Agriculture and Environment: Bananas

Better Management Practices: Reduce Fertiliser Use

Most banana producers apply fertiliser regularly to their crops.

They do this through calculations that are made in advance of actual needs. Little monitoring is undertaken to insure that the plants actually need or take up the fertiliser used.

Assessing the genuine need for fertilisers
Setting up systems to gather information and monitor the use of and need for chemical fertilisers would reduce use over time. Such a system would require more labour, but it would likely reduce overall expenditures for fertilisers and might extend the life of the plantation.

The migration of fertiliser from banana plantations to other areas is a serious problem. There is no universal solution. However, progress can be made in addressing the problem by reducing the amount of fertiliser that is exposed on the surface of the land.

Avoiding chemical leaching
Applying only the amount of fertiliser that the plants need reduces the excess amount in the environment that is available for leaching. There are now experiments with precision application in bananas that could help.

Stimulating root health & development
Producers should also make sure that roots are healthy and numerous so as to reduce runoff. One strategy to stimulate root development is to apply humic acids, substances found in and extracted in liquid form from compost and well-decomposed organic matter. These can be purchased or made on the farm from composted wastes.

Use of burned/quick lime
Another hidden environmental issue is the use of burned lime, also called quick lime (calcium oxide). In some areas, burned lime is used to provide calcium for neutralising soil acidity on banana plantations. For example, in Belize, some 900 kilograms of burned lime are applied per hectare per year on banana plantations.

Dolomitic lime is available from local mines, but it takes longer to break down in the soil. Burning the limestone converts it to a compound that breaks down very quickly, so it does a much faster job of neutralising soil acidity than unburned limestone.

If banana producers in places like Belize began to use some dolomitic lime when applying smaller amounts of burnt lime (which is absorbed more quickly), in three years they would be able to convert totally to dolomitic lime. This is important in a country like Belize because the fuel wood required to burn limestone results in deforestation.

Crop rotation and fallowing
Another strategy to minimise or avoid the use of lime altogether is fallowing or green manuring. Acidity (low soil pH) is raised to near neutral in fallowed fields. If the fallows are well managed, they can also reduce contamination of and demand for natural resources at minimum cost (Panfilo Tabora, personal communication).

There is, of course, the short-term opportunity cost while the land is taken out of production and devoted to production of green manure during the fallow, but this needs to be evaluated in light of the future reduction of input use, reduced downstream pollution/effluent liabilities, and improved long-term viability of the overall farming strategy.

An additional strategy for reducing fertiliser use is crop rotation in conjunction with fallowing. Crop rotation and fallowing can be profitable investments with returns that can rival net returns of bananas per hectare per year, based on savings in pesticides and fertilisers during the cropping years.

Cover crops not only provide organic material to replenish the soil, they also reduce soil erosion by reducing exposure to sun and rain, which maintains populations of beneficial soil microorganisms and protects the structure of the soil.