Hanks Saisai
Crop production is a common agricultural undertaking, conducted in Namibia’s seven major production zones, including the Zambezi, Kavango, Karstland (Grootfontein, Otavi & Tsumeb triangle), North-central, Central, South and Orange zones.
A common practice adopted by many farmers in the crop subsector is monoculture, which is a practice where a farmer grows the same crop species, such as white maize, on the same piece of land for consecutive seasons.
The practice has a number of positive benefits, such as increasing farming efficiency, reducing labour costs and simplifying crop harvesting. However, monoculture has several adverse effects, which are outlined in this article.
Monoculture has the potential to lead to negative environmental impacts. The implements used to cultivate a specific crop repeatedly, till the land at the same depth and in the same manner.
This practice can damage the soil structure of arable land, resulting in soil erosion as the soil particles become loose and are easily blown away
by the wind or washed away by surface run-off. Additionally, the breakage of soil structure negatively affects the
soil’s ability to retain water.
Another negative effect of monoculture is that it depletes soil nutrient reserves, as crops grown repetitively utilize the same major nutrients each season. For instance, if a farmer grows maize on the same piece of land in
consecutive years, the plants will use Nitrogen, Phosphorus and Potassium in large quantities.
Furthermore, if no
plans are in place to plough back the maize stalks, the soil nutrient reserves are depleted of essential macro-nutrients (Nitrogen, Phosphorus & Potassium). Therefore, growing maize on this piece of land will require farmers to use synthetic fertilizers to meet the crop’s nutritional requirements.
Monoculture is also associated with a high prevalence of pests and diseases. For instance, if a farmer grows maize, the common pests and diseases associated with maize tend to thrive under ideal conditions, producing eggs that later hatch into pests that chew on the leaves, bore on the cobs and eat the roots. A common example of such pests is the migratory red locust that has become a common sight in the Zambezi and two Kavango regions.
This
is a consequence of growing the same crop repeatedly, as this does not break the life cycle of the pests. If the maize is attacked by a disease in a particular season and the farmer grows maize again in the coming season, the pathogen that causes such a disease has a chance of attacking the crops again.
Overall, the above effects have the potential to impact crop yields for many farmers, especially communal farmers who produce cereal grains such as maize and pearl millet (mahangu) that are part of their staple diets.
It is highly recommended that farmers avoid monoculture and adopt Good Agricultural Practices such as crop rotation to prevent environmental damage and reduce the vulnerability of crops to pest and disease outbreaks.
Additionally, by practising crop rotation and incorporating legumes like beans, cow peas and groundnuts, farmers can restore nutrient levels, particularly Nitrogen in the soil.
Hanks Saisai is the Technical Advisor: Crops & Poultry at Agribank
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