Zimbabwe: Global Climate Change Affects Production

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The Herald (Harare)

9 October 2008
Posted to the web 9 October 2008

Harare

The impact of global climate change on agricultural crop production may be significant and with technological advances in plant breeding, fertilizers and irrigation systems, climate remains a key factor in agricultural production.

A study by Agritex indicates that in the 1980s, continued deterioration of food production in Africa was caused by extended drought and soil degradation.

Maize is the primary staple food crop and occupies about half of the agricultural land in Zimbabwe.

Ambient temperature, precipitation and soil moisture, as well as frequency of heat waves and droughts are significant factors influencing production in Southern Africa.

Global climate change scenarios suggest maize productivity in Zimbabwe will decrease dramatically under non-irrigated or irrigated conditions in some regions of agricultural production.

The reductions are primarily attributed to ambient temperature increases, which shorten the crop growth period, particularly the grain-filling period.

If climate effects occur farmers may find maize production an unacceptably risky activity.

Adaptation options are available but financial costs may be prohibitive to communal area farmers.

Early-planted maize under all climate scenarios gives the highest yields in most farming areas and the yields are consistently higher under normal climate conditions and yields for late planted maize compare quite well with the early planted crops.

An analysis done at four irrigation schemes revealed that in all scenarios irrigation raised the production of maize. However, even though irrigation improves the growing conditions of maize, the yields are lower under climate change conditions than under normal climate.

It is not known if irrigation water will be available under climate change conditions in quantities adequate to meet the irrigation requirements.

A study of season length per given climate scenario revealed that growing seasons under existing climate are longer regardless of the planting date, however changes in climatic conditions may mean a decrease in season length which could have an effect by way of reducing the potential yield of long season varieties.

Some results of the study show that global climate change may significantly influence future maize yields in the country but also gives rise to fluctuating yields, thus making production a more risky agricultural activity for farmers.

Late-planted crops will not produce yields that make agronomy a viable activity under climate change conditions. Climate change will result in significant yield increases in some regions and this will depend on proper timing of planting dates to achieve the maximum production.

Even though irrigation will boost maize production in all areas, the yields will be lower under climate change conditions than under existing climate.

Crop growing season length may be shortened under climate change conditions and this may limit production to short season varieties.

Rainfall available each season will be reduced and the water available for irrigation purposes may be affected accordingly.Possible adaptation strategies include changes in the management practices of the maize varieties (planting date and irrigation); and shifting to varieties that may withstand the effects of climate change.

Any increases in ambient temperature would contribute to a loss of soil moisture that is critical to the agronomic crops, especially under rainfed agriculture.

Other strategies that could be employed include the growing of small grains such as millet, sorghum and sunflowers (although maize currently has the comparative economic advantage); grow short-season varieties; change plant population by altering plant spacing; apply appropriate fertilizers and insecticides as needed; rotate cereal crops with legumes.

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