A fertilizer-use study by researchers on East African highland bananas showed that moderate application of mineral fertilizers could double the production of the crop. However, the study also found that majority of the banana growers in the region do not use fertilizers, missing out on the opportunity to maximize their crop's food security and economic potentials. Over 70 million people in the East African highlands depend on banana as their primary source of food and income.

The USAID-funded study carried out by the International Institute of Tropical Agriculture (IITA) in nearly 200 farmer fields in Uganda -- the second largest producer and consumer of bananas in the world -- showed that modest fertilizer use can significantly increase the crop's yield.

In Central Uganda, for example, annual yields doubled from 10 to 20 tonnes per hectare with modest fertilizer application.

The research was led by Piet van Asten, IITA agronomist based in Uganda, and Lydia Wairegi, a PhD student at Makere University.

"The application of fertilizers not only increases bunch weight but also shortens the crop cycle so the plants produce more bunches in a year," says van Asten.

However, the study also found that less than 5 percent of the farmers apply fertilizer on their banana crop. They cited fertilizers' high cost, erratic supply, and inconvenient packaging as the main reasons for their non-use. The farmers also indicated the lack of access to credit facilities, limited knowledge on fertilizer use, and the perceived negative effect on soil quality and on the taste of the bananas.

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To debunk the latter, a related farmer sensory evaluation conducted by IITA and Uganda's National Agricultural Research Organization (NARO) showed that that moderate application of fertilizer use not only increased yields, but also improved the quality of the fruit to make matooke -- a popular local delicacy made from steamed bananas.

The evaluation showed that fertilizer treatment actually improved the appearance, odor, texture, and overall acceptability of the steamed bananas.

Although the study showed proof of the positive effect of fertilizers on banana production, van Asten cautions that fertilizer use has to be very strategic. For example, the practice only becomes more profitable when it is specific to a crop and a region, and targeted at only those nutrients that are most deficient.

"Most farmers follow blanket fertilizer recommendations which can be very inefficient and therefore expensive. Farmers should apply only as much nutrient as needed for a realistic yield increase for their specific locality," he says.

He adds that another consideration is distance to the markets. "Bananas are perishable and costly to transport because of their bulkiness. One needs to be close to the market to fetch a really good price," he says. "Uganda's production zones are too far from markets, some more than 150 kilometers away. This leads to low banana prices at the farm gate. Fertilizer use in such cases becomes risky and, therefore, may not be recommended."

Fertilizers also help replace lost soil nutrients. For example, the study estimated that more than 1.5 million tons of potassium (K) are removed from the rural areas where the bananas are grown and transported to Kampala where most of the markets are. These nutrients are mined by farmers, but not immediately replaced. Over time, this nutrient mining could diminish the soil's ability to sustain profitable banana production.

To guide East African highland banana farmers, IITA and its partners have developed several site-specific recommendations for the application of fertilizer based on the region and the distance to markets. The institute is also encouraging the private, public, and non-government sectors to address fertilizer packaging to suit the specific needs of farmers.