Processing for development

Learning to reason agro-ecologically to design and manage more efficient, productive, profitable and clean Musa production

Analyzing the concepts of a Musa-based agro-ecosystem

What is an agroecosystem?
An agro-ecosystem is a physical unit of land and its organisms, some of which are managed for human use. This term indicates that agriculture is subject to the same ecological processes as natural ecosystems such as forests or swamps or savannas.


Banana in a traditional homegarden in a forest area	Highland bananas

How are these ecosystems similar? How are they different? What are the components of their food web? How do nutrients and water cycle in the system? How much is harvested by humans?

Abiotic factors – temperature, wind, water, sunlight and soil
The physical unit of land which delimits the agro-ecosystem receives a daily input of solar energy and is subject to a temperature and rainfall regime. Depending on the type and amount of soil and subsoil a stock of nutrients is also available.

Living organisms forming a food web
The living organisms in an agro-ecosystem are the biotic component. The organisms can be analyzed as a food web that represents the transfer of material and energy from one group of organisms to another. For a food web analysis, organisms are grouped by their function in the flow of energy and nutrients rather than by their classification into genus and species. All the plants in an agro-ecosystem make up the primary producers and provide the basis of the food web. Plants capture solar energy through their leaves and in combination with water and nutrients from the soil and carbon dioxide from the air generate plant material. The next level of organisms is the herbivores that live off the nutrients and energy provided by plants or primary producers. Many different types of organisms can be herbivores - birds, insects, nematodes, fungi, bacteria and virus. In turn, the energy and nutrients in herbivores are exploited for growth and reproduction by another group of organisms called secondary consumers. Animals that live off the energy and nutrients in the substance of secondary consumers are called tertiary consumers. Many different types of organisms can also be primary, secondary and tertiary consumers.

The many plant and animals in an agro-ecosystem can be viewed as a food web.



Healthy corm (producer)	Weevil (herbivore)	Beauveria (secondary consumer)

In this simple food chain, the banana plant captures sunlight to grow, the weevil feeds on the corm and the Beauveria fungus feeds on the weevil. Which transfer of energy and material should we increase through management? Which should we decrease?

Decomposers form the detritus web
The food web also contains organisms that make up an important part of the soil food web, because they feed on dead material. Dead leaves, stems, roots, flowers and fruits from plants and waste material and body parts from animals are decomposed by fungi, bacteria and other fauna into smaller and smaller fragments. In this way the nutrients locked up in the plants and animals are released and become available to living organisms, recycling the nutrients back to new plant growth. The soil engineers break down plant and animal materials, while at the same time making channels in the soil, moving detritus from the surface to the sub-surface and among layers and forming soil aggregates. Microbial transformers act on whole material and detritus converting it into soil organic matter and nutrients.
Also in the soil are root and corm feeders which feed on living plant material and fungi and bacteria which are associated with living roots such as mycorrhiza and endophytic organisms.
The soil eco-system also has many secondary consumers which feed on earthworms, nematodes, bacteria and fungi.



Green cut banana leaves on soil	Leaf pieces decomposing

Who did this?

The soil food web has many organisms feeding both on living and dead plant material. Thus, the many organisms derive energy to grow and reproduce and eventually nutrients tied up in plant and animal material is available again for plant growth.

Structure and functioning of musa-based agro-ecosystems
The physical components of an agro-ecosystem make up the structure. Plants represent the largest amount of material in an eco-system, although the biomass and species of other organisms are also important in the structure. Bananas for export, often grown as a mono-culture, have quite a different eco-system structure than bananas grown in association with shaded coffee or for home food production. Not only is the plant component different, but also the associated food web.


Plantain intercropped with cassava and pineapple	Export banana	Agroforestry banana

Which one of these agro-ecosystems has more different types of plant material produced? Which one has a more diverse food web?

The functioning of an agro-ecosystem is based on dynamic processes. Energy enters the system as sunlight; a percentage is captured by plants. Of the plant material, 10 to 40% is extracted by humans for their use. Another part may be consumed by herbivores, some is recycled directly to decomposers and much is lost as heat. The cycling of macro- and micro-nutrients and water can also be traced in an agro-ecosystem.


Plantain with few stems and limited canopy	Vigorous plantain

In which system is more sunlight captured by Musa? In which system is more biomass recycled?

Bananas or plantains are an important primary producer in a Musa-based agro-ecosystem. Each Musa stem is tree-like with an elongated stalk and a canopy of up to 10-15 leaves. The stalk is herbaceous rather than woody and is made up of the individual leaf bases tightly wrapped cylindrically to form the pseudostem, a trunk-like structure. Each new leaf originates from the corm at ground level, grows upwards through the centre of the pseudostem and emerges at the top to form part of the leaf canopy.
Banana flowering is not strongly induced by photoperiod or low temperature, but only occurs once the stem produces a certain number of leaves. After the appearance of 30-45 leaves, a flower stalk grows upwards through the center of the shoot and gives rise to the fruit bunch. Before flowering, the corm gives rise to several new shoots which will produce the next generation of flowers and bunches. The rate of leaf production depends on temperature, water, light and nutrients. We will look at these factors more closely in the next section. Understanding these environmental factors helps us to understand the growth cycle of Musa and its productivity in different environments.

Musa plants are usually not the only primary producers in an agro-ecosystem. Depending on the availability of light and water, a farm household may plant other crops – annuals, roots and tubers, perennial crops. In addition, conditions often favor diverse volunteer vegetation which we often call weeds. The presence of other crops and weeds may increase the capture of sunlight, although they may also compete with bananas for light, water or nutrients.

All the primary producers in an agro-ecosystem are the source of energy and nutrients for herbivores. We are usually most concerned about those that damage crops, referring to them as pests and diseases. In this guide we will concentrate on sigatoka leaf disease, bacterial wilts, fusarium wilt, nematodes and weevils, but additional sections on other pests and diseases will be added to the guide in the future. Each of these pests represents a different type of organism. However, we need similar information about them to guide our management strategies. For example - what abiotic conditions reduce or increase their reproduction and damage to the crop? How can we strengthen the crop against their damage? We also need to take into account the organisms that feed on the pests and diseases. These organisms provide natural biological control and are often referred to as beneficial organisms. These secondary consumers are also affected by abiotic factors such as temperature, humidity and light. This will be presented in greater detail in the next section.

What other organisms are present in an agro-ecosystem based on banana in your area?