How Banana Peels Can Become Plant Fertiliser

Discarding a banana peel means throwing away a ready-made fertiliser that has been shown to improve plant and crop growth.

Research indicates that simply adding banana peels to soil can enhance plant growth and health compared with standard untreated conditions.

Bananas rank among the world’s leading fruit crops, with recent harvests of roughly 116 million tons.

As peels account for a quarter of the weight of each fruit, vast quantities of skins are discarded in kitchen bins rather than reused as plant fertiliser.

Banana peels, plants, and soil

The new review was led by Nokuthula Khanyile, a researcher at the University of Mpumalanga in South Africa.

Her work examines ways to convert agricultural waste, including banana peels, into safer fertilisers that benefit crops as well as soil organisms.

For a recent review, her team compiled findings from 126 studies examining banana peel-based fertilisers across a wide range of crops.

In these experiments, plants treated with peel-based products frequently grew taller, developed more leaves or germinated more quickly than those cultivated in untreated soil.

Macronutrients and soil chemistry

Banana peels contain abundant macronutrients, the nutrients plants require in comparatively large quantities.

Chemical analyses reveal substantial potassium levels, along with nitrogen, phosphorus, calcium and magnesium - the same elements farmers purchase in commercial fertiliser mixtures.

At present, most banana peels are sent to landfill, where decomposing food waste contributes to greenhouse gas emissions while all those nutrients are lost.

Using them as fertilisers instead connects an everyday practice, eating bananas, with cleaner agriculture and reduced demand for newly mined or manufactured nutrients.

From kitchen scraps to biofertiliser

Researchers use the term biofertiliser, meaning fertiliser produced from living or once-living materials, for many of these peel-based products.

Certain approaches are straightforward: peels can be sun-dried, ground into a coarse powder and incorporated directly into soil before planting.

The review repeatedly identified one formulation: dried banana peels combined with dried orange peels as a fertiliser. In the trials it covered, this fruit-peel mixture often improved leaf area and root length more than untreated soils.

Other research groups mashed fresh peels into a slurry, heated them with simple ingredients and then filtered the liquid to create a concentrated fertiliser.

This liquid can be mixed with water and applied to soil, allowing plants to absorb its nutrients through their roots.

Some projects take the process further by fermenting banana peels with coffee grounds or other plant waste. As this happens, microbes gradually release nutrients into the liquid, and initial tests indicate that the resulting fertilisers can accelerate the growth of leafy vegetables.

Testing banana peels on plants

One pea-plant experiment assessed banana peels left to decompose in soil for varying periods.

Peels decomposed for around two months delivered the strongest germination and growth, whereas longer decomposition weakened the plants.

The same research also examined peels decomposed in water rather than soil. These achieved the highest germination rate after approximately six months, although plant height ceased improving as decomposition continued.

For fenugreek, scientists compared dried banana peel powders with liquid extracts produced from the same material. Plants receiving the liquid extract grew taller and yielded more greens in the same timeframe than those treated with dry powder.

In okra trials, researchers mixed banana peel powders with other fruit peels, applying them before planting and then again later around the stems.

This regime resulted in deeper leaf colour, greater leaf area and heavier pods than soil receiving only conventional chemical fertiliser.

Implications for fertilisers

Modern agriculture remains highly dependent on synthetic NPK fertilisers: factory-made nitrogen, phosphorus and potassium blends that rely on fossil fuels.

Although these products have increased yields for decades, excessive use allows surplus nitrogen to run into waterways and cause eutrophication, an overgrowth of algae that damages fish populations.

One worldwide analysis estimated that synthetic nitrogen fertilisers account for about 2 percent of all human greenhouse gas emissions. This is a substantial proportion for a single agricultural input, meaning that any safe substitute for part of this nitrogen is important.

The Environmental Protection Agency (EPA) has associated excess fertiliser nitrogen with smog, fine-particle pollution and unsafe nitrate concentrations in drinking water.

As banana peel-based fertilisers release nutrients gradually and use recycled waste, they provide a potential way to reduce losses while maintaining yields.

Gardening lessons from banana peels

The takeaway for home gardeners and small farms is simple. Banana peels, orange peels, coffee grounds and comparable scraps can be made into valuable fertiliser using basic equipment rather than being thrown away.

The research also identifies approaches that are less effective. Banana peel biochar, a charcoal-like soil amendment created by heating plant waste, often produced little change in plant height at the tested application rates.

Many reviewed trials ended during the seedling or early-growth phase. Long-season field studies are still required to track crops through to harvest and assess not only yields, but also nutrient content and shelf life.

Banana peel chemistry varies according to variety, climate and storage conditions, so future research must establish formulations that farmers can rely on from one season to the next.

This means assessing not just nutrient concentrations in the fertilisers, but also the effects of each mixture on soil structure and root microbes.

If even a portion of the world’s banana peels were converted into thoroughly tested fertilisers, farmers could reduce their reliance on expensive synthetic products.

The latest research into kitchen-waste-based fertilisers indicates that a cleaner fertiliser future may already be waiting in compost buckets on kitchen worktops.