, which can kill the bacteria.

Common mistakes

Expecting a one-week green-up. Biochar fertilizer builds soil over weeks. If the crop needs an urgent feed, the liquid Vertelizer Plus acts faster.
Applying to dry, hard soil and leaving it. The microbes need water to move to the roots.
Using cooking charcoal. It isn't made for soil, has no microbes, and large lumps do little.
Stopping after one application. The recommended plan is three applications: the first, then monthly for two months.

Frequently asked questions

What is biochar fertilizer made of?

Biochar fertilizer is made of biochar, a porous charcoal from heated plant material, combined with beneficial soil bacteria. The biochar holds water and nutrients, and the bacteria make nitrogen and phosphorus available to plant roots.

How much biochar fertilizer should I use per hectare?

For Vertelizer granules, apply 100 kg per hectare, or about 10–20 kg on a small plot. Apply before planting or after germination, then once a month for two months.

Is biochar the same as charcoal?

No. Biochar is made for soil, at controlled temperatures, and ground fine so its pores can hold water, nutrients and microbes. Cooking charcoal is made for burning and does little for soil.

Does biochar fertilizer work on sandy soil?

Yes. Sandy, low-fertility soils usually gain the most, because biochar helps them hold water and nutrients that would otherwise drain away. Results vary with soil type and the biochar used.

Can I use biochar fertilizer with NPK?

Biochar can help soil hold on to nutrients from NPK so less washes away. Apply them separately rather than mixing in one bag, and ask your supplier about rates.

Build soil that keeps working

Biochar fertilizer is a long-term investment in your soil. It holds water through dry spells, keeps nutrients where roots can reach them, and feeds the soil life that feeds your crop.

Want to know how much you need? Tell us your crop and farm size and we'll work it out with you.

Call +234 803 618 6987 · Email info@vertexagroltd.com · See Vertelizer →

Sources

International Biochar Initiative, What is Biochar? fact sheet
Carvalho et al. (2020), biochar on a tropical sandy Oxisol, Agriculture (MDPI)
Razzaghi et al. (2020), meta-analysis of biochar and soil water retention, Geoderma
Vertex Agro company profile (Feb 2025): Vertelizer mode of action