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This is a topic which can interact with the maintenance of soil structure, weed control and irrigation.

A mulch can be defined as a material which is applied to the soil surface in order to reduce water loss, suppress weeds, reduce fruit splashing, modify soil temperatures and generally improve crop productivity.

Mulches reduce water loss from the soil by acting as a barrier to evaporation, in addition they help to reduce soil compaction and therefore allow rain and irrigation water to reach the plant's root zone. The longer term effect is to increase water penetration rate, reduce surface run off and soil erosion and also increase the soil's organic matter content.

Dry materials, such as plant straw, may use more nitrogen in the short term but will have the same advantages in the medium and long term. Another possible benefit is that the soil is insulated from high temperatures. This is a major advantage if soil borne pathogens such as Fusarium are present because this disease thrives under the higher soil temperatures. There are some other advantages because some plant nutrients are less likely to be leached and lost from the plant's root zone when a mulch is on the soil surface.

Mulching materials

Several types of organic material are suitable as mulches. They include a wide range of plant debris such as trash from previous crops (either grown as early cover crops in the same plot as the peppers or carried in from other crops which have finished), composted organic materials, well rotted manures or mowed-off weeds which have not yet seeded. Figure 18 illustrates the use of banana leaves as a mulch. None of the mulches used should contain weed seeds, pests or diseases which are likely to affect the pepper crop. Related crops should either be well decomposed or used elsewhere.

FIGURE 18. Mulch with banana leaves

Cover crops

These may be inter planted with the peppers. There are several possible crops but the choice will depend on markets, potential income, season of production and their intercropping abilities. Commonly cultivated cover crops include cucurbits (especially pumpkins) and legumes (various types of peas and beans). When the cover crop has finished producing a useful product it can be chopped up and used as a mulch. By this time the main crop of peppers will have formed a good canopy. There are many traditional reasons for growing cover crops, such as providing an insurance in the case of a crop failure. Recent findings suggest that a mix of plant species in a plot of vegetables will deter insect pests which may fly in. Awell organised and suitable cover crop will assist the control of weeds by suppressing them. However, it must be appreciated that a cover crop may increase the demand for water on a plot which would otherwise be kept weed free.

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